Question 1

What stage of prophase I is usually recognized by the dissolution of the synaptonemal complex and the tendency of homologous chromosomes of the bivalents to pull away somewhat from each other?

Accepted Answer

Diplotene is the stage in prophase I of meiosis where the synaptonemal complex dissolves, allowing the homologous chromosomes to begin to separate from each other, though they remain connected at chiasmata.

Question 2

What event marks the end of zygotene?

Accepted Answer

The end of zygotene is marked by the completion of synapsis, which is when homologous chromosomes come together and form pairs (bivalents) held together by the synaptonemal complex. Therefore, the correct answer is C, the end of synapsis. The beginning of synapsis (A) and the formation of the synaptonemal complex (E) occur during zygotene, but do not mark the end of it. Genetic recombination (B) also occurs during zygotene, but is not a defining event for its end. The start of metaphase (D) comes after zygotene, during which the bivalents align at the equator of the cell.

Question 3

What is required for the separation of homologous chromosomes at anaphase I of meiosis I?

Accepted Answer

The dissolution of the chiasmata, which are the points where homologous chromosomes are connected due to crossing over, is required for their separation at anaphase I of meiosis I. This allows the homologous chromosomes to move to opposite poles of the cell.

Question 4

Why do the centromeres of sister chromatids stay firmly connected during anaphase I of meiosis I?

Accepted Answer

The centromeres of sister chromatids stay firmly connected during anaphase I of meiosis I because the cohesin situated at the centromeres is protected from proteolytic attack. This allows the sister chromatids to remain attached until they are pulled apart during anaphase II.

Question 5

Mice with mutations that prevent the clustering of telomeres in leptotene develop defects. What do these defects suggest the purpose of clustering telomeres may be?

Accepted Answer

Clustering of telomeres in leptotene facilitates synapsis, genetic recombination, and gamete formation. Therefore, mice with mutations that prevent clustering of telomeres develop defects, suggesting that the purpose of clustering telomeres may be to facilitate these crucial reproductive processes.

Question 6

During which stage of prophase I does the bulk of oocyte growth occur?

Accepted Answer

During the diplotene stage of prophase I, the bulk of oocyte growth occurs. This stage is characterized by the arrest of oocytes in many species, allowing for significant growth and the accumulation of maternal mRNAs and proteins necessary for early embryonic development.

Question 7

The random assortment of chromosomes at anaphase I accounts for a large amount of the _________ within a species.

Accepted Answer

The random assortment of chromosomes at anaphase I during meiosis results in the production of genetically diverse gametes. This leads to increased genetic variability within a species, as the offspring will inherit a unique combination of genes from each parent, resulting in different traits and characteristics. Therefore, option B is the correct answer.

Question 8

What is the presently accepted function of the synaptonemal complex thought to be?

Accepted Answer

The synaptonemal complex is thought to function primarily as a scaffold to allow interacting chromatids to complete crossover activities during meiosis. It facilitates homologous chromosome pairing and promotes stability during recombination.

Question 9

Due to the reciprocal exchange of DNA strands that occurs during genetic recombination, the two duplexes are covalently linked to one another to form a joint molecule called a(n)__________ that contains a pair of DNA crossovers called __________.

Accepted Answer

The joint molecule that forms due to genetic recombination is a Holliday junction and it contains a pair of DNA crossovers called heteroduplexes, because they are formed by the exchange of DNA strands between two different duplexes. Option A is incorrect because homoduplex refers to a DNA molecule where both strands are identical, which is not the case in genetic recombination. Option C is incorrect because the order of the words is incorrect, as it should be Holliday junction before heteroduplexes. Option D is incorrect because the crossovers formed are between different duplexes, not between identical ones. Option E is also incorrect as it is not a recognized term in genetics.

Question 10

Crossing-over is important for ___________. (Select all correct choices)

Accepted Answer

Crossing-over during meiosis ensures proper chromosome segregation by promoting the alignment of homologous chromosomes and facilitates the exchange of genetic material between them. Through this process, new combinations of alleles are created, increasing genetic variation in the population. Delaying meiosis is not a function of crossing-over, and ensuring proper chromosome miscegenation is not a necessary process.

Question 11

During which stage of meiosis do the chromosomes become recompacted after interkinesis?

Accepted Answer

After interkinesis (the short period between meiosis I and meiosis II), the chromosomes do not replicate again. Instead, they remain in their condensed state and move directly into prophase II, where they become even more condensed.

Question 12

During what stage do studies of mice and yeast cells suggest that DNA breaks leading to recombination begin?

Accepted Answer

Studies of mice and yeast cells suggest that DNA breaks leading to recombination begin during the leptotene stage of meiosis. This is an early stage of prophase I, where chromosomes start to condense and become visible, but homologous chromosomes have not yet aligned.

Question 13

What stage of prophase I of meiosis begins when synapsis ends?

Accepted Answer

Pachytene is the stage of prophase I that begins after synapsis has occurred and homologous chromosomes have paired up to form bivalents.

Question 14

During which phase of meiosis do the kinetochores of sister chromatids face opposite poles as they line up in the center of the cells, with the centromeres of sister chromatids attached to chromosomal spindle fibers from opposite spindle poles?

Accepted Answer

During metaphase II of meiosis, the kinetochores of sister chromatids face opposite poles as they align at the metaphase plate, with the centromeres of sister chromatids attached to spindle fibers from opposite poles. This is a key feature distinguishing it from metaphase I, where homologous chromosomes, rather than sister chromatids, align at the metaphase plate.

Question 15

In meiosis I, kinetochores of sister chromatids are connected as a unit to microtubules from __________.

Accepted Answer

In meiosis I, sister chromatids are held together and their kinetochores are connected as a unit to microtubules from the same spindle pole. This contrasts with mitosis and meiosis II, where sister chromatids are pulled towards opposite poles.

Question 16

Which molecules and components are found within the plant cell preprophase band? (Select all correct choices)

Accepted Answer

The answer of Which molecules and components are found within...

Question 17

The generally short-lived stage between the two meiotic divisions is called ________.

Accepted Answer

The term "interkinesis" specifically refers to the stage between the two meiotic divisions, also known as meiosis II. This stage is a relatively short period of time in which there is no DNA replication, but the chromosomes may still be visible as extended chromatin threads.

Question 18

At meiosis metaphase I, the two homologous chromosomes of each bivalent are connected to spindle fibers from the _________.

Accepted Answer

At meiosis metaphase I, the homologous chromosomes of each bivalent are connected to spindle fibers from opposite spindle poles, which allows for segregation of the homologous chromosomes during anaphase I.

Question 19

Synapsis is accompanied by the formation of a complex, ladder like structure made of three parallel bars with transverse protein filaments connecting its central element with two lateral elements. What is the name of this structure?

Accepted Answer

The described structure is known as the synaptonemal complex.

Question 20

As they separate, homologous chromosomes are seen to remain attached to each other at specific points by X-shaped structures at the crossover sites called _________.

Accepted Answer

Homologous chromosomes are held together by a structure called a chiasma (plural: chiasmata) at the site of crossover during meiosis.

Quiz 14: Cellular Reproduction

What stage of prophase I is usually recognized by the dissolution of the synaptonemal complex and the tendency of homologous chromosomes of the bivalents to pull away somewhat from each other?

What event marks the end of zygotene?

What is required for the separation of homologous chromosomes at anaphase I of meiosis I?

Why do the centromeres of sister chromatids stay firmly connected during anaphase I of meiosis I?

Mice with mutations that prevent the clustering of telomeres in leptotene develop defects. What do these defects suggest the purpose of clustering telomeres may be?

During which stage of prophase I does the bulk of oocyte growth occur?

The random assortment of chromosomes at anaphase I accounts for a large amount of the _________ within a species.

What is the presently accepted function of the synaptonemal complex thought to be?

Due to the reciprocal exchange of DNA strands that occurs during genetic recombination, the two duplexes are covalently linked to one another to form a joint molecule called a(n) that contains a pair of DNA crossovers called .

Crossing-over is important for ___________. (Select all correct choices)

During which stage of meiosis do the chromosomes become recompacted after interkinesis?

During what stage do studies of mice and yeast cells suggest that DNA breaks leading to recombination begin?

What stage of prophase I of meiosis begins when synapsis ends?

During which phase of meiosis do the kinetochores of sister chromatids face opposite poles as they line up in the center of the cells, with the centromeres of sister chromatids attached to chromosomal spindle fibers from opposite spindle poles?

In meiosis I, kinetochores of sister chromatids are connected as a unit to microtubules from __________.

Which molecules and components are found within the plant cell preprophase band? (Select all correct choices)

The generally short-lived stage between the two meiotic divisions is called ________.

At meiosis metaphase I, the two homologous chromosomes of each bivalent are connected to spindle fibers from the _________.

Synapsis is accompanied by the formation of a complex, ladder like structure made of three parallel bars with transverse protein filaments connecting its central element with two lateral elements. What is the name of this structure?

As they separate, homologous chromosomes are seen to remain attached to each other at specific points by X-shaped structures at the crossover sites called _________.

Quiz 14: Cellular Reproduction

What stage of prophase I is usually recognized by the dissolution of the synaptonemal complex and the tendency of homologous chromosomes of the bivalents to pull away somewhat from each other?

What event marks the end of zygotene?

What is required for the separation of homologous chromosomes at anaphase I of meiosis I?

Why do the centromeres of sister chromatids stay firmly connected during anaphase I of meiosis I?

Mice with mutations that prevent the clustering of telomeres in leptotene develop defects. What do these defects suggest the purpose of clustering telomeres may be?

During which stage of prophase I does the bulk of oocyte growth occur?

The random assortment of chromosomes at anaphase I accounts for a large amount of the _________ within a species.

What is the presently accepted function of the synaptonemal complex thought to be?

Due to the reciprocal exchange of DNA strands that occurs during genetic recombination, the two duplexes are covalently linked to one another to form a joint molecule called a(n) __________ that contains a pair of DNA crossovers called __________.

Crossing-over is important for ___________. (Select all correct choices)

During which stage of meiosis do the chromosomes become recompacted after interkinesis?

During what stage do studies of mice and yeast cells suggest that DNA breaks leading to recombination begin?

What stage of prophase I of meiosis begins when synapsis ends?

During which phase of meiosis do the kinetochores of sister chromatids face opposite poles as they line up in the center of the cells, with the centromeres of sister chromatids attached to chromosomal spindle fibers from opposite spindle poles?

In meiosis I, kinetochores of sister chromatids are connected as a unit to microtubules from __________.

Which molecules and components are found within the plant cell preprophase band? (Select all correct choices)

The generally short-lived stage between the two meiotic divisions is called ________.

At meiosis metaphase I, the two homologous chromosomes of each bivalent are connected to spindle fibers from the _________.

Synapsis is accompanied by the formation of a complex, ladder like structure made of three parallel bars with transverse protein filaments connecting its central element with two lateral elements. What is the name of this structure?

As they separate, homologous chromosomes are seen to remain attached to each other at specific points by X-shaped structures at the crossover sites called _________.

Due to the reciprocal exchange of DNA strands that occurs during genetic recombination, the two duplexes are covalently linked to one another to form a joint molecule called a(n) that contains a pair of DNA crossovers called .