exam 2: chromosome theory of inheritance

Question 1

what does gametogenesis do?

Answer 1

uses both mitosis & meiosis to produce haploid gametes every generation

-haploid gametes fuse during fertilization to reconstitute 2n in the embryo

Question 2

when and who proposed the Chromosome Theory of Inheritance?

Answer 2

in 1903 and Sutton
-proposed chromosome movement paralleled movement of Mendel’s “particles”

Question 3

**what are Sutton’s evidence for the Chromosome Theory of Inheritance?

Answer 3

1. every cell has 2 copies of every chromosome and (from mendel) every cell has 2 copies of every gene
2. chromosomes (like genes) dont change when passed from parent to offspring

Question 4

what experiment provided additonal evidence to the theory

Answer 4

breedinng experiments conducted by Thomas Hunt Morgan

Question 5

Thomas Hunt Morgan’s breeding experiment

Answer 5

worked w D. melanogaster
-noticed unusal pattern in F1:
2/3 red-eyed flies were female and all of the white-eyed flies were male

discovered: pattern of eye color inheritance appeared to follow pattern of X chromosome inheritance: SEX LINKED

Question 6

on what type of chromosome does sex linkage in human

Answer 6

carry on sex chromosome

Question 7

an example of X-linked traits in humans

Answer 7

-X-linked recessive traits appear more often in males than females.
why? males only have 1X so will express it

red/green colorblindness: X-linked recessive
hemophilia: X-linked recessive (multifactorial+heterogenous

Question 8

examples of Y-linked traits in humans

Answer 8

-passed from father to son
-“maleness” is the only Y linked trait known
why? Y chromosome only carry genes for maleness

Question 9

sex-limited traits

Answer 9

*affect structure/ process that is found in one sex but not the other

For example: stuck in D. melanogaster
-autosomal recessive (mutant) mutation that makes it difficult for males to retract the ejaculatory duct after mating
-homozygous recessive females sre phenotypically normal because they dont have the duct
(expressed in males only because only the male have the duct)

Question 10

sex influenced trait

Answer 10

*appear in both sexes but expression may differ
-not carry on sex chromosomes, autosomal

example: male pattern baldness
-homozygous is dominant to heterozygous
-heter males starts losing hair in their 20s but lose less than homo males
-heter females do not lose hair but homo females do
-homo females lose a lot less hair thn affecte females and dont start to lose it until menopause (testererone increases hair loss)
=trait is dominant in men and recessive in women

Question 11

sex-linkage traits vs sex limited vs sex influenced

Answer 11

-sex-linkage: gene is carried on a sex chromosome (X/Y)

-sex-limited: gene carried on autosome and only expressed in one gender

-sex-influenced: gene carriedn on autosome, appear in both sexes, but expression differ based on the sex