106 Cards in this Set
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interphase
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cell growth phase where a cell increases in size, carries on metabolism, and duplicates chromosomes prior to division.
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prophase
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the stage of mitosis and meiosis immediately following interphase during which the chromosomes condense
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Metaphase
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chromosomes line up along central axis of cell
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Anaphase
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The sister chromatids separate into individual chromosomes and are moved apart
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Telophase
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the fourth and final stage of mitosis, during which daughter nuclei form at the two poles of a cell. usually occurs with cytokinesis.
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homologues
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same banding pattern
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heterologues
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different banding patterns, not homologues
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Leptonema
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Chromosomes condense. Homology searching begins
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Zygonema
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Prophase I
Synapsis begins and chromosomes condense further.
Form a very tight synaptonemal complex.
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pachynema
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crossing over occurs, and by the end synaptonemal complex is disassembled and the chromsomes have started to elongate
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Diplonema
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sister chromatids begin to separate. homologs remain attached at chiasmata.
Stage IV of Prophase I of Meiosis
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Diakinesis
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nucleoli disappear, spindle formation, nuclear envelope breaks down
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Metaphase I
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Homologous pairs lines up at the equatorial plane and each pair attaches to a separate spindle fiber by its kinectochore
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Anaphase I
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pairs of homolgous chromosomes separate
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Telophase I
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A nuclear membrane forms around each new nucleus. At this point, each chromosome still consists of sister chromatids joined at the centromere.
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interphase
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chromosomes are unpaired
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Prophase II
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If chromosomes decondensed in telophase I, they recondense here
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Cohesion complex
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Holds two sister chromatids to each other. Contain SCC1 and SCC3
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mitosis
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a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus. typical of ordinary tissue growth
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MEISOIS
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The process of cell reduction division.
This reduces the number of chromosomes from 2 parent sex cells with 23 chromosomes each [which would = 46] to one cell with 23 chromosomes.
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events in meiosis, not mitosis
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synapsis and crossing over
-tetrad formation
-separation of homologues
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oogenesis development
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constant number of eggs, eggs locked in prophase I, meiosis I forms primary oocyte, meiosis II forms secondary oocyte, only forms one viable egg
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spermatogenesis
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mitosis generates spermatogonia, develop into primary spermatocyte, meiosis I forms secondary spermatocyte, meiosis II forms spermatids, forms four sperm cells
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cytoplasmic bridges
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at every stage of spermatogenesis, bridges between sperm cells to share genetic information and ensure synchronous development
due to incomplete cytokinesis
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Cortical granules
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Small, enzyme-filled activated during fertilization. Remove critical sperm receptors from outer egg by changing composition (deters polyspermy)
- creates fertilization envelope
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eschericia coli
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-rod shaped bacteriums
-advantages-- singular chromosome, simple mechanisms, study major players and events during DNA replication, cheap to maintain, easy to harvest
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saccharomyces cerevisiae
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-baker's yeast
-unicellular fungus
-reproduces sexually and asexually
-advantages--eukarytoic cells, sexual reproduction, cheap and easy to grow
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drosophila melanogaster
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-fruity fly
-advantges- multicellular, processes such as cell differentiation, short life span, easily cultured, screening for mutants
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caenorhabditiselegans
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-round worm
-model for animal development,
-hermaphroditic
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mus musculus
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-the mouse
-biomedical research
-comparative genomics
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arabidopsis thaliana
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-self fertilizing
-model for agriculturally significant plants
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Crossing over
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Chromosomal segments are exchanged between a pair of homologous chromosomes
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Genetic Variation in Meiosis
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Random arrangements of chromosome pairs lead to different combination of chromosomes in egg and sperm. Crossing over of chromosomes.
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Mendel's 7 characters
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Height
Flower color (purple vs white)
Flower position (axial vs terminal)
Seed color (yellow vs green)
Seed shape (round vs wrinkled)
Pod color (green vs yellow)
Pod shape (smooth vs constricted)
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Trait
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The specific way a feature is expressed in an individual organism.
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Allele
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Dif. forms the gene can take on
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principle of dominance
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In a heterozygote, one allele dominates over the other one, concealing its phenotype.
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principle of segregation
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In a heterozygote, two different alleles segregate from each other during the formation of gametes.
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p generation
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parent generation
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F1 generation
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offspring of parent generation
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F2 Generation
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the offspring of self-pollinated F1 generation plants.
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chi-square test equation
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χ² = Σ (O-E)²⁄E
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Chi-square test
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An inferential statistic used to test hypotheses about relationships between two or more variables in a cross-tabulation
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Degrees of Freedom
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In statistics, the number of degrees of freedom is the number of values in the final calculation of a statistic that are free to vary
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if chi square is less than critical value
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there is more than 5% probability it could occur, therefore the difference between the expect and observed data is due to chance and the results of a cross are consistent with a hypothesis, do not reject null
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Null Hypothesis
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The hypothesis that an effect or relationship does not exist (or exists in the opposite direction of the alternative hypothesis) in the population
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If chi square is greater than the critical value....
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We can reject the null hypothesis and say that the observed frequencies deviate from expected
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Dihybrid Cross
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follows 2 pairs of contrasting traits simultaneously from pure-breeding parents (P) through hybrid offspring (F1) to 3rd generation (F2)
-cannot seperate traits
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What is the ratio for a Dihybrid*Dihybrid cross?
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9 Dominate/dominate
3 Dominate/recessive
3 Recessive/dominate
1 Recessive/recessive
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principle of independent assortment
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The alleles of different genes segregate, or as we sometimes say, assort, independently of each other.
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3 methods to predict outcomes of crosses
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punnett square, forked line method, probability method
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probability
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is the frequency of that event in the sample space
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Sample Space
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Set of all possible outcomes in probability experiment
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multiplicative rule
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If the events A and B are independent, the probability that they will occur together, denoted P(A and B), is P(A) �� P(B).
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the additive rule
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If the events A and B are independent, the probability that at least one of them occurs, denoted P(A or B), is given by P(A) + P(B) �� [P(A) �� P(B)].
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mutually exclusive events
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two events do not overlap in the sample space
P(A) x P (B) = 0
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obstacles to human genetic analysis
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-incomplete family records
-small number of progeny
-uncontrolled environment
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dominant traits in humans
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dwarfism, short fingers, night blindness, huntington's, widow's peak
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recessive traits in humans
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albinism, cystic fibrosis, duchenne dystrophy, tay sachs
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pedigrees
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shows the relationships of the members of a family
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inheritance of dominant trait
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Every individual who carries the dominant allele manifests the trait.
Every affected individual is expected to have at least one affected parent.
If a dominant trait is associated with reduced viability or fertility, most people who show the trait are heterozygous, and half their ch…
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inheritance of recessive trait
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Recessive traits may occur in individuals whose parents are not affected.
Rare recessive traits are most likely to appear in a pedigree when spouses are related to each other.
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Y-linked inheritance
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affects male only; females never have the trait, affected father has all affected sons, unaffected father cannot have an affected son
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x linked recessive inheritance
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carrier females have 50% chance of passing trait on to her sons, and making her daughters carriers
affected males cannot pass the trait on to his sons, but makes all his daughters carriers
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X-linked dominant trait
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Expressed in female in one copy, expressed much more severely in male, high rates or miscarriage, due to early lethality in males
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mendel's model of inheritance
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--one gene -> one trait
-dominant and recessive allele
--genotype to phenotype
-central dogma of biology
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current model of inheritance
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-gene has multiple alleles
-allelic variation determines phenotypic variation
-complete dominance, incomplete dominance, co-dominance
-gene network determines one trait
-pleiotropy
-genes interact with the environment to determine phenotypes
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allelic series
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the set of known alleles of one gene
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Complementation test
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determins if 2 mutations are in the same gene
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Epistasis
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phenotypic expression of a gene at one locus alters that of a gene at a second locus
ex. genes that determine pigment deposition
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pleiotropy
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single gene mutation can cause more than one phenotype
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incomplete penetrance
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some carriers do not express the disease
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Variable Expressivity
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Not all signs of a disorder appear phenotypically
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complete dominance
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one dominant allele masks recessive alleles
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albinism
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-complete dominance
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haplosufficiency
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-one copy of normal gene can produce enough functional proteins
-ex. complete dominance
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haploinsufficien
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-expression of one copy of the normal gene is not enough to produce enough functional proteins
--ex. semidominace, dosage dependence
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Codominance
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The expression of both alleles of a heterozygote.
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blood types and dominance
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-codominance
-3 alleles--IA, IB, i
--genotypes
IAIA, IAIB, IAi, IBi, IBIB, ii
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multiple alleles
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Three or more alleles of a single locus (in a population), such as the alleles governing the ABO series of blood types.
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wild type
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the gene that predominates in a population
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mutant allele
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alleles that have been created by altering a wild-type allele by mutation
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polymorphic
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gene with multiple forms
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null / amorphic allele
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nonfunctional, loss of function
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Hypomorphic Allele
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Partial loss of function
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What is a hypermorphic allele?
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A mutant allele that either produces more of a protein, or produces a more effective version of a protein.
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loss-of-function allele
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the effect of a gene mutation that eliminates the function of a gene
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gain-of-function allele
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protein function works better, increased or new protein activity
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Silent Mutation
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no amino acid change
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Temperature Sensitive Alleles
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encode protein that is functional at permissive temperature but not at restrictive temperature
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Visible Mutations
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Affects morphological traits.
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Sterile Mutations
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the new alleles limit reproduction
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Lethal mutations
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Results in death of cell/organism
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Incomplete (semi) dominant
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In some disorders, the phenotype in homozygous individuals is more severe than in heterozygous individuals
-Achondroplasia and Marfan-homozygosity is lethal in utero
-familial hypercholesterolemia
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polydactyly
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-gain of function dominant mutation
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Genetic Studies
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Goal of figuring out the role that genes play
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Testing for Allelism
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Cross a new recessive mutation with a known recessive homozygous for the same phenotype and see is the offspring show mutant (yes alleles) or wild-type (not alleles) phenotypes
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ebony and black body mutations in flies
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complement each other, affect the same gene
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cinnabar and scarlet mutations
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do not complement, affect different genes
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epistasis
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In epistasis, an allele of one gene overrides the effect of other genes on the phenotype. (therefore, two traits do not assort independently of each other)
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white mutation is ___ to the cinnabar mutations
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epistatic,
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Recessive Epistasis
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Recessive allele of one gene blocks second gene.
9:3:4 ratio
Ex. coat color in labs
3 Phenotype classes
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Dominant epistasis
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only a single copy of an allele is required to inhibit the expression of the allele at a different locus
12:3:1 ratio
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Duplicate Dominant Epistasis
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Complete dominance at both gene pairs, however when either gene is dominant, it hides the effects of the other gene
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sphepherds purse plant
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-one dominant of either gene will give heart shaped
-homozygous recessive yields narrow
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application of epistasis analysis on genes
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Epistasis shows the interaction between two genes which are involved in the same genetic pathway.
Mutation in each gene affects the same trait.
A dihybrid cross of these two genes produces progenies with fewer than 4 phenotypes.
Based on the ratio of the resulting phenotypes, one…
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BIOL 3303: TEST 2