Genetics

Somatic Cells Review Autosomes: Pairs that Call for anything but Gender (22 pairs) Sex Chromosomes: (1 pair): XX=female XY=male

Gametes: Review Have 23 chromosomes produced by meiosis. Occurs in sex cells (egg and sperm). Gametogenesis is the production of sex cells (going from diploid or 23 pairs of chromosomes to haploid 23 total chromosomes)

Genetic Vocabulary Gene= single piece of DNA that has instructions to produce a certain proteins. Locus= place on a chromosome where a gene lives. Allele=all the different types of things one gene could call for (i.e hair color could be red, blonde, brown, black, grey etc..)

Vocabulary continued… Genome= all of an organism’s genetic material (unless you’re an identical twin yours is unique) Genotype=genetic makeup of a specific set of genes (i.e haircolor) indicated by a two letter combination Phenotype=physical characteristics of those sets of genes. (i.e RED hair)

Genotypes and Phenotypes: Because one gene is donated from mom and one is donated dad, genotypes typically have two letters. The dominant allele is that trait that is expressed when two different alleles or two dominant alleles are present. A recessive allele is that allele that is only expressed when two of the same are present.

Genotype and Phenotype continued… The dominant allele is usually indicated as the capitol letter. (ex: R of RR or Rr) The recessive allele is usually indicated as the lower case letter. (ex: r of rr or Rr) Dominant doesn’t mean, better, stronger or more frequent. It just means that it is expressed when the other is present.

Example:

Vocabulary continues… Homozygous allele: two of the SAME alleles at a specific locus. (Two alleles that call for red hair on both chromatids) Heterozygous allele: two DIFFERENT alleles at a specific locus. (One for red hair and one for blonde).

purplewhite

Before Mendel (don’t copy this) Many theories (Hippocrates, Aristotle, and the idea of “preformation”) abundant from 400 BC to late 1800’s. Essentially it was an idea the a blending of each of the parts (male and female) formed a new organism.

Homonculus

Mendel (don’t copy this either) Austrian monk in Brno (which is in Hungary) He came along and very, very carefully isolated distinct identifiers that were passed on from parent to offspring. He used pea plants. (Easy to control, grow and see the results)

Mendel continued.. (still not copying) He isolated 7 traits that he controlled (bred) for in these pea plants. By carefully studying and recording each cross and the results of each cross for 8 years, he developed a very solid theory of how things were passed from parent to offspring.

Mendel’s Principles of Genetics 1. Traits are inherited as distinct units. 2. Organisms inherit two copies of each gene, one from each parent. 3. Organisms donate only one copy of each gene in their gametes. (and the copies separate during gamete formation (gametes are haploid remember?).