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BIO105 - Genetics > Chapter 3d - Genes of Variable Expressivity > Flashcards

Chapter 3d - Genes of Variable Expressivity Flashcards

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1
Q

Genes of Variable Expressivity

A
  1. Pleiotropy
  2. Penetrance
  3. Phenocopy
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2
Q

single mutation simultaneously affects several traits

A

pleiotropy

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3
Q

examples of pleiotropy

A
  1. sickle cell anemia
  2. phenylketonuria (PKU)
  3. Marfan syndrome
  4. porphyria variegata (vampire’s disease)
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4
Q

what does the alleles of the b–globin gene influence

A
  • type of hemoglobin produced
  • red blood cell shape
  • susceptibility to anemia
  • malaria resistance
  • organ function
  • life-span
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5
Q
  • rare inherited disorder that causes an amino acid called phenylalanine to build up in the body
  • caused by a change in the phenylalanine hydroxylase (PAH) gene. This gene helps create the enzyme needed to break down phenylalanine
A

phenylketonuria (PKU)

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6
Q

caused by defects in gene called fibrillin-1, an important building block for connective tissues in the body

A

Marfan Syndrome

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7
Q

manifestations of Marfan Syndrome

A
  1. Pectus excavatum
  2. arachnodactyly
  3. dilation of aorta
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8
Q
  • group of rare, genetic blood disorders that impact the production of hemoglobin, the iron-rich protein that transports oxygen in the blood
  • Cutaneous porphyrias (porphyrias affecting the skin) leads to sensitivity to sun and light
A

porphyria variegata (vampire’s disease)

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9
Q

Ex. of people with Marfan Syndrome

A
  1. Abraham Lincoln
  2. Osama bin Laden
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10
Q

Ex. of people with porphyria variegata

A
  1. King George III
  2. Vincent van Gogh
  3. Nebuchadnezzar
  4. Paula Frias Allende
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11
Q

given genotype may or may not show phenotype

A

penetrance

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12
Q

Two types of penetrance

A
  1. complete penetrance
  2. incomplete penetrance
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13
Q

all individuals express a given genotype

A

complete penetrance

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14
Q

not all would express a given genotype

A

incomplete penetrance

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15
Q

ex. of incomplete penetrance

A
  1. Harelip
  2. Dominant retinoblastoma
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16
Q
  • malignant eye tumor in children
  • 90% penetrance
A

dominant retinoblastoma

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17
Q

when penetrant:
degree in which a particular phenotypic effect is exhibited in an individual

A

expressivity

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18
Q

two types of expressivity

A
  1. constant expressivity
  2. variable expressivity
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19
Q

trait in all individuals is identical

A

constant expressivity

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20
Q

ex. of constant expressivity

A
  1. kinky hair
  2. vestigial wings in Drosophila
21
Q

not identical expression of trait

A

variable expressivity

22
Q

ex. of variable expressivity

A
  1. polydactyly
  2. mouse spotting
23
Q

penetrance and expressivity

A
  1. penetrance, with complete expression
  2. penetrance, with moderate expression
  3. penetrance, with minimal expression
  4. no penetrance, thus no expression
24
Q

what influence the degree of penetrance and expressivity

A
  • modifier genes
  • environment
25
Q

identical known genotypes yield 100% expected phenotype

A

complete penetrance

26
Q

identical known genotypes yield <100% expected phenotype

A

incomplete penetrance

27
Q

identical known genotypes with no expressivity effect yield 100% expected phenotype

A

constant expressivity

28
Q

identical known genotypes with an expressivity effect yield a range of phenotypes

A

variable expressivity

29
Q

identical known genotypes produce a broad range of phenotypes due to varying degrees of gene activation and expression

A

incomplete penetrance with variable expressivity

30
Q
  • environmentally-induced phenotype which closely resembles the phenotype by a known recessive gene
  • or ‘aritifical phenotype’
A

phenocopy

31
Q

ex. of phenocopy

A
  1. insulin-dependent diabetics
  2. thalidomide babies
  3. phenylketonuria of normal babies with mothers with PKU
32
Q
  • used as sleeping pill and tranquilizer in the early 1960s taratogenic when used during the first trimester of pregnancy
  • mimics a recessive disorder, phocomelia, characterized by abnormalities in the bones of arms and/or legs
A

thalidomide

33
Q

what does thalidomide babies mimic

A

phocomelia

34
Q

what helps determine expression of genotype

A

environmental conditions

35
Q

what changes the color of hydrangea flowers

A

pH of soil

36
Q

carries allele specifying heat-sensitive enzyme for melanin production

A

himalayan rabbit

37
Q

some effects of the environment

A
  1. age of onset (male pattern baldness)
  2. sex (male pattern baldness)
  3. temperature
38
Q

what does temperature influene

A
  • enzymes
  • coloration in Siamese cats
  • sex determination in reptiles
39
Q

occurs more often in females than males due to the presence of estrogen

A

rheumatoid arthritis

40
Q

baldness:
BB

A

bald in either sex

41
Q

baldness:
Bb

A

bald in males only

42
Q

baldness:
bb

A

normal hair in both

43
Q
  • traits where an allele is dominant in one sex but recessive in the opposite sex
  • does not mean sex-linked
A

sex-influenced traits

44
Q

sex influence is a phenomenon of __

A

heterozygotes

45
Q

sex-influenced traits are __, meaning it is not sex-linked

A

autosomal

46
Q

ex. of sex-influenced traits

A

scurs (hornlike growth) in cattle

47
Q

found in both sexes but manifested only in one sex due to physiological/anatomical reasons

A

sex-limited traits

48
Q

ex. of sex-limited traits

A
  1. genes for milk production in both bulls and cows
  2. genes for long pointed feathers in cocks and hens
  3. genes for beard development in men and women

BIO105 - Genetics (19 decks)

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