chromosomes

Chromosomes

 Tightly coiled DNA found in the nucleus of a dividing cell during M-Phase
- Each one represents one highly coiled DNA molecule; visible in cell
- rod-shaped or X shaped depending on when they are observed

Chromatin

- DNA in a non-dividing cell that is not tightly coiled; not visible
- allows transcription/translation to occur in the cell between cell divisions

Centromere

- Structure which holds together the sister chromatids in a doubled chromosome

Histone

- Proteins that help organize DNA; DNA is wound around histone “spools”

Nucleosome

- group of 8 histones; nucleosome wind into helix; helix condenses into visible chromosome 

Homologous chromosome

– chromosome pairs that contain the same genes, in all sexually reproducing organisms, chromosomes appear in pairs called homologous chromosomes; look like all other chromosomes, but contain genes which are different than all other chromosome

- May or may not show “sister chromatids” depending on stage of cell cycle

Sister Chromatids

- result of DNA replication, genetically identical duplicate DNA molecule making up two halves of a doubled chromosome

Sex chromosomes

- determine gender; known as X and Y

Autosomes

- chromosome #1- #22

Humans = 

22 homologous pairs of autosomes
1 pair of sex chromosomes

23 homologous pairs or 46 total chromosomes

Diploid Cell

- contains both halves of each homologous pair of chromosomes
- contains a full set of genetic information (2N)

Human Cheek Cell

= 46 chromosomes (23 homologous pairs)
(somatic/body cells)

Haploid Cell

- contains ½ of the full set of genetic information
- contains only one chromosome from each homologous pair (1N)

Human Sex Cell

= 23 chromosomes (0 homologous pairs)
(gametes)

Male Gonads

=  testes

Male gametes

= sperm

Female Gonads

= ovaries

Female gametes

= egg cell (ova)