AP Biology : Understanding Meiosis

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #31 : Understanding Meiosis

Human gametes are produced by the process of __________.

Possible Answers:

cytokinesis

mitosis

binary fission

meiosis

fertilization

Correct answer:

meiosis

Explanation:

Gametes are haploid cells that produced via meiosis. During meiosis, diploid cells divide into four nonidentical haploid daughter cells. Mitosis produces two identical diploid somatic cells from one parent cell.  

Example Question #31 : Understanding Meiosis

Meiosis in humans results in cells that have what number of chromosomes?

Possible Answers:

Correct answer:

Explanation:

Meiosis results in cells with 23 chromosomes (22 autosomes and 1 sex chromosome). Note that these cells are haploid since n=23, and nonidentical, due to crossing over during prophase I.

Example Question #33 : Understanding Meiosis

What would happen if gametes were made by mitosis instead of meiosis?

Possible Answers:

Each generation of cells would have 23 chromosomes

More than one of these

Each generation of cells would have 44 chromosomes

With each generation, the number of chromosomes in each cell would double

Each generation of cells would have 46 chromosomes

Correct answer:

With each generation, the number of chromosomes in each cell would double

Explanation:

Gametes are made via meiosis which produces cells with n=23 instead of diploid cells. If gametes were produced instead by mitosis each gamete would be diploid not haploid. During fertilization of diploid gametes, the zygote would become 4n=92. With each new generation the number of chromosomes would double.  

Example Question #34 : Understanding Meiosis

Which of the following is a haploid cell?

Possible Answers:

Epithelial cell

Neuron

Red blood cell

Sperm cell

Correct answer:

Sperm cell

Explanation:

In biology, the term “ploidy” refers to the number of chromosome sets per cell. Haploid cells have half of the number of chromosomes as parent cells, meaning that they only carry a single copy of each gene. Haploid cells are formed during meiosis and, in humans, produce gametes, which mature into sperm and egg cells.

Example Question #32 : Understanding Meiosis

Diploid cells contain how many times more chromosomes than haploid (n) cells?

Possible Answers:

Four times as many (4n)

Twice as many (2n)

Three times as many (3n)

The same amount (n)

Correct answer:

Twice as many (2n)

Explanation:

Diploid cells contain two copies of each chromosome, therefore containing twice as many (2n) chromosomes as a haploid cell (n), which contain only one copy of each chromosome. In humans, diploid somatic cells contain 46 chromosomes, or 23 pairs of chromosomes.

Example Question #36 : Understanding Meiosis

What is the cell division error that causes trisomy 21, or Down syndrome?

Possible Answers:

Nondisjunction

Nucleotide deletion

Telomere shortening

Organelle partitioning

Correct answer:

Nondisjunction

Explanation:

Trisomy 21, or Down syndrome results when a human individual inherits three copies of chromosome 21, instead of the normal two copies (one maternal and one paternal). This is caused by nondisjunction, or the improper segregation of chromosomes during cell division. In the case of trisomy 21, nondisjunction leads to a failure of chromosome 21 segregation during meiosis (most of the time during anaphase I). This results in either an egg or sperm carrying two copies of chromosome 21 instead of one. The zygote formed by fertilization develops into an individual that has three copies of chromosome 21. Trisomy 21 manifests in physical growth delays, intellectual disabilities, and distinctive facial features. 

Example Question #37 : Understanding Meiosis

Which molecular mechanism is not a possible cause of nondisjunction?

Possible Answers:

Maternal gametes have a higher chance of exhibiting nondisjunction

Error in cytoplasmic partitioning

Older age of an individual leads to weaker cohesin complexes at the centromere

Failure to pass the spindle assembly checkpoint

Correct answer:

Error in cytoplasmic partitioning

Explanation:

Nondisjunction is the improper segregation of chromosomes during meiosis or mitosis. The molecular causes behind nondisjunction are (1) increased rate of nondisjunction in female cells, (2) failure to properly pass the spindle assembly checkpoint, and (3) weakening of the cohesion complex at the centromere due to age.

Example Question #38 : Understanding Meiosis

Which of the following organisms do not perform meiosis?

Possible Answers:

Mammals

Flowering plants

Bacteria

Mosses

Correct answer:

Bacteria

Explanation:

Meiosis is a process that produces gametes in sexual reproduction. Therefore, organisms that undergo sexual reproduction or feature sexual life stages undergo meiosis. Mammals produce haploid sperm and eggs through meiosis, which fuse to form a diploid zygote. In mosses, reproduction is called the alternation of generations, meaning that generations alternate between haploid and diploid forms. In this system, meiosis produces haploid spores during the sporophyte generation, which germinate to form gametophyte precursors. In flowering plants, cells in male and female sexual organs undergo meiosis to form precursor sex cells, called spores. Prokaryotes, including bacteria, perform asexual reproduction that does not include the process of meiosis. Types of asexual reproduction include fission, budding, and fragmentation. In the case of bacteria, cells reproduce by binary fission, or cellular division without mitotic spindles.  

Example Question #39 : Understanding Meiosis

What enzyme aids in chromosomal crossing over during prophase I of meiosis?

Possible Answers:

Recombinase

DNA polymerase

Protein kinase

DNA ligase

Correct answer:

Recombinase

Explanation:

During crossing over in prophase I of meiosis, there is a physical exchange of genetic material between homologous chromosomes. This exchange occurs at the sites of double stranded breaks, where recombinase enzymes facilitate the invasion of the other chromatid. The original strand and invading strand anneal following this invasion. When this happens between two chromosomes, the strands form a tetrahedral arrangement called a Holliday junction. Other recombinase enzymes move the junction down the strands, furthering recombination.

Example Question #40 : Understanding Meiosis

What is the term for the structural arrangement of chromatids undergoing crossing over during meiosis?

Possible Answers:

Holliday junction

Kinetochore

Telomere

Equatorial plane

Correct answer:

Holliday junction

Explanation:

During prophase I of meiosis, homologous chromosomes exchange genetic material in a process called crossing over. Double stranded breaks and recombinase enzymes facilitate chromatid invasion and annealing. The tetrahedral structure formed through strand invasion between two chromosomes is called the Holliday junction.

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