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BIOL 1105 > 16: Inheritance of Genetic Information I > Flashcards

16: Inheritance of Genetic Information I Flashcards

Module 3, Lesson 5

1
Q

The first detailed experiments on genetic inheritance were performed by…

A

Gregor Mendel

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2
Q

Mendel’s experiments used ____ plants.

A

Pea

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3
Q

List three reasons why Mendel used pea plants for his experiments.

A
  1. They have multiple traits
  2. They are small and easy to grow
  3. They can either cross-fertilize or self-fertilize
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4
Q

Why was it important that pea plants can either cross-fertilize or self-fertilize?

A

This enables plant mating to be closely controlled

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5
Q

Mendel’s initial experiments used the ____ experimental design.

A

Monohybrid cross

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6
Q

Mendel’s ____ exhibited true-breeding strains of two variations of interest.

A

Parent variation

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7
Q

In order for a parent to be “true-breeding”, all its offspring must…

A

Exhibit the trait of interest

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8
Q

Mendel’s ____ were created by cross-fertilizing the true-breeding parents.

A

F1 generation

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9
Q

What percentage of the F1 generation exhibited the dominant trait (purple flowers)?

A

100%

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10
Q

Mendel’s ____ was created by self-fertilizing the F1 plants.

A

F2 generation

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11
Q

True or false:

All of the F2 plants exhibited the dominant trait (purple flowers).

A

False

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12
Q

What percentage of the F2 plants exhibited the dominant trait?

A

75%

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13
Q

What percentage of the F2 plants exhibited the recessive trait (white flowers)?

A

25%

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14
Q

Mendel’s ____ were created by self-fertilizing the F2 plants.

A

F3 generation

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15
Q

True or false:

The F2 and F3 generations had the same ratio of dominant-to-recessive phenotypes.

A

True

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16
Q

What percentage of the recessive F2 plants were true-breeding?

A

100%

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17
Q

What percentage of the dominant F2 plants were true-breeding?

A

33%
(one-third)

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18
Q

What percentage of the F2 plants were not true-breeding?

A

66%
(two-thirds)

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19
Q

The F2 plants had a phenotype ratio of 3:1 but a genotype ratio of…

A

1:2:1
(one true-breeding dominant,
two not true-breeding dominant,
one true-breeding recessive)

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20
Q

Today, we call the “true-breeding” plants…

A

Homozygous

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21
Q

Today, we call the “not true-breeding” plants…

A

Heterozygous

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22
Q

List the two main conclusions Mendel came to from his initial experiments.

A
  1. Parents transmit discrete factors to their offspring
  2. A gene may have different variations called alleles
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23
Q

We now know that the “discrete factors” Mendel identified are…

A

Genes

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24
Q

An organism with two copies of the same allele is…

A

Homozygous

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25
Q

An organism with one copy of the dominant allele and one copy of the recessive allele is…

A

Heterozygous

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26
Q

The total set of alleles an organism contains make up its…

A

Genotype

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27
Q

An organism’s physical appearance is its…

A

Phenotype

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28
Q

True or false:

Two organisms with different genotypes can have the same phenotype.

A

True

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29
Q

The principle of segregation states that…

A

Each individual receives one copy of each allele from each parent because the chromosomes segregate during meiosis

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30
Q

True or false:

Mendel knew about chromosomes and meiosis when he developed his theories.

A

False

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31
Q

When writing a Punnett square, a capital letter (“P”) represents a ____ allele.

A

Dominant

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32
Q

When writing a Punnett square, a small letter (“p”) represents a ____ allele.

A

Recessive

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33
Q

True or false:

The offspring of homozygous parents will always be heterozygous.

A

True
Each parent can only give its offspring one kind of allele.

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34
Q

Each parent donates ____ allele(s) to each individual in the new generation.

A

One

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35
Q

Each box of a Punnett square shows the offspring’s…

A

Genotype

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36
Q

The left and top edges of a Punnett square represent…

A

Haploid parent cells

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37
Q

The boxes in a Punnett square represent the…

A

Diploid offspring cells

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38
Q

List the possible genotypes of offspring of parents whose genotypes are both Pp.

A

One PP
Two Pp
One pp

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39
Q

A ____ experimental design follows the behavior of two different traits in a single cross.

A

Dihybrid cross

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40
Q

What question was Mendel aiming to answer with his dihybrid cross experiments?

A

Do different traits behave independently in hybrids?

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41
Q

Organisms that are doubly heterozygous (heterozygous for two different traits) are called…

A

Dihybrid

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42
Q

Mendel’s dihybrid parent generation was ____ for both traits.

A

Homozygous

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43
Q

Which two traits was Mendel observing in his dihybrid cross experiments?

A

The shape and color of pea plants’ seeds

44
Q

Mendel’s dihybrid ____ generation were doubly heterozygous.

A

F1

45
Q

What percentage of Mendel’s dihybrid F1 plants had seeds that were yellow and round?

A

100%

46
Q

If each trait behaves independently during a dihybrid cross experiment, ____ different types of gametes should be produced.

A

Four

47
Q

Plants in Mendel’s dihybrid ____ generation had one of ____ possible phenotypes.

A

Four

48
Q

What was the ratio of phenotypes in Mendel’s dihybrid F2 plants?

A

9:3:3:1

49
Q

What fraction of F2 dihybrid plants had round and yellow seeds?

A

9/16

50
Q

What fraction of F2 dihybrid plants had round and green seeds?

A

3/16

51
Q

What fraction of F2 dihybrid plants had wrinkled and yellow seeds?

A

3/16

52
Q

What fraction of F2 dihybrid plants had wrinkled and green seeds?

A

1/16

53
Q

The results of Mendel’s dihybrid cross experiments ____ the idea that each allele behaved independently.

A

Supported

54
Q

The principle of independent assortment states that…

A

The segregation of different allele pairs is independent

55
Q

Why is the segregation of allele pairs independent?

A

Different homologous chromosomes align independently during metaphase 1 of meiosis.

56
Q

In humans, it is often more practical to use ____ instead of Punnett squares.

A

Pedigrees

57
Q

List three reasons why pedigrees are often more practical than Punnett squares for humans.

A
  1. Humans tend to have fewer offspring
  2. Humans are highly selective about mate choices
  3. Most of our knowledge of human genetics depends on analyzing family histories
58
Q

A ____ is a graphical representation of mating history over several generations.

A

Pedigree

59
Q

Each individual in a pedigree is represented by a…

A

Shape

60
Q

On a pedigree, biological males are indicated by ____ and biological females are indicated by ____.

A

Squares ; circles

61
Q

On a pedigree, a single horizontal line indicates…

A

Mating

62
Q

On a pedigree, a vertical line indicates…

A

Two individuals’ offspring

63
Q

On a pedigree, shaded shapes represent…

A

Affected individuals
(show the phenotype of the trait)

64
Q

On a pedigree, unshaded shapes represent…

A

Unaffected individuals

65
Q

A dominant pedigree tracks…

A

A dominant allele

66
Q

True or false:

The expression of dominant alleles may skip generations.

A

False

67
Q

True or false:

Parents who are both affected by a dominant allele can have unaffected offspring.

A

True

68
Q

Dominant pedigrees can be used to predict…

A

The genotypes and phenotypes of future offspring

69
Q

A recessive pedigree tracks…

A

A recessive allele

70
Q

On a pedigree, a double horizontal line represents…

A

Mating between related individuals

71
Q

On a recessive pedigree, a half-shaded shape indicates…

A

A heterozygous carrier

72
Q

In order to be affected by a recessive allele, an individual must be…

A

Homozygous recessive

73
Q

True or false:

Parents who are affected by a recessive allele can have offspring who are unaffected.

A

False

74
Q

True or false:

The expression of recessive traits can skip generations.

A

True

75
Q

In order to express a recessive trait, an individual must inherit the recessive allele from ____ parent(s).

A

Both

76
Q

Affected offspring become more frequent when…

A

The parents are related

77
Q

List the three assumptions that must be true for Mendel’s original model to work.

A
  1. Each trait is controlled by a single gene
  2. Each gene has only 2 possible alleles
  3. A clear dominant-recessive relationship exists between the alleles
78
Q

True or false:

Most human genes can be explained using Mendel’s model.

A

False

79
Q

True or false:

There may be more than two alleles for a gene in a population.

A

True

80
Q

Human ABO blood typing is an example of both ____ and ____.

A

Multiple alleles and co-dominance

81
Q

Which allele(s) for expressing antigens on the surface of red blood cells are dominant?

A

A and B

82
Q

Which allele(s) for expressing antigens on the surface of red blood cells are recessive.

A

O (denoted i)

83
Q

How many different genotypes are there for human ABO blood types?

A

Six
(AA, Ai, BB, Bi, AB, ii)

84
Q

How many different phenotypes are there for human ABO blood type?

A

Four
(A, B, AB, and O)

85
Q

Type ____ blood has no sugars on the outside of blood cells.

A

O
(ii)

86
Q

Type ____ blood has two types of sugars on the surface of the red blood cells.

A

AB
(both A and B sugars present)

87
Q

Type AB blood is an example of…

A

Codominance

88
Q

The dominant allele for the Rhesus factor…

A

Codes for surface proteins on red blood cells

89
Q

The recessive allele for the Rhesus factor…

A

Does not code for any surface proteins on red blood cells

90
Q

A “positive” blood type is a result of expressing the ____ Rh allele.

A

Dominant

91
Q

____ occurs when multiple genes control the expression of a single trait.

A

Polygenic inheritance

92
Q

In a population, traits controlled by polygenic inheritance usually…

A

Show continuous variation and a normal distribution over a range

93
Q

Human height is an example of…

A

Polygenic inheritance

94
Q

True or false:

Polygenic traits can be affected by an individual’s behavior and environment.

A

True

95
Q

Traits that use polygenic inheritance are also sometimes called…

A

Quantitative traits

96
Q

____ occurs when a single gene affects multiple phenotypes.

A

Pleiotropy

97
Q

List two reasons why the affects of pleiotropy can be difficult to predict.

A
  1. The gene often affects other unknown traits
  2. The allele may be dominant with respect to one trait but recessive with respect to another
98
Q

Cystic fibrosis is an example of…

A

Pleiotropy

99
Q

____ occurs when a heterozygous phenotype is an intermediate form of the homozygous phenotypes.

A

Incomplete dominance

100
Q

A cross between red and white flowers that produces pink flowers is an example of…

A

Incomplete dominance

101
Q

____ occurs when a heterozygote shows aspects of both homozygous phenotypes.

A

Codominance

102
Q

True or false:

Mendel’s model assumed that the products of genes do not interact.

A

True

103
Q

____ occurs when genes that code for different traits show some form of dependence at the level of function.

A

Epistasis

104
Q

What happens to a dihybrid cross if the two alleles are involved in/affect the same pathway?

A

The expected ratio of phenotypes changes

105
Q

____ occurs when the expression of one gene is in some way controlled, altered, or dependent on the expression of another.

A

Epistasis

106
Q

True or false:

Phenotypes can be influenced by the environment.

A

True

107
Q

Why is a Siamese cat’s head and torso white while its extremities are dark?

A

The protein that affects coat color is heat-sensitive and is only active in the cooler extremities.

BIOL 1105 (22 decks)

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