BLY 121 Test 3 Study

An experiment in DNA editing using CRISPR is carried out in which the editing template DNA contains a G-A mismatch in the region to be edited. At the same nucleotide site in the resulting edited targeted DNA, the base pair is expected to be:

C-T

Which of Mendel's findings is not applicable when predicting the results of crosses involving genes that are closely linked?

the law of independent assortment

A genotype is:

the particular combination of alleles present in a given organism.

Reciprocal translocations can affect gene dosage because:

the two chromosomes involved in the translocation may not assort together during meiosis.

Consider an X-linked restriction-fragment length polymorphism with alleles A1, A2, and A3. In the mating A1/A3 female × A2, male, what are the possible genotypes of the daughters? (Select all that apply.)

-A1/A2 -A2/A3

The most frequent kind of mutation, a point mutation, occurs when: (Select all that apply.)

-DNA repair mechanisms fail. -a single base pair is replaced by another.

In what ways do human X and Y chromosomes differ from one another? (Select all that apply.)

-The X chromosome has about 1000 genes and the Y chromosome only about 50. -The X chromosome is larger than the Y chromosome.

Copy-number variation (CNV) can be produced by: (Select all that apply.)

-deletion. -duplication.

Polyploidy, which is widespread among plants, can arise from which of the following processes? (Select all that apply.)

-duplication of a complete set of chromosomes in a single species -hybridization between related species followed by duplication

Organisms that have been modified to contain DNA from other species are known as: (Select all that apply.)

-transgenic organisms. -genetically modified organisms (GMOs).

Flower color in snapdragons is due to a gene with incomplete dominance: CRCR plants have red flowers, CRCW have pink flowers, and CWCW plants have white flowers. What types and ratios of flower color are expected among the progeny of a cross of pink × white?

1 pink:1 white

Suppose that, in humans, ability to roll the tongue (R) is dominant to being unable to roll (r), and having freckles (F) is dominant to having no freckles (f). If a woman heterozygous for both traits married a man with no freckles who couldn't roll his tongue, what is the probability that they would have a freckled, tongue-rolling child?

1/4

A woman and a man are both heterozygous for a recessive allele for a rare genetic disease. If they have one child, what is the probability that he or she will be affected? If they have two children, what is the probability that at least one of them will be affected?

1/4, 7/16

In living organisms, on average, about one nucleotide in every _____ is mistakenly substituted for another during each round of DNA replication.

10 billion

According to Figure 14.2, the average number of new mutations that occur across an entire human genome in one generation is approximately _____ times higher than in nematodes.

100

DNA replication in human cells occurs at a rate of about 50 base pairs per second, and the length of the longest human chromosome (chromosome 1) is 249 Mb. If DNA replication took place continuously from one end of chromosome 1 to the other, it would take approximately:

2 months

In the F2 generation of a homozygous round (AA) × homozygous wrinkled (aa) cross in peas, two round seeds are chosen at random. What is the probability that one is AA and the other Aa?

2(2/3)(1/3)

Approximately what percentage of the human genome actually codes for proteins?

2.5%

How many pairs of chromosomes does the human genome normally have?

23

A new nucleotide can only be added to the _____ end of a growing DNA strand. DNA therefore always grows in the _____ direction.

3′; 5′ to 3′

The leading strand is the daughter strand that has its _____ end pointed toward the replication fork and is therefore synthesized _____.

3′; continuously

Imagine that blending inheritance was true, and black and white rabbits mated as in the example in the book. If the offspring show only half the intensity of black pigment after one generation, how many generations would be required for them to show 1/16th the intensity of black pigment?

4

Consider a normal human cell in which one chromosome undergoes nondisjunction in mitosis. What chromosome numbers would be found in the daughter cells?

45 and 47

The oligonucleotide primers used in the polymerase chain reaction are typically 20-30 nucleotides in length or longer; however, for purposes of this problem let's assume that 6 nucleotides is long enough. You wish to amplify the fragment shown below (the raised dots indicate several kilobases of DNA sequence not shown) and decide to design primers corresponding to the regions that are underlined. What primer sequences would you use? 5'-ATGCTGAAACTTCTC···GGGATGAAATCAGTTT-3' 3'-TACGACTTTGAAGAG···CCCTACTTTAGTCAAA-5'

5'-TGAAAC-3' and 5'-CTGATT-3'

The maximum frequency of recombination between two genes is:

50%

How many chromosomes are in a human cell that is triploid?

69

The human genome has 23 distinct types of chromosomes. How many individual DNA molecules would be present in the nucleus of a human skin cell just before mitosis?

92

Consider an A-T versus G-C single-nucleotide polymorphism (SNP) in the human genome. This means that the DNA molecules in the population at this site have which combinations of base pairs?

A-T or G-C

In replication of a linear double-stranded DNA molecule, one end of each strand becomes shorter in each round of replication. This happens because:

All of these choices are correct

The enzyme that catalyzes the addition of new nucleotides to a growing DNA strand is:

DNA polymerase.

The enzyme _____ repairs 99% of mismatched bases immediately during replication.

DNA polymerase

The enzyme responsible for proofreading a growing DNA strand and for replacing mismatched nucleotides is:

DNA polymerase.

The enzyme responsible for replacing RNA primers with DNA is a type of:

DNA polymerase.

To discover the location of a genetic mutation that causes disease in humans, scientists use genetic mapping. Specifically, they look for genetic markers, or previously discovered DNA polymorphisms, that show statistical association with the disease gene. The statistical association means that the:

DNA polymorphism and the disease gene are linked.

The MOST common syndrome resulting from nondisjunction is:

Down syndrome.

Which of the following BEST describes the development of sexual structures in mammals?

Embryos initially develop both male and female structures; once SRY becomes active, female structures degenerate and male structures continue to develop.

Which one of the following BEST describes genotype-by-environment interactions?

Genetic and environmental factors combine to influence phenotype.

For the majority of SNPs implicated in disease, how does carrying a copy affect a person's risk for acquiring that disease?

It increases it moderately.

On police procedural TV shows, the brilliant detective sometimes gets a DNA sample from a paper coffee cup that the suspect has touched. Is this fantasy made up for television, or is it scientifically sound?

It is possible and fairly easy.

A restriction-fragment length polymorphism at a site in the X chromosome has three alleles, A1, A2, and A3. The gel below is the DNA fingerprint for two prospective parents (Mo and Fa) as well as DNA types that may (or may not) correspond to their possible offspring. What are the possible phenotypes of sons from this mating?

K and Q

Mendel's experiments with garden peas differed from those of other plant hybridizers of the time in that:

Mendel studied true-breeding strains, focused on a small number of easily contrasted traits, and quantified results.

What is a single-nucleotide polymorphism?

None of the answer options is correct.

_____ mutations affect only the individual in which they occur; _____ mutations are passed from parent to offspring.

Somatic; germ-line

Figure 15.1 shows the three alleles for the beta-globin gene. Which of the following statements BEST describes the effect of having the S allele, which codes for sickle-cell anemia?

The effect depends on whether the allele occurs in its homozygous or heterozygous form, and the environment (i.e., whether malaria is present).

A reproductive cell, or gamete, has:

one allele of each gene.

Sequences of genomic DNA, and its corresponding messenger RNA (mRNA), are often compared to obtain valuable information for genome annotation. Why is this comparison useful?

The exclusion of introns in mRNA reveals the intron-exon structure of many protein coding genes.

Which statement BEST explains why embryos with a missing autosome are not always factored into statistics about spontaneously aborted fetuses?

The fetus is aborted before the pregnancy is recognized.

Which one of the following BEST describes why genome sequencing can be complicated by repeated sequences?

The repeated sequences are often longer than the sequences obtained by automated sequencing.

A photon of ultraviolet light hits double-stranded DNA and creates a covalent cross-link between adjacent thymines in the same strand (a thymine dimer). What is likely to happen?

The thymine dimer will be repaired by enzymes that break the cross-link.

Pairing of homologous chromosomes at metaphase of meiosis I appears to be critical for proper alignment, crossing over, and subsequent separation. This pairing is facilitated by sharing of sequence homology. If X and Y chromosomes are so different, how can they achieve the necessary pairing?

They share short homologies at their respective tips.

Would you consider the SNP associated with sickle-cell hemoglobin to be a risk factor for sickle-cell anemia?

Yes, because individuals homozygous for the SNP have the condition.

In crosses involving linked genes, recombinant offspring result from:

a crossover.

A family can share a genetic risk of developing cancer if:

a germ-line mutation in one of the genes implicated in the cancer occurred in an ancestor.

The Y-linked trait of hairy ears has been passed down for many generations in a certain family. A hairy eared male in this family should definitely have:

a paternal grandfather with hairy ears.

According to the phylogenetic tree showing evolutionary relationships among viruses in Figure 13.6 below, which one of the following is MOST closely related to the human lentivirus HIV2?

a simian lentivirus

Each DNA parent strand within a replication bubble acts as a template strand that produces:

one leading strand and one lagging strand.

A Y-chromosome haplotype is a set of Y-linked nucleotides that:

allow one Y chromosome to be distinguished from another.

The transformation step in creating bacteria genetically engineered to produce human proteins involves:

bacteria taking up the recombinant DNA in the form of the vectors.

According to Figure 13.8 below, which one of the following accurately lists the taxonomic groups in order of INCREASING genome size (i.e., from smallest to largest)?

bacteria, teleosts, mammals, salamanders

Insertions and deletions of single nucleotides:

cause frameshift mutations.

Chromosomal mutations that are MOST likely to cause serious damage to an organism are those that affect the:

centromere

Genes that are _____ do not assort independently and are said to be _____.

close to each other on the same chromosome; linked

Phenotypic variation among individuals is not always visible and can include which of the following trait characteristics?

developmental, physiological, and behavioral differences

You are examining a human pedigree for a trait. You notice that the trait appears in every generation; is equally likely to occur in males and females; and, when one parent is affected, about half of his or her offspring are affected. The trait is MOST likely:

dominant

One characteristic of restriction enzymes is that they cut:

double-stranded DNA strands at specific sites.

When one gene is able to modify the effect of a second gene, the phenomenon is known as:

epistasis

If you crossed a true-breeding yellow-seed plant (AA) with a heterozygous yellow-seed plant (Aa), offspring:

genotypes would be 1 AA:1 Aa.

Telomerase is fully active in _____ and _____ cells, but almost completely inactive in _____ cells.

germ; stem; somatic

Sometimes a single-stranded molecule of RNA is able to fold back on itself because the nucleotide sequence on one part of the RNA is complementary to another part. This sequence motif results in a:

hairpin-shaped structure.

Which one of the following is NOT found in a bacterial nucleoid?

histones

A testcross involves crossing with a(n) _____ individual and is used to determine the _____ of the tested parent.

homozygous recessive; genotype

Genes that are linked do not show:

independent assortment.

Chromosomes in which the normal order of a block of genes is reversed contain a(n):

inversion.

A trait with incomplete penetrance is one that:

is only expressed in some of the individuals that have the genotype for that trait.

A mutation with a deleterious effect on the function of a protein encoded by a human mitochondrial gene will be:

maternally inherited.

The polymerase chain reaction (PCR) is used to generate:

multiple copies of a targeted region of DNA.

In large genomes, MOST reciprocal translocations occur in:

noncoding DNA.

Which of the following processes would result in gametes that violate Mendel's principle of segregation?

nondisjunction

An X-linked ichthyosis is a recessive form of a family of skin diseases caused by a hereditary deficiency of the steroid sulfatase (STS) enzyme. A woman heterozygous for this mutation mates with the phenotypically normal man and produces an XXY son who suffers from the disorder. What kind of nondisjunction can explain this result?

nondisjunction in meiosis II in the mother

The failure of a pair of chromosomes to separate during anaphase is referred to as:

nondisjunction.

Point mutations that cause amino acid replacements are called:

nonsynonymous (missense) mutation.

An allele is:

one of several forms of a gene.

As a piece of linear DNA is replicated, the leading strand will have _____ RNA primer(s) and the lagging strand will have _____ RNA primer(s).

one; many

Which of these is necessary for only the FIRST step of PCR?

original template DNA

The substitution of one base pair for another in double-stranded DNA is called a(n):

point mutation.

When nonhomologous chromosomes exchange parts, a(n) _____ has occurred.

reciprocal translocation

The type of genetic engineering that often involves isolating genes from one species and introducing them into another is called _____ technology.

recombinant DNA

In a long DNA molecule, each origin of replication produces a _____ with a _____ on each side.

replication bubble; replication fork

What process can account for a normal XY male producing a sperm carrying two Y chromosomes?

second-division nondisjunction

The gel diagram below shows the bands obtained for a single variable number tandem repeat (VNTR) in evidence obtained at a crime scene (W) and genomic DNA from four suspects (A-D). Which suspect CANNOT be ruled out as the source of the DNA in the sample?

suspect C

A point mutation that causes no change in the amino acid sequence of a protein is called a:

synonymous (silent) mutation.

In DNA replication, each individual parent strand acts as a _____ strand for the synthesis of a _____ strand.

template; daughter

Genes that are close together in the same chromosome:

tend to be transmitted together.

Although a match between the DNA in a sample and the genomic DNA of a particular individual for a single variable number tandem repeat (VNTR) is not sufficient to establish identity, a mismatch is definitive. The primary reason is that:

the DNA in the sample must match its origin.

A phenotype is:

the expression of a trait in an individual.

Movable DNA sequences are called:

transposable elements.

In humans, one reason why mitochondrial inheritance is strikingly different from nuclear inheritance is that:

unlike nuclear inheritance, both parents do not contribute mitochondrial DNA.

Using PCR to amplify the same region of the genome from different individuals can identify differing lengths due to different numbers of repeated sequences referred to as:

variable number tandem repeats.

The statement that, in garden peas, yellow seed is dominant to green seed means that:

when a true-breeding yellow seed parent is crossed with a true-breeding green seed parent, all offspring will have yellow seeds.

Thomas Hunt Morgan crossed a white-eyed male with red-eyed females in a parental generation and then brother-sister mated the F1 offspring and examined their F2 progeny. Morgan observed all of the following in his crosses. Which of these observations is NOT expected of simple Mendelian inheritance of a recessive allele?

white eyes appeared only in males in the F2 generation