A&P 2 Lab-Mitosis and Meiosis

Prophase I

Chromatin condenses to form the chromosomes. The homologous chromosomes form pairs in an event called "synapsis". Chromosomes can cross-over during synapsis. During cross-over, the chromatids of homologous chromosomes can exchange segments of the chromatids. The results of cross-over is sister chromatids of one chromosome are no longer genetically identical. Cross over is one of the mechanisms that generates genetic variability. The nuclear envelope disappears and the spindle apparatus forms during late prophase I. The cell has 46 double chromosomes at this stage.

Homologous chromosomes

Chromosomes identical in size, shape, and posses the same genes. Humans have 23 pairs.

Telophase

Chromosomes reach the poles of the cell, begin to unwind, and then assume the form of chromatin.Has 46 single chromosomes at this stage.

Cytokinesis

Division of this not part of mitosis, but it usually occurs at the same time. Here, the cells divide in half. Each half receives approximately half of this.

Prophase

First phase of mitosis. Chromosomes condense from chromatin and the nuclear membrane disappears. It has 46 double chromosomes at this stage.

Diploid

Having two haploid sets of homologous chromosomes. This number is the normal number of chromosomes in body cells. This number in humans is 46.

Oogenesis

Is the term for gametogenesis in females. It is the formation of a haploid secondary oocyte and two or three polar bodies by the process of Meiosis.

Chromatin

It literally means "colored material". This is the term for the uncoiled DNA in nucleus when the cell is undergoing its normal activity. They form the chromosomes

Chromosomes

Literally means "colored bodies". These are the rod- shaped structures of DNA present in the cell during cell division.

Meiosis II

Meiosis II consists of prophase, metaphase, anaphase, and telophase. The only notable event to occur in meiosis II is the separation of the two chromatids of each chromosome. This results in four haploid cells, each containing 23 different chromosomes. Otherwhise, meiosis II is very similar to mitosis.

Meiosis

Process that reduces the diploid chromosomes from 46 to the haploid number of 23 to produce the gametes,eggs and sperm.

Metaphase

Second phase of mitosis. Chromosomes line up along the cell's equator.It has 46 double chromosomes at this stage.

Spermatogenesis

Term for gametogenesis in males. It is the formation of sperm by the process of Meiosis and differentiation.

Interphase

The chromosomes take the form of chromatin during this phase, and they replicate to produce the two chromosomes.

Metaphase I

The homologous chromosomes pair along the equatorial plane of the cell so each homolog is on the opposite side of the plane.. It has 46 double chromosomes at this stage.

Telophase I

The homologous chromosomes reach the poles of the cell, and cytokinesis occurs. The resulting two cells each have the haploid number of chromosomes. Has 23 double chromosomes at this stage.

Anaphase I

The homologous chromosomes separate and are drawn to the poles of the cell. It has 23 double chromosomes at this stage

Haploid

The number of chromosomes found in eggs or sperm. It is one half of the diploid number of chromosomes. This number in humans is 23.

Chromatids

The two identical strands of DNA which form a chromosome after DNA replication. They are separated into two different cells during mitosis.

Anaphase

Third phase of mitosis. Sister chromatids on each chromosome separate, and begin to move towards the poles of the cells.Has 46 single chromosomes at this stage.