Unit 4 - Ch 11 - Sex Determination

Question 1

Autosomes

Answer 1

Non-sex chromosomes that contain autosomal traits

In Humans, chromosomes 1-22 are autosomal (44 total, 22 homologous pairs). The remaining two are sex chromosomes.

Question 2

Heterosomes

Answer 2

Chromosomes that determine sex

Human Males - XY; allele on Y promotes testes development

Human Females - XX

Question 3

Barr Bodies

Answer 3

Condensed, inactivated X chromosome found only in females.

• females have one barr body per cell (Olympic sex test)

Lyon’s Hypothesis - barr bodies form randomly during development

1. Calico cat - usually female; heterozygous for orange and black
2. Sweat glands - heterozygous females (human) have patches of skin with and without sweat glands. They form randomly.

Question 4

X-Linked Traits

Answer 4

Found on the non-homologous portion of the X chromosome in both males and females

Examples:
Hemophilia - recessive (Xh) more common in males
Red/Green Colorblindness - recessive (Xb) more common in males
Brown Teeth Spotting - dominant (XS)

Question 5

Y-Linked Traits

Answer 5

On the non-homologous portion of the Y chromosome

Holandric traits - only found in males.
Example: hairy ears

Question 6

Sex-Influenced Traits

Answer 6

Autosomal traits influenced by the sex hormones (not on X or Y)

Example
Pattern Baldness - dominant autosomal allele
Females: BB=bald, Bb and bb = not bald
Males: BB and Bb = bald, bb=not bald

Question 7

Sex-Limited Traits

Answer 7

Autosomal traits found only in one sex due to hormonal or anatomical differences

• 0% penetrance in one sex

Examples - both male and female carry the gene, but it is only expressed in one sex

            1. Form of Uterine Cancer
            2. Deer Antlers
            3. Milk Production

Question 8

Male gametes

Answer 8

heterogametic

Androsperms - Y-bearing

Gynosperms - X-bearing

Question 9

Female gametes

Answer 9

homogametic

Females only produce X gametes

Question 10

Sex Ratio # males: # females

Answer 10

Humans
114 males : 100 females at fertilization (primary)

106 males : 100 females at birth (secondary)