BIOL1001 Lecture Notes - Lecture 22: Y Chromosome, Chromosome, Tangled

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24 Jul 2018

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Female (xx) x male (xy: however, although the expected ratio of males:females = 1:1, the actual ratio with age: varies. Males: 22 pairs of autosomes + 1 pair of sex chromosomes (xx, 22 pairs of autosomes + 1 pair of sex chromosomes (xy) Normal female 44a + xx: heterogametic (two different gametes) 22a + y: homogametic (all gametes same) Female phenotype, sterile, late sexual maturity, webbing of skin, upturned fingernails. Molecular basis of sex determination: sex is controlled by the sex determining region y (sry) gene ie: male gamete dependent, maleness requires: A testis determining factor- the sry locus on y chromosome. A receptor for male steroid hormones- the androgen receptor on x chromosome: sex development ie: the affect of sry factor: Sex-linked pedigrees: x chromosomes are significantly larger than y chromosomes genes on the parts of the x and y chromosomes that do not pair show sex linkage, example: color blindness. 2 allels- c = normal, c = colorblind.

Related Questions

11) CIRCLE ALL CORRECT ANSWERS: Human males are hemizygous for

a) Sxl gene b) pseudoautosomal region of the Y c)SRY d) gene for testis determining factor e) Xist gene

12) The X inactivation center codes for

a) gonadal ridges to form ovaries b) gonadal ridges to form testes c) RNA d) testosterone e) protein enhancing transcription of sex linked genes

13) CIRCLE ALL CORRECT ANSWERS: The pseudoautosomal region is found on

a) autosomes in males b) autosomes in females c) X chromosome d) Y chromosome e) both the X and Y chromosome f) could occur in fruit flies

14) Comparing two monozygotic XX twins to two monozygotic XY twins

a) XX are more identical b) XY are more identical c) monozygotic twins do not occur

EXPLAIN YOUR ANSWER:

15) CIRCLE ALL CORRECT ANSWERS: Butterflies and Habrobracon differ in

a) which sex is homogametic b) which sex is monoploid c) one has sex chromosomes and the other does not d) one produces some gametes by mitosis, the other does not

The fruit fly Drosophila has 8 chromosomes (2n = 8). This includesone pair of sex chromosomes (XX in females and XY in males). Theother three pairs of chromosomes are autosomes. I give you a vialof flies with two dominant mutations: the first one Stubble, Sb,makes the bristles short and stubby (wild type bristles are longerand pointed; Sb+), whereas the other one, Serrate, Ser, makes theedge of the wing serrated (wild type wings have a smooth, notserrated margin Ser+). The genes encoding both these traits are onchromosome 3.

I give you a vial of flies that carry both these dominantmutations. Set up a cross to determine if the two mutations are incis (that means that the mutant alleles are on the same homolog) orif they are in trans. Write out the cross along with the possibleoutcomes. Consider one possibility at a time.

maroonbeetle203

1. An animal (called a Box) is diploid, and has 5 types of chromosomes (4 autosomes, 1 pair sex chromosomes). Box sex chromosomes are designated W and Z. Box males are heteromorphic (WZ), and Box females are homomorphic (WW).

Boxes are covered in a thick coat of hair. There is a disease in Box, called hairlessness, that has an inheritance pattern that is W-linked and recessive. The allele used to designate this disease is h. Haired Box are wild-type (allele = h+) and hairless Box are mutant (allele = h). In general (not thinking about Box and hairless) when we say that an inheritance pattern is recessive, we automatically know some things about the genotype of affected/diseased individuals.

A) Is the trait simple, or some other type?

B) Does the presence of one diseased allele cause disease, or are two needed?

C) What other name do we use to describe a heterozygous individual?

In the case of Box and the hairless phenotype, what are all the possible genotypes for a hairless female? What are all the possible genotypes for a hairless male? (You do not need to use complete sentences here)

A heterozygous female is mated with an affected male. Indicate what gametes these two individuals can produce. (You donât need to use complete sentences here)

D) Draw a Punnett square for all the possible offspring that these two Box can create. Place the female gametes across the top of the square, and the male gametes down the left side. Insert a picture of your drawing below.

E) What is the ratio of unaffected to affected female offspring for these parents? For male offspring?

F) Choose one female offspring and one male offspring from the F1 and draw a Punnett Square for a mating between those two individuals (F2). Place the female gametes across the top and the male gametes down the left side. Take a picture of the square and insert it below.

BIOL1001 Lecture Notes - Lecture 22: Y Chromosome, Chromosome, Tangled

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