Biology 1001A Chapter Notes - Chapter 11.2: Testis Determining Factor, Sex Linkage, Y Chromosome

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3 Feb 2017

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In many organisms, one or more pairs of chromosomes are different in males from those in females. Genes located on these chromosomes are called sex-linked genes. Chromosomes other than sex chromosomes are called autosomes and the genes on these chromosomes have the same pattern of inheritance in both sexes. 11. 2a females are xx and males are xy in both humans and fruit flies. In most species with sex chromosomes, females have 2 copies of a chromosome known as the x chromosome, forming a fully homologous xx pair, whereas males only have one. X and the y chromosome instead of the second x. Each normal gamete produced by an xx female carries and x chromosome. Half the gametes produced by an xy male carry an x chromosome and half carry a y. When a sperm cell carrying an x chromosome fertilizes an x-bearing egg cell, the new individual develops into an xx female.

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

Why are recessive X-linked traits seen more often in human malesthan in human females? (Select all that apply.)

Males have an X chromosome, but females do not.

Actually, X-linked traits are seen more often in females than inmales, because they have two X chromosomes.

Males donât have a second X chromosome to mask the effects ofthe first one.

This phenomenon is due to X-inactivation.

While females would need two of these alleles to express therecessive phenotype, males only need one.

Sperm are more likely to carry an X chromosome than a Ychromosome.

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Please explain, and no hand-written work please, please type answer

Sex-Linked Traits (traits located on the sex chromosomesâusually the X chromosome)

Follow the directions for the lab. Enter data you obtain for the following crosses and answer questions on this answer sheet. (NOTE: The traits used in this Module 3 Lab are sex-linked. Therefore, you CANNOT click the âignore sexâ button for these crosses. You need to see separate results for males and females to analyze data for sex-linked traits.)

Question: In this lab exercise, should you click the "ignore sex" button for the crosses?

1. a. Perform a monohybrid cross between a female fly with a tan body and a wild-type male fly. Show results for the F₁ offspring. (NOTE: You will use these F₁ flies in the next cross.)
ENTER DATA HERE:

Question: Are the phenotypes of the F₁ offspring what you would have predicted for this cross: why or why not?

Question: Each F₁ female received a tan allele from her mother and a wild allele from her father. Why do all of the F₁ females show the wild-type phenotype?

Question: Compare the number and type (X or Y) of sex chromosomes found in female and male flies.

Question: Compare the number of alleles present on the X and Y chromosomes.

Question: How can you tell that tan body is a sex-linked trait?

Question: How can you tell whether tan body is located on the X chromosome or the Y chromosome?

Question: If tan body was located on the Y-chromosome, what would be the phenotype of all the male F₁ offspring? Is this what you obtained for the cross above?

Question: If tan body was located on the Y-chromosome, could females even show the trait? (HINT: When analyzing the cross results, remember that Y-linked traits are passed down only from affected males to their sons. Females cannot display Y-linked traits since they do not have Y chromosomes. On the other hand, both males and females can inherit X-linked traits since they both have X chromosomes.)

PUNNETT SQUARE:

List the genotypes of the parent flies in this cross (HINT: You must use X and Y symbols):

List the gametes produced by each parent fly in this cross:

Show the Punnett Square for the above cross.

Biology 1001A Chapter Notes - Chapter 11.2: Testis Determining Factor, Sex Linkage, Y Chromosome

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