ch 3 notes

ch 3 notes - Text Box: By the end of chapter 3 you should...

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Text Box: By the end of chapter 3 you should be able to: By the end of chapter 3 you should be able to: Text Box: Define important terms (ex., hemizygous, nondisjunction, Barr body, X- inactivation, autosome, heterogametic, homogametic) Carry out sex-linked crosses and determine outcomes Calculate outcomes of dihybrid crosses involving sex-linked and autos •Define important terms (ex., hemizygous, nondisjunction, Barr body, X-inactivation, autosome, heterogametic, homogametic) •Carry out sex-linked crosses and determine outcomes•Calculate outcomes of dihybridcrosses involving sex- linked and autosomalgenes•Distinguish between the different types of sex Sex chromosomes pair during meiosis and segregate, but they are not homologous Y and X chromosomes—differ in size and shape Sexual reproduction—formation of genetically distinct offspring In eukaryotes, alternate between ________ and _________ cells Sex = Most organisms have two phenotypes—male and female Difference is gamete size—males produce small gametes, females produce large gametes
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Define sex of individual based on which gametes the individual produces Females are usually Males are usually Can have differences—rare individuals with male anatomy but have 2 X chr They are genetically female, but sexual phenotype is male X chrdiscovered in grasshoppers—1891 In 1905 discovered that females have 2 Xs and males have 1 X X and Y—_____ chromosomes Non-sex chromosomes— Morgan discovered 1 male fly with white eyes instead of red Performed crosses to try to explain finding 1stgeneration appears consistent with Mendel’s findings— homozygous dominant x
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homozygous recessive Morgan’s explanation: •eye color locus on X chr•Females (XX)—can be homozygous or heterozygous at locus•Males (XY)—only 1 X, 1 copy of allele--__________ To confirm hypothesis, crossed white-eyed female with red-eyed male In Morgan’s 1stexperiment—white-eyed male x red-eyed female All 1237 offspring had red eyes except 3 white-eyed males Thought they were mutations, but kept happening too often Graduate student, Calvin Bridges, set out to study this further When white-eyed female crossed with red-eyed male, ~2.5% of males had red eyes and 2.5% of females had white eyesAll males should have ______ eyesAll females should have ____ eyes Bridges hypothesized that occasionally Xs in females fail to separate during Anaphase I of meiosis—called ______________ Sex is determined by the X:A ratio= #X chr/#haploid sets of autosomes
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Bridges was able to predict a fly’s chromosomal makeup using its eye-color genotype This proved that sex-linked genes are located on X chrand that the chrtheory of inheritance is correct Other X-linked inheritance:
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This note was uploaded on 03/20/2008 for the course ANS 215 taught by Professor Ashwell during the Fall '07 term at N.C. State.

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ch 3 notes - Text Box: By the end of chapter 3 you should...

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