What fraction of offspring of the cross Aa ? Aa is homozygous for the dominant allele?

1/64
1/32
1/16
1/8
1/4

1/4
What fraction of the offspring of the cross AaBb ? AaBb would show the dominant phenotypes for both genes?

3/16
6/16
9/16
12/16
1/3

9/16
Suppose unattached earlobes are a dominant trait. Phil and Maggie both have unattached earlobes but their daughter, Celia, does not. If Phil and Maggie have a second child, what is the probability that he or she will have attached earlobes?

1/8
1/4
1/2
3/4
1

1/4
The cross AaBb ? AaBb is an example of a _______ cross; the results of such crosses led Mendel to propose what we now call the law of _______.

self; segregation of genes
dihybrid; segregation of genes
dihybrid; independent assortment
test; segregation of genes
test; independent assortment

dihybrid; independent assortment
In a test cross, peas of an unknown genotype are crossed with peas of a known genotype. In this example, smooth peas are the unknown and wrinkled peas are the known (rr). If half of the offspring from that cross are smooth and half are wrinkled, what is the genotype of the unknown plant?

Heterozygous: Rr
Homozygous dominant: RR
Homozygous recessive: rr
Homozygous dominant: rr
Homozygous recessive: RR

Heterozygous: Rr
The 9:3:3:1 ratio is obtained

through a dihybrid cross in which the genes are linked on the same chromosome.
through a dihybrid cross in which the genes are on different chromosomes.
when crossing over occurs.
in a test cross.
through codominance.

through a dihybrid cross in which the genes are on different chromosomes
_______ is the term for when heterozygous offspring have superior fitness than their homozygous parents.

Heterosis
Incomplete dominance
Codominance
Epistasis
Linkage

Heterosis
Codominance

occurs when heterozygotes show a phenotype intermediate between those of the
two homozygotes.
involves the expression of both alleles at a locus producing two different
phenotypes.
is only found in mammalian enzyme production.
involves one allele having more than one phenotypic effect.
would result in pink flowers from a cross between white and red flowers.

involves the expression of both alleles at a locus producing two different
phenotypes.
Incomplete dominance

results in a phenotypic ratio of 1:2:1 in the F2 generation from a monohybrid cross.
causes epistasis.
is the same as codominance.
involves the distinct expression of both alleles, as in the ABO blood group system.
occurs only in X-linked genes.

results in a phenotypic ratio of 1:2:1 in the F2 generation from a monohybrid cross.
A woman of blood group A has a child with a man of blood group B. The child’s blood is type O. What are the genotypes of the parents?

A) Mother: IAIA; father: IBIa
B) Mother: IAIO; father: IBIb
C) Mother: IAIO; father: IBIO
D) Mother: IAIB; father: IBIO
E) It is impossible for these individuals to have a child with type O blood.

C) Mother: IAIO; father: IBIO
Coat color in rabbits involves the effects of multiple gene interactions. If a rabbit has two recessive alleles (cc) for coat color, it is always albino no matter what the genotype of other genes involved in coat color. This is an example of

A) pleiotropy.
B) incomplete dominance.
C) codominance.
D) a hierarchy of dominance.
E) epistasis.

E) epistasis.
The fact that a trait such as height in humans varies over a wide range of values is due to

A) penetrance.
B) expressivity.
C) multiple alleles and the environmental influences on the expression of these genes.
D) epistasis.
E) discrete and qualitative genomic variation.

C) multiple alleles and the environmental influences on the expression of these genes.
When a true-breeding red flower is crossed with a white flower, and all the F1 flowers are pink, this is due to

A) epistasis.
B) crossing over.
C) a mutation.
D) codominance.
E) incomplete dominance.

E) incomplete dominance.
Which statement about linkage of genes is false?

A) Genes on the same chromosome are said to be linked.
B) Genes on the same chromosome assort independently.
C) Crossing over between two linked genes can alter phenotypes of progeny.
D) Crossing over results in recombinant phenotypes.
E) Genes on the same chromosome that are far apart have a higher recombination
frequency than those that are close together.

B) Genes on the same chromosome assort independently.
In many animals, including humans, sex is determined by a single _______, or by a pair of them. Both males and females have two copies of each of the rest of the chromosomes, which are called _______.

A) sex chromosome; autosomes
B) gene; autosomes
C) autosome; sex chromosomes
D) gene; sex chromosomes
E) allele; genes

A) sex chromosome; autosomes
In sex-linked inheritance of a recessive gene, if a normal male and a heterozygous female carrier mated, all

A) male offspring would show the trait.
B) female offspring would be carriers.
C) female offspring who receive the mutant X chromosome would show the trait.
D) male offspring who receive the mutant X chromosome would show the trait.
E) female offspring would not carry the trait.

D) male offspring who receive the mutant X chromosome would show the trait.
Wild-type fruit flies have red eyes. A white-eyed female fly is crossed with a red-eyed male fly. All of the females from the cross are red-eyed and all of the males are white-eyed. What type of inheritance pattern is this?
A) Independent assortment
B) Autosomal dominant
C) Autosomal recessive
D) Incomplete dominance
E) Sex-linked on X chromosome
E) Sex-linked on X chromosome
Genes located on mitochondrial DNA are usually inherited

A) randomly.
B) from the mother.
C) from the father.
D) evenly from both the mother and the father.
E) by independent assortment.

B) from the mother.
The pedigree below shows an inheritance pattern for congenital cataract, a mutant phenotype in humans. The black circles and black squares represent the individuals showing symptoms. What type of genetic disorder is this? (Has Picture)

A) Autosomal intermediate
B) Sex-linked recessive
C) Sex-linked dominant
D) Autosomal dominant
E) Autosomal recessive

D) Autosomal dominant
Lateral gene transfer between individuals of a species

A) does not occur in bacteria.
B) occurs by sexual reproduction in bacteria.
C) can result in bacterial strains resistant to antibiotics.
D) occurs only with plasmid DNA.
E) always involves recombination.

C) can result in bacterial strains resistant to antibiotics.
If adenine makes up 20 percent of the bases in a sample of double-stranded DNA, what percentage of the bases would be uracil?
A) 0
B) 10
C) 15
D) 20
E) 30
A) 0
If adenine makes up 20 percent of the bases in a sample of double-stranded DNA, what percentage of the bases would be cytosine?

A) 15
B) 30
C) 35
D) 40
E) 70

B) 30
A-T base pairs in a DNA double helix

A) are not accessible to DNA binding proteins.
B) form three hydrogen bonds with each other.
C) are of a different length than G-C base pairs.
D) are more heat stable than G-C base pairs.
E) are chemically distinct from G-C base pairs.

E) are chemically distinct from G-C base pairs.
Which statement about DNA structure is false?

A) The 3′ end is phosphorylated.
B) It is a double-stranded helix.
C) It has a uniform diameter.
D) It is a right-handed helix.
E) It is antiparallel (the two strands run in opposite directions).

A) The 3′ end is phosphorylated.
In many eukaryotes, there are repetitive sequences at the ends of chromosomes called telomeres. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand.

A) lagging; telomerase
B) leading; DNA polymerase
C) leading; DNA helicase
D) lagging; DNA polymerase
E) leading; telomerase

A) lagging; telomerase
In multicellular organisms

A) somatic mutations are passed on to offspring produced by sexual reproduction.
B) somatic mutations may be passed to daughter cells by mitosis.
C) all mutations produce phenotypic changes.
D) meiosis is not required for the transmission of germ line mutations to the next
generation.
E) all mutations are point mutations.

B) somatic mutations may be passed to daughter cells by mitosis.
A silent mutation
A) is the result of a change in a codon for an amino acid in a protein to a stop codon.
B) results in a shorter mRNA transcript of the gene.
C) results in a protein that is truncated from the N terminal end.
D) would likely not affect the activity of a protein.
E) would not affect the primary structure of a protein.
D) would likely not affect the activity of a protein
A point mutation
A) is a result of a chromosomal deletion.
B) is always silent.
C) does not occur in noncoding regions of DNA.
D) is a change in a single nucleotide of DNA.
E) is not transmitted to daughter cells.
D) is a change in a single nucleotide of DNA.
Watson and Crick’s model allowed them to visualize all of the following except
A) the molecular bonds of DNA.
B) the sugar and phosphate component of the DNA molecule’s surface.
C) how the purines and pyrimidines fit together in a double helix.
D) the antiparallel design of two strands of the DNA double helix.
E) that DNA replication was semiconservative.
E) that DNA replication was semiconservative
The primary function of DNA polymerase is to

A) add nucleotides to the growing daughter strand.
B) seal nicks along the sugar-phosphate backbone of the daughter strand.
C) unwind the parent DNA double helix.
D) generate primers to initiate DNA synthesis.
E) prevent reassociation of the denatured parental DNA strands.

A) add nucleotides to the growing daughter strand.
Proofreading and repair occur

A) at any time during or after synthesis of DNA.
B) only before mitosis.
C) only in the presence of DNA polymerase.
D) only after replication is complete.
E) only during replication.

A) at any time during or after synthesis of DNA
Which of the following statements about DNA replication is false?

A) Okazaki fragments are synthesized as part of the leading strand.
B) Replication forks represent areas of active DNA synthesis on the chromosomes.
C) Error rates for DNA replication are reduced by proofreading of the DNA
polymerase.
D) Ligases and polymerases function in the vicinity of replication forks.
E) The sliding clamp protein increases the rate of DNA synthesis.

A) Okazaki fragments are synthesized as part of the leading strand.
Which chemical will not cause an induced mutation?

A) Nitrous acid (HNO2)
B) Benzopyrene
C) Aflatoxin
D) Free radicals
E) Salt (NaCl)

E) Salt (NaCl)
A mutant strain of yeast grows well at 20°C, but not at 37°C, whereas the wild-type strain grows well at both temperatures. The mutation is an example of a _______ mutation.
A) conditional
B) silent
C) point
D) sensitive
E) gain-of-function
A) conditional
RNA primers are necessary in DNA synthesis because

A) DNA polymerase is unable to initiate replication without an origin.
B) the DNA polymerase enzyme can catalyze the addition of deoxyribonucleotides
only onto the 3′ (—OH) end of an existing strand.
C) RNA primase is the first enzyme in the replication complex.
D) primers mark the sites where helicase has to unwind the DNA.
E) they are the source of nucleotides for DNA polymerases.

B) the DNA polymerase enzyme can catalyze the addition of deoxyribonucleotides
only onto the 3′ (—OH) end of an existing strand.
Which statement about mutations is false?

A) Mutations are the raw material of evolution.
B) Lethal mutations can kill an organism during early development.
C) Mutations can be harmful if they result in the loss of functions of genes.
D) Somatic mutations either have no effect or are harmful to the organism.
E) Environmental change may alter whether a mutation is harmful or advantageous.

D) Somatic mutations either have no effect or are harmful to the organism.
The loss of a chromosomal segment is a(n)

A) deletion
B) inversion.
C) point mutation.
D) translocation.
E) duplication.

A) deletion
The cells at the base of your skin frequently divide. Based on this, you would expect these cells to

A) have high levels of telomerase.
B) have very low levels of telomerase.
C) undergo the polymerase chain reaction.
D) lack DNA polymerase.
E) lack Okazaki fragments.

A) have high levels of telomerase.
What is structure A?
(With Picture)

A) RNA polymerase
B) The lagging strand
C) The primer
D) An Okazaki fragment
E) A dNTP

C) The primer
Why do eukaryotes typically have multiple origins of replication while most prokaryotes typically have just one?
A) Eukaryotes are diploid, while prokaryotes are haploid.
B) Eukaryotes don’t have DNA helicase.
C) Eukaryotes have much larger genomes.
D) Eukaryotes have a less efficient DNA polymerase.
E) Eukaryotes don’t have Okazaki fragments.
C) Eukaryotes have much larger genomes.
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