Chapter 7 sex determination and sex chromososmes

Question 1

What is phenotypic dimorphism?

Answer 1

sex chromosomes determine phenotypes

Question 2

hetermorphic chromosomes

Answer 2

x and y chromosomes, cant differentiate on morphology have to run tests

Question 3

Sex determination is

Answer 3

by specific genes not entire chromosomes

Question 4

1. heterogametic vs homogametic
2. give an example in mammals and in frogs

Answer 4

homo-same genotype hetero- diff genotype
mammals- usually XX (female) are homogametic, XY (male) heterogametic. Frogs and birds ZW is female and heterogametic, male is ZZ homogametic

Question 5

how is drosophilias sex determined?

Answer 5

ratio of x to haploid sets of autosomes(long ones only) (X:2A male)

Question 6

How is reptile sex determined?

Answer 6

Temperature
extreme, low, extreme high, or both can produce and increased number of females

Question 7

The human karyotype contains…

Answer 7

22 pairs of autosomal chromosomes and 2 sex chromosomes

Question 8

What do the Y chromosomes do in males? What about the X in females?

Answer 8

y- “maleness” testes, spermatogenesis, produces SRY gene (testes determining factor)
x- ovaries, follical cells

Question 9

What are the three key parts of the Y chromosome?

Answer 9

1. SRY gene- sex determining region (has TDF protein, testes det. factor)
2. PAR gene - pair x/ x chromosomes in prophase 1, located at the ends of chromosomes
3. MSY- male specific region, contains every thing except PAR region, includes heterochromatin and euchrommatin

Question 10

Why doesn’t the ZW chromosome in flys, code for maleness?

Answer 10

W does not code for anything, it is without a transcription factor for maleness and it not expressed, haploinsufficiency

Question 11

What is a haploinsuficiency?

Answer 11

One copy of a gene is inactive (repressed/ deleted, and the remaining copy is not enough to code for any gene

Question 12

x- linked genes in female mammals often demonstrate….

Answer 12

phenotypic mosacism

Question 13

what are the products of non disjunction at meiosis 1 and 2?

Answer 13

meiosis 1 - 2 trisomic, 2 monosomic
meiosis 2 - 2 normal, 1 trisomic, 1 monosomic

Question 14

what are the results of female non-disjunction?

Answer 14

kleinfelters, non viable (Y), turners, triplo x

Question 15

what are the reuslts of male non-disjunction in meiosis 1?

Answer 15

turners, kleinfelters

Question 16

what are the results of male non-disjunction in meiosis 2?

Answer 16

turners, triplo x, jacobs syndrome