Mendel and Genetics

Gregor Mendel Called the “Father of Genetics” because he was the first to study genetics Researched how traits are inherited in pea plants

Mendel’s Experiments:

Mendel’s Experiments:

Mendel discovered that: Parents transmit info about traits to offspring (he called them “factors”, but we know now that they are genes) Each individual has 2 factors for each trait; 1 from each parent - this may result in homozygous (WW or ww) or heterozygous (Ww) combinations

The alternate forms of a factor are alleles The presence of an allele doesn’t mean that the trait is expressed (seen) the dominant allele is seen the recessive allele is only seen if an individual has 2 recessive alleles

For example, in pea plants: W = purple flower purple is dominant, therefore a capital letter w = white flower white is recessive, therefore a lower case letter WW = purple flower ww = white flower Ww = ?

Predicting offspring Punnett squares help to predict what alleles offspring might inherit

Step 2 of Mendel’s Experiment:

Step 3 of Mendel’s Experiment:

Analyzing Results: Probablility– the likelihood that something will happen Example: the probability of a coin landing with heads or tails is 50% Ratio – describes the probability of each phenotype or genotype The ratio of heads:tails is 50:50, or 1:1

Ratio of tall to short (PHENOTYPE) ___:___ Ratio of TT:Tt:tt (GENOTYPE) ___:___:___

% of brown rabbits ___ % of black rabbits ___ % of homozygous dominant (BB)___ % of heterozygous (Bb)___ % of homozygous recessive (bb) ___ Ratios can also be fractions, like these What are the possible phenotypes of the rabbits? _________ What are the possible genotypes of the rabbits? ________

How to set up a Punnett Square If you cross a heterozygous tall pea plant with a homozygous short pea plant what will the genotypic and phenotypic ratio be? Identify the letter to use to represent the trait. List the possible combinations Place the letter on the outside of the punnett square. Solve.