BIO207H5 Lecture Notes - Lecture 8: Sister Chromatids, Gonad, Eye Color

53 views3 pages

whitelouse363

1 Feb 2017

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Fruit fly research is used to study x-linked inheritance. Eye colour is encoded by many genes, however, we are focusing on the white gene. It is called the white gene because it results in white eyes. In the f1 generation, all the females and males have red eyes: we can say that red eyes is dominant because of mendelian genetics. The ratio of the f2 generation from heterozygous parents is 3:1 (phenotypically), 1:2:1 (genotypically) The results violates the expected ratio: there are 2 red eyed females, there is 1 red eyed male and 1 white eyed male. The white gene is found on the x chromosome. The male is hemizygous (1 copy of the allele) It is carrying the mutation of the white gene. The f1 females are heterozygotes: carries the mutant allele for the white gene from the father and the other x+ is from the mother.

Related Questions

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?

fuchsiagerbil537

The following question is a sex-linked trait. Review the patterns of inheritance of sex-linked traits before answering the following questions. Make sure to indicate chromosomes and alleles in your answers when necessary.

Hemophilia is a caused by a recessive mutation found on the X chromosome in humans. The recessive allele (X^h) is associated with abnormal blood clotting (hemophilia), while the dominant allele (X^N) causes normal blood clotting.

A man with normal blood clotting and woman who is heterozygous are going to have a child. What is the probability of an offspring who is a carrier of hemophilia, and if so, the sex(es) of the offspring?

A. Chances are 25% of a son who is a carrier

B. There is no chance of an offspring who is a carrier

C. Chances are 50% of either a son or a daughter who is a carrier

D. All offspring, male or female, will be carriers

E. Chances are 1 in 4 of a daughter who is a carrier

2. Two fruit flies, one with red eyes and one with white eyes mate and have an offspring with white eyes. Having red eyes is a dominant trait (R) while white eyes (w) is recessive. Based on this information, what must be the genotypes of the parental white-eyed fruit fly and the parental red-eyed fruit fly?

A. Red-Eyed fruit fly: Rw

White-eyed fruit fly: ww

B. Red-Eyed fruit fly: RR

White-eyed fruit fly: wR

C. Red-Eyed fruit fly: R

White-eyed fruit fly: w

D. Red-Eyed fruit fly: rr

White-eyed fruit fly: wr

E. Red-Eyed fruit fly: RR

White-eyed fruit fly: ww

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!)

mauvepug893

BIO207H5 Lecture Notes - Lecture 8: Sister Chromatids, Gonad, Eye Color

Document Summary

Get access

Related textbook solutions

Molecular Cell Biology

Biology: Science for Life with Physiology

Concepts of Biology

Biology

Essentials of Biology

Related Documents

BIO207H5 Lecture Notes - Lecture 7: Xyy Syndrome, Vas Deferens, Uterus

BIO207H5 Lecture Notes - Lecture 6: Allosome, Y Chromosome, Wild Type

BIO207H5 Lecture Notes - Lecture 12: Epistasis, Summer Squash, Wild Type

Related Questions