Notes-Genetics 1. Genetics is the study of how hereditary traits are passed between generations.

2. A gene is a segment of DNA 2. A gene is a segment of DNA on a chromosome that codes for a specific trait.

3. Different forms of a gene are called alleles 3. Different forms of a gene are called alleles. For example, the gene that controls stem height in pea plants has one allele for tall and one for short.

4. One trait can be dominant. (mask) over the other form of the trait 4. One trait can be dominant (mask) over the other form of the trait. *Example: Brown eyes is dominant over blue. Blue eyes are recessive.

5. Genotype is the allele combination (BB, Bb, bb). 6.Phenotype is the appearance or visible feature of what a living thing looks like (dimples, no dimples).

What will the baby frogs look like?

7. Genotype terms and codes:. A. Pure: both alleles (genes) 7.Genotype terms and codes: A. Pure: both alleles (genes) for a trait are the same (HH or hh) Pure = Homozygous…they are synonyms

Hybrid = Heterozygous…also synonyms B. Hybrid: both alleles (genes) for a trait are different (Hh) Hybrid = Heterozygous…also synonyms

9. A punnett square is a tool used by geneticists to visualize all possible combinations of alleles from parents to offspring.

Black in rats is dominant = A White is recessive = a

Black in rats is dominant = A White is recessive = a

Lets do an example…to have dimples is dominant (D) Lets do an example…to have dimples is dominant (D). No dimples (d) is recessive. Do a cross of a pure dominant female and pure recessive male.