Lecture 01: Sex Determination (Pozor) Flashcards Preview

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Flashcards in Lecture 01: Sex Determination (Pozor) Deck (40):
1

3 stages of sexual differentiation

1) chromosomal (XX or XY)
2) gonadal (ovary or testis)
3) phenotypic (male or female)

*each stage depends on the previous one*

2

what does chromosomal sex drvie?

gonadal differentiation

3

Main precursor to gonads

genital ridge

4

Mesonephros develops into what structures?

small structures near but not IN the gonads

5

Where is genital ridge located?

next to mesonephros and mesonephric ducts

6

yolk sac

first fetal membrane that provides nutrition to developing embryo. Where Primordial germ cells are located before they migrate to genital ridge to become gametes

7

gametes

spermatozoa and oocytes

8

precursor to gametes

primordial germ cells (PGCs)

9

migration of PGCs (start & end)

start --> yolk sac
end --> genital ridge, where they colonize

10

What initiates testis differentiation?

Sry (sex determining region) gene on Y chromosome (TDF - Testis determining factor)

11

T or F: ovarian differentiation is a default process

FALSE! Needs 2 copies of key genes from 2 X chromosomes to occur

12

precursor to female sexual organs

Paramesonephric duct (Mullerian duct)

13

precursor to male sex organs

Mesonephric duct (Wolffian duct)

14

Influence of testicular hormones

presence or absence influences development of tubular tract

15

Precursor to epididymis

mesonephric duct

16

What hormone do leydig cells produce?

Testosterone

17

What hormone do sertoli cells produce?

Anti-Mullerian Hormone (AMH) (causes regression of the mullerian duct system and induction of wolffian duct system) *****

18

lack of AMH -->

maintenance of female tract

19

3 components of wolffian duct system

epididymis, deferent duct, urethra

20

4 components of mullerian duct system

oviducts, uterus, cervix, crania vagina

21

precursor to cranial vestibule

urogenital sinus

22

what hormones cause physical masculinization? (2)

testosterone and DHT

23

Absense of testosterone/DHT -->

female physical differentiation

24

Most common cause of chromosonal disorder of sex. differentiation

non-disjunction of sex chromosomes or chromatids **

25

Meiosis I =

first division of meiosis

26

Meiosis II =

second division of meiosis

27

nondisjunction in meiosis II leads to what kind of zygotes?

half normal, and half trisomic and monosomic

28

Turner's Syndrome

XO (monosomy X). underdeveloped but gonadally/phenotypically FEMALE. Usually sterile

29

Klinefelter's Syndrome

XXY. Gonadally and phenotypically MALE due to Sry, but abnormal and usually sterile.

30

Trisomy X Syndrome

XXX. Gonadally and phenotypically FEMALE, but abnormal/UNDERdeveloped.

31

Mosaic and cause

all cells originate from single zygote. cause usually = non-disjunction during mitosis of early embryo

32

Chimera

cells originate from more than one zygote. Can be naturally or experimentally occuring. During development, placentas from twin pregnancies fuse and blood from the two fetuses mixes before gonadal differentiation leading to hormonal mixture and masculinization of female fetus

33

Tortoiseshell cats

(Fur color carried on X chromosome) Tortoiseshell cats are heterozygous for orange fur, but random X-inactivation results in females that are mosaics and have orange and black fur.

34

Freemartin

An example of chimera. Calf contains a portion of cells originating from its twin due to mixed vascular beds in utero. Results in masculinization and sterility of female twin

35

Test for freemartin

can't fit 10cc of fluid in vagina (freemartins have short vagina)

36

Sex reversal

when chromosomal sex and gonadal sex don't agree (i.e. XY with ovaries)

37

Sex reversed female

Y chromosome is present but Sry is non-functional. Undifferentiated "streak" gonads. Underdeveloped female

38

Sex reversed male

2 causes:
1) Sry translocated to X chromosome during meiosis and causes masculinization
2) Mutation in gene downstream of Sry

39

Polled Intersex Syndrome (PIS)

heritable condition in goats in which homozygous dominant for polled also results in expression of recessive intersex gene, which inactivates important genes for gonadal development. Results in sterility and male differentiation in females, and sperm granulomas in males. Tx = keep horned buck

40

**see flow chart at end of Notability lecture**

:)

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