Monohybrid Crosses

Monohybrid Crosses

Allele = two or more alternate forms of a gene. Alleles are located on the same location of homologous chromosomes

Dominant = the allele that determines expression

Recessive = these alleles are overruled by dominant alleles.

Genotype = which alleles the organism contains

Phenotype = observable traits of an organism

Homozygous= both alleles are the same

Heterozygous = the two alleles are different

You can determine the genotype and the phenotype of progeny by doing a monohybrid cross and using a Punnett square.

Using Mendel's work, we cross one round plant (Rr) with one wrinkled plant (rr). What are the potential genotypes and phenotypes of the F1 generation.

Solution:

	r	r
R	Rr	Rr
r	rr	rr

Genotypes : 2/4 are Rr, 2/4 are rr

Phenotypes: 2/4 are round, 2/4 are wrinkled.

Now let's cross two heterozygous plants. What does this mean?? Rr. What is the phenotype of these plants? Round (because it is dominant).

	R	r
R	RR	Rr
r	Rr	rr

Genotypes of the F1 generation? ¼ RR, 2/4 Rr, ¼ rr

Phenotypes of the F1 generation? ¾ round, ¼ wrinkled.