Chromosomes and Gametes

Flashcards about Chromosomes and Cellular Reproduction

Chromosomes

Structures within living cells that contain genetic material. Genes are physically located within them and contain a specific nucleotide sequence.

Each chromosome contains

A very long segment of DNA, which is the genetic material, and proteins, which are bound to the DNA and provide it with an organized structure.

Chromatin

The complex of DNA and proteins found within chromosomes.

Chromatin in Prokaryotes

Circular chromosomes.

Chromatin in Eukaryotes

Linear chromosomes = DNA + proteins.

Centromere

The constricted region of the chromosome where the kinetochores form and the spindle microtubules attach.

Telomeres

The stable ends of chromosomes.

Linked genes

Genes located close together on the same chromosome are more likely to be inherited together.

Unlinked genes

Genes located on different chromosomes or far apart on the same chromosome are less likely to be inherited together.

Homologous chromosomes

Chromosomes that have the same genes, but may have different alleles.

Alleles

Different versions of the same gene.

Diploid (2n)

Double set of chromosomes, found in somatic cells and zygotes.

Haploid (1n)

One single chromosome set, half set of chromosomes, found in germ line cells and gamete cells.

Mitosis

The production of somatic cells.

Meiosis

Reduces the number of chromosomes to half (2n to n).

Chromatin/chromosomes in G1 phase

Uncondensed & unreplicated; 2n. Cell grows and prepares for M phase.

Chromatin/chromosomes in S phase

Uncondensed & replicated; 2n. Cell grows & carries out normal metabolism; most organelles increase in size or #. DNA synthesis.

Chromatin/chromosomes in G2 phase

Uncondensed & replicated; 2n.

Meiotic Cell Division

A meiotic cell division is more complicated than a mitotic cell division and involves two division events: Meiosis I and Meiosis II.

Meiosis

Nuclear division in cells involved in sexual reproduction, resulting in gamete cells that are haploid and contain a mix of genetic information from the previous generation.

Function of Meiosis

Reduces the chromosome number from diploid to haploid, ensures that each haploid has a complete set of chromosomes, and generates diversity among the products.

Metaphase I

Homologous pairs of chromosomes line up on the metaphase plate.

Spermatogenesis

Results in 4 gametes per meiotic division. Includes cell differentiation and sperm formation.

Oogenesis

Results in 1 gamete per meiotic division.

Gametogenesis in Males vs. Females

The formation of sperm takes place continuously in a male throughout his adult reproductive life, while the formation of gametes in females is discontinuous and may take 30-40 years.