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Week 2 Flashcards

Modifications of Mendelian Ratios

1
Q

define: incomplete dominance

A

the F1 hybrid resembles neither purebred parent (often an intermediate phenotype)

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2
Q

define: codominance

A

alternative traits are both visible in the F1 hybrid

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3
Q

what is an example of incomplete dominance

A

snapdragon colour [red: ArAr, pink: ArAw, white: AwAw]

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4
Q

what is the phenotypic ratio of incomplete dominance and codominance

A

1:2:1

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5
Q

what is the genotypic ratio of incomplete dominance and codominance

A

1:2:1

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6
Q

what is the proper way to designate incompletely dominant or codominant alleles

A

in uppercase

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7
Q

what is the genetic explanation for snapdragon colour displaying incomplete dominance

A

the allele Ar produces a red pigment and the allele Aw produces a white pigment

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8
Q

what is the mode of colour inheritance if grey parents produce black offspring (cows)

A
  1. grey AWAB is heterozygous incomplete dominance phenotype, black is homozygous ABAB
  2. grey Gg is heterozygous dominant phenotype, black is homozygous recessive gg
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9
Q

is colouring in zebras a result of codominance

A

no, if it was then there would be pure white and pure black zebras

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10
Q

what alleles are present in ABO blood groups

A

IA, IB, and i

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11
Q

what dominance relation does ABO blood groups have

A

IA and IB are codominant to each other and both are dominant to the i allele

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12
Q

why are IA and IB codominant

A

these alleles code for enzymes that attach A and B sugars to the surface of red blood cells

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13
Q

are variations on complete dominance consistent with Mendel’s law of segregation

A

yes

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14
Q

define: dominance series

A

alleles are listed in order from dominant to recessive

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15
Q

how are dominance relationships established

A

reciprocal crosses between pure-breeding lines

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16
Q

when dealing with multiple alleles with only one wild-type, how is the wild-type allele denoted

A

with a superscript A+

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17
Q

what is the purpose of doing reciprocal crosses

A

ensures that the trait is not sex-linked

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18
Q

what are the four rabbit coat colours

A

agouti, albino, chinchilla, himalayan

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19
Q

how do new alleles arise

A

through mutation

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20
Q

do different alleles imply different phenotypes

A

no, a change in the DNA sequence doesn’t always imply a difference in the protein product

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21
Q

define: allele frequency

A

percentage of the total number of copies of a gene in a population represented by a particular allele

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22
Q

define: wild-type allele

A

has a frequency of >1%

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23
Q

define: mutant allele

A

has a frequency of <1%

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24
Q

what is another definition of a monomorphic gene

A

gene with only one wild-type allele

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25
what is another definition of a polymorphic gene
gene with more than one wild-type allele
26
define: pleiotropy
multiple phenotypic effects caused by a single gene
27
what is an example of pleiotropy
sickle cell anemia [destruction of red blood cells, circulatory blockages, and damage to organs]
28
what does it mean for an allele to be lethal
the allele affects viability in addition to visible phenotype
29
what is the phenotypic ratio for a heterozygous cross when there is recessive lethal alleles
2:1
30
what is an example of lethal recessive alleles
Manx cats
31
in pleiotropy, does being dominant in one phenotype imply it is dominant for all
no, it may be recessive for other phenotypes
32
what are the phenotypes when there is pleiotropy with 1 dominant and 1 mutant allele
there are multiple phenotypes
33
define: multifactorial inheritance
a phenotype arising from the action of two or more genes (polygenic) or from interactions between genes and the environment
34
define: polygenic
a phenotype arising from the action of two or more genes
35
what is the phenotypic ratio for a trait determined by 2 genes
9:3:3:1
36
define: complementary gene action
two or more genes can work in tandem, in the same biochemical pathway to produce a particular trait
37
define: heterogeneous trait
a mutation at any one of a number of genes can give rise to the same phenotype
38
what are examples of heterogeneous traits
- drosophila body colour (flies) - pea flower colour - deafness in humans - albinism
39
how can a wild-type phenotype be rescued when it is a heterogeneous trait
complementation [*eeb+b+* (black fly) x *e+e+bb* (black fly) => *e+eb+b* (wild-type colour fly)]
40
what is the phenotypic ratio of complementary genes [ex. pea flower colour]
9:7
41
define: non-complementation
when two organisms carrying mutations in the same gene for a heterogeneous trait is crossed
42
define: complementation
two mutants have mutations in differing genes, allowing for wild-type offspring
43
define: epistasis
a gene interaction in which the effects of an allele at one gene hide the effects of alleles at another gene
44
define: epistatic
control over another gene
45
what is an example of recessive epistasis
coat colour in Labrador retrievers [_ _ ee => yellow, B_E_ => black, bbE_ => brown]
46
what is the phenotypic ratio of recessive epistasis
9:3:4
47
what does recessive epistasis look like in human blood groups
*H/h* controls production of lipid H to which A and B sugars are attached, *hh* means the lipid is not produced example of blood types: *IA_hh* => type O *IA_Hh* => type A
48
what is an example of dominant epistasis
summer squash colour [*C_* => white, *ccG_* => yellow, *ccgg* => green]
49
what are the hypothesis testing rules
- true breeding homozygous parents will produce heterozygous F1 offspring - test cross F1 heterozygotes - phenotypic ratios of F2 indicate the mode of inheritance
50
how do you find the genotype of an F2 individual showing recessive epistasis
cross it with an individual that is known to be homozygous for the recessive allele of the masked trait and homozygous for the antagonist trait (*_ _ cc* x *bbCC*)
51
what is a way to find inheritance mode in humans since test-crossing is not possible
pedigree analysis
52
does the same genotype always result in the same phenotype
no, there are other influences such as the environment, modifier genes, and chance
53
define: penetrance
percentage of the population with a particular genotype that demonstrate the expected trait
54
define: expressivity
the degree or intensity with which a particular genotype is expressed in a phenotype within a population
55
what is an example of variable expression
- coat pattern in beagles - retinoblastoma (75% penetrance, 30% expressivity or getting it in one eye)
56
define: sex-linked traits
due to genes on the X or Y chromosome
57
what are examples of sex-linked traits
- hemophilia - colour blindness
58
define: sex-limited trait
affect a structure of process that is found in one sex but not the other
59
what are examples of sex-limited traits
- bright plumage in male birds - traits involving milk production - traits involving horns/antlers
60
define: sex-influenced traits
show up in both sexes but their expression may differ between the two sexes
61
what are examples of sex-influenced traits
- pattern baldness - height
62
how does pattern baldness differ between men and women
baldness is dominant in men and recessive in women
63
how does the genotype affect pattern baldness in men
if it is heterozygous, the onset is later than homozygous dominant
64
what is an example of the environment affecting the phenotypic expression of a genotype
Himalayan coat pattern in cats and rabbits, cooler temperatures are required to produce melanin => dark fur
65
define: conditional lethality
an allele which is lethal under only certain conditions
66
define: restrictive [conditional lethality]
conditions that contribute to lethality
67
define: permissive [conditional lethality]
conditions that don't contribute to lethality
68
what is an example of a conditionally lethal allele
malignant hyperthermia, genetic disease triggered by certain anaesthetics

BIOL 239 (12 decks)

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