Genetics Study Guide
Use this guide to help you review topics from Unit 5 in preparation for the upcoming test. This guide is
intended to help you prepare, but not to be your only way to prepare. There may be items on the test not
included in this study guide. Also, review ppts, study guides, review sheets, virtual labs, and activities. As
always, do your best to use active and not passive review techniques.
Chromosome Numbers Practice
1. A dog normally has 39 pairs of chromosomes. Answer the following questions:
a. What is the diploid number?
b. What is the haploid number?
c. How many chromosomes in an egg cell?
d. How many chromosomes in a brain cell?
e. How many chromosomes in a skin cell?
f. How many pairs of homologous chromosomes?
g. How many chromosomes in a cell produced by mitosis?
h. How many chromosomes in a cell produced by meiosis?
i. How many tetrads are there in prophase of meiosis I?
2. Answer A-J above for a goldfish, which has 94 chromosomes in a liver cell.
3. Answer A-J above for a cat, which has 19 chromosomes in a sperm cell.
4. Answer A-J above for an elephant, which receives 28 chromosomes from each parent.
Part A: Respond to each of the following.
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Review the steps of meiosis. Be able to recognize, name, describe each step.
Compare and contrast meiosis with mitosis.
Discuss the ways that meiosis is important for sexual reproduction.
Review chromatin, chromatid, chromosome, centromere, and centrosome.
Understand and be able to explain the role of microtubules in cell division.
Why is Gregor Mendel considered the father of genetics?
Define the following vocabulary words: law of independent assortment, law of segregation, dominant,
recessive, homozygous, heterozygous, haploid, diploid, homologous chromosomes, sister chromatids,
phenotype, genotype, allele, gene, chromosome, somatic cells, gametes, zygote, karyotype, monosomy,
trisomy.
Understand what is meant by a Mendelian experiment and be able to show and explain the process.
What is a sex-linked trait? Who is more likely to inherit a sex-linked disorder? Why?
Name and describe five different external factors that can influence phenotype. Give examples of how each
affects phenotype.
What determines the sex of a child?
What is polygenic inheritance? What type of distribution does it have in the populations?
Describe a trait that has multiple alleles.
Be able to read and interpret a karyotype.
Part B: Read each statement and decide whether they are true or false. If a statement is true, write, “This
statement is true”. If a statement is false, rewrite it so that it is true.
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Being heterozygous is an example of phenotype.
Having brown eyes is an example of genotype.
If a person has one dominant allele and one recessive allele, they will have the dominant trait.
It is always possible to figure out genotype if you know a person’s phenotype.
It is always possible to figure out phenotype if you know a person’s genotype.
If a person is heterozygous for brown eyes, they cannot have a blue-eyed child.
If a person is homozygous dominant, they can have a child who looks like the recessive trait.
Part C: For each of the following examples, work a Punnett Square and give the genotypic and phenotypic
ratios of each cross.
1. In cows, having no horns is dominant to having horns. Show a cross between a heterozygous cow and a
horned cow.
2. In beans, curly leaves are dominant to flat leaves. Show the cross Ll x Ll.
3. In humans, long eyelashes are dominant to short lashes. Show a cross between a homozygous dominant
person and a heterozygous person.
4. Hemophilia is a sex-linked bleeding disorder. Show a cross between a woman who carries the disorder and a
man who does not have it.
5. In peas, yellow is dominant to green, and wrinkly is dominant to round. Show a dihybrid cross between two
pea plant that are heterozygous for yellow wrinkly peas.
6. Color-blindness is a sex-linked disorder. Show a cross between a man who has it and a woman who does not
carry the gene.
7. Human nose width shows incomplete dominance. Show a cross between two people with medium-width
noses.
8. In cattle, the red and white hair alleles show codominance. Show a cross between a heterozygous cow and a
cow that is homozygous for the red allele.
9. In pea plants, green seeds are dominant over yellow seeds, and being tall is dominant over being short.
Show a dihybrid cross between two pea plants that are heterozygous for both traits.
Part D: Pedigrees: Draw a pedigree for each example. Determine whether the trait is dominant or recessive,
and whether it is sex-linked or autosomal. Be sure to identify any heterozygous individuals in the pedigree.
1. Michelle has a brother and an uncle on her mother’s side with Menke’s Disease. Neither her parents, two
sisters, nor her husband have the disorder, but she has a son who does. None of her grandparents have the
disorder, and neither does her mother’s sister.
2. Bill has Waardenburg Syndrome, as does his father and his father’s sister. Of Bill’s aunt’s children, his
cousin, Claire, has Waardenburg, but his cousin Mike does not. Bill’s grandmother on his father’s side has
the disorder, but his grandmother does not. On his mother’s side, he has two aunts, but none of them, nor his
maternal grandparents have Waardenburg.
3. Connie developed Wilson disease in her early thirties, as did her grandfather on her mother’s side. Neither of
her two brothers have the disorder. Her mother has a sister and a brother, and they are also free of the
disorder.