Page 36 - CB1.3 Genetic Varation sciPAD

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36 CB 1.3 GENETIC VARIATION
TRACKING GENES
1. Use a Punnett square to show the expected phenotypic and genotypic ratios of the
offspring produced from the following crosses:
(a) Two homozygous dominant plants.
Genotype of parent 1: Genotype of parent 2: 
Genotypic ratio of the offspring: 
Phenotypic ratio of the offspring: 
(b) Two heterozygous plants.
Genotype of parent 1: Genotype of parent 2: 
Mendel’s Peas
Gregor Johann Mendel (1822-1884), often called the “father of
genetics”, was an Austrian monk and scientist.
Mendel was curious about how traits were transferred from one
generation to the next, so he set out to study the principles of
inheritance in the mid-1860s. Peas were a good model system,
because he could easily control their fertilisation by transferring
pollen with a small paint brush.
One of Mendel’s most famous studies involved the inheritance of
round and wrinkled peas. He found that the alleles for round peas
were dominant to that of wrinkled peas.
Homozygous dominant
Genotype: RR
Phenotype: Round
Heterozygous
Genotype: Rr
Phenotype: Round
Homozygous recessive
Genotype: rr
Phenotype: Wrinkled
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