High School Biology : Cell Division

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Crossing Over

What structures exchange genetic material during crossing over?

Possible Answers:

Non-homologous chromosomes

Sister chromatids

Egg and sperm chromosomes

Nonsister chromatids

Correct answer:

Nonsister chromatids

Explanation:

During crossing over, homologous chromosomes come together in order to form a tetrad. This close contact allows the nonsister chromatids from homolgous chromosomes to attach to one another and exchange nucleotide sequences. The word "nonsister" implies that the chromatids have the same genes, but are not exact copies of one another, as they come from separate chromosomes.

Example Question #1 : Understanding Crossing Over

Crossover of homologous chromosomes in meiosis occurs during which phase?

Possible Answers:

Anaphase I of meiosis

Prophase I of meiosis

Anaphase II of meiosis

Prophase II of meiosis

Correct answer:

Prophase I of meiosis

Explanation:

The crossing over of homologous chromosomes occurs in prophase I of meiosis. Prophase I of meiosis is characterized by the lining up of homologous chromosomes close together to form a structure known as a tetrad. A tetrad is composed of four chromatids.

Anaphase I is marked by the separation of homologous chromosomes, whereas in anaphase II there is the separation of sister chromatids. In anaphase I sister chromatids are still intact and connected at the centromere. Prophase II is similar to prophase in mitosis in that there is the break down of the nuclear membrane and the formation of spindle fibers in preparation for the separation of sister chromatids.

Example Question #1 : Understanding Crossing Over

During crossing over, two homologous chromosomes pair to form which of the following choices?

Possible Answers:

None of these

Base Pair

Tetrad

Chromatid

Mitotic Bond

Correct answer:

Tetrad

Explanation:

The tetrad, which divides into non-sister chromatids, exchanges genetic information in order to make the genetic pool more variant, and result in combinations of phenotypic traits that can occur outside of linked genotypic coding.

Example Question #1 : Understanding Crossing Over

Chromosomal crossover occurs in which phase of meiosis?

Possible Answers:

Anaphase II

Prophase I

Metaphase I

Prophase II

Anaphase I

Correct answer:

Prophase I

Explanation:

During prophase I, homologous chromosomes pair with each other and exchange genetic material in a process called chromosomal crossover. The exchange occurs in segments over a small region of homology (similarity in sequence, ie., the same alleles). The new combinations of DNA created during crossover provide a significant source of genetic variation.  

Example Question #2 : Understanding Crossing Over

Crossing over is a phenomenon that happens during Meiosis I in the attempt to create genetic diversity. Crossing over typically occurs between which of the following structures?

Possible Answers:

Tetrads

Chromatin

Homologous chromosomes

Sister chromatids

Correct answer:

Homologous chromosomes

Explanation:

Crossing over occurs when chromosomal homologs exchange information during metaphase of Meiosis I. During this stage, homologous chromosomes line up on the metaphase plate and exchange genetic information.

Example Question #1 : Understanding Crossing Over

When in meiosis does crossing over occur?

Possible Answers:

Telophase I

Prophase I

Anaphase I

Interphase

Metaphase I

Correct answer:

Prophase I

Explanation:

Crossing over occurs during prophase I when parts of the homologous chromosomes overlap and switch their genes.

Example Question #1 : Understanding Oogenesis

How is oogenesis different from spermatogenesis? 

Possible Answers:

Only spermatogenesis involves crossing over

Oogenesis results in one egg cell, while spermatogenesis results in four sperm cells

Oogenesis results in a diploid germ cell, while sperm cells are haploid

One uses meiosis, while the other uses mitosis

Correct answer:

Oogenesis results in one egg cell, while spermatogenesis results in four sperm cells

Explanation:

When a primary oogonium undergoes meiosis, it will only result in one viable germ cell, or egg. The other smaller cells are called polar bodies and typically disappear following division. Spermatogenesis will result in four separate sperm cells, each capable of producing offspring.

Both eggs and sperm are haploid, and both processes can involve crossing over during meiosis.

Example Question #282 : High School Biology

Which of the following best defines oogenesis?

Possible Answers:

The inability to form egg cells during mitosis

The formation of egg cells during prophase

The inability to form egg cells during meiosis

The formation of egg cells during anaphase

The formation of egg cells through meiosis

Correct answer:

The formation of egg cells through meiosis

Explanation:

Gametes are formed during the process of meiosis. Oogenesis is the process by which the female games are produced, which occurs in the ovary. The product of oogenesis is one mature egg from one primary oocyte; this occurs about once every four weeks in humans.

Example Question #51 : Cell Division

When would an extra copy of chromosome 21 be introduced into the genetic pool?

Possible Answers:

During mitosis

During meiosis

During fertilization

During early cell divisions in the embryo

During implantation

Correct answer:

During meiosis

Explanation:

Down's syndrome is caused by an extra copy of chromosome 21. This trisomy is a result of nondisjunction, which can occur during either meiosis I or meiosis II. Nondisjunction most often occurs during anaphase I of meiosis. Note that most other trisomies and monosomies are lethal.

Example Question #21 : Meiosis

Many secondary processes enable the primary processes of human gametogenesis to occur smoothly. One important secondary process during human oogenesis is ovarian follicle atresia.

Which of the following is closest to the definition of "ovarian follicle atresia"?

Possible Answers:

The process by which FSH triggers the development of primary follicles into secondary follicles which are ready for ovulation.

The process by which a follicle develops into a corpus luteum following ovulation, which will later release the hormone progesterone into the body.

The process by which the dominant follicle releases large amounts of estradiol during the late follicular phase, preparing the follicle for the LH surge.

The process by which all but one primary ovarian follicle degenerates and are absorbed back into the ovary, allowing the surviving follicle body to develop into a corpus luteum following ovulation.

The process by which estradiol and luteinizing hormone interact in a positive feedback loop, severely heightening the level of LH and developing the secondary follicle into a tertiary follicle.

Correct answer:

The process by which all but one primary ovarian follicle degenerates and are absorbed back into the ovary, allowing the surviving follicle body to develop into a corpus luteum following ovulation.

Explanation:

Follicular atresia is a hormone-controlled, apoptotic (cell-suicide) process by which immature follicles degenerate and are resorbed into the main body of the ovary, leaving one out of typically 20 primary follicles standing as a secondary follicle. This process, moderated by follicle stimulating hormone and tumor necrosis factor alpha (TNF), assists the body in forming the corpus luteum out of the remaining follicle following ovulation, as the body would otherwise not be able to generate enough progesterone to continue the process.

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