Sex Chromosomes (2)

Question 1

Heterogametic sex

Answer 1

Gametes with different chromosome positions.

In humans, this is the male bc of the X, Y.

In some species the female would be the heterogametic sex and it would be denoted ZZ/ZW instead of XX/XY.

Question 2

Homogametic sex

Answer 2

Has 2 of the same sex chromosomes (XX)

Question 3

What determines maleness in humans?

Answer 3

The presence of a Y chromosome

Question 4

Kleinfelter syndrome

Answer 4

47,XXY
(47 chromosomes including XXY; Have an extra X chromosome)

“Intersexuality”:
Tall, long limbs
Have genitalia and internal ducts but can’t produce sperm. Also have some feminine features such as gynecomastia (enlargement of breasts), + rounded hips.

Result from nondisjuction

Question 5

Turner syndrome

Answer 5

45, X (missing an X or a Y)

Female external & internal genitalia but they are rudimentary (don’t work).

3 S’s: Short, Skin flaps on neck, Small breasts (broad chest)

Normal intelligence

Results from non disjunction

Question 6

Triple X

Answer 6

47,XXX

Can be normal or mentally retarded with sterility and delayed development

rare:
Tetra X or penta X - results more severe

Question 7

47, XYY

Answer 7

Having an additional Y chromosome. Linked to dangerous/ criminal propensities. Tall height and lower intelligence.

Question 8

Gonadal ridges in a human embryo- what forms male and what forms female

Another name for these ridges?

Answer 8

FEMALE:
Cortex: develops into Ovaries
Mullerian ducts

MALE:
Medulla: develops into testes
Wolffian ducts

Another name: Bipotential gonads

Question 9

What is the difference between primary and secondary sexual differentiation

Answer 9

Primary involves only the gonads (where gametes are produced)

Secondary involves external genitalia, mammary glands, etc

Question 10

What is located on the short arm of a Y chromosome?

Answer 10

PAR (pseudoautosomal region)
SRY (which makes testis determining factor)
Euchromatin (contain functional genes)

Question 11

What’s located on the long arm of the Y chromosome

Answer 11

Euchromatin
Heterochromatin
PAR

Question 12

What is mullerian inhibiting substance (MIS)?

Answer 12

Secreted by cells of developing testes to degrade the Müllerian duct, preventing formation of female reproductive tract.

Question 13

Is sex determination from the chromosome or a gene?

Answer 13

Specific genes, not entire chromosomes

Question 14

What’s the mode of sex determination of a protenor butterfly?

Answer 14

XX/XO

If only one X is present, male
XX is female

Question 15

What is sex determination of a Lygaeus (milkweed bug)?

Answer 15

XX/XY like humans

Question 16

What are the 3 regions of the male specific region of the Y chromosome? (MSY)

Answer 16

15% X-transposed
20% X degenerative
30% ampliconic (encodes proteins specific to development of testis)

Question 17

Hemizygous

Answer 17

Having a gene present in a single dose in an otherwise diploid cell.

(Usually applied to genes on X chromosome in heterogametic males)