Sex Chromosomes and Disorders Flashcards

1
Q

What do SRY and SOX9 do?

A

produce AMH and cause regression of the paramesonephric duct

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2
Q

What happens during the 4th week of conception?

A

the germ cells form in the wall of the yolk sac

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2
Q

The most common cause of ambuiguous genitalia in a female is _____.

A

21-hydroxylase deficiency

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3
Q

What is sex chromosome aneuploidy?

A

disorders that don’t have the normal # of X or Y chromosomes

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3
Q

Mesonephric/Wolffian ducts result in _____ structures because of the ____ and _____ genes.

A

male; SRY; SOX9

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4
Q

What are the signs and symptoms for Triple X Syndrome?

A

females with tall stature, learning disabilities, delayed speech and motor milestones, seizures, kidney problems

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4
Q

What is the incidence rate for Triple X Syndrome?

A

1:1000 newborn females

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4
Q

Which chromosome carries the AR gene?

A

X

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5
Q

What is the incidence rate for Jacobs Syndrome?

A

1:1000 newborn males

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6
Q

What is the incidence rate of Kleinfelter Syndrome?

A

1:500 newborn males

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7
Q

What is the karyotype of Kleinfelter Syndrome?

A

47XXY

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7
Q

What happens during the 8th week of conception in a male?

A

Leydig cells make T; Sertoli cells make AMH; sex cords differentiate

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8
Q

What happens during the 5th week of conception?

A

the coelomic epi becomes the genital ridge

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9
Q

Half of a female’s cells express the _____ inherited X, while the other half express the _____ inherited X chromosome.

A

maternally; paternally

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10
Q

Females are ______ for their X chromosome.

A

mosaic

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11
Q

X chromosome inactivation wont occur without ____.

A

XIST

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12
Q

WNT4 protein _________.

A

differentiates the ovary

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13
Q

What happens during the 7th week of conception?

A

the genital ridge begins to differentiate

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13
Q

Under the influence of ________, the paramesonephric ducts become the _______.

A

Estrogen, uterus, cervix, broad ligament, Fallopian tube, and upper 1/3 of the vagina

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14
Q

When is X chromosome inactivation skewed?

A

when females have X-linked recessive conditions, the normal gene is sometimes turned off, allowing the female to express the phenotype

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15
Q

x chromosome inactivation

A

one x chromosome is randomly turned off

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16
Q

How would you test a child with disorder of sexual differentiation?

A

1) FISH for X and Y 2) check hormone levels 3) check for mutations

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16
Q

What is the result of 5-alpha reductase deficiency?

A

decreased ability of the body to convert T to dihydrotestosterone

17
Q

What does FGF9 do?

A

differentiates the testes

18
Q

What are the signs and symptoms of Kleinfelter Syndrome?

A

learning disabilities, tall stature, small testicles, reduced body hair, infertile, hypospadias, gynocomastia

19
Q

What does SF1/NR5A1 do?

A

stimulates differentiation of Sertoli and Leydig cells

20
Q

The X chromosome has about _____ genes.

A

1000

20
Q

Ectopic presence of SRY gene in 46XX results in ____.

A

a phenotypically normal male

22
Q

Where is XIST located? What expresses it?

A

On the X chromosome; the inactive X

23
Q

When does X chromosome inactivation occur?

A

in week 1 of embryogenesis

24
Q

What is the karyotype for 5-alpha reductase deficiency?

A

46XY

26
Q

What is primary sex determination?

A

determination of the gonads

27
Q

Both male and female external genitalia originate from the _____.

A

urogenital sinus

28
Q

What happens during the 6th week of conception?

A

the primordial germ cells migrate to the dorsal mesentery and enter the gonad; sex cords form

29
Q

What is the karyotype for Androgen Insensitivity Syndrome?

A

46XY

31
Q

What is the karyotype for Triple X Syndrome?

A

47XXX

32
Q

What is the phenotype of 5-alpha reductase deficiency?

A

at birth, undervirilized genitalia but this improves at puberty

33
Q

When does nonrandom X chromosome inactivation occur?

A

when there is a structurally abnormal X chromosome- more of the normal X is turned on

34
Q

What is the karyotype for Jacobs Syndrome?

A

47XYY

35
Q

21-hydroxylase deficient patients have a karyotype of _____.

A

46XX

36
Q

What is secondary sex determination?

A

the gonads determine the 2a sex characteristics

37
Q

What happens during the 8th week of conception in a female?

A

sex cords dissociate; Medullary cords regress; cortical cords are formed to become follicular cells

38
Q

The mesonephric duct, because of T, will become the ____, _____, and _____.

A

epidymis, seminal vesicles, vas deferens

40
Q

What is X chromosome aneuploidy?

A

no matter how many X chromosomes are present, all but one are always inactivated

41
Q

Gonad determination Is ______.

A

chromosomal

43
Q

There are about ____ genes on the Y chromosome.

A

200

44
Q

Denys-Drash and Frasier Syndrome pts phenotypically _____.

A

have sex reversal and kidney issues

45
Q

Barr body

A

the inactivated X chromosome clumped up

46
Q

Which gene inactivates the X chromosome?

A

XIST

47
Q

What complicates 21-hydroxylase deficient patients?

A

salt wasting- decreased Na and Cl with increased K

49
Q

What prevents the inactivated X chromosome from being expressed?

A

methylation of the promoter region

52
Q

Mutation of the AR gene causes what phenotypes?

A

mild under-virilization to full sex reversal

53
Q

Mutations of SRY in a 46XY individual results in _____.

A

reduced or absent production of anti-Mullerian hormone and under virilization of the male

54
Q

What are the 2 pairs of genital ducts in both males and females at 6 weeks?

A

Mesonephric (Wolffian) and Paramesonephric (Mullerian)

55
Q

Denys-Drash and Frasier Syndrome is due to a mutation in ____.

A

WT1 gene

56
Q

What are the signs and symptoms for Jacobs Syndrome?

A

learning disabilities, speech delays, developmental delays, behavioral issues, autisms, tall stature

57
Q

The paramesonephric or Mullerian ducts result in ____ structures because ___ and ____ are not present.

A

female; SRY; SOX9