Meiosis

Why does meiosis occur?

To produce reproductive cells with half the number of chromosomes.

Are the genes on a recombinant chromatid the same as the original chromitad?

Yes. Each chromosome in the homologous pair has the same genes in the same place on the chromosome so a switch between chromosomes does not affect anything.

zygote

a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.

ovum

a mature female reproductive cell, especially of a human or other animal, that can divide to give rise to an embryo usually only after fertilization by a male cell.

gamete

a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote.

What is a homologous pair?

a set of 2 chromosomes that are part of the same pair.

Why aren't the cells at the end of telophase 1 genetically identical?

Because the homologous pairs separated and the alleles on each homologous pair are not necessarily identical

Why does the secondary oocyte divide unevenly during meiosis II?

Because the ovum will receive more organelles, which provides zygote with all its cytoplasm and organelles, but nuclear division is needed to produce the correct number of chromosomes in the oocyte.

Recombinant chromatids

Chromatids after the cross over takes place and the homologous chromosomes separate

What event takes place in interphase before cell division?

DNA replication

Is the ploidy of the zygote produced by fertilization haploid or diploid?

Diploid

When does cytokinesis occur?

During the telophase

Allele

Alleles are the different types of genetic material that code for a specific protein - or gene

Are the 4 daughter cells at the end of meiosis II diploid or haploid?

Haploid because they each contain one chromosome (sister chromatid) from each homologous pair so each chromosome has a complete set of genes.

In meiosis I, during anaphase I, what structures separate?

Homologous structures

Are the alleles on a recombinant chromatid the same as the original chromatid?

No. The chromosomes in the homologous pair can have different alleles for each gene, so a switch in a portion of the chromosomes would affect that info in that chromatids.

What happens to the secondary oocyte before fertilization?

Proceeds to meiosis II

What stages of meiosis 1 are the cells diploid?

Prophase, Metaphase and Anaphase

What happens to the chromatids during crossover?

Sections of the homologous pair switch places on the chromatids.

What type of organs are the cellos that enter meiosis I found?

Sex organs (ovaries and testes)

What two structures make up a single replicated chromosome?

Sister chromatids

What cells are produced at the end of meiosis II in males?

Spermatids

What stages of meiosis 1 are the cells haploid?

Telophase, after the cell has split

What is a pair of chromosomes called?

Tetrads

What may happen when chromosomes come together as homologous pairs?

The arms of the sister chromatids may cross over.

What is a secondary oocyte?

The cells produced at the end of meiosis I in females

What is a secondary spermatocyte?

The cells produced at the end of meiosis I in males

The origin of the chromosomes found in the zygote.

The homologous pairs of chromosomes found in the zygote are from each parent. One half of each pair is maternal and the other half in paternal.

What is the relationship between the cells at the end of meiosis II and the original cell?

The new cells have one copy of half of the genetic info in the original cell

What is the relationship between the cells at the end of telophase I and the original cell?

The new cells have two copies of half of the genetic information of the original cell

Cell with a full set of chromosomes

diploid or 2n

Cell with half the set of chromosomes

haploid or n

fertilization

the action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote.

ploidy

the number of sets of chromosomes in a cell, or in the cells of an organism.

Gametogenesis

the process in which cells undergo meiosis to form gametes.

How many replicated chromosomes are in each of the two cells and the end of meiosis I?

2

Which stage in meiosis I do the pairs of homologous structures come together?

Late prophase I

What do spermatids eventually become?

Mature sperm

What cell come together in fertilization?

Mature sperm and secondary oocyte.

Where do the cells come from that started in meiosis II?

Meiosis I

In meiosis II, during anaphase II, what structures separate?

The sister chromatids