ch 9 practice quiz bio

The best definition of a true-breeding plant is one that ______.

self-fertilizes to produce offspring identical to the parent

A mating between a true-breeding purple-flowered pea plant and a true-breeding white-flowered pea plant would produce a(n) ______.

hybrid

Alleles are described as ______.

alternate versions of a gene

A true-breeding plant that produces yellow seeds is crossed with a true-breeding plant that produces green seeds. The seeds of all of the offspring are yellow. Why?

The yellow allele is dominant to the green allele.

The parents of a child with unusual disease symptoms take the child to a doctor for help. The doctor suspects that the condition might have a genetic basis. She recommends that the child be taken to a specialty clinic where physicians and staff members are trained to diagnose genetic diseases and counsel parents. Ultimately, the child is diagnosed with a rare recessively inherited disease. The parents are tested for the gene, and both are found to be heterozygous. The parents want to have another child but are afraid this child will also be affected.

What would genetic counselors say is the probability that the second child will have the disease?

1/4

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?

3:1

According to Mendel’s law of segregation, ______.

gametes have one copy of each allele

Attached earlobes are recessive to free earlobes. What genotypic ratio is expected when an individual with attached earlobes mates with an individual heterozygous for free earlobes?

1:1

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 ______.

dominant

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?

50%

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

An individual who is homozygous ______.

carries two copies of the same allele for a gene

Which of these crosses will only produce heterozygous offspring?

AA × aa

What name is given to the specific location of a gene on a chromosome?

locus

Round seeds () are dominant to wrinkled seeds (), and yellow seeds () are dominant to green seeds (). What is the expected phenotypic ratio of a cross between an RrYy and an rryy individual?

1:1:1:1

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

Mendel’s law of independent assortment

To determine the phenotype of an individual who expresses a dominant trait, you would cross that individual with an individual who ______.

is homozygous recessive for that trait

A couple has two female children. What is the probability that their next child will be male?

50%

In humans, free earlobes () are dominant to attached earlobes () and the presence of freckles () is dominant to the absence of freckles (). If an individual heterozygous for both of these traits were to mate with an individual with attached earlobes and no freckles, what is the probability of having a child with attached earlobes and freckles?
A. 100%

25%

The ______ is most commonly found in nature

wild-type trait

An individual heterozygous for cystic fibrosis ______.

is a carrier

Achondroplasia is a form of dwarfism caused by a dominant allele. The homozygous dominant genotype causes death, so individuals who have this condition are all heterozygotes. If a person with achondroplasia mates with a person who does not have achondroplasia, what percentage of their children would be expected to have achondroplasia?

50%

Which of the following techniques is used to collect fetal cells during pregnancy for genetic testing?

amniocentesis

What is the key to the recognition of incomplete dominance?

The phenotype of the heterozygote falls between the phenotypes of the homozygotes.

An individual with (naturally) curly hair and an individual with (naturally) straight hair mate; all of their offspring have (naturally) wavy hair. What is the relationship between the alleles for hair texture?

incomplete dominance

An individual with (naturally) curly hair and an individual with (naturally) straight hair mate; all of their offspring have (naturally) wavy hair. If an individual with wavy hair mates with an individual with straight hair, what is the probability that their child will have curly hair?

0%

What is the key to the recognition of codominance?

The heterozygote expresses the phenotype of both homozygotes.

An individual with the blood group genotype LMLN has the phenotype MN. What is the relationship between the LM and LN alleles?

Codominance

Marfan syndrome is the result of inheriting a single allele. Individuals with Marfan syndrome are tall and long-limbed, and have both cardiovascular and eye defects. The inheritance of Marfan syndrome is an example of ______.

pleiotropy

What is the key to the recognition of a trait whose expression is determined by the effects of two or more genes (polygenic inheritance)?

The trait varies along a continuum in the population.

In humans, the inheritance of ______ is best explained as being polygenic.

height

Many human traits, such as our performance on intelligence tests or our susceptibility to heart disease, are ______.

influenced by both genes and the environment

In the accompanying art you see a table with the actual number of offspring that resulted from a dihybrid cross. The numbers do not show the 9:3:3:1 ratio predicted. One phenotype occurred more than predicted; another occurred less. The reason could be because ______.

some of the alleles were linked

Recombinant offspring were produced by the mating shown in the accompanying art. What is the recombination frequency of purple round and red long offspring?

11%

______ genes violate Mendel’s principle of independent assortment.

Linked

What is the best explanation for a BbCc × bbcc cross producing offspring in a 5:5:1:1 phenotypic ratio?

linked genes

A dihybrid cross produces 30 recombinant offspring out of a total of 1,000 offspring. What is the recombination frequency of the two gene pairs?

3%

The recombination frequency between gene and gene is 11%. The recombination frequency between gene and gene is 5%. The recombination frequency between gene and gene is 15%. What would be the arrangement of these genes on a linkage map?

DBC

Chromosomes that are not sex chromosomes are called ______.

autosomes

Assume that having three nostrils is inherited as a sex-linked trait on the Y chromosome. A man with three nostrils has a daughter who has a son with a man who has only two nostrils. What is the probability that the three-nostriled man’s grandson has three nostrils?

0%

Red-green color blindness is inherited as a sex-linked recessive trait. The gene is found on the X chromosome. How can a man with normal color vision father a daughter who is red-green color-blind?

He can’t (unless there is a mutation).

Hypophosphatemia (vitamin D-resistant rickets) is inherited as an 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?

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

Widow’s peak, a pointed hairline on the forehead, is a genetic trait caused by a dominant allele. It can be traced back through a family’s history using pedigree analysis. The pedigree shown here shows three generations of a family. Notice that some individuals (shown in gray) have a widow’s peak (W = dominant allele and w = recessive allele

Mary has the genotype ______.

Ww

Janice’s genotype is _______.

WW or Ww

This pedigree supports the fact that widow’s peak is due to a dominant allele, because if it were due to a recessive allele and both parents show the recessive phenotype, then ______.

all of the offspring would have a widow’s peak