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January 11, 2012
BIO 12: Genes and Heredity Questions
Read (don’t just skim!) pages 128-135 in Nelson Biology 11 text and answer the
following questions in the spaces provided.
1. Define heredity.
The passing of traits from parents to offspring.
2. The father of genetics is Gregor Mendel. Who was he?
An Austrian Monk whose experiments laid the foundation for the science of genetics.
3. What species did Mendel use for his investigations into heredity? Why was this a
good choice?
Mendel used garden peas: yellow and green, smooth and wrinkled.
It was a good choice because: 1) there are a number of characteristics expressed
one of two ways, which made it easier to see which had been inherited and which
was dominant/recessive. 2) the plant reproduced two ways - sexually and asexually.
4. Mendel didn’t know about genes at the time. He referred to things called “factors”
which we now know to be genes. Write a definition for a gene as you understand it
now (this question is not from the text).
Genes carry the instructions that dictate your physical traits.
5. What are alleles? Provide an example.
Two or more alternate forms of a gene. The alleles are located at the same position
on one of the pairs of homologous chromosomes. An example: eye color gene,
alleles = brown, blue, green, etc.
6. Explain the relationship between dominant and recessive traits.
Dominant and recessive traits are alleles. When a dominant and recessive allele are
together, the dominant allele will be the trait expressed.
Example - Brown Eyes is the dominant allele to Blue Eyes.
(B)
(b)
Bb
7. State Mendel’s Law of Dominance.
The dominant allele of a gene is always expressed when the recessive allele is
present.
8. State Mendel’s Law of Segregation.
A pair of alleles separate or segregate during the formation of sex cells.
9. Distinguish between genotype and phenotype.
Genotype = the alleles an organism contains (example : Bb)
Phenotype = the observable traits of an organism that arise because of the
interaction between genes and the environment. (example: Bb – brown eyes
10. What is the difference between homozygous and heterozygous? Provide an
example of each.
Heterozygous: A genotype in which alleles of a pair are different. Example – Bb
Homozygous: A genotype in which both alleles are the same. Example – BB or bb
11. What does F1 and F2 mean refer to?
F stands for “filial”. F1 = first generation
F2 = second generation
12. Study Figure 5 on page 132. The figure looks at the creation of round and wrinkled
peas.
a) Which is the dominant trait? Which is the recessive trait?
b) If a pea were to be wrinkled, which alleles must they receive from each
parent? Why?
c) If a pea were to be round, which alleles did they receive from each parent?
d) How do we represent dominant and recessive alleles using letters. Provide an
example using figure 5.
13. Brown hair is dominant to blond hair. Write your own letters to represent brown hair
as dominant, and blond hair as recessive.
14. How is it possible for two parents with dark brown hair to have a child with red hair?