|
Application
Activity 2. Answers
1. Sex is expressed at the chromosomal level as inheriting XX
or XY; at the gonadal level by developing ovaries or testes; at the phenotypic
level by developing male or female internal and external structures; and
at the gender identity level by feelings.
2. Genes in the pseudoautosomal region are the same as certain
X-linked genes, but X-Y genes share only sequence similarities.
3. a. female b. female c. female
4. Sustentacular cells secrete anti-Mullerian hormone, which stops
development of female reproductive structures. Interstitial cells
secrete testosterone, which promotes development of male reproductive structures.
5. Absence of the SRY gene product causes the Mullerian ducts
to develop into ovaries. The ovaries produce female hormones, which
influence the development of external and internal reproductive structures.
6. Feelings of very young children; twin studies in which identical
twins are more likely to both be homosexual than are fraternal twins; fruit
fly behavior; genes on the X chromosome that segregate with homosexuality.
7. A female homozygous dominant for an X-linked dominant allele
would probably be so severely affected that she would not be alive, or
healthy enough reproduce.
8. Coat color in cats in X-linked. in females, one X chromosome
in each cell is inactivated, and the pattern of a calico cat's coat depends
on which cells express which coat color allele. A male cat, with
only one coat color allele, would have t inherit an extra X chromosome
to be tortoiseshell or calico.
9. Inactivation of the gene in some cells but not others results
in a patchy phenotype.
10. Each cell in a female's both contains only one active X chromosome,
which makes females genetically equivalent (in terms of X-linked genes)
to males.
11. An X-linked trait appears usually in males and may affect
structures or functions not distinct to one sex. A sex-limited trait
affects a structure or function distinct to one sex. A sex-influenced
trait is inherited as a recessive in one sex and dominant in the other.
12. Mouse zygotes with 2 female pronuclei or 2 male pronuclei
are abnormal. In humans 2 male and one female genome in the same
embryo yields a placenta, while two female and one male genome yields a
normal embryo with an abnormal placenta. Hydatidiform moles (placental
tissue with no embryo) consist of cells with 2 male genomes; a teratoma
contains cells with 2 female genomes.
top
|
