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BIO310 > Chapter 23 > Flashcards

Chapter 23 Flashcards

1
Q

When multiple phenotypes or genotypes exist in the population that can be considered “wild type,” what are they called?

A

Genetic polymorphisms

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2
Q

Are blue eyes and brown eyes considered genetic polymorphisms?

A

Yes

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3
Q

Are most loss-of-function alleles recessive or dominant?

A

Recessive

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4
Q

Are most gain-of-function alleles recessive or dominant?

A

Dominant

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5
Q

What term describes a gene where having less than two wild-type alleles results in a phenotype?

A

Haploinsufficient

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5
Q

What is an example of a dominant gain-of-function allele that can lead to cancer?

A

Oncogene

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6
Q

What is a dominant lethal allele?

A

An allele that allows a heterozygote to survive but prevents offspring from developing if they inherit two copies.

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7
Q

What phenotype ratio is associated with dominant lethal alleles in heterozygous crosses?

A

2:1

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8
Q

Name a disorder caused by a dominant lethal allele.

A

Huntington’s disease

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9
Q

If a green snake becomes more yellow in a cooler environment, what might explain this?

A

A temperature-sensitive mutation

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9
Q

What term describes a gene that is not always expressed due to environmental factors?

A

Incomplete penetrance

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10
Q

What type of dominance occurs when a heterozygote shows a blend of two phenotypes?

A

Incomplete dominance

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10
Q

In human blood type, which alleles are dominant to O?

A

A and B

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10
Q

What is the term for variation in the degree to which a phenotype is expressed?

A

Expressivity

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11
Q

What mechanisms allow identical DNA sequences to be expressed differently?

A

Epigenetic mechanisms (e.g., chromatin modifications or DNA methylation)

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12
Q

What are temperature-sensitive alleles?

A

Alleles that produce proteins prone to denaturing at certain temperatures.

13
Q

What animals are good examples of temperature-sensitive mutations affecting pigmentation?

A

Siamese cats and Himalayan rabbits

14
Q

What is the phenotype ratio in the offspring of two pink heterozygous snakes?

A

1 red: 2 pink: 1 white

15
Q

What is the default color when a pigment gene is knocked out?

A

White

15
Q

What type of dominance occurs when both phenotypes appear distinctly in a heterozygote?

A

Codominance

16
Q

In human blood type, which alleles are codominant to each other?

A

A and B

17
Q

If a blood cell expresses the B allele, can it also receive the A sugar?

A

No

18
Q

What genotypes result in an “A” blood type?

A

AA or AO

18
Q

Does the O allele add any sugars to red blood cell proteins?

A

No

19
Q

Will the immune system of someone with A blood type attack O blood cells?

A

No

20
Q

Will the immune system of someone with A blood type attack AB blood cells? Why?

A

Yes, because AB blood contains B antigens, which are foreign to them.

21
Q

In a pedigree showing a dominant trait, what must be true of affected individuals?

A

One parent and one child must have the phenotype.

22
Q

What blood type must a person with “AB” blood be?

A

Heterozygous for the blood type gene.

23
Q

In a colony of tailless mice, why is the allele for wild-type tails not a dominant lethal?

A

A dominant lethal would result in no surviving offspring with the wild-type phenotype.

24
Q

What is a genetic polymorphism?

A

It refers to the existence of multiple phenotypes or genotypes in a population that can be considered “wild type.”

25
Q

What does incomplete penetrance mean in genetics?

A

It means that a genetic disorder may not always be expressed, even if the genotype for it is present, due to environmental factors or other influences.

26
Q

What is expressivity in terms of genetics?

A

It refers to the degree to which a genotype is expressed in an organism, with some individuals showing more pronounced phenotypic traits than others, even with the same genotype.

27
Q

How can epigenetic mechanisms affect gene expression?

A

Epigenetic mechanisms, like chromatin modifications or DNA methylation, can lead to different levels of gene expression despite identical DNA sequences.

28
Q

What is a temperature-sensitive allele, and give an example.

A

A temperature-sensitive allele is one that produces a protein that can denature at certain temperatures, such as the pigmentation gene mutations in Siamese cats or Himalayan rabbits.

29
Q

If a snake changes color from green to yellow due to environmental temperature, what might this indicate?

A

This could indicate a temperature-sensitive mutation affecting the snake’s pigmentation.

30
Q

What type of genetic inheritance is demonstrated when a heterozygote expresses a phenotype that is a blend of both parental phenotypes?

A

Incomplete dominance

BIO310 (6 decks)

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