Chapter 15.2 Sex-linked genes exhibit unique patterns of inheritance

Question 1

How is sex of mammals determined

Answer 1

The sex of a mammalian offspring depends on whether the sperm cell contains an X chromosome or a Y.

. In mammalian testes and ovaries , the 2 sex chromosomes segregate during meiosis and each gamete gets one. Each egg contains an x chromosome. In contrast, sperm fall int 2 categories: Half the sperm cells a male produces contain an X chromosome and half contain a Y chromosome

Question 2

SEX LINKED GENES

Answer 2

A gene located on either sex chromosome : Y-linked gene and X- Linked gene

Question 3

X linked traits

Answer 3

. Fathers pass X-linked alleles to all of their daughters but to none of their sons
. Mothers can pass Xl-inked alleles to both sons and daughters
.If X-linked trait is due to a recessive allele, a female will express the phenotype only if she is homozygous for that allele
. A male receiving the recessive allele from his mother will express the trait ( far moer males than females have x-linked recessive disorders ( e.g color blindness, hemophilia)

Question 4

HEMIZYGOUS

Answer 4

alleles on y chromosomes

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Question 5

X - Inactivation

Answer 5

Females have 2 x chromosomes in each cell , However one x is randomly turned off

Question 6

BARR BODY

Answer 6

The inactive X in each cell of a female condenses into a compact object, which lies along the inside of the nuclear envelope

Question 7

When are Barr bodies reactivated

Answer 7

In the ovaries, Barr body chromosomes are reactivated in the cells that give rise to eggs, so every female gamete has an active X.

Question 8

Mosaic

Answer 8

having 2 type of cells active and in active at random. ( all mitosis descendants of that inactive x gene cell will also have this inactivation.