 DNA is our genetic “code”.  Our code is located on our chromosomes inside the nucleus of our cells.  One chromosome is made up of many genes.  One gene has information for one trait. /genetics/zoomIn/inde x.html

 Karyotype – when we organize our chromosome in pairs and organize them from biggest to smallest. The last pair are the sex chromosomes (determine sex). The sex chromosomes are not organized by size.

 Sex-linked genes – Carried on the X or Y (sex chromosomes) chromosome (usually the X), most are recessive and usually seen only in males (ex: balding). X - X-YX-Y Bbb Female Male B - normal hair (with hair) (bald) b – bald

Gregor Mendel

 Heredity – Passing traits from parents to offspring.  Genetics –The branch of biology that focuses on heredity.  Monohybrid Cross – a cross that involves only one pair of contrasting traits.  True-breeding – all of the offspring of a cross will display only one form.

An Austrian monk who carried out experiments with pea plants to formulate theories on heredity. He was the first to establish rules that predict patterns of heredity. Mendel crossed varieties of garden peas with contrasting traits, counted the number of each kind of offspring and collected data. Cross means the breeding of 2 individuals

 Mendel preformed monohybrid crosses using pea plants. P generation On1 of the 2 colors is in the F1 generation (dominant form). The other (recessively) will reappear in the F2 generation (in a 3:1 ratio).

 Alleles – the different versions of a gene, each is inherited from one parent. (so there are 2 alleles for each gene). There can be dominant or recessive alleles.  Homozygous – when 2 alleles in an individual are the same.  Heterozygous – when the 2 alleles in an individual are different.  Genotype – the set of alleles organism has  Phenotype – physical appearance of a character

PPunnett square – used to predict the outcome of a genetic cross. The two colors of flower (purple and white) - Alleles Both parents have 2 different alleles – (Bb) Heterozygous

 Monohybrids are when we use Punnett Squares to compare only one trait.  Ratios

 Can You Guess what these are?  Two traits at a time  Ratios

 The traits will blend together. This is because once trait cannot mask (cover) the other trait.

 Each allele is shown to it’s fullest abilities

 Law of Segregation – two alleles for a gene will separate when gametes are formed. (you get one from each parent)  Meiosis It’s like mitosis but it happens twice. When the cells undergo PMAT for the second time they never have as S phase where the chromosomes are copied. In the end, the two cells (gametes) have only half the number of organisms. Remember it’s here where nondisjunction and chromosomal mutations occur.

 Law of Independent Assortment – two or more pairs of alleles will separate independently of one another during gamete formation. For example a cat with brown hair will not always have long hair  Traits are given independently Hair Eye Color Height

 Genetic variation within a population  Caused by mutations  Anything that changes the gene pool results in evolution.

 The frequency of an allele in a stable population will not vary.  P+Q=1 or P+PQ+Q=1  Genotypes will tend to remain the same  Used to determine recessive alleles  Used to see natural selection.

 A randomly mating population must be free from mutations, migrations and natural selection  Frequencies of alleles will not change over time  And populations match the equation P+PQ+Q=1 Remember mutations are a good thing too or else we wouldn’t walk on two legs. It drives evolution.

Certain genes are more prevalent in a population than others (because they are more helpful for the survival of an organism) can’t survive - can’t reproduce