BIOL207 Lecture Notes - Lecture 5: Epistasis, Meiosis, Thomas Hunt Morgan

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ivoryfox572

12 Feb 2014

School

University of Alberta

Department

Biology (Biological Sciences)

Course

BIOL207

Professor

Mike Deyholos

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Document Summary

Thomas hunt morgan crossed red-eyed fruit flies and red-eyed fruit flies: the gene that controls red eyes called wildtype white. Males are more likely to have this disease; if you"re female, this is an x-linked recessive trait, so you have to inherit the bad allele from both parents. One of the homologs is randomly inactivated in an early stage of the embryo, that inactivated homolog becomes a barr body, remains tightly packed through the life of the individual. The small o does not make orange pigment. Not all organisms worry about barr bodies; birds don"t have the patchy all homozygotes are uniform. The male carries 2 different alleles, but they are not mosaics with a quarter shell pattern. Non-white ww; recessive at the white locus; Cat fur phenotypes: optional assignment (fill out survey on e-class: score the cat(s) you know based on the following fur phenotypes, each controlled by these different genes. (from christensen (2000) genetics.

Related Questions

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

When someone is said to have inherited a predisposition to cancer, what is meant by that?

There is a germ-line mutation

The gene involved shows incomplete penetrance

The disorder has variable expressivity

There is a somatic mutation

Imagine you observe the following in a data set: more males affected than females; approximately half the grandsons of affected males are affected; some females are affected but usually only if their maternal grandfather was affected and their mother married an affected male. What type of inheritance might you suspect?

sex-linked recessive

autosomal dominant,sex-limited

sex-linked dominant

recessive epistasis

A cross of fruit flies was conducted. White-eyed males were cross with pink-eyed females. All F1 flies had normal eye color. F1âs were intercrossed yielding F2 flies as follows: 890 wildtype females, 455 wildtype males, 605 white-eyed males, 140 pink-eyed males, and 310 pink-eyed females. Give a genetic explanation consistent with these data.

white is autosomal recessive and epistatic to pink

pink is autosomal recessive and dominant over white

pink and white are x-linked recessive with white dominant to pink

white is x-lined recessive, pink is autosomal recessive; white is recessive epistatic to pink

An avid gardener decides to plant seeds from disk-shaped squashes she raised during the previous summer. To her surprise, 89 of her plants bear disk-shaped squashes while 61 plants produce spherical squashes and 10 produced elongate shaped squash. What is the mode of inheritance of fruit shape in these squash?

Codominance

Recessive epistasis

Duplicate interaction

Epistasis

Based on what you know about translation, what does âreverse translationâ mean?

Determining a DNA sequence from an amino acid sequence

Determining a RNA sequence from a DNA sequence

Translating in the 3â to 5â direction

Transcribing first, then translating

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!)

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BIOL207 Lecture Notes - Lecture 5: Epistasis, Meiosis, Thomas Hunt Morgan

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