Chapter 11: Sexual Reproduction & Meiosis

Asexual reproduction

Occurs when an organism makes more of itself without exchanging genetic information with another organism through sex.

Sexual reproduction

Process in which new organisms are created, by combining the genetic information from two individuals of different sexes.

Somatic cells

Any cell in the body that are not gametes (sperm or egg), germ cells (cells that go on to become gametes), or stem cells. All cells that make up an organism’s body and are not used to directly form a new organism during reproduction.

Gametes

A reproductive cell of an animal or plant. Female - ova/egg cells, male - sperm

Zygote

The cell formed when two gametes fuse during fertilization.

46 chromosomes

The typical number of chromosomes found in a human cell.

23 chromosomes

The number of chromosome pairs found in a human cell

Spermatological stem cells

A group of cells in the testis that are responsible for sperm production and male fertility.

Oogonial cells

Diploid germ cells that produce eggs in female animals.

Meiosis

Type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes

Genotype

Responsible for the genetic makeup in an organism.

Phenotype

Responsible for the set of observable characteristics of an organism.

Haploid

A cell that contains a single set of chromosomes.

Diploid

Cell with two complete sets of chromosomes.

Homologous chromosomes

A pair of chromosomes where one comes from the mother and one is from the father, that have the same genes in the same order.

Locus

The specific physical location of a gene on a chromosome.

Alleles

An alternative form of a gene(1 or pair), that is located at a specific position on a specific chromosome.

Independent assortment

Principle that states different genes independently separate from one another when reproductive cells develop.

Crossover

The exchange of DNA between paired homologous chromosomes that occurs during the development of eggs & sperm cells(in meiosis).

Meiosis I

Type of cell division unique to germ cells, homologous chromosomes pair and then separate.

Meiosis II

Mitotic division of the haploid cells produced in meiosis I. Sister chromatids w/in 2 daughter cells separate, forming 4 new haploid gametes.

Sister chromatids

Identical copies of a chromosome that are created during DNA replication and are joined at the centromere.

Recombinant chromosomes

The rearrangement of DNA sequences by the breakage & rejoining of chromosomes/chromosome segments.

Prophase I

The first stage of meiosis, the process by which germ cells divide to produce gametes.

Tetrad

A 4 part structure that forms during prophase 1 of meiosis and consists of 2 homologous chromosomes, each composed of 2 identical chromatids.

Metaphase I

When homologous chromosomes line up along the equator of the cell.

Chiasma

The point at which paired chromosomes remain in contact during the first metaphase of meiosis, & at which crossing over & exchange of genetic material occur between strands.

Anaphase I

The stage in meiosis I where homologous chromosomes separate & are pulled apart towards opposite poles of the cell.

Telophase I

Final stage of the first division of meiosis, when homologous chromosomes separate & move to opposite ends of the cell.

Prophase II

The 1st stage of meiosis II, where chromosomes condense, the nuclear envelope breaks down, & a new spindle apparatus forms.

Metaphase II

Stage in meiosis II where the chromosomes line up along the equator of the cell, attaching to spindle fibers.

Anaphase II

Stage in meiosis II where the sister chromatids of each chromosome separate at the centromere and are pulled apart by the spindle fivers, moving towards opposite poles of the cell, essentially dividing the genetic material into four haploid daughter cells.

Telophase II

The final stage of the 2nd meiotic division, where the chromosomes gather at opposite poles of the cell, a nuclear membrane reforms around each set of chromosomes, & the ell prepares to divide into 4 haploid daughter cells by undergoing cytokinesis.