Name: _____________________
Genetics Practice Questions
Complete the following crosses on the Punnett squares below. First fill in the parental
genotypes and then fill in the possible genotypes of the offspring. Under each square, list
the percentages of the phenotypes of the offspring.
Gene ‘P” controls flower colour, where ‘P” is dominant, producing purple flowers, and gene p
is recessive, producing white coloured flowers. Determine the results of the following
crosses.
1. Homozygous Purple x White
2. Heterozygous Purple x Heterozygous Purple
3. Heterozygous Purple x White
Gene ‘H’ controls if humans have hairy toes. H is dominant, resulting in hairy toes, and h is
recessive, resulting in smooth toes. Determine the results of the following crosses.
4. Homozygous hairy-toed x heterozygous hairy-toed
5. Heterozygous hairy-toed x homozygous smooth-toed
6. smooth-toed x smooth-toed
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Incomplete Dominance
Complete the following crosses on the Punnett squares below. First fill in the parental
genotypes and then fill in the possible genotypes of the offspring. Under each square, list
the percentages of the phenotypes of the offspring.
The ‘T’ gene controls height in Daffodils, with the T gene demonstrating incomplete
dominance over the recessive ‘t’ gene. Describe the results of the following crosses:
1. Tall x Normal
2. Normal x Normal
3. Tall x Short
Using the flower example in your textbook on page 399, determine the resulting offspring of
the following crosses:
4. Red x Pink
5. Pink x White
6. Pink x Pink
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Codominance and Multiple Gene Interactions
Complete the following crosses on the Punnett squares below. First fill in the parental
genotypes and then fill in the possible genotypes of the offspring. Under each square, list
the percentages of the phenotypes of the offspring.
Using what you know about human blood type, determine the outcomes of the following
crosses.
1. IAIB x IAIB
2. IAi x IBIB
3. ii x IAi
4,5. A man with blood type AB has a child with a woman who has type A blood. Show the
two possible crosses that could result.
6. Show an example of a cross that would allow two parents with different blood types to
produce offspring with an equal chance of getting any of the 4 blood types. (A, AB, B, or
O) (*Tricky*)
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Two-trait Cross: In peas, yellow seed colour (Y) is dominant over green seed colour (y), and
round seed shape (R) is dominant over wrinkled seed shape (r).
Cross 7:
Cross 8:
Cross a YYrr female with a yyRR and list the phenotype(s) of the offspring
underneath. (use special Punnett square on back).
Do a cross of the offspring from #7. Work out the ratio of phenotypes of the
offspring underneath.
7
Phenotype:
8
Ratio of phenotypes:
Sex-Linked Genes
Complete the following crosses on the Punnett squares below. First fill in the parental
genotypes and then fill in the possible genotypes of the offspring. Under each square, list
the percentages of the phenotypes of the offspring. (e.g. 50% normal vision, 50% colourblind etc.). Indicate which children are CARRIERS, if applicable.
Using what you know about colour-blindness, complete the following crosses. (remember,
the allele for colour vision is carried on the X chromosome!):
1. homozygous normal female and a normal male
2. colour-blind female and a colour-blind male
3. colour-blind female and a normal male
4. carrier female and a colour-blind male
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Why are men more likely to be colour-blind that women?