Mendelian Genetics

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Mendelian Genetics
Heredity is the passing of genetics from your parents to you. The characteristics you have resemble the characteristics that your parents have. There can be patterns to heredity. Mendel’s studies were the first to accurately predict those patterns. These patterns form the basis of genetics. Before Mendel’s experiments people thought that offspring were a blend of traits. Through his experiments he discovered this is not the case.

Offspring have two separate heritable factors for each character, one from each parent. The different versions of a gene are called alleles. There are both dominant and recessive alleles. You could have two dominant alleles, two recessive alleles, or one dominant and one recessive allele. Having two of the same alleles means you are homozygous. Having two different alleles means you are heterozygous.

Genotype is the set of alleles a person carries for a character. Phenotype is the physical appearance of a character. Depending on the alleles your parents’ carry determines the alleles you will inherit. If one of your parents had two dominant genes and the other has two recessive genes. Then those genes will separate. These are now called gametes. During fertilization, the offspring receives one allele from each parent. In this case the offspring would inherit one dominant gene and one recessive gene. Although the offspring will physically show the dominant gene they still have the ability to pass on the recessive gene.

A punnett square can be used to predict the outcome of a genetic cross. If two heterozygous people produce offspring, there is a 25% chance the offspring will be homozygous dominant. A 25% chance the offspring will be homozygous recessive, and a 50% the offspring will be heterozygous. This means that the offspring will most likely be heterozygous; the offspring will physically show dominant traits but will still be able to pass on recessive traits.
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