BIOL299 Lecture Notes - Dosage Compensation, Sex Linkage, Y Chromosome

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ivoryfox572

15 Feb 2014

School

University of Alberta

Department

Biology (Biological Sciences)

Course

BIOL299

Professor

Darren De Lorey

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Document Summary

2: homozygotes and hemizygotes all have uniform color, birds, flies have sex chromosomes but do not inactivate whole chromosomes for dosage compensation (see turkey example, 3. 5. 3) 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. <100% white fur ww piebald spotting orange fur dilute pigmentation tabby sex. < 50% white patches no white patches all orange fur tortise shell variegation. Xoxo or xxy no orange fur pigmentation is intense dd or dd pigmentation is dilute (e. g. gray rather than black; cream rather than orange; light brown rather than brown) tabby pattern solid coloration female male dd. If the cat has red eyes it is albino, not w_. W is epistatic to all other fur color genes; if cat is. W_, can"t infer genotypes for any other fur color genes. S is incompletely dominant and shows variable expressivity.

Related Questions

1.) In tomato plants, spines (s) are recessive to nospines (S), and white fruit color (w) isrecessive to red fruit color (W). The genes for spines andfruit color are located on the same chromosome; findings frommapping experiments indicate that they are 13.2 m.u. apart. Atomato plant having spines and white fruit color is crossed with aplant that is homozygous for no spines and red fruit color. The F1are crossed with plants that have spines and white fruit color.Which of the following phenotypes and proportions are expected inthe progeny of this cross? Check all that apply.

a) Red, no spines = 43.4%; white, spines = 43.4%

b) White, no spines = 43.4%; red, spines = 43.4%

c) Red, no spines = 6.6%; red, spines = 6.6%

d) White, no spines = 6.6%; white, spines = 6.6%

e) White, no spines = 6.6%; red, spines = 6.6%

f) Red, no spines = 43.4%; red, spines = 43.4%

g) Red, no spines = 6.6%; white, spines = 6.6%

h) White, no spines = 43.4%; white, spines = 43.4%

2.) In Drosophila, the map positions of genes are givenin map units numbering from one end of a chromosome to the other.The X chromosome of Drosophila is 66 m.u. long.The X-linked gene for body color-with two alleles,y ⁺for gray body and y foryellow body-resides at one end of the chromosome at map position0.0. A nearby locus controlling bristle form, withf ⁺for normal bristles and ffor forked bristles is located at map position 1.5. A thirdX-linked gene for eye color, with alleles w⁺for red eye and w for white eye, islocated at map position 56.7. Each gene resides on the Xchromosome, and at each locus the wild-type allele is dominant overthe mutant allele. Do you expect any of these gene pair(s) toassort independently?

a) Yes, y and w are each expected to assortindependently of f

b) Yes, all the genes are expected to assort independently

c) Yes, y and f are each expected to assortindependently of w

d) No, there are no genes expected to assortindependently

rubywallaby524

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

___1. Nationally, the most common cause of Down Syndrome is
a. nondisjunction of Chromosome 21 during meiosis
b. translocation of Chromosome 21 onto another chromosome
c. inversion of a large section of Chromosome 21
d. deletion of the Down Syndrome gene
___2. In humans, sex is determined by
a. The presence or absence of the Y chromosome
b. The ratio of X chromosomes to sets of autosomes
c. The temperature during fetal development
d. Which parent is stronger at the time of conception
___3. A translocation is
a. a chromosomal abnormality in which a piece of one chromosome breaks off and attaches to a different chromosome
b. an abnormality in which the chromosomes are translocated out of the nucleus
c. a condition in which the chromosome has broken in two places and come back together with the middle segment backward
d. an abnormality in which there is an extra copy of one chromosome
___ 4. In snapdragons, a red-flowered plant crossed with a white-flowered plant produces all pink-flowered offspring. But crossing two pink-flowered plants produces red, pink, and white in a 1:2:1 ratio. This is a good example of
a. Incomplete dominance
b. Dominance of the red allele over the white allele
c. Lethal effects of the pink allele
d. Sex-linkage of the flower-color alleles
___ 5. If a person with type AB blood marries a person with Type O blood, what blood types are possible in their children? (Assume this trait is a single-gene trait, not complicated by interaction with other genes).
a. A, B, AB, or O
b. A or B only
c. AB or O only
d. AB only 2
___6. In what phase of meiosis are haploid nuclei first formed? a. Anaphase I b. Metaphase II c. Telophase II d. Metaphase I e. Telophase I
___7. What is the phenotype of a heterozygous tall pea plant? a. tall b. Tt c. TT d. tt e. dominant
___ 8. If genes A and B are far apart on a chromosome, and A and C are close together, which of the following observations is expected?
a. Crossing over will occur more often between A and C than between A and B
b. Crossing over will occur at equal frequencies between A and C, and between A and B
c. Crossing over will occur more often between A and B than between A and C
___9. Sometimes an organismâs genotype for one gene masks the effect of a different gene. This phenomenon is called
a. Dominance
b. Incomplete dominance
c. Co-dominance
d. Epistasis
e. Variable expressivity
___10. The dominant allele of a gene is
a. The one that is expressed most often in a population
b. The one that is expressed most often in any particular cross
c. The one that is expressed in an individual that has two different alleles
d. The one that is most healthy to have, that gives the greatest fitness
___11. In human cells, DNA replication occurs
a. In S phase of interphase
b. In G1 phase of interphase
c. In G2 phase of interphase
d. In prophase of mitosis
e. Whenever the cell needs to read the DNA to make proteins
___ 12. A process in which recipient cells take up genes from DNA molecules floating free in the surrounding medium is called
a. conjugation
b. specialized transduction
c. generalized transduction
d. transformation 3
___ 13. Most calico cats are female. However, a few rare males are observed. What is the genotype of a male calico cat?
a. X BX 0
b. X OY
c. X BY
d. X BYY
e. X BX OY
___ 14. A type of red-green color-blindness is a sex-linked (X-linked) recessive trait in humans. Can a woman have this type of color-blindness?
a. Yes, a woman could be color-blind if her mother and father were both heterozygous.
b. Yes, a woman could be color-blind but only if she has an abnormal number of sex chromosomes.
c. No, women can't show sex-linked traits because they lack a Y chromosome.
d. No, women can't show sex-linked traits because they have two X chromosomes.
e. Yes, a woman could be color-blind if her father was color-blind and her mother was a carrier (heterozygous).

BIOL299 Lecture Notes - Dosage Compensation, Sex Linkage, Y Chromosome

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