AP Bio 15/01/26 Quiz

Nucleotide

The basic building block of DNA and RNA, composed of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Chromosome

A structure composed of DNA and protein that contains genetic information; prokaryotes typically have circular chromosomes, while eukaryotes have linear chromosomes.

Plasmid

A small, circular piece of DNA that can replicate independently of chromosomal DNA, commonly found in prokaryotes.

Histone Protein

Proteins that help package DNA into a compact, organized structure called chromatin.

Nucleosome

A structural unit of eukaryotic chromatin consisting of a segment of DNA wound around a core of histone proteins.

Antiparallel Strands

Describes the orientation of the two strands of DNA, where one strand runs in the 5' to 3' direction and the other runs in the 3' to 5' direction.

DNA Replication

The process by which a cell duplicates its DNA prior to cell division.

Helicase

An enzyme that unwinds the DNA double helix by breaking hydrogen bonds between the two strands.

Okazaki Fragments

Short, discontinuous segments of DNA synthesized on the lagging strand during DNA replication.

Ligase

An enzyme that connects the sugar-phosphate backbone of DNA fragments by forming phosphodiester bonds.

Semiconservative Replication

The mechanism of DNA replication where each new DNA molecule consists of one original strand and one newly synthesized strand.

Base Pairing Rules

The rules that dictate the pairing of nitrogenous bases in DNA: Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

Exonucleases

Enzymes that remove RNA primers from the newly synthesized DNA strand during replication.

Topoisomerase

An enzyme that alleviates the tension created by the unwinding of DNA, preventing supercoiling.

Leading Strand

The DNA strand that is synthesized continuously towards the replication fork during DNA replication.

Lagging Strand

The DNA strand that is synthesized discontinuously away from the replication fork, characterized by Okazaki fragments.

RNA Primer

A short segment of RNA synthesized by primase that provides a starting point for DNA polymerase during DNA replication.

Meiosis

A process that results in the formation of gametes (eggs/sperm) and ensures genetic diversity through processes like crossing over and independent assortment.

Gametes

Haploid cells (eggs/sperm) that combine to form a zygote.

Diploid

Cells that contain two complete sets of chromosomes, one from each parent (2n).

Haploid

Cells that contain one complete set of chromosomes (1n).

Homologous Chromosomes

Chromosomes that are the same length, with the same genes in the same position, but may have different alleles.

Crossing Over

The exchange of genetic material between homologous chromosomes during Prophase I of meiosis, creating recombinant chromosomes.

Independent Assortment

The random alignment of homologous chromosome pairs during Metaphase I, contributing to genetic diversity.

Aneuploidy

An abnormal number of chromosomes resulting from nondisjunction during meiosis.

Nondisjunction

Errors in chromosome separation during meiosis that can result in gametes with abnormal chromosome numbers.

Trisomy

A condition where an individual has three copies of a chromosome instead of the normal two.

Monosomy

A condition where an individual has only one copy of a chromosome instead of the normal two.

Phenotypic Effects

The observable effects on an organism caused by changes in chromosome number or structure.

Zygote

The fertilized egg formed by the union of male (sperm) and female (egg) gametes.

Erwin Chargaff investigated the nucleotide composition of DNADNA. He analyzed DNADNA from various organisms and measured the relative amounts of adenine (AA), guanine (GG), cytosine (CC), and thymine (TT) present in the DNADNA of each organism. Table 1 contains a selected data set of his results.

Table 1. Nucleotide composition of sample DNADNA from selected organisms

Which of the following statements best explains the data set?

A

Since the %A%A and the %G%G add up to approximately 50 percent in each sample, adenine and guanine molecules must pair up in a double-stranded DNADNA molecule.

B

Since the %A%A and the %T%T are approximately the same in each sample, adenine and thymine molecules must pair up in a double-stranded DNADNA molecule.

C

Since the %(A+T)%(A+T) is greater than the %(G+C)%(G+C) in each sample, DNADNA molecules must have a poly-AA tail at one end.

D

Since the %C%C and the %T%T add up to approximately 50 percent in each sample, cytosine and thymine molecules must both contain a single ring.

B

Since the %A%A and the %T%T are approximately the same in each sample, adenine and thymine molecules must pair up in a double-stranded DNADNA molecule.

A model of a process involving nucleic acids is shown in Figure 1.

Figure 1. Model of a process involving nucleic acids

Which of the following best explains what process is represented in Figure 1 ?

A

New DNADNA strands are being synthesized in the 3'3′ to 5'5′ direction from their DNADNA templates.

B

New DNADNA strands are being synthesized in the 5'5′ to 3'3′ direction from their DNADNA templates.

C

A new RNARNA strand is being synthesized in the 3'3′ to 5'5′ end from its DNADNA template.

D

Two new RNARNA strands are being synthesized in both directions from their DNADNA templates.

B

New DNADNA strands are being synthesized in the 5'5′ to 3'3′ direction from their DNADNA templates.

Figure 1 shows some relevant details of a model of how a deoxynucleotide, in this case dTMPdTMP, is added to a growing strand of DNADNA.

Figure 1. Model showing details of adding a deoxythymidine monophosphate (dTMPdTMP) nucleotide to a growing strand of DNADNA

The features of this model provide evidence for which explanation of why all growing strands are synthesized in a 5′5′ to 3′3′ direction?

A

The two strands need to be antiparallel to bond properly.

B

Thymine and adenine would not bond properly if the strand grew from 3′3′ to 5′5′.

C

The translation of mRNAmRNA occurs in the 5′5′ to 3′3′ direction; therefore, the growing DNADNA strand must also grow in the 5′5′ to 3′3′ direction.

D

The phosphate group, attached to the 5′5′ carbon of the dTMPdTMP, forms a covalent bond with the oxygen atom attached to the 3′3′ carbon of the growing strand.

D

The phosphate group, attached to the 5′5′ carbon of the dTMPdTMP, forms a covalent bond with the oxygen atom attached to the 3′3′ carbon of the growing strand.

Which of the following correctly explains where DNA replication will begin on the strand oriented 5'→3', reading from left to right?

A

DNA replication will be randomly initiated along the unwound portion of the DNA strand since base pairing will occur.

B

DNA replication cannot occur since there is already RNA base pairing with the template strand.

C

DNA replication will be initiated immediately to the left of the RNA, since DNA polymerase requires an RNA primer.

D

DNA replication will be initiated at the site of the topoisomerase since that is where DNA begins to uncoil.

C

DNA replication will be initiated immediately to the left of the RNA, since DNA polymerase requires an RNA primer.

Antibiotics can be used to kill the specific pathogenic bacterium, Mycobacterium tuberculosis, that causes tuberculosis. The appearance of antibiotic-resistant strains has made it more difficult to cure M. tuberculosis infections. These antibiotic-resistant bacteria survive and pass on the genes to their offspring, making the resistant phenotype more common in the population.

DNA analysis indicates that the genes for antibiotic resistance are not normally present in bacterial chromosomal DNA.

Which of the following statements best explains how the genes for antibiotic resistance can be transmitted between bacteria without the exchange of bacterial chromosomal DNA?

A

The antibiotic-resistant bacteria release a hormone that signals neighboring bacteria to become resistant.

B

The genes for antibiotic resistance are located on a plasmid that can be passed to neighboring bacteria.

C

The antibiotic-resistant bacteria are the result of bacteria that specifically modify their own chromosomal DNA to neutralize the antibiotics.

D

The antibiotic alters the bacterial genome of each bacterium, which results in an antibiotic-resistant population.

B

The genes for antibiotic resistance are located on a plasmid that can be passed to neighboring bacteria.

Which of the following statements best explains the structure and importance of plasmids to prokaryotes?

A

Plasmids are circular, single-stranded RNA molecules that transfer information from the prokaryotic chromosome to the ribosomes during protein synthesis.

B

Plasmids are circular, double-stranded DNA molecules that provide genes that may aid in survival of the prokaryotic cell.

C

Plasmids are single-stranded DNA molecules, which are replicated from the prokaryotic chromosome, that prevent viral reproduction within the prokaryotic cell.

D

Plasmids are double-stranded RNA molecules that are transmitted by conjugation that enable other prokaryotic cells to acquire useful genes.

B

Plasmids are circular, double-stranded DNA molecules that provide genes that may aid in survival of the prokaryotic cell.

Which of the following best explains why ligase is required for DNA replication?

A

The lagging strand cannot be replicated continuously, and ligase is needed to join the fragments.

B

Ligase forms the hydrogen bonds between complementary bases in the two strands of DNA.

C

Ligase facilitates the binding of RNA polymerase to the promoter region.

D

Ligase enables the newly synthesized DNA to twist into a double helix.

A

The lagging strand cannot be replicated continuously, and ligase is needed to join the fragments.

Which of the following samples most likely contains a double-stranded RNA virus?

A

Sample 1

B

Sample 2

C

Sample 3

D

Sample 4

A

Sample 1

Within a forest ecosystem, there is a large amount of diversity among members of a warbler species. Of the following stages of meiosis illustrated for a typical cell, which contributes most to diversity among the warblers?

A anaphase 1

B anaphase 2

C prophase 1

D prophase 2

C prophase 1

The diploid number of chromosomes in the cell of a domesticated dog is 78. Which of the following options includes the correct number of chromosomes in a cell after each cellular process (G2 checkpoint, meiosis, and fertilization, respectively)?

A

After G2 Checkpoint (156)

AfterMeiosis (78)

AfterFertilization (39)

B

After G2 Checkpoint (78)

AfterMeiosis (39)

AfterFertilization (78)

C

After G2 Checkpoint (156)

AfterMeiosis (39)

AfterFertilization (78)

D

After G2 Checkpoint (78)

AfterMeiosis (78)

AfterFertilization (39)

B

After G2 Checkpoint (78)

AfterMeiosis (39)

AfterFertilization (78)

During prophase I replicated homologous chromosomes pair up and undergo synapsis. What testable question is generated regarding synapsis and genetic variability by Figure 1 ?

A

Is the distance between two gene loci related to crossover rate?

B

Does crossing over occur more often in some chromosomes than in others?

C

Is crossing over inhibited by methylation?

D

Is crossing over promoted by methylation?

A

Is the distance between two gene loci related to crossover rate?

Scientists have found that DNA methylation suppresses crossing-over in the fungus Ascobolus immersus. Which of the following questions is most appropriately raised by this specific observation?

A

Is the level of genetic variation in the gametes related to the amount of DNAmethylation observed?

B

Without crossing-over, will gametes be viable and be able to produce zygotes?

C

Does DNA methylation result in shorter chromosomes?

D

Is this species of fungus a diploid organism?

A

Is the level of genetic variation in the gametes related to the amount of DNAmethylation observed?

A model showing two possible arrangements of chromosomes during meiosis is shown in Figure 1.

Figure 1. Two possible arrangements of chromosomes during meiosis

Which of the following questions about genetic diversity could most appropriately be answered by analysis of the model in Figure 1 ?

A

Does crossing-over generate more genetic diversity than the fusion of gametes does?

B

Does DNA methylation prevent independent assortment during metaphase II?

C

How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity?

D

Do daughter cells that are not genetically identical to parent cells produce viable zygotes?

C

How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity?

Table 1 shows the stage and number of cells and chromosomes per cell at the end of the stage in a 2n=24 organism.

Which of the following statements correctly describes the chromosomes in each daughter cell at the end of meiosis I?

A

Each daughter cell contains 12 chromatids. Each chromatid is one of two from a single chromosome with the other one of the pair found in the other daughter cell.

B

Each daughter cell contains 12 chromosomes, each composed of two chromatids. Since the chromosomes were randomly divided, one daughter cell may contain both of a pair of homologous chromosomes, while the other cell contains both of another pair of homologous chromosomes.

C

Each daughter cell contains 12 chromosomes, each composed of two chromatids. Each chromosome is one of a pair of homologous chromosomes from the parent cell, with the other homologue found in the other daughter cell.

D

Each daughter cell contains 24 separate chromatids. Since every two chromatids were originally joined, forming one homologous chromosome, the number of chromatids is divided by two to determine the number of chromosomes.

C

Each daughter cell contains 12 chromosomes, each composed of two chromatids. Each chromosome is one of a pair of homologous chromosomes from the parent cell, with the other homologue found in the other daughter cell.

Both mitosis and meiosis begin with a parent cell that is diploid. Which of the following best describes how mitosis and meiosis result in daughter cells with different numbers of chromosomes?

A

In mitosis, the chromosomes consist of a single chromatid, which is passed to two haploid daughter cells. In meiosis, the chromosomes consist of two chromatids during the first round of division and one chromatid during the second round of division, resulting in two haploid daughter cells.

B

In mitosis, synapsis of homologous chromosomes results in four haploid daughter cells after one division. In meiosis, synapsis of homologous chromosomes occurs during the second division and results in four diploid daughter cells.

C

Mitosis produces one identical daughter cell after one round of division. Meiosis has two rounds of division and doubles the number of chromosomes in the second round of division, producing four diploid cells.

D

Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.

D

Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.

Which of the following best explains why triploid bananas do not produce seeds?

A

The cells of the banana plant are unable to replicate DNA, thus preventing cell division and limiting growth.

B

The banana plants lack enough genetic diversity to properly hybridize.

C

The production of gametes is disrupted because of unequal pairing of homologous chromosomes during meiosis.

D

The production of seeds is not required because triploid plants produce gametes without fertilization.

C

The production of gametes is disrupted because of unequal pairing of homologous chromosomes during meiosis.

Saccharomyces cerevisiae is a diploid yeast species that can reproduce either sexually or asexually. An experiment was performed to induce mitotically dividing S. cerevisiae cells in G2 to undergo meiosis. Which of the following best describes the steps these cells will follow to form gametes?

A

The first division will result in crossing over between homologous chromosomes, and the second division will reduce the original number of chromosomes by half in the daughter cells.

B

The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will result in each daughter cell having one-fourth of the original number of chromosomes.

C

The first division will move single chromatids to each daughter cell, and the second division will double the number of chromosomes in each daughter cell.

D

The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.

D

The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.

Stages of Mitosis

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Stages of Meiosis

Meiosis 1

Prophase 1 - crossing over

Metaphase 1

Anaphase 1

Telophase 1

Meisosis 2

Prophase 1

Metaphase 2

Anaphase 2

Telophase 2