BY 123 Lecture Notes - Lecture 15: Thomas Hunt Morgan, Mendelian Inheritance, Y Chromosome

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18 May 2017

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According to the chromosome theory of inheritance, mendelian genes have a specific loci along the chromosomes, and it is the chromosomes that undergo segregation and independent assortment. Prolific: a single mating will produce hundreds of offspring. Males have an x chromosome and a y chromosome. Wild type, or the red eyed fruit fly. Mutant phenotype, or the white eyed fruit fly. Found first in the male fruit fly. Bred the white eyed male with red eyed female. Bred f2 male back to f1 female and got 88 white eyed female offspring. Can"t get white from red eyed males. This trait is sex linked to the x chromosome. A sex-linked gene is a gene located on either sex chromosome. Only thing on the y-chromosome says that you"re going to be a male. X gets expressed in males since no other x to counteract. X-chromosome has many traits, so one is inactive in females.

Related Questions

Genes located on mitochondrial DNA are usually inherited in whatfashion?
A. Randomly
B. From the mother
C. From the father
D. Evenly from both the mother and the father
E. By independent assortment

Wild type fruit flies have red eyes. A white-eyed female fly iscrossed with a red-eyed male fly. All of the females from the crossare red-eyed and all of the males, white-eyed. What type ofinheritance pattern is this?
A. Independent assortment
B. Autosomal dominant
C. Autosomal recessive
D. Incomplete dominance
E. Sex-linked on X chromosome

What fraction of the offspring of the cross AaBb

The white eye mutation studied by Thomas Hunt Morgan is X-linkedand recessive to wild-type red eyes. When true-breeding white-eyedmales carrying the white mutation were crossed with true-breedingpurple-eyed females, all the F1 progeny had wild-type (red) eyes.When the F1 progeny were intercrossed, the F2 progeny emerged inthe following ratio:

3/8 wild-type females
1/4 white-eyed males
3/16 wild-type males
1/8 purple-eyed females
1/16 purple-eyed males.

Formulate a hypothesis to explain the inheritance of these eyecolors and match the correct genotype with each individual listedbelow.

P Generation Male:

P Generation Female:
F1 Generation Male

F1 Generation Female:

F2 Generation Purple-eyed Female

F2 Generation White-eyed Male

F2 Generation Wild-type Male:

F2 Generation Purple-eyed Male:

F2 Generation Wild-type Female:

Options:

w+/Y; p+/_

w/Y;_ _

w+/_; p/p

w+/Y;p+/p

w+/_;p+_

w/Y; p+/p+

w+/W+; p/p

w+/Y; p/p

emeraldswan267

3. Consider a cross between white-eyed female flies and red-eyed male flies. Importantly, the white gene is X-linked. Write out the punnett square here. Be sure to define your allele symbols then indicate the probability (a ratio is fine) of observing any one of the following phenotypes:

a. Red-eyed females _________

b. Red-eyed males _________

c. White-eyed females ________

d. White-eyed males. __________

4. You want to build a double mutant (ab/ab) between two genes, A and B, that are 10 map units apart. You first cross a/a into b/b to create the dihybrid: a+/+b. Next, you do an F1 cross and search the F2 generation for the rare double mutant: ab/ab. What percent of the progeny (offspring) will have the double mutant phenotype in the F2 generation? Show your equation. 5. EXTRA CREDIT. It should be noted that white was not the first sex-linked mutation discovered. In the currant moth Abraxus, DONCASTER and RAYNOR (1906) described a trait called lacticolor segregating among wild females but not among males. How might one explain this?

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BY 123 Lecture Notes - Lecture 15: Thomas Hunt Morgan, Mendelian Inheritance, Y Chromosome

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