1. 8 th Grade Science Unit 5: Heredity and the Environment: Traits and Genetics Lesson 2: Genetics Vocabulary of Instruction

2. 1. Allele  Alternate versions or forms of the same gene that are located in a specific position of a chromosome. Different alleles of a gene give rise to different expressions of a character.

3. 2. Dominant Trait  An inherited trait that the offspring has if the dominant gene for that trait is present. It is represented by capital letters (BB, RR).

4. 3. Genetics  The study of how the traits of an individual are passed on to its offspring through genes.

5. 4. Genotype  The genetic make-up of an individual, determined by the alleles found on the homologous chromosomes.

6. 5. Heterozygous  An organism that has two different alleles on its homologous chromosomes for a particular trait.

7. 6. Homozygous  An organism has the same allele on both of its homologous chromosomes.

8. 7. Percentage  A given part or amount in a given 100. A numerical expression that includes a percent sign, with 100 assumed as the denominator.

9. 8. Phenotype  The outward physical expression of an organism that depends on the relationship between the genes and the environmental conditions where the organisms are developed.

10. 9. Punnett square  Is a diagram or chart used by geneticists to predict the outcome or all possible allelic combinations of gametes of a particular cross or breeding experiment with known genotypes. It is named after Reginald C. Punnett.

11. 10. Ratios  Proportional relation, relationship of quantity or size between two things.  The relation between two similar magnitudes with respect to the number of times the first contains the second: the ratio of 5 to 2, written 5:2 or 5/2.

12. 11. Recessive trait  An inherited trait that can be carried in a person's genes without physically appearing in that person. It is represented by lower case letters (r, s, t).