X and Y linked traits and Sex Determination

Question 1

X-linked recessive inheritance

Answer 1

more common in males than females

Question 2

X-linked dominant inheritance

Answer 2

males pass the trait to all their daughters but none of their sons; affected females married to normal males pass their trait to 1/2 of their sons and daughters

Question 3

Examples of X-linked recessive traits

Answer 3

hemophilia, color blindness, muscular dystrophy, testicular feminizing syndrome

Question 4

Examples of X-linked dominant traits

Answer 4

faulty tooth enamel, vitamin D-resistant rickets

Question 5

Y-linked traits

Answer 5

are holandric (entirely male); such traits should be transmitted to all sons

Question 6

Testis determining factor (TDF)

Answer 6

causes sex determination; directs gonad differentiation to testes rather than ovaries

Question 7

Sry gene

Answer 7

located on the Y chromosome and is a transcription factor expressed just before testis formation that encodes TDF

Question 8

XO individuals

Answer 8

one X and no Y; develop as females but are sterile (1/10,000 but 99% die before birth); Turner syndrome: survivors nearly normal until puberty, then fail to develop normal sexual organs

Question 9

XXY individuals

Answer 9

develop as males (1/1000 births); Klinefelter syndrome: underdeveloped testes, tall, some develop breasts

Question 10

XYY individuals

Answer 10

develop as males (1/1000 births) near normal

Question 11

XXX individuals

Answer 11

develop as females (1/1000 births) near normal

Question 12

non-disjunction

Answer 12

causes abnormal X and Y chromosome #s in individuals (occurs during meiosis)

Question 13

What is the difference between non-disjunction occurring in meiosis I and meiosis II?

Answer 13

Meiosis I: paired homologous chromosomes are unable to separate correctly

Meiosis II: sister chromatids are unable to separate correctly

Question 14

Chromosome theory of inheritance

Answer 14

by Calvin Bridges and TH Morgan showing chromosomes carrying genes as X chromosome non-disjunction can produce progeny w/ unexpected phenotypes

Question 15

What is an example of environment determining sex and environment conditioning sex?

Answer 15

Alligators: 86 F or lower temp. in nest during 7-21 days of egg incubation leads to females, higher temp. leads to males

Question 16

Sex of Drosophila chromosome number variants

Answer 16

If X and autosomal chromosome ratio (X:A) >1 = female

If X and autosomal chromosome ratio (X:A)<1 and > 0.5 = intersex

If X and autosomal chromosome ratio (X:A) < 0.5 = male

Question 17

In animals, males or females could be the heterogametic sex? T or F?

Answer 17

T

Question 18

Gynadromorphs

Answer 18

half male/half female

Question 19

Dosage compensation

Answer 19

mechanisms to equalize gene expression between sexes; in mammals, there is dosage compensation to inactivate all but one of the X chromosomes in females making it mostly heterochromatic

Question 20

What are three ways dosage compensation is used?

Answer 20

Lowering gene expression in the X chromosomes of females to be equal to the singular X chromosome in males, increasing gene expression in the singular X chromosome of males to be equal to the X chromosomes of females, or inactivating one X chromosome in female

Question 21

What is the inactive X visible as in female cells?

Answer 21

Barr body