8th Grade ScienceUnit 5:

Heredity and the Environment: Traits and Genetics

Lesson 2: Genetics

Vocabulary of Instruction

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.

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).

3. Genetics

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

4. Genotype

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

5. Heterozygous

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

6. Homozygous

An organism has the same allele on both of its homologous chromosomes.

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.

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.

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.

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.

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).