Chromosomes You have 2 major types of cells: Somatic cells- body cells Asexual Gametes- Germ cells/sex cells such as sperm and egg sexual

*Every species has a specific number of chromosomes. Only duplicated in “Synthesis” phase of cell cycle (for mitosis) *Every species has a specific number of chromosomes. Humans= 46 chromosomes (these come in 23 pairs)

Diploid Chromosome Number http://www.vivo.colostate.edu/hbooks/genetics/medgen/chromo/species.html Common Name Genus and Species Diploid Chromosome Number Buffalo Bison bison 60 Cat Felis catus 38 Cattle Bos taurus, B. indicus Dog Canis familiaris 78 Donkey E. asinus 62 Goat Capra hircus Horse Equus caballus 64 Human Homo sapiens 46 Pig Sus scrofa Sheep Ovis aries 54

Body cells and gametes have different numbers of chromosomes! Diploid(2n)= 2 copies of each chromosome (46) Haploid(n)= 1 copy of each chromosome (23) Meiosis divides diploid cells into haploid cells!

1) Autosomes= Chromosome pairs #1-22 (related to body appearance; not body sex) 2) Chromosomes come in homologous pairs- (2 chromosomes each: 1 from mom, 1 from dad) *homo= same (same length/size/genes) 3) Sex Chromosomes= Chromosome pair #23 (sex chromosomes, X and Y, determine gender in mammals)

Karyotype- Image of all cell chromosomes #1-22= autosomes #23= Sex chromosomes

XX = Female XY = Male *Male determines sex of child! Abnormalities in Chromosomes Autosome abnormalties: Down syndrome (trisomy 21): The result of an extra copy of chromosome 21. Down syndrome affects 1:800 children

Down syndrome http://www.biology.iupui.edu/biocourses/N100/2K2humancsomaldisorders.html http://www.impactlab.com/wp-content/uploads/2008/10/downschild-255.jpg

Sex Chromosome abnormalties: Klinefelter syndrome: 47, XXY males. Male sex organs; unusually small testes, sterile. Breast enlargement and other feminine body characteristics. Normal intelligence.

47, XYY males: Individuals are somewhat taller than average and often have below normal intelligence. At one time (~1970s), it was thought that these men were likely to be criminally aggressive, but this hypothesis has been disproven over time.

Trisomy X: 47, XXX females. 1:1000 live births - healthy and fertile - usually cannot be distinguished from normal female except by karyotype.

Monosomy X (Turner's syndrome): 1:5000 live births; the only viable monosomy in humans - women with Turner's have only 45 chromosomes!!! XO individuals are genetically female, however, they do not mature sexually during puberty and are sterile. Short stature and normal intelligence. (98% of these fetuses die before birth)

Sexual Reproduction- Fission of 2 gametes (= genetic mixture of parents) Actual fission of egg and sperm = Fertilization Meiosis- Process of making new sex cells.