SOPHIA_Unit_6_Tutorials_Genetics_and_Biotechnology 2020 - Southern New Hampshire University | SOPHIA_Unit_6_Tutorials_Genetics_and_Biotechnology 2020

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SOPHIA_Unit_6_Tutorials_Genetics_and_Biotechnology 2020 - Southern New Hampshire University Unit 6 Tutorials: Genetics and Biotechnology INSIDE UNIT 6 Genetics and DNA Structure of DNA and Chromo... somes Mitosis Meiosis and Genetic Variability DNA Replication Protein Synthesis, Part 1: Transcription Protein Synthesis, Part 2: Translation DNA Sequencing DNA Technology and Research Genetics and Inheritance Heredity Punnett Squares Codominance Polygenic Traits and Pleiotropy Pedigrees Chromosome Structure Changes Chromosome Count Changes Autosomal Recessive Traits and Disorders Autosomal Dominant Traits and Disorders X-Linked Traits Structure of DNA and Chromosomes by Sophia Tutorial  T his lesson will discuss the structure of chromosomes by looking at: 1. Chromosome Structure & Function 2. Chromosome Number & Location 3. DNA Structure a. Nitrogenous Bases WHAT'S COVERED © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 1b. Base Pairs c. Nucleotide Sequence 1. Chromosomes When a cell is getting ready to divide, genetic information in the form of DNA will condense into structures called chromosomes. This is how genetic information is passed from parent to offspring. Homologous chromosomes are chromosomes that contain the same set of genes and are the same length and shape. One is from the mother of the offspring, and other is from the father. There are two types of chromosomes within our body: Sex chromosomes: Chromosomes associated with sex and gender Autosomes: All the chromosomes in our body except for the sex chromosomes  TERMS TO KNOW Chromosome A condensed DNA structure. Homologous Chromosomes Chromosomes paired together that are the same length and shape and contain the same sets of genes; typically, one of the homologous pair is contributed by each parent. Sex Chromosomes Chromosomes associated with sex and gender. Autosomes All of the chromosomes in the body except for sex chromosomes. 2. Chromosome Number and Location The chromosome number is the number of chromosomes in a species' cells. Each species has its own number of chromosomes.  EXAMPLE For humans, the chromosome number is 46. This means that we have 46 chromosomes, or 23 pairs of homologous chromosomes, in our cells. Of those 46 chromosomes, most of them are autosomes. Only two of those chromosomes are sex chromosomes. A mouse has a total of 40 chromosomes. Chromosomes are only visible in this form when the cell is preparing to divide. The rest of the time, our genetic information can be found in the form of chromatin, which has a balled-up thread-like form and is found within the cell's nucleus. © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 2This makes sense; when the cell isn't dividing, the DNA is more stretched out so its information is physically accessible. When the cell is dividing, The DNA has to move all the way across the cell. It's not being accessed for much information, so it's better to be wound up tight with a bunch of protective proteins. It's like packing a suitcase: It's easier to take everything you need if all the clothes are rolled up tightly (just as the DNA is condensed into visible chromosomes) than if you just throw clothes in a pile in your suitcase (like when the DNA is stretched out). 3. DNA Structure DNA is said to be in the structure of adouble helix, or a "twisting ladder". The outside parts of the ladder (the "side rails") are made up of a phosphate-sugar backbone--that is, phosphate and deoxyribose sugar molecules. In DNA, the sugar within its nucleotides is called deoxyribose; in RNA, the sugar within its nucleotides is called ribose. © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 33a. Nitrogenous Bases The "rungs" of the ladder are made up of four nitrogenous bases: Adenine Thymine Cytosine Guanine These nitrogenous bases compose two base pairs. Adenine always pairs with thymine, and cytosine always pairs with guanine.  TERMS TO KNOW Double Helix The shape of the DNA molecule; often is referred to as the “twisted ladder” and is the title to the book about Watson & Crick's discovery of DNA's structure. Adenine (A) A nucleotide building block of DNA and RNA, adenine is classified as a purine and complements thymine (T) in DNA and uracil (U) in RNA. Thymine (T) A nucleotide building block of DNA, thymine is classified as pyrimidine and complements adenine (A) in DNA; thymine is not found in RNA. Guanine (G) A nucleotide building block of DNA and RNA, guanine is classified as a purine and complements cytosine (C) in DNA and RNA. Cytosine (C) A nucleotide building block of DNA and RNA, it is classified as pyrimidine and complements guanine (G) in © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 4DNA and RNA. 3b. Base Pairs The phosphate, the sugar, and the nitrogenous base together make anucleotide, and each "rung" of the double helix (and the rung's small portion of "side rail") is made of two nucleotides facing each other. In DNA, the two nucleotides that make up a particular rung of the twisted ladder are called a base pair. Adenine always pairs with thymine, and cytosine always pairs with guanine.  TERMS TO KNOW Nucleotide Organic molecules that consist of a five-carbon sugar (ribose in the case of RNA and deoxyribose in the case of DNA), a phosphate group and a nitrogenous base; nucleotides are the building blocks of nucleic acids (DNA & RNA). Base Pair The way that nucleotides interact with one another, A bonds with T and C bonds with G in DNA, while C bonds with G and A bonds with U (uracil) in RNA; the sequence of base pairs creates the genetic code that is transcribed and translated into proteins. 3c. Nucleotide Sequence If you follow one of the "rails" of the DNA's "twisting ladder", you will see the nucleotides' order (A, T, C, etc.). This is called a nucleotide sequence. The order of letters (nucleotides) in the nucleotide sequence is very important because the sequence contains instructions or "recipes" for all our thousands of proteins. These "recipes" for our proteins are called genes. Any change in the nucleotide sequence is amutation, and can have a negative impact on a protein's structure or production. For example, one of the genes for making hemoglobin is 1,605 nucleotides long. Within that stretch of DNA, there is a sequence of three nucleotides that reads "GAG", but in some people, the nucleotide sequence at that location reads "GTG". It's like a typo; instead of saying "Shall I compare thee to a summer's day" the gene says "Shawl I compare thee to a summer's day". Hemoglobin produced from this mutated gene is more likely to clump. If only one the two copies of chromosome 11 (one of its two homologous pairs) has this mutation, it means only half of the hemoglobin the person produces is clumpy, and the person is less vulnerable to malaria. But if both of the homologous chromosomes have the mutated genes, all of the hemoglobin produced is clumpy, and the person will suffer from sickle cell anemia.  TERMS TO KNOW Nucleotide Sequence The arrangement of nucleotides (the order of A's, C's, G's and T's) that form genes in strands of DNA. Gene A segment of DNA that codes for a specific protein, genes are a sequence of nucleotides. Mutation A change in the nucleotide sequence.  Chromosomes are the form DNA takes when a cell is getting ready to divide, and are only visible during this time. Homologous chromosomes are chromosomes that contain the same set of genes. There are two types of chromosomes within our body: Autosomes and sex chromosomes. The chromosome number is the number of chromosomes a species has in its cells.DNA, the genetic information that makes up chromosomes, come in the form of a double helix. It is made up of phosphate and deoxyribose sugar molecules as the backbone of the structure with adenine/thymine SUMMARY © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 5or cytosine/guanine base pairs in between. Keep up the learning and have a great day! Source: SOURCE: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND  ATTRIBUTIONS Chromosomes | Author: Wikipeda | License: Creative Commons Cell Nucleus and Chromosomes | Author: Wikipeda | License: Creative Commons Double Helix | Author: Wikipeda | License: Creative Commons  Adenine (A) A nucleotide building block of DNA and RNA, adenine is classified as a purine and complements thymine (T) in DNA and uracil (U) in RNA. Autosomes All of the chromosomes in the body except for sex chromosomes. Base Pair The way that nucleotides interact with one another. In DNA, A bonds with T, and C bonds with G. In RNA, C bonds with G, and A bonds with U (uracil). The sequence of base pairs creates the genetic code that is transcribed and translated into proteins. Chromosome A condensed DNA structure. Cytosine (C) A nucleotide building block of DNA and RNA, cytosine is classified as pyrimidine and complements guanine (G) in DNA and RNA. Double Helix The shape of the DNA molecule; often is referred to as the “twisted ladder” ("Double Helix" is the title to the book about Watson & Crick's discovery of DNA's structure). Gene A segment of DNA that codes for a specific protein, genes are a sequence of nucleotides. Guanine (G) A nucleotide building block of DNA and RNA, guanine is classified as a purine and complements cytosine (C) in DNA and RNA. Homologous Chromosomes Chromosomes that are paired together that are the same length and shape and contain the same sets of genes. Typically, one of the homologous pair is contributed by each parent. TERMS TO KNOW © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 6Mutation A change in the nucleotide sequence. Nucleotide Organic molecules that consist of a 5 carbon sugar (ribose in the case of RNA, and deoxyribose in the case of DNA), a phosphate group and a nitrogenous base; nucleotides are the building blocks of nucleic acids (DNA & RNA). Nucleotide Sequence The arrangement of nucleotides that form genes in strands of DNA. Sex Chromosomes Chromosomes associated with sex and gender. Thymine (T) A nucleotide building block of DNA, thymine is classified as pyrimidine and complements adenine (A) in DNA; thymine is not found in RNA. © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 7Mitosis by Sophia Tutorial  T his lesson will cover the role of Mitosis in the cell cycle by looking at: 1. The Cell Cycle 2. Interphase 3. Mitosis Phases 4. Cytokinesis 1.The Cell Cycle Mitosis is a part of the cell cycle. The cell cycle describes events that happen from the time a cell is formed until it divides. Mitosis is a type of cell division that happens in somatic cells (all the cells in your body except for gametes). This process produces new cells. Cells are constantly going through the cell cycle and producing new cells. As cells grow old and die, they need to be replaced by new ones.  TERM TO KNOW Cell Cycle Describes the events that occur from the time a cell is formed until it divides. 2. Interphase Interphase is the first part of the cell cycle, but it's not considered to be a part of mitosis. Interphase is the part of the cycle where the cell is getting ready to divide but is not dividing yet. It is the longest phase of the cell cycle and is where the cell spends most of its life. There are three sub-phases to interphase: G1 Phase: Part of interphase is when the cell will start to increase in size and grow in preparation for cell division. S Phase: During this part, DNA is copied (DNA synthesis), and chromosomes are duplicated G2 Phase: Cell grows, making its final preparations in order to get ready to divide WHAT'S COVERED © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 8Typically in interphase, chromosomes are not visible. Genetic information, or DNA, is found in the form of chromatin, which is like a thread-like ball of yarn that's found within the nucleus. As a cell is preparing to divide, that DNA will then condense into chromosomes which will be copied in preparation for division. Chromosomes are made of sister chromatids attached in the middle at a point called thecentromere.  TERMS TO KNOW Interphase A phase of the cell cycle in which a cell carries out its normal functions; includes all parts of a cell’s life except for when the cell is dividing. G1 Phase The portion of interphase in which a cell grows in size. S Phase The portion of interphase in which a cell’s DNA is copied. G2 Phase The portion of interphase in which a cell makes final preparations for cell division. Sister Chromatid A duplicate of an original chromosome produced during mitosis. Centromere The point at which sister chromatids are attached to one another. 3. Mitosis Phases Mitosis actually includes four phases: © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 9Prophase. During this phase, the nuclear envelope that normally surrounds the genetic information will start to break down. Poles will form on opposite ends of cells; they become the attachment points to each sister chromatid's centromere so that each new cell gets exactly one of the two sister chromatids for each chromosome. Metaphase. Chromosomes will line up on the metaphase plate, which is an invisible line in the middle of the cell. Spindle fibers are attached to the centromeres of the chromosomes to prepare these chromosomes to be pulled apart to separate ends of the cell. Anaphase. Sister chromatids are separated and moved to opposite ends of the cell. Telophase. The nuclear envelope will begin to reform around the chromosomes, and the plasma membrane will start to pinch off. This area where it's pinching off is called the cleavage furrow.  TERM TO KNOW Prophase The first phase of mitosis in which chromosomes are condensed, the nuclear membrane breaks down, and poles at opposite ends of the cell begin to form. Metaphase The second phase of mitosis in which chromosomes line up on the metaphase plate and are attached at the centromere to spindle fibers. Anaphase The third phase of mitosis in which sister chromatids are separated and pulled by spindle fibers toward opposite poles of the cell. Telophase The final phase of mitosis in which the plasma membrane begins to pinch off and the nuclear membrane begins to reform; chromosomes begin to return to their thread-like state. Cleavage Furrow The pinching off of the plasma membrane to produce two new cells. 3. Cytokinesis © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 10Cytokinesis follows mitosis. Cytokinesis is were two completely new individual cells exist. These two separate cells are diploid daughter cells. They are calleddiploid because they each contain 46 chromosomes (23 chromosomes from each of the two parents), the same number as the original cell. These diploid cells are also identical to the original cell. At this point, the nuclear envelope has completely reformed, and the DNA will return to its thread-like form.  TERMS TO KNOW Cytokinesis The end result of mitosis in which two diploid daughter cells are produced which are identical to the parent cell. Daughter Cells The name for cells produced by the process of mitosis. Diploid Cells that contain two copies of each chromosome (one copy from our mother, and one copy from other father).  Mitosis the part of the cell cycle where a cell divides to reproduce. Interphase is the part of the cycle where a cell spends most of its life and is preparing for mitosis. There are three phases to interphase. G1 is the phase where the cell is growing, S phase is where DNA is copied, and G2 is where the cell makes final preparations for mitosis. During interphase, chromosomes are normally not visible, but as the cell prepares to divide it will condense and become visible. Once duplicated sister chromatid are held together by a centromere. There are four phases of mitosis. Prophase is when the nuclear envelope breaks down, and poles are formed at opposite ends of the cell. Metaphase is when the chromosomes start to line up in the middle of the cell, and spindle fibers attach to the centromeres of the chromosomes. During anaphase, sister chromatids are separated and move to the poles. Finally, in telophase, the nuclear envelope will begin to reform around the chromosomes, and the plasma membrane will pinch off. SUMMARY © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 11Cytokinesis follows mitosis and is where two completely new daughter cells exist. Keep up the learning and have a great day! Source: SOURCE: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND  ATTRIBUTIONS Sister Chromatids | Author: Wikipeda | License: Creative Commons Mitosis | Author: Wikipeda | License: Creative Commons  Anaphase The third phase of mitosis in which sister chromatids are separated and pulled by spindle fibers toward opposite poles of the cell. Cell Cycle Describes the events that occur from the time a cell is formed until it divides. Centromere The location at which sister chromatids are attached to one another. Cleavage Furrow The pinching off of the plasma membrane to produce two new cells. Cytokinesis The end result of mitosis in which two diploid daughter cells are produced which are identical to the parent cell. Daughter Cells The name for cells produced by the process of mitosis. Diploid Cells that contain two copies of each chromosome. G1 Phase The portion of interphase in which a cell grows in size. G2 Phase The portion of interphase in which a cell makes final preparations for cell division. Interphase A phase of the cell cycle in which a cell carries out its normal functions; includes all parts of a cell’s life except for when the cell is dividing. TERMS TO KNOW © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 12Metaphase The second phase of mitosis in which chromosomes line up on the metaphase plate and are attached at the centromere to spindle fibers. Prophase The first phase of mitosis in which chromosomes are condensed, the nuclear membrane breaks down and poles at opposite ends of the cell begin to form. S Phase The portion of interphase in which a cell’s DNA is copied. Sister Chromatid A duplicate of an original chromosome produced during mitosis. Telophase The final phase of mitosis in which the plasma membrane begins to pinch off and the nuclear membrane begins to reform. Chromosomes begin to return to their thread-like state. © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 13Meiosis and Genetic Variability by Sophia Tutorial  T his lesson is going to cover the process of Meiosis by looking at: 1. Meiosis Overview 2. Meiosis I a. Phases of Meiosis I b. Difference Between Mitosis 3. Meiosis II 1. Meiosis Overview Meiosis is a type of cell division that is specific togerm cells, or cells that give rise to gametes. In this type of cell division, germ cells are going through a division to form gametes. Gametes are the sperm cells in men and the oocytes in women. The result of meiosis is haploid daughter cells, and haploid cells contain half as many chromosomes as the original germ cell.  EXAMPLE In humans, meiosis starts out with a germ cell of 46 chromosomes and ends up with haploid daughter cells that each have 23 chromosomes. Each round of meiosis is similar to mitosis. There are two types of meiosis, depending on if it is creating a sperm or an egg gamete: Spermatogenesis is meiosis in sperm cells and leads to four sperm cells. Oogenesis is the formation of egg cells and leads to one oocyte. While four cells are generated in oogenesis (just as in spermatogenesis), only one becomes an oocyte; the others disintegrate. Whether it's spermatogenesis in men or oogenesis in women, meiosis involves two rounds of cellular division: Meiosis I and meiosis II.  TERMS TO KNOW Meiosis A type of cell division that occurs in germ cells to produce haploid gametes. Germ Cell A cell that gives rise to gametes. Gamete A cell which contains a haploid number of chromosomes (male gametes are sperm; female gametes are oocytes). Haploid The number of chromosomes in the gametes of an organism which is equal to half of the number of chromosomes of somatic (all non-gamete) cells. Spermatogenesis The process that forms four haploid sperm cells. Oogenesis The process that forms a haploid egg cell. WHAT'S COVERED © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 142. Meiosis I Meiosis I is the first round of meiosis. The process of meiosis is similar to mitosis. Before meiosis begins, the germ cell has undergone interphase: There was growth (G1), synthesis (S) of DNA to make two copies of every chromosome, and more growth (G2). As a result of DNA synthesis, the germ cell looks a lot like a somatic cell that's about to divide: Its 23 pairs of homologous chromosomes (46 total) now each have two sister chromatids (92 chromatids total). 2a. Phases of Meiosis I Prophase I : The germ cell begins in prophase I. In this phase, similar to prophase of mitosis, homologous chromosomes (each with two identical sister chromatids) will condense. Also during this stage, the nuclear envelope will break down, and spindle microtubules will attach to the centromeres. Metaphase I : Chromosomes will line up in pairs ofhomologs (each member of a pair of homologous chromosomes is called a homolog). Remember that for each chromosome, one homolog was inherited from your mother, and one homolog was inherited from your father. Both have the same set of genes (e.g., both copies of your 11th chromosome have a gene for hemoglobin), but the homolog from your mother will have a slightly different nucleotide sequence than the homolog from your father (e.g., somewhere in the hemoglobin gene from your father's homolog is a GTG instead of a GAG). Sometimes, a gene that started on your mother's homolog will get swapped with the gene on your father's homology, creating more genetic variation between your kids and your siblings' kids, for example. This process of swapping genetic material between homologous chromosomes is called crossing over. Anaphase I : This is where anaphase in meiosis looks very different from mitosis: It's in the process of disjunction, which is how the chromosomes separate. In mitosis, the sister chromatids from each homolog split and move toward opposite poles, so that each cell gets one chromatid from your maternal homolog and one chromatid from your paternal homolog (just like the original cell had). In anaphase of meiosis I, © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 15both sister chromatids of one homolog go to one pole, and both sister chromatids from the other homology go to the other pole. That means that Daughter Cell A might get Chromosome 1, 3, and 10-23 from your dad and Chromosome 2 and 5-9 from your mom. Daughter Cell B will, therefore, get the opposite: Chromosome 1, 3 and 10-23 from your mom and Chromosome 2 and 5-9 from your dad. It's completely random which parent's homolog will end up in which daughter cell. This means that the odds of you producing the exact same gamete twice are 1 in 2 , or roughly 1 in 8 billion! This creates genetic diversity even among siblings. Telophase I : The nuclear envelope then starts to reform, and we end up with one homolog of each chromosome instead of two, but each homolog has two sister chromatids. The cells still need to go through another round of cell division to ensure they end up with only 23 chromosomes in each cell.  TERMS TO KNOW Meiosis I The first round of cell division in meiosis. Homolog One of the members of a pair of homologous chromosomes; with homologous chromosomes, one homolog is inherited from your father, and one homolog is inherited from your mother. Crossing Over A process in which homologous chromosomes will exchange genetic material with one another, resulting in genetic variation. Disjunction The process of separating chromosomes; it occurs in meiosis I when homologous chromosomes are separated, and in meiosis II when sister chromatids are separated. 2b. Difference Between Mitosis You can illustrate the difference between mitosis and meiosis I on your fingers. Hold up your index finger on each hand, and pretend that your index fingers are homologous chromosomes. Your right finger is the homolog you inherited from your mom, and your left finger is the homolog you inherited from your dad. Now, pretend your chromosomes are undergoing S-phase, so they both get synthesized. To represent this, both hands should now be holding up your index and middle finger on each hand, close together. This represents both homologs having two sister chromatids. 23 © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 16In mitosis, one sister chromatid from each of your parents would go into each new daughter cell (just like the original). You can represent this by facing your palms toward each other, having both hands form "peace" signs. Thus, your index fingers are going in one direction (the right index finger is the homolog from mom, and the left index finger is the homolog from dad), into Daughter Cell A. Similarly, your middle fingers split off in the same direction (the right finger from mom, the left finger from dad), into Daughter Cell B. Here's how meiosis I is different: Start at S-phase, with two "sister chromatids" on each hand. The pair of sister chromatids from mom will head over to Daughter Cell A, while dad's pair of sister chromatids head over to Daughter Cell B. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- OPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 672. Common Autosomal Dominant Disorders The following are examples of autosomal dominant disorders: Huntington's Disease: A disease that can be inherited, but the symptoms don't show up until adulthood. Often, people don't realize that they have Huntington's disease until they've already reproduced and passed it on to their children. Marfan Syndrome: This disorder causes a weakening of the aorta, meaning that the aorta can rupture over time. Generally, people with this disorder are very, very tall and lanky. However, the weakening of the aorta is the most serious aspect of Marfan syndrome since rupturing can occur with intense physical activity. Achondroplasia: This disorder results in a person who has short arms and legs, and who is short overall. Most people with this type of disorder only get to be about 4 to 4.5 feet tall, so achondroplasia affects a person's height, and then--as a result--causes shortness of the arms and legs. Familial Hypercholesterolemia: This disorder leads to high blood cholesterol. This is because the cholesterol in the blood of people with this disorder won't bind to LDLs, which is the first step in removing the cholesterol from the body. Therefore, most people with familial hypercholesterolemia often don't have as long of a lifespan as other people as a result of their very high cholesterol.  TERMS TO KNOW Huntington's Disease An autosomal dominant disorder which does not show up until later in life often after the gene has been passed onto offspring; it is a neurodegenerative disorder that causes motor and cognitive impairment and eventually becomes fatal. Marfan Syndrome A genetic disorder of connective tissue that causes people to have a certain appearance: Being abnormally tall with long limbs and digits; it can also affect other connective tissues such as heart valves, and can be fatal. Achondroplasia An autosomal dominant disorder in which the person is abnormally short in stature with short arms and legs. Familial Hypercholesterolemia An autosomal dominant disorder in which a person has chronic high cholesterol.  In this lesson, you learned that the cause of autosomal dominant traits or disorders is the inheritance of at least one dominant allele on an autosome. In other words, if one parent has one dominant allele, there is a chance that the children will have the dominant trait as well, even though the other parent does not have that dominant allele, which can be shown in a Punnett square. You now understand that some common examples of autosomal dominant disorders are Huntington's disease, Marfan syndrome, achondroplasia, and familial hypercholesterolemia. Good luck! Source: ADAPTED FROM SOPHIA TUTORIAL BY AMANDA SODERLIND.  Achondroplasia An autosomal dominant disorder in which the person is abnormally short in stature with short arms SUMMARY TERMS TO KNOW © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 68and legs. Autosomal Dominant A trait or disorder caused by the inheritance of at least one dominant allele on an autosome. Familial Hypercholesterolemia An autosomal dominant disorder in which a person has chronic high cholesterol. Huntington's Disease An autosomal dominant disorder which does not show up until later in life, often after the gene has been passed onto offspring. It is a neurodegenerative disorder that causes motor and cognitive impairment and eventually becomes fatal. Marfan Syndrome A genetic disorder of connective tissue that causes people to have a certain appearance: being abnormally tall with long limbs and digits. It can also affect other connective tissues such as heart valves, and can be fatal. © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 69X-Linked Traits by Sophia Tutorial  T his lesson will cover traits and disorders associated with the sex chromosomes by looking at: 1. X-Linked Traits & Disorders a. X-linked Recessive Disorders b. X-linked Dominant Disorders 2. Inheritance 1. X-Linked Traits and Disorders Sex chromosomes are the chromosomes that are related to our gender. Human females have sex chromosomes composed of two X chromosomes, and males have sex chromosomes composed of one X chromosome and one Y chromosome. X-linked traits are disorders related to a person's X chromosomes. Both males and females can be affected by X-linked traits; however, males are generally more at risk of being afflicted by an X-linked trait because they only have one X. If one X chromosome is affected in a female, the other X will generally mask the effect.  TERM TO KNOW Sex Chromosome The chromosomes that, when paired, determine the sex/gender of the organism, in humans XX = female while XY = male. 1a. X-linked Recessive Disorders X-linked traits or disorders can be caused by recessive alleles or a dominant mutant allele on an X chromosome. The following are examples of X-linked recessive disorders: Hemophilia: A bleeding disorder in which blood doesn't properly clot. Red-green color blindness: A disorder where a person can't distinguish between the colors red and green. Duchenne's muscular dystrophy: A disorder in which muscles begin to degenerate over time.  TERMS TO KNOW Hemophilia An X-linked recessive disorder that affects the blood's ability to clot. Red-Green Color Blindness An X-linked recessive disorder in which a person cannot distinguish between the colors red and green. Duchenne Muscular Dystrophy An X-linked recessive disorder in which the muscles deteriorate over time. 1b. X-linked Dominant Disorders Disorders caused by a dominant mutant allele on the X chromosome are much less common. Faulty enamel trait is an example of an X-linked dominant disorder. The enamel that protects your teeth doesn't properly develop in people with this disorder. Their teeth will rot easily because they don't have protective enamel on their teeth.  TERM TO KNOW WHAT'S COVERED © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 70Faulty Enamel Trait A disorder caused by a dominant mutant allele on the X chromosome in which enamel that protects teeth does not properly develop. 2. Inheritance Using hemophilia as an example, it is possible to look at how these types of disorders can be passed on. A father can pass on a X and a Y allele, while the mother can pass on one of two X chromosomes. On the Punnett square below, the alleles listed on the top are the sperm a father can supply, and the alleles listed on the left side are the possible eggs a mother could supply. This example shows the mother as a carrier for hemophilia. The X shown in red is the recessive allele that is affected. Because the mother has a normal X chromosome, any effect the recessive X would have is probably masked. She is only a carrier, and she has a 50% chance of passing this chromosome on to any of her children. The Punnett square shows she has a 25% chance of creating a daughter that is a carrier like her, and a 25% chance of having a son that has hemophilia. She also has a 50% chance of passing on a X that is not affected. She has a 25% chance of having a daughter that is not a carrier and a 25% chance of a son that is not affected. This illustrates how X-linked traits can be passed on from parents to offspring and why males are generally more susceptible to inheriting these disorders. If they inherit the X chromosome from their mother that is affected, they will automatically get that disease. Many X-linked disorders follow common patterns of inheritance. There are lots of different patterns of inheritance like this that geneticists can study to understand these diseases and the patterns in which these diseases are passed through generations. Pedigrees are another useful tool in tracking these disorders as well because you can follow the family history of a disease.  EXAMPLE One type of inheritance pattern is that only daughters can inherit recessive alleles from their affected father because the sons will get the Y chromosome. In other words, if a father is affected, he can only give an affected X chromosome. His daughters, therefore, will either be affected or be carriers.  X-linked traits or disorders are those located on the X sex chromosome. They can be caused by a recessive allele or a dominant mutant allele on the X chromosome. Hemophilia, red-green color blindness and Duchenne’s muscular dystrophy are examples of X-linked recessive disorders, and faulty enamel trait is a disorder caused by a dominant mutant allele. These disorders can be inherited. Women are generally only carriers of X-linked recessive traits because the second X they have can mask the affected X. Men are most susceptible to X-linked recessive disorders because they only have one X. Geneticists can study patterns of inheritance to understand these diseases, and SUMMARY © 2019 SOPHIA Learning, LLC. SOPHIA is a registered trademark of SOPHIA Learning, LLC. Page 71pedigrees can be a helpful tool for them. Keep up the learning and have a great day! Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND  Duchenne Muscular Dystrophy An X-linked recessive disorder in which the muscles deteriorate over time. Faulty Enamel Trait A disorder caused by a dominant mutant allele on the X chromosome, in which enamel that protects teeth does not properly develop. Hemophilia An X-linked recessive disorder that affects the blood's ability to clot. Red-Green Color Blindness An X-linked recessive disorder in which a person cannot distinguish between the colors red and green. Sex Chromosome The chromosomes that, when paired, determine the sex/gender of the organism, in humans XX = female while XY = male. [Show More]

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