DNA

The Discovery of DNA

Gregor Mendel - The father of genetics Mendel studied pea plants to determine how parents passed their genes down to their offspring. He discovered half of a gene from each parent was passed to the offspring. This is called an allele. One allele for each trait is contained in each sex cell created during meiosis. Two sex cells join, one from each parent, during fertilization, to create a set of genes.

Punnett Square

Cross A Homozygous green (yy) pea plant with a homozygous yellow pea plant (YY). How many Homozygous yellow offspring do you get? How many Homozygous green? How many heterozygous yellow? Why won't you have heterozygous green pea plants?

Cross two of the offspring from the previous cross, homozygous (Yy). How many Homozygous yellow offspring do you get? How many heterozygous yellow? How many Homozygous green?

Now Cross a Homozygous green (yy) with a Heterozygous yellow (Yy). How many yellow offspring? How many green offspring? How many Heterozygous yellow? How many Homozygous green? How many Homozygous yellow?

[|Genetics Practice Problems] [|Introducing Punnett Squares] [|Crosses]

DNA MODEL

Create DNA models from common household materials.

Each model must be at least 20 nucleotides long and form two turns of the helix. Remember that there are 10 bases per turn.

Include a key to show how the phosphates, sugars and nitrogen bases are represented. (Nitrogen Bases are Adenine, Thymine, Guanine and Cytosine)

Remember to include the correct number of hydrogen bonds between the bases.