Biology Answers Genetics

1 of 20

AABB x AAbb represents a

Dihybrid cross.

Homozygous condition.

Monohybrid cross.

Heterozygous condition.

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2 of 20

What is the condition called when an expressed trait is somewhere between homozygous dominant and homozygous recessive?

Heterozygous

Incomplete Recessive

Incomplete Dominance

Incompletely Heterozygous

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3 of 20

Which of the following refers to the genetic make-up of an individual?

Phenotype

Allele

Genotype

Parental generation

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4 of 20

Which of the following examples illustrates pleiotropy?

In fruit flies, the genes for scarlet eyes and hairy body are located on the same chromosome.

The human cystic firbrosis gene causes many symptoms, from respiratory distress to digestive problems.

Matings between earless sheep and long-eared sheep always result in short-eared sheep.

Wheat kernels can range from white to red in color, a trait controlled by several genes.

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5 of 20

A true-breeding plant that produces yellow seeds is crossed with a true-breeding plant that produces green seeds. The F1 plants have yellow seeds. What is the expected phenotypic ratio of seed color of the offspring of an F1 × F1 cross?

1:2:1

2:1

3:1

9:3:3:1

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6 of 20

A brown mouse is mated with a white mouse. All of their offspring are brown. If two brown offspring are mated, what fraction of their offspring will be white?

All

None

one-half

one-fourth

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7 of 20

Mendel crossed true-breeding purple-flowered plants with true-breeding white-flowered plants, and all of the resulting offspring produced purple flowers. The allele for purple flowers is

segregated.

monohybrid.

dominant.

recessive.

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8 of 20

Kelly is blood group AB, Jacob is blood group B, and their daughter is blood group B. Given this information, it would be impossible for the couple to have a child with which of the following blood groups?

O

A

B

AB

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9 of 20

Attached earlobes are recessive to free earlobes. What is the probability of having a child with attached earlobes when an individual with attached earlobes mates with an individual heterozygous for free earlobes?

0%

25%

50%

100%

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10 of 20

Which of the following human genetic disorders is sex-linked?

PKU

Hemophilia

Cystic fibrosis

All of the above

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11 of 20

In humans, the presence or absence of dimples is a trait controlled by a single gene. What is the genotype of an individual who is heterozygous for dimples?

DD

dd

DI

Dd

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12 of 20

Mendel made some crosses where he looked at two characteristics at once: round yellow peas crossed with wrinkled green peas, for example. He did this because he wanted to find out

whether different characters were inherited together or separately.

how plants and animals adapt to their environments.

how new characters originated.

whether the characters influence each other; for example, whether color affects degree of roundness.

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13 of 20

An individual with the genotype AaBb produces four different gametes in equal proportions. This is a demonstration of

linkage.

Mendel's law of independent assortment.

Mendel's principle of segregation.

crossing over.

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14 of 20

Most sex-linked traits in humans are carried on the ________ chromosome, and the recessive phenotypes are seen most often in __________.

X; women

X; men

Y; women

Y; men

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15 of 20

Chromosomes that are not sex chromosomes are called

centrosomes.

allosomes.

dominant.

autosomes.

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16 of 20

A pea plant with purple flowers is heterozygous for flower color. Its genotype is Pp. The P and p alleles in the pea plant's cells are located

at corresponding locations on homologous chromosomes.

on the X and Y chromosomes.

next to each other on the same chromosome.

at different locations on the same chromosome.

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17 of 20

Hypohosphatemia (vitamin D-resistant rickets) is inherited as a sex-linked dominant trait. The relevant gene is found on the X chromosome. What is the expected outcome of a cross between a homozygous recessive woman and a man with hypophosphatemia?

Fifty percent of their daughters and 50% of their sons exhibit hypophosphatemia.

Seventy-five percent of their offspring exhibit hypophosphatemia.

All of their daughters and none of their sons exhibit hypophosphatemia.

All of their sons and none of their daughters exhibit hypophosphatemia.

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18 of 20

When looking at the inheritance of a single character, Mendel found that a cross between two true-breeding peas (between purple and white, for example) always yielded a ______ in the F2 generation.

1:1 phenotypic ratio

3:1 genotypic ratio

1:1 genotypic ratio

3:1 phenotypic ratio

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19 of 20

Which genotype would result in an individual with the recessive phenotype?

aa only

Aa only

Aa or aa

AA only

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20 of 20

How many different types of gametes can be generated by an individual with genotype AaBB?

1

2

4

8

Answers