Chapter 2 Flashcards

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1
Q

Incomplete dominance meaning

A

Incomplete dominance means that neither trait is dominant, so that
an intermediate phenotype exists, which is a blending
ex. flowers in snapdragons Fig 3.3

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2
Q

Codominance meaning

A

phenotypic detection of both gene products (from both parents)
ex. Lentils (spotted or dotted)
In both cases F2 progeny phenotypic ratios mirror genotypic ratios

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3
Q

Complete dominance meaning

A

Complete dominance means that Hybrid resembles one of the two parents

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4
Q

How much an individual diploid organism has alleles?

A

An individual diploid organism has two alleles at each genetic locus, with one allele inherited from
each parent.

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5
Q

What are the kinds of blood types (genotypes/phenotypes)?

A
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6
Q

What is a wild type allele?

A

Wildtype alleles is a term used to refer to most
common allele in the population
a. displayed as (+)

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7
Q

What is a mutant allele?

A

b. Mutant allele is a rare allele (less than 1% of pop.)

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8
Q

Monomorphic gene meaning

A

Monomorphic gene is the gene that has only one common wild type allele
Ex. Agouti color in mice

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9
Q

Polymorphic gene meaning

A

Polymorphic gene is the gene that has more than one common allele (not wild type, but rather common variants)
Ex. ABO blood typing

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10
Q

Pleiotrophy meaning

A

It’s a single gene that determines several distinct and seemingly unrelated characteristics. The gene that has different effects in different tissues
Ex. Marfan syndrome

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11
Q

Lethal allele meaning

A

It’s an allele that has the potential to cause death of an organism,
because it encodes an essential gene for survival (1/3 of our genes) ????

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12
Q

What are the 3 kinds of lethal alleles?

A

a. Recessive lethal allele
b. Delayed lethality and
c. Dominant lethal allele

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13
Q

What is a Recessive lethal allele?

A

an allele that negatively affects the survival of a homozygote.
Ex. Coat color in mice:
•Recall our dominance structure A^Y >A > a^t > a
•Two alleles A^Y A^Y (2 copies) in mouse can not occur —> fatal,
>we need only one allele (1 copy) of yellow coat

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14
Q

What is Delayed lethality?

A

Delayed lethality- homozygotes (recessive) survive, but die later
from consequences from genetic defect
Ex. Tay Sachs

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15
Q

What is Dominant lethal allele?

A

It the delayed onset lethal alleles, which kills organism from any point in life (from birth) or delayed
Ex. Huntington’s disease

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16
Q

Additive interaction

A

yields 4 distinct F2 phenotypes
9 to 3 to 3 to 1 phenotypic/genotypic ratio
Ex. Seed color in lentils

17
Q

Epistasis meaning

A

Epistasis is a circumstance where the expression of one gene is modified (e.g., masked) by the expression of one or more other genes.

18
Q

Hypostasis meaning

A

A gene interaction in which the effects of one gene hides the effects of another gene

19
Q

Epistatic vs hypostatic

A

gene doing the masking vs gene being masked

20
Q

Recessive (Suppression ) Epistasis meaning?

A

-Homozygous recessive condition at one locus masks the expression of a second locus.
9:3:4 ratio in F2 progeny of dihybrid
crosses indicates recessive epistasis
Ex. The Bombay phenotype for ABO blood groups,
coat color in Labrador Retrievers
Genotype ee masks the effect of all B genotypes

21
Q

What is recessive epistasis ratio?

A

9:3:4 ratio in F2 progeny of dihybrid crosses
indicates recessive epistasis
9/16 black (B— E—)
3/16 brown (bb E—)
3/16 yellow (B— ee)
1/16 yellow ( bb ee)
Genotype ee masks the effect of all B genotypes

22
Q

What is the precursor to the “A” and “B” antigens (blood type)?

A

H protein. Without the H substance, neither the A or B can be added
to the cell surface so type O phenotype is expressed.

23
Q

What is Dominant Epistasis?

A

Dominant allele of one gene hides effects of
both alleles of the other gene
12:3:1 ratio in F2 progeny of dihybrid crosses
indicates dominant epistasis
b. Ex color in summer squash

24
Q

What is the genotypic/phenotypic ratio of dominant epistasis?

A
12:3:1 phenotypic ratio in F2 progeny of dihybrid crosses 
indicates dominant epistasis
12/16 white (A— B—, aa B—)
3/16 yellow (A— bb)
1/16 green (aa bb)
25
Q

Reciprocal recessive epistasis meaning?

A

When homozygous, recessive allele of each gene masks the dominant allele of the other gene
9:7 ratio in F2 progeny of dihybrid crosses indicates
9/16 purple (A—B—)
7/16 white (A— bb, aa B—, aa bb)

26
Q

Phenotypic variation for some traits can occur because of??

A
  • Effects of modifier genes
  • Effects of environment
  • Pure chance
27
Q

Penetrance definition

A

Penetrance is the percentage of individuals with a particular genotype that
show the expected phenotype
Penetrance is a measure of the proportion of individuals in a population who carry a specific gene and express the related trait.
•Can be complete (100%) or incomplete

28
Q

Expressivity definition

A

Expressivity is the degree or intensity with which a particular
genotype is expressed in a phenotype
•Can be variable or unvarying

29
Q

Expression of phenotype depends on?

A

the environment and genes

30
Q

3 Environmental Effects on Phenotype?

A
  1. the environment and genes
  2. product of genotype is a range of phenotypic possibilities
    - variation due to environmental differences
  3. Temperature
31
Q

Phenocopy meaning

A

Phenocopy - phenotype arising from an environmental agent
that mimics the effect of a mutant gene
•Examples in humans
Genetic predisposition to lung cancer is strongly affected by cigarette smoking

32
Q

Discontinuous traits vs Continuous traits

A

Discontinuous traits
a. clear-cut, “either-or” phenotypic differences between
alternative alleles (white or pink)
Continuous traits
2. Also called quantitative traits because the traits vary
over a range that can be measured
3. Usually polygenic

33
Q

True breeding parent means

A
Homozygous genotype (one parent dominant and 
the other parent recessive)
34
Q

Redundancy meaning

A

Only one dominant allele of either of two genes is necessary
to produce phenotype
15:1 phenotypic ratio in F2 progeny of dihybrid crosses
indicates dominant epistasis