1. Basic Elements of Genetics By Jane Horlings

2. Genetics The alternate forms of a gene are called alleles Alleles are denoted by a letter or letters; dominant genes are typically denoted by a capital letter, recessive genes with a lower case letter

3. Genetics If cells have the same allele for a certain trait, they are homozygous – We can say characterize this as homozygous dominant or homozygous recessive

4. Genetics If cells have different alleles for the trait, it is termed heterozygous – A heterozygote would have one dominant and one recessive allele – A plant might have one allele for yellow seeds and one allele for green seeds

5. Genetics Heterozygotes carry two different alleles (e.g. Hh); homozygotes carry identical alleles (HH or hh) Heterozygotes have a recessive and a dominant allele for a particular characteristic (Hh)

6. Genetics We refer to the genetic makeup of an organism as its genotype – The genotype is what is in the genes The physical appearance is the phenotype – The phenotype is what is “seen”

7. Genetics The genotype of these peas might be Ww (one dominant gene, smooth, and one recessive gene, wrinkled) The phenotype is smooth

8. Genetics The phenotype of an individual does not always reveal its genotype Heterozygotes (e.g. Hh) show the dominant trait H; the recessive trait h is masked The phenotype of the homozygous dominant (HH) and the heterozygote (Hh) is typically identical

9. Genetics