Frundemental Genetics Exam 1
Frundemental Genetics Exam 1 85033 - GEN 3000 - 002
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85033 - GEN 3000 - 002
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This 7 page Study Guide was uploaded by Lisa Blackburn on Saturday January 23, 2016. The Study Guide belongs to 85033 - GEN 3000 - 002 at Clemson University taught by Kate Leanne Willingha Tsai in Fall 2015. Since its upload, it has received 223 views. For similar materials see Fundamental Genetics in Biomedical Sciences at Clemson University.
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Date Created: 01/23/16
Exam 1 Chapters 1-4 Chapter 1: Model organisms importance: Early theories of hereditary transmission: o Pangenesis: gemmules carry information from the body to reproductive organs. The information carried tells the embryo what to form and are passed to the embryo at conception. (If the parents have x trait, the gemmules tell the embryo to have x trait). Term “gene” comes from pangenesis. o Inheritance of acquired characteristics: skills from the parents are passed down to the offspring through gemmules. The Greeks believed that if parent is good at art the child would be too. The belief of pangenesis lead/supported this concept. o Preformationism: Tiny adult version inside the egg or sperm, called homunculus. After fertilization, the tiny version grows o Blending inheritance: offspring are a mixture of the parents. A blend of both parental traits. Important people and their contributions: o Schwann and Schleiden: Came up with the cell theory. Cells are basic unit of all living things and cells can only arise from preexisting cells (cannot be created from nothing). o Darwin: Came up with the theory of evolution through natural selection. Passing genes down allows for evolution to take place and natural selection. Organisms can evolve and the ones with undesirable traits will die off (natural selection). Darwin came up with this at a population level, too big of a concept for people to understand. (Basic concepts were left unexplained) o Mendel: Father of genetics -> discovered basic principles of heredity by crossing pea plants. Wasn’t recognized for work at the time. Chromosomes were yet to have been discovered o Flemming: Witnessed the division of chromosomes (contain heredity information) o Weismann: Disproved the inheritance of acquired characteristics. He did this by cutting off tails of mice for multiple generations. Since the length of the tail of the descendants did not change, the theory was disproven. Proposed new theory: Germ-plasma theory -> reproductive cells contain complete set of genetic information o Sutton: proposed that genes are on chromosomes Chapter 2 Prokaryotic vs. Eukaryotic o Prokaryotic cells: undergo Binary Fusion for replication. Binary Fusion: 1. Chromosome copies itself. 2. Plasma membrane grows and the cell starts to split. 3. Two identical cells are formed. o Eukaryotic cells: Have two sets of chromosomes due to sexual reproduction (one from mom, one from dad-> called homologous pair). 2 sets of genetic info means the cell is diploid (2n), this is for most of the eukaryotic cells 1 set of genetic info means the cell is haploid (n), this is for the reproductive cells, also known as the gametes Homologous pairs: alike in structure, carry the same genetic info for same characters, can have different alleles (different forms of the same gene) Prokaryotic Cells Eukaryotic Cells Nucleus No Nucleus Has Nucleus Cell Diameter Small in size Large in size Genome One circular DNA Multiple linear DNA DNA Not complex, histones Complex with histones uncommon Amount of DNA Small amount Large amount Membrane Bounded No membrane bounded Has membrane bounded Organelles organelles organelles Cytoskeleton No cytoskeleton Has cytoskeleton Ploidy: number of sets of chromosomes in a cell Chromosomes Structure: o Chromatin: chromosome + proteins/histones o Telomere: cap on the ends of chromosomes. Example: caps on the ends of shoelaces, keep the shoelace from unraveling. o Centromere: the chromosomes would be lost without this, used to identify chromosomes, kinetochore connection spot, used to count chromosomes o Kinetochore: instrumental for movement of the chromosome o Chromatid: one of the sister chromosomes that are connected together Centromere Identification of chromosomes: o P arm: the shorter arm of the chromosome o Q arm: the longer arm of the chromosome o Metacentric: p and q arm are relatively the same size, centromere in the center o Submetacentric: p arm is slightly shorter than the q arm, centromere shifter slightly to one side o Acrocentric: p arm is significantly shorter than the q arm, centromere almost all the way to one side o Telocentric: p arm is almost nonexistent, centromere all the way to one side Cell Cycle: o Interphase: G -G 1 ce2l growth, longer process o Mitosis: M phase, cellular division, shorter process o G : 1tarting point of cell cycle, where cell growth occurs o G : 0on dividing stage, can enter this stage to keep the cell from dividing, or can re-enter G 1tage to fix itself and can then divide o G /S1Checkpoint: if passes this point, the cell is committed to divide, checkpoint to make sure the cell is okay to divide o S: Where DNA synthesis occurs, all genetic info is replicated o G : 2rowth point of the cell, grows enough for cytokinesis, makes enough cytoplasm for division. o G /M2Checkpoint: makes sure the cell is okay to divide, full checklist, needs to have enough cytoplasm, and needs to make sure DNA is fully synthesized o M: Where division of the cell occurs o Cytokinesis: The cytoplasm is divided and the result is two identical cells Mitosis: o Prophase -> Metaphase -> Anaphase -> Telophase o Prophase: chromosomes condense from long squiggly lines to linear chromosomes (sister chromosomes), centrosomes move to poles, mitotic spindle forms from centrosomes (in animals only). o Prometaphase: nuclear envelope fully disappears, microtubules reach the kinetochores of individual chromatids o Metaphase: chromosomes move independently to a single plane (the metaphase plate) o Anaphase: the sister chromosomes are pulled apart and towards separate poles by the spindle fibers (this is called disjunction) and become individual chromosomes o Telophase: chromosomes arrive at the poles, nuclear membrane begins to reform (2 nuclei in one cell), chromosomes disappear, and cell begins to pinch in on the sides. This occurs at the same time as cytokinesis. o Cytokinesis: not part of mitosis, step after mitosis/occurs during telophase of mitosis. Full division of the cytoplasm, creates two cells Spindle fibers and how it moves chromosomes: o Spindle fibers are made up of tubulin subunits that can be added or taken away, which in turn, lengthens/moves chromosome from pole or shortens/moves chromosome to pole. Meiosis: o Meiosis vs. Mitosis Mitosis Meiosis Has 1 nuclear division Has 2 nuclear divisions Cells end in the same Cells end with ½ the number of chromosomes number of chromosomes they start off with they start off with Cells are genetically Cells are genetically identical to each other variable to each other (gives unique cells) o Meiosis I: Prophase I -> Metaphase I -> Anaphase I -> Telophase I -> Meiosis II: Prophase II -> Metaphase II -> Anaphase II -> Telophase II o Middle Prophase I: chromosomes begin to condense from squiggly lines, spindle fibers form o Late Prophase I: Homologous chromosomes pair together, this is known as synapsis when the homologous chromosomes line up. One chromosome is from mom while the other is from dad. Crossing over takes place here. Nuclear membrane begins to break down. Crossing Over: occurs between two nonsister chromatids. Chiasma is the area that the crossing over takes place. Occurs between an allele of a chromatid that are not identical. Example, the allele could be for eye color but be for different colored eyes. Chromatid 1 of mom and Chromatid 2 of dad cross over each other, then the breaks and rejoins creating a new type of chromatid (3 and 4). Allows for four unique chromatids. o Metaphase I: Homologous pairs of chromosomes line up on the metaphase plate and microtubules connect to one pair from each pole. o Anaphase I: The homologous pairs of chromosomes are separated from each other and are pulled to opposite poles. The chromosome from mom will go one way, while the other chromosomes from dad will go the opposite way. This is the step of Meiosis that reduces the number of chromosomes and is what makes the cells haploid in the end. o Telophase I: Nuclei reform, two in one cell. The cytoplasm divides after the chromosomes arrive at the poles. o Prophase II: Chromosomes re-condense and the nuclear envelope breaks down again o Metaphase II: the chromosomes align on the metaphase plate (looks like mitosis) o Anaphase II: sister chromatids are pulled apart and go in opposite directions to poles o Telophase II: Chromosomes arrive at the poles and the nuclear envelopes reform. Cytoplasm divides o Result: all four cells are haploid, each have one copy of chromatid, each are unique, genetically distinct o Cells are distinct because: 1. Crossing over makes sister chromatids not identical. 2. Random distribution of chromosomes in anaphase I (when the sister chromosomes are pulled apart they can be pulled apart in any pattern). o Female Meiosis: Unequal division occurs during telophase/cytokinesis during Meiosis I and Meiosis II. This causes a first polar body (meiosis I) and a second polar body (meiosis II). This occurs to allow the other resulting Ovum after meiosis II to have enough cytoplasm and other nutrients for fertilization. Chapter 3: Mendel: Father of genetics. Experimented with pea plants and studied the passing down of genes. His work was not recognized until the 1900s. Common terms of the chapter: o Gene: helps to determine a characteristic, a region of DNA o Allele: one of the alternate forms of a gene o Locus: the place on a chromosome that an allele is located at o Genotype: set of alleles that an individual may posses o Heterozygote: an individual that has two different types of alleles at a locus o Homozygote: an individual that has two of the same type of allele at a locus o Phenotype or trait: an appearance or manifestation of a character o Character or characteristic: an attribute or feature Mendel’s Experiments: o Crosses: Monohybrid Cross: parents differ in a single characteristic, focus on one characteristic at a time. In Mendel’s experiment: Parent 1 is green seeds and Parent 2 is yellow seeds. Mendel removed pollen from the male plant of one color with a paint brush and painted the female plant of the other color to fertilize it. This is to control which parent is contributing. Reciprocal cross: crossing in the opposite directions of the above, shows that it doesn’t matter on the gender, the outcome is still the same Backcross: Taking a hybrid and crossing it with one of the parents, or one genetically similar to its parent. This yields an offspring that is genetically closer to the parent of the hybrid. Test Cross: used to find out if an individual is a Dominant Dominant or Dominant Recessive (TT or Tt) individual. Cross the individual with a homozygous recessive individual. If TT and crossed with tt, the offspring will be Tt. If Tt and crossed with tt, the offspring will have a TT:tt 1:1 ratio. Dihybrid Cross: crossing of organisms that differ in two characteristics. Mendel crossed plants with round and yellow seed with wrinkled and green seeds. Dihybrid Test Cross: same as a normal test cross, but with two characteristics. Example: individual is possibly one of the following RrYy/RRYY/RRYy/RrYY and is crossed with rryy o Mendel’s experiment: A homozygous round seed is crossed with a homozygous wrinkled seed. The first generation F 1eneration creates four round seeds. These self-fertilize and create ¾ round seeds and ¼ wrinkled seeds. Dominant Trait: the traits that are observed in first generation. Are seen when there are two copies of the trait (Homozygous) or one copy of it (heterozygous) Recessive Trait: traits that hid in the first generation and reappear in the second. Only are seen when there are two copies of it (homozygous). Are still in the heterozygous, but hide o Principle of Segregation (Mendel’s First Law): Each individual diploid organism possesses two alleles for a characteristic. The two alleles separate into gametes and this is random. o Principle of Independent Assortment: alleles at different loci separate independently from each other Punnett Squares: t t T Tt tall Tt tall t tt short tt short o t and t represent the homozygous recessive parent o T and t represent the heterozygous dominant parent o The offspring are the ones in the middle Produces: Genotypic ratio -> 1:1 Tt:tt Produces: Phenotypic ratio -> 1:1 tall:short Phenotypic and Genotypic Ratios: Genotypic Ratio Genotypes of Parents Genotypes of Offspring 1 : 2 : 1 Aa X Aa ¼ AA : ½ Aa : ¼ aa 1 : 1 Aa X aa ½ Aa : ½ aa Aa X AA ½ Aa : ½ AA Uniform AA X AA All AA aa X aa All aa AA X aa All Aa Phenotypic Ratio Genotypes of Parents Genotypes of Offspring 3 : 1 Aa X Aa ¾ A_ : ¼ aa ¾ Dominant : ¼ recessive 1 : 1 Aa X aa ½ Aa : ½ aa ½ dominant : ½ recessive Uniform AA X AA All AA (all dominant) aa X aa All aa (all recessive) AA X aa All Aa (all dominant) AA X Aa All A_ (all dominant) o Use “_” when the second trait is unsure if dominant or recessive Branch Diagram: forked diagram, can show genotypic and phenotypic ratios, sets out the proportions of genotypes or phenotypes Chapter 4: Allele: different form of same gene, can cause loss of function in a particular gene Loss-of-function mutation: a certain allele loses the ability to make that characteristic, might still make the characteristic but not enough of it to show Null allele: complete loss of characteristic from an allele Gain-of-function mutation: allele for one characteristic shows the characteristic of another Neutral mutation: a gene or allele is changed genetically, but no change phenotypically Gene interaction: multiple genes/allele affect one phenotype/characteristic X-linkage: the change of genes when allele are located on an X chromosome Incomplete Dominance: phenotype of the heterozygote is in between the phenotypes of the two homozygotes. RR= red rr= white Rr= pink Codominance: phenotype of heterozygote includes the phenotypes of both homozygotes. BB= blue bb=white Bb= blue AND white Multiple alleles: more than two forms of an allele at one locus Lethal alleles: alleles that cause death, can be recessive or dominant. If recessive, a heterozygous individual can be a carrier (Aa) Epistasis: one gene is dependent on the presence of one or more modifier genes
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