Heredity

Monohybrid Crosses

Heredity

Understand these?

Recessive: The member of the alleles which is blocked by the dominant allele. The trait only shows when dominant is absent. "x" is recessive to "X"

Homozygous: Two identical alleles for a trait. 'XX' or 'xx'

Heterozygous: Two different alleles for a trait. 'Xx'

Gene: A basic unit of heredity which control a specific trait.

Alleles: Two/alternate forms of genes which controls specific trait. Example XX, Xx, xx.

Dominant: One of the two alleles which dictates the trait. "X" is dominant over "x".

• One of the traits Mendel observed is the one seen in the diagram.

• some pea plants had green pods while others had yellow pods

• These are two different forms of a single trait (Pod color), either yellow or green

​monohybrid cross

The 1st plant is homozygote for green pod (GG) and is dominant over the recessive trait in the 2nd plant, yellow pod.(gg)


All the offspring produced between the green pod pea plant & yellow pod pea plant will have green pods.



Reason: All the offspring will inherit a dominant allele (G) from the dominant plant which will dictate/block the recessive allele (g) making all their pods green with alleles (Gg).

​1st

​2nd

All the offspring produced between the green pod plant and the yellow pod plants are heterozygote dominant for green pod. (Gg)


If two of the plants are crossed as seen the diagram, there will be a 25% chance that an offspring produced between them with have a yellow pod (gg).



GG = homozygote green (Dominant)
Gg = heterozygote green (Dominant)
gg = homozygote yellow (Recessive)

​Use all the information given to complete the worksheet.