Mendelian Genetics
- Overview worksheet Station 1 - The Punnett Square
a) Describe what the Punnett Square is used for/shows.
b) Briefly explain what the letters stand for and why there are capital and lower-case letters.
c) Draw a Punnett Square of your own, making up two homozygous parents (plants or animals) with their
corresponding traits (colour of…/size etc.). Choose letters that make sense in this context.
(Reminder: the choice of letters is guided by the dominant allele, e.g. Y (yellow) and y (green, = not yellow)
Station 2 - Dominance of Alleles
a) Briefly state the difference between incomplete dominance and codominance.
b) Name an example for each kind of dominance.
Station 3 - The Second Mendelian Law
a) Formulate the Second Mendelian Law in your own words and in the style of the Law of Dominance.
b) As a fan of Guinea pigs you have decided to breed them yourself as you want to determine their fur
colour. You have bought two Guinea pigs, one male (brown fur) and one female (white fur) animal. You
know that the brown fur colour is dominant over the white fur colour.
I. Determine the phenotype of the F1 generation.
II. If you could cross two individuals of the F1 generation, which possible genotypes would be there in the
F2 generation? Draw a Punnett Square to emphasise your answer.
III. Match the terms homozygous and heterozygous (or hybrid) to the offspring in F2.
Station 4 - Vocabulary
Do the different vocabulary exercises on the worksheets provided.
Final: Write down three questions you still have or you could ask your class mates in a quiz. Write them
on an extra piece of paper as they will be collected later on.
The Second Mendelian Law
Mendel did not stop after his first experiments with the P-generation plants. He went on and
crossed two plants of the F1-generation with themselves.
First Crossing of P generation
Result is the F1 generation with
identical heterozygous plants (4
possibilities).
Second Crossing of F1
generation
a) Using the circled blossoms as the new P generation, draw a Punnett Square and calculate the
possible genotypes of their offspring. The next generation will then be called F2 generation.
(Help: D = red, r= white)
b) Write down the different phenotypes and count them - how many possible offspring of each
phenotype do you get? Note down the ratio (Verhältnis)
c) The text below describes the second Mendelian Law. Circle the correct words in bold (fett).