Name: ______________Date: ______________

Genetics, Probability, and Punnett Squares…Oh My!

One reason people study genetics is to ______________________________________ that someone will inherit a particular _____________.

This __________________ is used by breeders to develop plants, pets, and livestock but it has also been used to trace genetic traits in families.

In humans, we have ____________ pairs of chromosomes (____total) in every cell.

_______ from each biological parent.

Genes are a distinct sequence of bases (AGTC) which form part of a _______________________ - the order determines what amino acids (and therefore proteins) a cell will make

Mother Father

ALLELES – the_________ or variation of the gene,

any of several __________ of a gene

Ex. Gene = ____________

Gene

Gene

GG

Name: ______________Date: ______________

Alleles = _______________________________________________

Genotype describes the ___________________________ of an organism (the combination of alleles),

Phenotype describes the __________________ characteristics that the organism has. (How it physically exhibits the alleles that it’s coded for)

For each type of gene, we get one allele from our biological mother and one allele from our biological father from their chromosomes.

_____________________________ produce the same phenotype whether its paired allele is identical or different (this trait is always expressed/seen)

_____________________________ produce its characteristic phenotype only when its paired allele is identical (this trait isn’t as commonly expressed/seen)

Example:

Name: ______________Date: ______________

Heterozygous - ______________________________________________

Homozygous - _______________________________________________

PUNNET SQUARES – PREDICTING PROBABILITY

Place the genotype of one parent across the top and the genotype of the other parent across the side. Fill in the boxes with the possible combinations.

B= Brown eyes

(Capital letter for dominant)

b= blue eyes

(Lower case letter for recessive)

Bob’s mum: Bb

She is ______________________________________________________

Bob’s dad: BB

He is _______________________________________________________

What will Bob have? ___________________________________________

Reginald Punnet was a scientist (one of the first geneticists!) who understood that each parent provides an allele for any given gene from the gamete (egg or sperm). The alleles from each parent combine independently to create genetic variation in the population. By examining all possible combinations of the alleles, the probability that a particular trait is carried or expressed (seen) can be determined.

Ex. One pea plant has yellow seeds (YY) and one pea plant has green seeds (gg). What is the likelihood of green seeds?

Name: ______________Date: ______________

PUNNET SQUARE PRACTICE!