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BIOL 1240 > exam 3 ppt 3 > Flashcards

exam 3 ppt 3 Flashcards

1
Q

what is the problem with Mendel’s discoveries?

A

genetic complexities exist that would not have allowed Mendel to make his discoveries

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2
Q

definition of incomplete dominance

A

heterozygote displays intermediate phenotype

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3
Q

definition of codominance

A

heterozygote displays BOTH phenotypes at once

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4
Q

definition of X-linked traits

A

offspring have sex-dependent inheritance patterns

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5
Q

definition of multiple alleles

A

hierarchy of dominance

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6
Q

definition of epistasis

A

gene interactions

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7
Q

definition of genes x environment

A

environment influences phenotype

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8
Q

what genetic complexities exist that would not have allowed Mendel to make his discoveries? (listed)

A

incomplete dominance, codominnce, X-linked traits, multiple alleles, epistasis, genes x environment

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9
Q

what do karyotypes reveal?

A

they reveal the biological sex of an individual

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10
Q

what are the female sex chromosomes?

A

XX

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11
Q

what are the male sex chromosomes?

A

XY

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12
Q

definition of sex chromosomes

A

one of the pair of chromosomes that determine the sex of an individual

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13
Q

definition of autosomes

A

chromosomes that are not sex chromosomes

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14
Q

what do many animal species have regarding sex chromosomes?

A

many animal species have unmatched sex chromosomes

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15
Q

in mammalian biological sex determination, what does the sex-determining region Y gene (SRY) gene do?

A

it encodes a protein called Testis determining factor (TDF), a transcription factor that turns on expression of other genes that results in development of male reproductive structure

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16
Q

what is the testis determining factor (TDF) in mammalian biological sex determination?

A

a transcription factor that turns on expression of other genes that results in the development of male reproductive structures

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17
Q

why is the SRY gene Y linked?

A

it is Y linked because it is only found on the Y chromosome

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18
Q

what does the segregation of sex chromosomes during meiosis predict regarding the sex of offspring?

A

segregation of sex chromosomes during meiosis predicts a 1:1 ratio of males to females

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19
Q

what does meiosis in a female result in?

A

meiosis in a female results in X-bearing eggs only

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20
Q

what does meiosis in a male result in?

A

meiosis in a male results in a 1:1 ratio of X-bearing and Y-bearing sperm

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21
Q

what does it mean that males are hemizygous?

A

males are hemizygous for genes on the X chromosome; what they have they got from their mother

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22
Q

definition of hemizygous

A

a gene present on the X chromosome that is expressed in males in both the recessive and dominant condition (gotten from their mothers)

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23
Q

definition of sex-linked inheritance

A

inheritance of a genetic trait located on the sex chromosomes

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24
Q

regarding sex-linked inheritance, how many copies do females have? what does this result in?

A

females have two copies, and can be homozygous or heterozygous

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25
Q

regarding sex-linked inheritance, how many copies do males have? what does this result in?

A

males have only one copy, are hemizygous, and express the phenotype of the only allele they have

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26
Q

exp of X-linked inheritance

A

human red-green color blindness

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27
Q

what happens with red-green color blindness regarding males vs. females?

A

a heterozygous female has normal vision, but a male is colorblind if he has a mutated X allele

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28
Q

are there Y-linked genes?

A

yes

29
Q

definition of Y-linked genes

A

genes found on the Y chromosome

30
Q

what discovery was the follow-up of Mendel’s?

A

Morgan’s discovery of X-linked genes

31
Q

what is Morgan’s discovery of X-linked genes?

A

haploid gametes; 2 parents swap phenotypes; in the F1 generation, all of the offspring have red eyes; in the F2 generation, white eyes reappear in the next generation, but only in males, all of the females have red eyes and among the males the ratio of red:white eyes is 1:1

32
Q

definition of a reciprocal cross

A

a cross in which the phenotypes of the male and female are reversed compared with a prior cross

33
Q

what offspring can males pass their traits down to?

A

only can pass down to their daughters

34
Q

what are the two halves of the reciprocal cross in the F1 generation?

A

in one half, all of them have red eyes because they all inherit the X gene from mother; in the other half, half of the offspring get it because the male is dominant

35
Q

what are the two halves of the reciprocal cross in the F2 generation?

A

in one half, all females have red eyes and only 50% of men have red eyes (X-linked, 3:1); in the other half, 2 have red eyes and 2 have white eyes

36
Q

what is Morgan’s explanation?

A

the w gene (for white eyes) must be on the X chromosome

37
Q

in the inheritance of X-linked genes, what do XX offspring show?

A

XX offspring show that a male can only transmit his X chromosome to his daughter (XX)

38
Q

in the inheritance of X-linked genes, what do XY offspring show?

A

they show that a male inherits his X chromosome from his mother

39
Q

do X-linked genes show distinct patterns in pedigrees?

A

yes

40
Q

can you distinguish between autosomal and X-linked dominant traits?

A

not really (look pretty similar)

41
Q

definition of X-linked recessive traits

A

pattern in which displayed traits are due to inheritance of recessive alleles carried on the X chromosome

42
Q

definition of X-linked dominant traits

A

all females of the affected father are diseased

43
Q

exp of X-linked recessive trait

A

red-green color blindness

44
Q

exp of X-linked dominant trait

A

hypophosphatemia

45
Q

regarding X-linked inheritance, would it be possible for an unaffected female to have female offspring with red-green color blindness?

A

yes-> daughters get it from their fathers, mother just has to be a carrier

46
Q

is meiosis always perfect?

A

no -> nondisjunction

47
Q

definition of nondisjunction

A

when homologous chromosomes fail to seoarate properly (chromosome pairs) -> results in extra or not enough chromosomes

48
Q

what fails to separate with nondisjunction?

A

homologs

49
Q

what results from nondisjunction?

A

aneuploidy -> all gametes have too many or too few chromosomes

50
Q

exp of aneuploidy

A

down syndrome/trisomy 21, etc

51
Q

can nondisjunction happen in meiosis?

A

yes, it can happen in meiosis II if sister chromatids are not separated

52
Q

definition of aneuploidy

A

extra or missing chromosomes in human births

53
Q

definition of euploid

A

normal # of chromosomes; 46, XX or 46 XY

54
Q

how many individuals per 10,000 human live births have extra or missing chromosomes?

A

33

55
Q

why does it work to have extra or fewer X/Y chromosomes?

A

males only have one of each; only one X chromosome in each of us is being expressed anyways (not two in females)- balance with males, one X turned off/not expressed

56
Q

what is down syndrome due to?

A

its due ro nondisjunction of chromosome 21 (gametes aren’t haploid now because of chromosome 21 having 3 copies)

57
Q

is there a higher rate of down syndrome per number of births in older mothers?

A

yes, births from older mothers are more affected; the longer the egg is waiting in meiosis, the greater chance that the mother will have a child with down syndrome

58
Q

in an X-linked recessive trait, are males or females more frequently affected?

A

males are affected more frequently than females

59
Q

in an X-linked recessive trait, are traits passed from father to son?

A

no, a trait is never passed from father to son (X is given to daughters)

60
Q

in an X-linked recessive trait, what is the genotype of mothers of affected sons?

A

affected sons are usually born to carrier mothers (heterozygous)

61
Q

in an X-linked recessive trait, how many sons of a carrier mother will be affected?

A

about 1/3 of the sons of a carrier mother will be affected

62
Q

in an X-linked recessive trait, what are the genotypes of daughters of an affected male and an unaffected non-carrier female?

A

all daughters of an affected male and an unaffected non-carrier female are carriers

63
Q

in an X-linked recessive trait, does the trait skip generations?

A

yes, the trait often skips generations

64
Q

in an X-linked dominant trait, are males or females more likely affected?

A

males and females are equally likely to be affected

65
Q

in an X-linked dominant trait, are the sons and daughters of an affected father affected or unaffected?

A

all daughters of an affected father are affected, but np sons

66
Q

in an X-linked dominant trait, what are the mothers always like of affected sons?

A

affected sons always have affected mothers

67
Q

in an X-linked dominant trait, how much of the offspring of an affected mother will be affected?

A

about 1/3 of the offspring of an affected mother will be affected

68
Q

in an X-linked dominant trait, can affected daughters have an affected mother or father?

A

yes, affected daughters can have an affected mother or father

69
Q

in an X-linked dominant trait, does the trait often skip generations?

A

no, the trait does not skip generations

BIOL 1240 (9 decks)

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