meiosis

Question 1

how do humans reproduce sexually?

Answer 1

by meiosis

Question 2

each cell contains how many chromosomes?

Answer 2

46

Question 3

N VS 2N?

Answer 3

The n represents haploid condition. It means the cell possesses a half number of chromosomes. For example, in human 23 chromosomes shows n condition. The 2n represents diploid condition. It means the cell possesses two sets of chromosomes.

Question 4

what are homologous chromosomes?

Answer 4

pairs that code for the same genes
each half is called a chromatid (sister chromatid)

Question 5

what is sexual reproduction?

Answer 5

there is half the number of chromosomes in order to produce an offspring
for humans that is 23 chromosomes

Question 6

what do each parent produce?

Answer 6

a sex gamete, sperm and egg

Question 7

how many phases of meiosis?

Answer 7

meiosis one and meiosis two

Question 8

what happens in interphase?

Answer 8

the cell replicates its DNA

Question 9

what happens in prophase 1 of meiosis?

Answer 9

Meiosis I, the first meiotic division, begins with prophase I. During prophase I, the complex of DNA and protein known as chromatin condenses to form chromosomes. The pairs of replicated chromosomes are known as sister chromatids, and they remain joined at a central point called the centromere.

Question 10

what happens in metaphase 1?

Answer 10

In metaphase I of meiosis I, the homologous pairs of chromosomes line up on the metaphase plate, near the center of the cell. This step is referred to as a reductional division. The homologous chromosomes that contain the two different alleles for each gene are lined up to be separated.

Question 11

what happens in anaphase 1?

Answer 11

reduces a diploid cell, containing two alleles for each gene, to a haploid cell, containing one allele for each gene12. This is achieved by the separation of homologous chromosomes, which are pairs of chromosomes that have similar genes but may have different alleles23. The homologous chromosomes are bound together by cohesin molecules during prophase I and are aligned on the metaphase plate during metaphase I2. During anaphase I, the spindle apparatus, a network of microtubules, pulls the homologous chromosomes to opposite poles of the cell, while the sister chromatids, which are identical copies of each chromosome

Question 12

what happens in telophase 1?

Answer 12

Meiosis contains two divisions, both of which contain a telophase stage. During telophase I, the homologous chromosomes get segregated into separate nuclei. Although another division must take place for meiosis to be complete, the cells must still reform the nuclear envelopes, disassemble the spindle fiber microtubules, and go through cytokinesis.

Question 13

what happens in prophase 2?

Answer 13

Prophase II is the first step of the second meiotic division of Meiosis. Explanation: In prophase II, the nucleoli and nuclear membrane disappear. The chromatids become short and thick. The centromeres move to the polar regions and arrange spindle fibres for the second meiotic division.

Question 14

what happens in metaphase 2?

Answer 14

The chromosomes line up at the metaphase II plate at the cell’s center. The kinetochore fibers of the sister chromatids point toward opposite poles. At the end of metaphase II of meiosis, the cell enters into anaphase II.

Question 15

what happens in anaphase 2

Answer 15

Sister chromatids separate and begin moving to opposite ends (poles) of the cell. Spindle fibers not connected to chromatids lengthen and elongate the cell. Once the paired sister chromatids separate from one an

Question 16

what happens in telophase 2

Answer 16

the chromosomes reach opposite poles and are surrounded by new nuclear membranes. The chromosomes also decondense.

Question 17

what happens in cytokenisis 2

Answer 17

the chromosomes reach opposite poles, cytokinesis occurs, the two cells produced by meiosis I divide to form four haploid daughter cells, and nuclear envelopes (white in the diagram at right) form.

Question 18

what is haploid?

Answer 18

having a single set of unpaired chromosomes

Question 19

what is diploid?

Answer 19

containing two complete sets of chromosomes, one from each parent. Compare with haploid

Question 20

whats the difference between mitosis and meiosis?

Answer 20

1. Cell Division

Mitosis: A somatic cell divides once. Cytokinesis (the division of the cytoplasm) occurs at the end of telophase.
Meiosis: A reproductive cell divides twice. Cytokinesis happens at the end of telophase I and telophase II.
2. Daughter Cell Number

Mitosis: Two daughter cells are produced. Each cell is diploid containing the same number of chromosomes.
Meiosis: Four daughter cells are produced. Each cell is haploid containing one-half the number of chromosomes as the original cell.
3. Genetic Composition

Mitosis: The resulting daughter cells in mitosis are genetic clones (they are genetically identical). No recombination or crossing over occur.
Meiosis: The resulting daughter cells contain different combinations of genes. Genetic recombination occurs as a result of the random segregation of homologous chromosomes into different cells and by the process of crossing over (transfer of genes between homologous chromosomes).
4. Length of Prophase

Mitosis: During the first mitotic stage, known as prophase, chromatin condenses into discrete chromosomes, the nuclear envelope breaks down, and spindle fibers form at opposite poles of the cell. A cell spends less time in prophase of mitosis than a cell in prophase I of meiosis.
Meiosis: Prophase I consists of five stages and lasts longer than prophase of mitosis. The five stages of meiotic prophase I are leptotene, zygotene, pachytene, diplotene, and diakinesis. These five stages do not occur in mitosis. Genetic recombination and crossing over take place during prophase I.
5. Tetrad Formation

Mitosis: Tetrad formation does not occur.
Meiosis: In prophase I, pairs of homologous chromosomes line up closely together forming what is called a tetrad. A tetrad consists of four chromatids (two sets of sister chromatids).
6. Chromosome Alignment in Metaphase

Mitosis: Sister chromatids (duplicated chromosome comprised of two identical chromosomes connected at the centromere region) align at the metaphase plate (a plane that is equally distant from the two cell poles).
Meiosis: Tetrads (homologous chromosome pairs) align at the metaphase plate in metaphase I.
7. Chromosome Separation

Mitosis: During anaphase, sister chromatids separate and begin migrating centromere first toward opposite poles of the cell. A separated sister chromatid becomes known as daughter chromosome and is considered a full chromosome.
Meiosis: Homologous chromosomes migrate toward opposite poles of the cell during anaphase I. Sister chromatids do not separate in anaphase I.

Question 21

whats the purpose of meiosis?

Answer 21

meiosis is a type of cell division that produces four unique haploid cells, each with half the number of chromosomes as the parent cell. the purpose of meiosis is to create genetic diversity in the offspring.

Question 22

what is crossing over, and what phase does it occur?

Answer 22

exchange of genetic material between homologous chromosomes that occur during prophase 1 of meiosis. this process results in the production of new combinations of alleles, increasing genetic diversity in the offspring

Question 23

what does the female contribute to the sexual reproduction?

Answer 23

the egg

Question 24

where are sperm produced?

Answer 24

in the testes

Question 25

paired chromosomes are called?

Answer 25

homologous chromosomes