A punnet square is a chart which predicts all possible gene combinations in a cross of parents. Punnett squares are named after an English geneticist. His name was Reginald Punnett. He found some basic rules of genetics.
Know I will tell you how to use a punnet square.
Example:
Why don't we use pea plants since a very famous monk studied them! His name was Gregor Mendel.
For pea plants, tall pea plants, always, are dominant over short pea plants. Using punnet squares, you can predict the offspring's genotype and phenotype. By a cross between a homozygous (purebred) tall pea plant and a homozygous (purebred) short pea plant.
Steps:
- Use letters that will represent the traits or genes. dominant= upper case letters recessive= lower case letters
- Write down each gene of both parents. These are sometimes given to you or possible to determine. TT x tt (tall) (short) - both homozygous (same) or purebred
- List the genes that each parent give. Parent 1 Parent 2- TT= T tt= t
- Draw a punnet square. they have 4 small squares in shape of a window. Draw the possible genes of a male parent across the top and another possible genes of a female parent across the left side of the punnett square.
- Fill in each box of the Punnett square by transferring the letter above and in front of each box into each appropriate box. As a general rule, the capital letter goes first and a lowercase letter follows.
- Then list all the possible genotypes and the phenotype.
phenotype= physical appearance
genotype= genetic makeup
ex.
phenotype- 100% of being tall
genotype- 100% of Tt
PUNNETT SQUARE:
Check out the site!!
http://www.usoe.k12.ut.us/CURR/Science/sciber00/7th/genetics/sciber/punnett.htm
Want to practice your punnett squares!!
