GENETICS INTRODUCTION

Things you need to know to talk like a real geneticist…

Genes, Heredity and Mendel

Those things on our chromosomes that make us the way we are

We get all of them from our parents…called HEREDITY

Mendel’s experiments– 1 Crossed two different true-breeding plants– 2 Self-crossed the results from the first

experiment

Phenotype – the visible expression of the gene (Tall, short)

Genotype – the types of genes present

Let’s try!

Using the trait for plant height in pea plants, where tall is dominant over short, and using the letters T and t for the alleles, answer the following….

Heterozygous – one of each type of gene – Aa

Homozygous – both genes the same – AA or aa

1)       What would be the symbol for a tall gene?

2)      What would be the symbol for a short gene

3)      What would be the genotype for a short plant?

4) What would be the two possible genotypes for a tall plant?

5) What would be the phenotypes for the following genotypes: a. Tt

b. TT

c. tt

6)       What would be the genotype for a heterozygous individual?

7)      What would be the genotype for a homozygous recessive individual?

8)      What would be the genotype for a homozygous dominant individual?

In pea plants, yellow pea color is dominant over green pea color. Using the letters G and g for the alleles, answer the following questions…

9)  What would be the genotypes for

a.     A green pea plant

b.     A heterozygous yellow pea plant

c.      A homozygous yellow pea plant

CONGRATULATIONS

You are now ready to take some parents & make some kids!

Genetics exceptions….

•Incomplete Dominance•Polygenetic Traits•One gene = more than 1 trait•Environmental Factors

Incomplete Dominance

Neither allele is dominant over the other

Instead of one “beating” the other, the resulting phenotype is a “mix” of the two

Snapdragon example

Polygenetic Traits

Traits controlled by more than one gene

Can get more variety that way

Eye color is an example

One gene: more than 1 trait

White fur, blue eyed tiger

Environmental Factors

Even though your genes code for a certain trait, they need to be provided the correct environment to become “real”

Nutrition, health care, etc.

Video game example