Monohybrid Cross Explained

Defining a Monohybrid Cross00:00:00

A monohybrid cross is a mating event between two heterozygous parents for a single gene. Each parent carries two different alleles, with 'mono' referring to the single gene and 'hybrid' to the mixed alleles.

Pea Plant Example: Yellow vs. Green Peas00:00:35

Using pea plants, yellow peas are produced by a dominant allele, and green peas by a recessive allele. A plant will have yellow peas if it's homozygous dominant or heterozygous, and green peas if it's homozygous recessive.

Predicting Offspring Genotypes with a Punnett Square00:01:07

When setting up a Punnett square for two heterozygous parents, offspring genotypes will be 1/4 homozygous dominant, 2/4 (1/2) heterozygous, and 1/4 homozygous recessive. This results in a 1:2:1 genotype ratio, typical for a monohybrid cross.

Predicting Offspring Phenotypes and Ratios00:01:43

Based on genotypes, 3/4 of the offspring will have yellow peas (dominant phenotype) and 1/4 will have green peas (recessive phenotype). This gives a 3:1 phenotype ratio, also typical for a monohybrid cross. If 100 offspring were produced, approximately 75 would be yellow and 25 green.

Recognizing a Monohybrid Cross from Phenotype Ratios00:02:18

If two organisms of the same phenotype for a given gene produce offspring with a 3:1 phenotype ratio, it indicates that both parents in that cross are heterozygotes.