Honors Biology 2011
Ms. Lidman & Mrs. Abbott
GENETICS STUDY GUIDE
VOCAB TO KNOW:
• heredity
• genetics
• homozygous
• heterozygous
• phenotype
• genotype
• dominant
• recessive
• allele
• gene
• Punnett square
• test cross
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monohybrid cross
P generation
F1 generation
F2 generation
dihybrid cross
incomplete dominance
non-disjunction
autosomes
sex chromosomes
co-dominance
epistasis
pleiotropy
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polygenic inheritance
autosomal recessive
autosomal dominant
mitochondrial linked
sex-linked (x or y) trait
sex-limited trait
sex-influenced trait
pedigree
carrier
gamete
zygote
karyotype
1. Why did Gregor Mendel, the father of modern genetics, study peas (as opposed to
humans, for instance)? Did he study traits with continuous or discontinuous variation?
When (approximately)?
2. Mendel crossed pure (homozygous) round seeded pea plants with pure wrinkled
seeded pea plants and all the F1 generation plants had round seeds. What would be
the phenotypic and genotypic ratios of the F2 generation if the F1 generation selffertilized?
3. Describe Mendel’s Law of Segregation and Independent Assortment. How do these
laws contribute to variability in offspring?
4. What does probability have to do with genetics? How are the principles of probability
used to predict the outcome of genetic crosses?
Honors Biology 2011
Ms. Lidman & Mrs. Abbott
5. In genetics, the larger the number of offspring examined, the closer the results should
approach the predicted ratio. Can you think of an example outside of biology in which
a large sample size is beneficial?
6. What is the binomial expansion for (a+b)3? If you flipped three coins 100 times, how
many times would you expect to have all heads?
7. Why is a X2 test useful? What does a p-value of less than 5% mean?
8. What is a test cross? Give an example of when you might use a test cross.
9. Give an example of a dihybrid cross. If you cross parents that are heterozygous for two
traits, what is the expected phenotypic ratio in their offspring (assuming mendelian
inheritance)?
10. How could you predict the outcome of a trihybrid cross without making a 64-box Punnett
square? Ex. What percentage of offspring of two pea plants heterozygous for height
(Tt), flower color (Pp), and seed texture (Rr) would display the dominant traits?
11. What does it mean if a trait exhibits non-mendelian inheritance? Describe and give an
example of each of the following:
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Incomplete dominance vs. co-dominance
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Multiple alleles
Honors Biology 2011
Ms. Lidman & Mrs. Abbott
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Epistasis
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Pleitropy
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Polygenic Inheritance
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Environmental Influences: Why do identical twins not typically weigh exactly the
same amount?
12. What happens during non-disjunction? What’s an example of a disorder caused by nondisjunction of sex chromosomes?
13. Why is a karyotype a useful test for diagnosing some genetic disorders? What are its
limitations? What would it look like for a girl with Down Syndrome?
14. What determines gender in Homo Sapiens (i.e. Why should Anne Boleyn not have been
blamed for an inability to bear sons)?
15. What are autosomes, and how many are there in humans? How many autosomes are in
individuals with Downs?
16. Color blindness is caused by a recessive, sex-linked trait. How come color blindness is
more common in men? What conditions must be present in a family in order for a
woman to be color blind?
Honors Biology 2011
Ms. Lidman & Mrs. Abbott
17. What are the most common and least common blood types in the US? Could someone
with type AB blood receive a transfusion of type A blood? Could someone with type O
blood receive a transfusion of type AB? What are the likely consequences of these
transfusions?
18. Understand what an autosomal dominant vs. autosomal recessive pedigree would look
like, as well as sex-linked recessive and sex-linked dominant. Explain the pattern of
inheritance below. Assign a genotype to each of the individuals.
19. Can the traits shown in the following pedigrees be autosomal dominant? Autosomal
recessive? X-linked recessive? X-linked dominant? Explain.
a.
b.
Review practice problems
(Punnett squares, blood types, binomial expansion, etc.)!