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genetics > chapter 4 part 2 > Flashcards

chapter 4 part 2 Flashcards

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Biology 101 flashcards
1
Q

what is the C gene responsible for in mammals

A

coat color

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2
Q

what does C gene produce

A

enzyme involved in melanin production

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3
Q

allelic series of C gene

A

C, c(ch), c(h), c

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4
Q

how many alleles are there of the C gene?

A

dozens

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5
Q

C

A

produces functional enzyme (tyrosinase enzyme that is 100% active) and full coat color

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6
Q

c(ch)

A

produces dilute phenotype called chinchilla

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7
Q

c(H)

A

produces phenotype called Himalayan with little pigment on body but full color on extremities

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8
Q

c

A

fully recessive null allele and produces an albino phenotype (amorphic)

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9
Q

is the C allele haplosufficient or haploinsufficient

A

haplosufficient

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10
Q

activity of enzyme produced by c(ch)

A

less than 20% active - hypomorphic

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11
Q

how is the c(h) allele temperature-sensitive?

A
  • functional at lower temperatures (extremities)
  • non-functional at higher temperature (core)
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12
Q

lethal alleles/mutations

A

inherited as recessive alleles (all homozygotes die)

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13
Q

how are lethal alleles detected

A

can be detected as distortions in segregation ratios caused by 1+ missing classes of progeny

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14
Q

what is the Agouti Locus an example of

A

lethal alleles

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15
Q

Agouti Locus

A
  • wild type coat color in mice = agouti, produced by combo of yellow/black pigments along each hair
  • Ay - dom allele, causes yellow pigment along entire hair in heterozygotes
  • Ay lethal in homozygous state
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16
Q

all yellow mice are _____________

A

heterozygous

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17
Q

outcome of cross A/Ay x A/Ay

A

1/4 AA Agouti
1/2 AAy yellow
1/2 AyAy, pre-implantation embryonic lethal

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18
Q

the Ay allele is…

A
  • dominant for yellow coat color
  • recessive for survival
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19
Q

what is the Ay mutation caused by

A

deletion that affects 2 genes, Agouti and RAly

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20
Q

Ray gene

A

produces protein essential for mouse development

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21
Q

what does the deletion between Agouti and Raly genes do

A

connect the Ray promoter to the Agouti gene, which destroys the Raly coding sequence

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22
Q

why do homozygous AyAy mice die?

A

due to lack of Raly protein, never implant in uterus

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23
Q

ex. of how genotypic and phenotypic ratios are complicated

A
  • delayed age of onset
  • sex-limited traits
  • sex-influenced traits
  • incomplete penetrance
  • variable expressivity
  • environmental modification
  • pleiotropic effects
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24
Q

delayed age of onset

A

abnormalities of dominant lethal alleles not expressed until after affected ind. has reproduced

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25
Q

how can dominant lethal alleles sidestep natural selection?

A

delayed age of onset

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26
Q

ex. of delayed age of onset

A

Huntington Disease

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27
Q

Huntington Disease

A

fatal neurodegenerative disorder which doesn’t usually show symptoms until late 30s/40s

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28
Q

sex-limited traits

A

both sexes carry the genes for such traits, but they are expressed only in one sex

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29
Q

ex. of sex-limited traits

A
  • mammalian breast and ability to produce milk = female
  • horn development sometimes limited to males
  • behavioral traits
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30
Q

what differentially influence the expression of genes and sex-limited traits?

A

sex hormones

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31
Q

the sex of an organism can influence gene expression due to ____________ ____________ _____________

A

differing hormone profiles

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32
Q

sex-influenced traits

A

those in which the phenotype corresponding to a particular genotype differs depending on the sex of the organism

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33
Q

ex. of sex-influenced traits

A

chin beard in certain goat breeds
- heterozygous for beard: phenotype influenced by presence/absence of androgenic (male) hormones

34
Q

penetrance

A

observed phenotype is consistent with genotype

35
Q

non-penetrance

A

phenotype associated with genotype is not visible

36
Q

fully penetrant

A

when expected phenotype is always expressed from a particular genotype

37
Q

incomplete penetrance

A

traits/genotypes that are nonpenetrant in a portion of the population

38
Q

ex. of penetrance

A

polydactyly - dominant allele is non-penetrant in about 25-30% of ind. carrying it

39
Q

polydactyly

A

autosomal dominant condition in which affected individuals have 5+ fingers and toes

40
Q

variable expressivity

A

seen in ind. who show a phenotype but to a varying degree of severity

41
Q

ex. of variable expressivity

A

Waardenburg syndrome - same genotype with different combination of symptoms

42
Q

4 principal features of Waardenburg syndrome

A
  • premature graying
  • white forelock
  • hearing loss
  • different-colored eyes
43
Q

ex. of environmental modification to prevent disease

A

phenylketonuria (PKU)

44
Q

phenylketonuria

A

autosomal recessive condition caused by the absence of an enzyme involved in phenylalanine breakdown

45
Q

hereditary disorder routinely screened for in infants

A

PKU

46
Q

what is the inability to break down phenylalanine toxic to

A

developing neurons

47
Q

key to preventing PKU

A

restricting phenylalanine in diet of infants
- can help people live normal lives

48
Q

pleiotropy

A

alteration of multiple distinct traits by mutation in single gene
- one gene has many effects

49
Q

ex. of pleiotropic gene

A

sickle cell disease

50
Q

sickle cell disease

A

autosomal recessive condition caused by mutation in B-globin gene
- red blood cells take on sick shape and cause numerous physical problems and conditions

51
Q

gene interaction

A

collaboration of multiple genes in the production of a single phenotypic characteristic or group or related characteristics

52
Q

anabolic pathways

A

involve biosynthesis of complex compounds

53
Q

catabolic pathways

A

involve degradation of complex compounds

54
Q

ex. of pathways that involve interaction of multiple genes

A

signal transduction, developmental pathways

55
Q

what does epistasis literally mean

A

“stands upon”

56
Q

epistasis

A

alleles of one gene modify or prevent expression of alleles of another gene

57
Q

mutation of one gene in a pathway may prevent what?

A

production of end product

58
Q

what can gene interaction lead to

A

altered phenotypic ratios of wild type and mutant progeny

59
Q

where is epistasis readily detected

A

among progeny of dihybrid crosses involving genes w/ both dom and rec alleles

60
Q

no interaction ratio

A

9:3:3:1

61
Q

no interaction

A
  • absence of epistasis
  • genes don’t interact to change expression of one another
62
Q

complementary gene interaction

A

two genes must interact to produce overall phenotype - when genes work in tandem to produce a single gene product

63
Q

duplicate gene action

A

redundant system in which a dominant allele at either locus gives rise to a wild type phenotype
- encode same product, or encode products that have same effect in pathway

64
Q

complementary gene interaction ratio

A

9:7

65
Q

duplicate gene action ratio

A

15:1

66
Q

dominant gene interaction ratio

A

9:6:1

67
Q

dominant gene interaction ex

A
  • summer squash have disk shaped fruit if at least one dom allele expressed
  • 1 of 2 dom alleles gives round fruit
  • only recessive gives long fruit
68
Q

recessive epistasis ratio

A

9:3:4

69
Q

recessive epistasis ex.

A

labradors
- one gene responsible for eumelanin production
- second gene responsible for distribution of pigment on hairs
- dogs that can’t produce eumelanin or distribute pigment have yellow coat

70
Q

recessive epistasis

A

homozygosity for recessive alleles at one locus will has the phenotypic expression of the alleles at a second locus

71
Q

dominant epistasis ratio

A

12:3:1

72
Q

dominant epistasis

A

dominant allele at one locus will bask the phenotypic expression of alleles at second locus

73
Q

dominant suppression ratio

A

13:3

74
Q

dominant suppression

A

dominant allele at one locus completely suppresses the phenotypic expression of alleles at second locus

75
Q

ex. of no interaction

A

green, blue, and yellow parrots

76
Q

ex. of complementary gene interaction

A

purple and white flowers

77
Q

ex. of duplicate gene action

A

purple and white flowers

78
Q

ex. of dominant gene interaction

A

squash (disk, sphere, and long)

79
Q

ex. of recessive epistasis

A

labradors

80
Q

ex. of dominant epistasis

A

white, yellow, and green squash

81
Q

ex. of dominant suppression

A

white and blue flowers

genetics (47 decks)

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