01 Development and defects

Question 1

Chromosomal sex

Answer 1

Determined at fertilization by the type of sex chromosome contributed by the sperm. Drives gonadal differentiation

Question 2

Gonadal sex

Answer 2

determined by the presence or absence or the Sry gene of the Y chromosome. Testes or ovaries

Question 3

Phenotypic sex

Answer 3

determined by the substances produced in the testes or the absence of the testes. Regulate the development of external genitalia

Question 4

Primordial germ cells originate in the yolk sac and migrate to the

Answer 4

genital ridge

Question 5

The genital ridge is the

Answer 5

precursor of the gonad (undifferentiated)

Question 6

Wolffian/mesonephric ducts

Answer 6

will form the epididymis, ductus deferens, and other structures in the presence of testosterone or regress in its absense

Question 7

Mullerian/ Paramesonephric ducts

Answer 7

Will form the oviducts, uterus, cervix and cranial vagina in females or will regress in males under the presence of MIH/AMH

Question 8

Bipotential

Answer 8

means the gonads can turn into either testes or ovaries

Question 9

Sry

Answer 9

gene on the Y chromosome that produces HY antigen (aka ‘SRY protein’ or testis determining factor’

Question 10

Anti-Mullerian hormone (AMH)

Answer 10

produced by sertoli cells. Causes the regression of the Mullerian duct system

Question 11

What causes the regression of the development and maintenance of the Wollfian duct system

Answer 11

The testosterone produced in the Leydig cells

Question 12

DHT

Answer 12

dihydrotestosterone. Is a hormone that is converted from testosterone by the enzyme 5-a-reductase. It acts like testosterone but is 10 times as potent

Question 13

Monosomy X (XO)

Answer 13

Turners syndrome. Patients are often small in stature, infertile, and usually have hypoplastic female reproductive tracts. External genitalia may be normal or underdeveloped

Question 14

XXY-syndrome

Answer 14

Klinefelter’s Syndrome. Phenotypically male due to the presence of Sry of the Y gene but extra X causes abnormal phenotype. Testicular development and spermatogenesis is inhibited resulting in small flaccid testes and azoospermia. The testes may be retained or descended. Penis may be normal or smaller than usual. Libido and sexual behavior is typically normal. Low testosterone may be noted

Question 15

XXX

Answer 15

Female phenotype but abnormal. Internal genitalia will often be abnormal

Question 16

Mosaic

Answer 16

term applied to an animal that has more than one genetically-distinct population of cells. i.e. in humans some cells might be 46 XX and some 47 XXX.

Question 17

How is mosaicism achieved

Answer 17

non disjunction during mitosis of an early embryo and the fraction of cells having each genotype is variable.

Question 18

Mosaicism can be viewed in what animals

Answer 18

calico cats

Question 19

A male calico cat probably has

Answer 19

klienfelter’s syndrome

Question 20

Chimeras

Answer 20

Individuals having cell lines from two different embryonic sources. i.e. Geep fusion of early embryos of sheep and goats

Question 21

Freemartins

Answer 21

Female cows that have a male twin in utero. Due to a fused placenta before sexual differentiation, testosterone can affect the cow and cause some degree of masculinization. Often infertile.

Question 22

Sex reversal

Answer 22

hermaphroditism. XX males or XY females. Can be caused my a lack of Sry or a translocated copy of Sry onto an X chromosome.

Question 23

Polled intersex Goats

Answer 23

Sry-negative XX sex reversed males. Close relationship between hornless goats and intersexuality. One P polled gene causes hornlessness. Two P polled genes causes intersex

Question 24

Pseudohermaphrodite male

Answer 24

XY with testes but female or ambiguous external genitalia

Question 25

Pseudohermaphrodite female

Answer 25

XX with ovaries and male or ambiguous external genitalia

Question 26

Testicular feminization

Answer 26

Patients are XY but testes are usually retained. External genitalia is either female or ambiguous. Caused by a defective androgen receptor.

Question 27

Congenital adrenal hyperplasoa

Answer 27

Individuals are XX with ovaries but external genitalia is male. Syndrome reuslts from deficiency in the enzyme 21-hydroxalaze

Question 28

Aneuploidy

Answer 28

increase or decrease in normal chromosome number usually by one chromosome. Can lead to trisomy or monosomy

Question 29

Hermaphrodite

Answer 29

an individual have both ovarian and testicular tissue