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01:119:115 Lecture Notes - Lecture 13: Thomas Hunt Morgan, Allosome, Embryology

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violetmouse157
27 Aug 2019
School
Rutgers University
Department
Biological Science
Course
01:119:115
Professor
Merchant

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Document Summary

1902: scientists began to develop the chromosome theory of inheritance . Evidence that chromosomes are the location of mendel"s heritable. Ex: white eyes (first mutant found in male) -> w. Heteromorphic- not morphologically similar meiosis, some regions synapse. Humans -> 2 sex chromosomes; x & y. Sperm: get x other get y. Xx genotype so all eggs have an x. Y-linked genes: on the y (few of these) most are related to sex determination. X-linked genes: on the x as many genes as in autosomes. X-linked recessive disorders -> more common in males than in females. Males: carry only one x = hemizygous hemi=half. All alleles on x are expressed recessive alleles cannot be masked. Female: always carry two xs = homozygous recessive alleles can be masked by other. 1 x randomly inactivated during embryonic development inactive x condenses -> Linked genes: on the same chromosome & tend to be inherited together.

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Related Questions

1. The eye color of wild-type Drosophila flies is red. Differentmutations in a single or in multiple genes lead to flies with whiteeyes. Mutations in the w gene on the X chromosome lead to whiteeyes instead of the normal red. You have isolated both a white-eyedmutation (designated W-1) that gives a dominant phenotype, and awhite-eyed mutation (designated w-2) that gives a recessivephenotype.

(a) A white-eyed male from the W-1 line is crossed to awild-type female. What color eyes will the female progeny from thiscross have?

(b) What color eyes will the male progeny from the cross in part(a) have?

(c) One of the female progeny from the cross in part (a) ismated to a white-eyed male from the w- 2 line. What fraction of thewhite-eyed progeny from this cross will be female?

2. The body color of Drosophila adult flies is regulated bymultiple genes, including the autosomal ebony gene. Ebony body (e)is recessive to the wild type (yellowish) body (e+). A second gene,which is X-linked, controls bristle shape. Normal bristle shape(f+) is dominant to the mutant forked bristles (f). A female withforked bristles that is heterozygous for the body color gene ismated with an ebony body male (his bristles are normal).

(a) What are the genotypes of the parents?

(b) Using a Punnett square, determine the expected proportionsof each possible progeny phenotype. Since there is a sex-linkedgene here, be sure to include consider sex as part of thephenotype.

3. Describe in your own words what a balancer chromosome is andwhy it is important in fly genetics (you will have to do someresearch for this one!)