Week 8 Test Answers

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Cystic fibrosis is a genetic disorder. It is a recessive trait that is determined by two alleles. Suppose two parents each carry at least one recessive allele, but neither of them has cystic fibrosis. Which statement reflects the likelihood of a child of these parents having cystic fibrosis?

The child cannot have the disease because only the dominant alleles will be passed on.

The child will have the disease because only recessive alleles will be passed on.

The child may or may not have the disease because a recessive gene from each parent may be passed on.

The child may or may not have the disease because the disease does not depend on the alleles of the parents.

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Which scenario breaks the law of segregation?

a gamete contains the father’s allele

the gametes produced each have 1 allele after meiosis II

a gamete produced has 2 of the same alleles after meiosis II

the gamete fertilized has the dominant trait

Which best describes a gene?

the short arm of a chromosome

tightly coiled strands of DNA

the center of a chromosome

a segment of chromosomal DNA

Some flowering plants appear to have offspring that have traits that are intermediate between those of the parents. Which type of dominance is exhibited by the offspring?

complete dominance

blended dominance

codominance

incomplete dominance

The diagram represents a dihybrid cross between two pea plants heterozygous for both seed color and seed shape.What is the phenotypic ratio of the offspring?

1:1:1:1:2:2:2:2:4

1:3:3:9

1:4

4:12

A cross is performed between a bird that is homozygous for red feathers and a bird that is homozygous for blue feathers. Purple offspring result due to incomplete dominance. Then, two of the purple offspring are crossed. What proportion of the offspring from the second cross will be purple?

1 in 4

2 in 4

3 in 4

4 in 4

A plant that has round and yellow seeds (RrYy) is crossed with a plant that has round and yellow seeds (RrYy). What is the ratio of the offspring that will have round and yellow seeds?Key: R = round r = wrinkled Y = yellow y = green

1:16

3:16

8:16

9:16

Mendel’s pea plants had either purple or white flowers. This means that the plants

can self-pollinate.

have two recessive traits.

have two alleles for the gene.

have two copies of a gene from one parent.

Parents with the genotypes AO and AB have a child. What are all the possible blood types of the child?

A, B

O, AB

A, AB, B

O, AB, A

Which blood type could be given as a transfusion for patient with AB blood when the RH factor is unknown?

O+

A+

AB+

AB–

Which are different forms of the same gene?

genotypes

phenotypes

alleles

traits

Mendel was able to study seven traits in all the pea plants in each generation. Which of his hypotheses allowed him to analyze each trait separately?

If two different alleles for a gene occur together, one of the alleles may be expressed while the other is hidden.

When gametes are formed, each gamete carries only one allele for the gene.

There are alternate versions of a alleles called genes.

For each inherited trait, there is only one copy of the gene that codes for that trait.

If Mendel had crossed a true breeding dominant plant with a true breeding recessive plant, in which of the three generations is the recessive trait visible?

F1 generation only

P generation only

F1 generation and F2 generation

P generation and F2 generation

What does a karyotype show?

genetic abnormalities

relationships among family members

carriers of a genetic disorder in a family

alleles on each chromosome

Which diagram correctly shows how homozygous alleles are found on homologous chromosomes?

A chromosome is labeled Upper A a.