1. BASIC GENETICS TERMS Terms you’ve gotta know

2. GENE Gene : a section of DNA that codes for a trait A chromosome is a chunk of DNA and genes are parts of chromosomes

3. ALLELE Allele : the different options for a gene Example: attached or unattached earlobes are the alleles for the gene for earlobe shape

4. DOMINANT/RECESSIVE Dominant : an allele that blocks or hides a recessive allele (UPPER CASE letter) A Recessive : an allele that is blocked by or hidden by a dominant allele (Lower case letter)a

5. HOMOZYGOUS/HETEROZYGOUS Homozygous : When a person’s two alleles for a gene are the same (AA or aa) Heterozygous : When a person’s two alleles for a gene are different (Aa) You get one allele from your mom and one from your dad. If you get the same alleles from your mom and dad, you are homozygous for that trait. If your mom gave you a different allele than your dad, you are heterozygous for that trait

6. GENOTYPE Genotype : A person’s set of alleles (gene options) Genotype is written in letters (Tt) It is usually the first letter of the dominant allele to make it easier Choose a letter for each of these traits. Write both the dominant and the recessive genotype allele letters Attached Earlobes Freckles Dimples Tongue-roller Tt

7. GENOTYPE Now, using your letters from before write a genotype for a person without freckles (Freckles are dominant) Write a genotype for a person with freckles

8. GENOTYPE-HETEROZYGOUS AND HOMOZYGOUS A Heterozygous genotype means an organism has both the dominant and the recessive allele (e.g. Aa) Homozygous recessive means an organism has 2 recessive alleles (e.g. aa) Homozygous dominant means an organism has 2 dominant alleles (e.g. AA)

9. PHENOTYPE Phenotype : A person’s physical features because of their genotype What you look like (your phenotype) is based on what your genotype is (your genes) What will the phenotype of these genotypes be: WW, Ww, ww (Widow’s Peak dominant over straight hair line) HH, Hh, hh (Hitch hiker’s thumb is dominant over a straight thumb) CC, Cc, cc (Curly hair is dominant over straight hair)

10. PRACTICE PROBLEMS One cat carries heterozygous, long-haired traits (Ss), and its mate carries homozygous short- haired traits (ss). Use a Punnett square to determine the probability of one of their offspring having long hair. One cat carries heterozygous, long-haired traits (Ss), and its mate carries homozygous short- haired traits (ss). Use a Punnett square to determine the probability of one of their offspring having short hair.

11. PRACTICE!! One flower is heterozygous red (Rr) and it is crossed with a homozygous white (rr) plant. Use a Punnett square to determine the probability of one of their offspring having a white color.