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IB 141 human genetics > chapter 6 - matters of sex > Flashcards

chapter 6 - matters of sex Flashcards

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Biology 101 flashcards
1
Q

biological maleness or femaleness is determined at _____

A

conception

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2
Q

SRY gene

A

in mice, sex-determining region of Y chromosome

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3
Q

TDF gene

A

testis determining factor in humans, essential for male development

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4
Q

Wnt4 gene

A

essential for development / maturation as a biological female

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5
Q

mutations in Wnt4 cause

A
  • XX females develop high levels of male sex hormones
  • lack of development of vaginal canal and uterus
  • ovaries do not develop properly
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6
Q

beta-catenin

A

induces ovary producing genes and blocks SRY (TDF)

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7
Q

heterogametic sex

A

males; have different sex chromosomes (XY)

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8
Q

homogametic sex

A

females; have the same sex chromosomes (XX)

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9
Q

how many genes in X chromosome

A

more than 1500 genes

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10
Q

the X chromosome is _______ than the Y chromosome

A

larger

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11
Q

X chromosome acts as a _____ to Y in males

A

homolog

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12
Q

how many genes are in the Y chromosome

A

more than 230 genes

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13
Q

Y chromosome does not _____ _____ along all of its length

A

cross over

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14
Q

the Y chromosome has many DNA segments that are _______ and may destabilize ___ ________

A

palindromes; DNA replication

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15
Q

Y chromosome anatomy

A

1 short arm, 1 long arm

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16
Q

pseudoautosomal regions of Y chromosome

A

PAR1 & PAR2

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17
Q

5% of the Y chromosome….

A

contains 63 genes shared with X chromosome that contribute to bone growth, cell division, etc

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18
Q

MSY

A

male specific region, most of the chromosome

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19
Q

MSY 3 classes of DNA sequences

A

1 - sequence almost identical to X chromosome. 2 - somewhat identical to X chromosome. 3 - palindromes

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20
Q

how many genes are in the MSY

A

22 genes

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21
Q

AZF gene

A

encodes a protein essential for producing sperm

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22
Q

AZF gene mutations cause

A

infertility

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23
Q

hermaphroditism

A

older/more general term for individual with male and female sexual structures

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24
Q

intersex

A

individuals whose internal structures are inconsistent with external structures or whose genitalia are ambiguous

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25
Q

pseudohermaphroditism

A

refers to the presence of both female/male structures but at different life stages

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26
Q

pseudohermaphroditism includes

A
  • androgen insensitivity syndrome, 5-alpha reductase deficiency, congenital adrenal hyperplasia
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27
Q

androgen insensitivity syndrome

A

mutation on the X - chromosome blocks formation of androgen receptors

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28
Q

5-alpha reductase deficiency

A

unable to convert testosterone to DHT, child has inside male anatomy but looks like a girl on the exterior

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29
Q

congenital adrenal hyperplasia

A

enzyme block causes androgens to accumulate, and can cause precocious puberty in males or male secondary sex characteristics to develop in females

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30
Q

in normal male prenatal development, activation of a set of genes beginning with SRY sends signals that destroy _____ _____, while activating the biochemical pathway that produces ______ and ________ ,which promotes the development of male structures

A

female rudiments; testosterone; dihydrotestosterone

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31
Q

congenital adrenal hyperplasia results in excess ____ and ____

A

testosterone and dihydrotestosterone

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32
Q

androgen insensitivity syndrome and 5-alpha reductase deficiency lower levels of _____ _____

A

male hormones

33
Q

same-sex attraction

A

person’s phenotype and genotype are consistent, but physical attraction is towards members of the same sex

34
Q

sex ratio

A

calculated by number of males / number of females, multipled by 1000

35
Q

primary sex ratio

A

at conception is 1000; equal

36
Q

secondary sex ratio

A

at birth is 1050; Y bearing sperm weight lighter than X bearing sperm, so it could enter the oocyte faster

37
Q

tertiary sex ratio

A

at maturity, doesn’t say what it is though

38
Q

Y-linked traits

A

-genes on Y chromosome
-very rare
-transmitted from male to male

39
Q

X-linked traits in females

A

passed like autosomal traits

40
Q

X-linked traits in males

A

a single copy of an X-linked allele causes expression of the trait or illness

41
Q

human male is considered _______ for X-linked traits

A

hemizygous

42
Q

X-linked recessive trait is always expressed in _____

A

male

43
Q

X-linked recessive trait is expressed in female _____ and very rarely in a female ______

A

homozygote; heterozygote

44
Q

X-linked recessive traits - affected female inherits from…

A

affected father and affected or heterozygote mother

45
Q

X-linked dominant trait is expressed in _____ in one copy

A

females

46
Q

X-linked dominant traits have more severe effects in _____

A

males

47
Q

X-linked dominant traits cause high rates of ______ due to early lethality in males

A

miscarriage

48
Q

X-linked dominant traits are passed from male to all ______ but not to ___

A

daughters; sons

49
Q

X-linked recessive trait is expressed in females if the allele is _____ _____ ___ ____

A

present in 2 copies

50
Q

examples of X-linked recessive traits

A

ichthyosis, colorblindness, hemophilia

51
Q

ichthyosis

A

enzyme deficiency blocks removal of cholesterol from skin cells

52
Q

colorblindness

A

about 8% of males of european ancestry have the condition

53
Q

hemophilia

A

disorder of blood-clotting

54
Q

hemophilia B is an X-linked _____ disease that usually passes from a _____ woman to ______ daughters or ______ sons.

A

recessive; heterozygous; heterozygous; hemizygous

55
Q

why are males that inherits x-linked dominant traits usually more severely affected?

A

he has no other allele to mask its effect

56
Q

most cases of x-linked dominant traits are a result of ____ _______, rather than ____ ____ __ _____

A

new mutations; transmission from a parent

57
Q

examples of x-linked dominant traits

A

rett syndrome, incontinentia pigment

58
Q

sex-limited traits

A

traits that affect a structure or function that is present in only 1 sex
- could be autosomal or x-linked

59
Q

sex-limited traits examples

A
  • beard growth
  • milk production
  • preeclampsia in pregnancy
60
Q

sex-influenced traits

A

allele is dominant in 1 sex but recessive in the other
- could be autosomal or x-linked
- difference in expression can be caused by hormonal differences between sexes

61
Q

sex-influenced traits examples

A

pattern baldness in humans - heterozygous male is bald heterozygous female is not, response to treatment for glioblastoma - female patients live longer than male patients after surgery, radiation and use of a drug, temozolomide

62
Q

X inactivation

A

balances the inequality of expression of genes on the X chromosome

63
Q

XIST gene

A

encodes an RNA that binds to and inactivates the X chromosome

64
Q

X inactivation occurs early in _____ _______

A

prenatal development

65
Q

X inactivation alters the _____ and not the ____.

A

phenotype; genotype

66
Q

barr body

A

inactive X chromosome

67
Q

manifesting heterozygote

A

female that expresses the phenotype corresponding to an X-linked gene

68
Q

X inactivation can be used to identify carriers of some X-linked disorders, such as

A

hunter syndrome, lesch-nyhan syndrome, affects the severity of rett syndrome

69
Q

unequal x inactivation pattern can occur if…

A

the 2 X chromosomes have different alleles for a gene that controls cell division, giving certain cells a survival advantage

70
Q

mechanisms of parent-of-origin effects

A

genomic imprinting

71
Q

genomic imprinting

A

parental effect on gene expression is seen as diseases inherited from a parent

72
Q

function of genomic imprinting

A

not super well understood, but may be a way to regulate abundance of key proteins in the embryo

73
Q

imprinted genes are in ____ along a chromosome, controlled by ______ _____

A

clusters; imprinting centers

74
Q

male genome controls _____ development, female genome controls ______ development

A

placenta; embryo

75
Q

humans have ____ imprinted genes. at least ____ of them affect health if they are abnormally expressed

A

150+; 60

76
Q

chromosome 15 deletion syndromes

A

prader-willi syndrome - inherited from father; angelman syndrome - inherited from mother

77
Q

abnormal imprinting is associated with:

A

diabetes mellitus, autism, alzheimers, schizophrenia, male-male attraction

78
Q
A

IB 141 human genetics (6 decks)

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