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SBI 3U Review Unit #1 – Genetics
Vocabulary:
genetics
Mendel
dominant
recessive
Law of Segregation
heterozygous
pure breeding plants
parentals
recessive
alleles
genotype
phenotype
homozygous
Principle of Dominance
monohybrid cross
Punnett Square
dihybrid cross
gametes
incomplete dominance
co-dominance
Law of Independent
Assortment
cell cycle
interphase
G1 phase
S phase
G2 phase
mitosis
somatic cell
chromosome
prophase
metaphase
telophase
cytokinesis
cell plate
meiosis
diploid
haploid
centrioles
tetrad
crossing-over
random assortment
homologous chromosomes
non-disjunction
sister chromatids
deoxyribose sugar
phosphate
nitrogenous base
double helix
nucleotide
complementary base
pairing
sex-linked trait
multi-allelism
Tay-Sachs disease
albinism
sickle-cell anemia
Huntington’s disease
cloning
karyotype
pedigree
mutations
deletion
duplication
inversion
translocation
genetic counselling
amniocentesis
ultrasound
GMOs
gene therapy
F1 generation
Diagrams to Know: Cell Cycle, Mitotic Cell Division, Meiotic Cell Division crossing over, Cytokinesis
Review Questions:
1. Why did Gregor Mendel use the garden pea plant to study genetics?
2. What is a recessive allele?
3. A mother has a widow’s peak hairline (she is heterozygous for this trait). Her husband also has a widow’s peak (he is
heterozygous for this trait too). W hat are the genotype and phenotype ratios for the hairline in their children?
4. If a purple flowered pea plant which has round seeds (heterozygous for both traits) is crossed with a white
flowered wrinkle-seeded plant, what are the phenotype ratios of the offspring? (purple is dominant to white;
round is dominant over wrinkled)
5. Two parents are double heterozygotes: they have hitch-hiker’s thumbs and can taste PTC. W hat are the
phenotype ratios in their children?
6. What phenotype and genotype ratios would be produced if two pink snapdragon plants were crossed?
7. A man who is blood type A and his wife who is blood type B have children. Is it possible for them to have a child with
blood type O? Prove your answer with a Punnett square.
8. If both parents are blood type AB, what different blood types are possible in their children?
9. Mr. Smith, type O blood and Mrs. Smith, type AB had a daughter named Debbie. Debbie married Jeff (type A) and they
had 4 children. Two of their children had type A blood, one had type B and one had type AB blood. What is Debbie’s
blood type and genotype?
10. Draw and label the cell cycle.
11. What is the overall purpose of mitotic cell division? How does it compare to a meiotic cell division?
12. State the phase of mitotic cell division in which each of the following occurs:
a. Chromosomes align at the equator.
b. A new nucleus forms around two sets of chromosomes
c. Spindle fibres first form
d. The nucleolus disappears
e. Chromosomes separate into 2chromatids
13. Draw a diagram of a chromosome. Label the centromere and sister chromatids.
14. What is meant by the term “diploid”? W hat is the diploid number for human cells?
15. What is a homologous chromosome?
16. A boy is red-green colour blind, which is a sex-linked recessive gene on the X chromosome. W ho did he inherit the
defective allele from? Explain. Will any of his children inherit this colour blindness if he marries a normal vision girl?
Explain with a Punnett square.
17. State all the events that occur during prophase, metaphase, anaphase and telophase of mitosis.
18. What is the overall purpose of meiosis?
19. How many cells are potentially produced in meiotic cell division from one diploid cell?
20. Answer the following regarding crossing over in meiosis?
a. When does it occur?
b. What kind of chromosomes are involved?
c. What is the end result and why is this so significant to the overall purpose of meiosis?
21. What other important event, other than crossing over, occurs during meoisis? Explain it and its significance.
22. What is non-disjunction, and what role does it play in Down syndrome?
23. Name the four nitrogenous bases.
24. What is complementary base pairing?
25. What are the three components of a nucleotide?
26. What is Tay Sachs disease, and what treatment is available?
27. What is wrong with the people who have sickle cell anemia?
28. What is a karyotype, and what information can be learned from it?
29. What traits are probably polygenic? (multifactorial) How do you know?
30. What things can be cloned? What is the purpose of cloning?
31. What is a pedigree?
32. Explain the four changes in chromosome structure; deletion, duplication, inversion and translocation (briefly)
34. Explain DNA replication, transcription and translation in detail (location in the cell, products of each process, structure
of DNA/RNA)
Other practice word problems:
1. In humans, albinism (lack of skin pigment) is due to a recessive gene. Suppose that two normally pigmented parents
produce an albino child. What would the genotypes of the parent have to be? Use a Punnett square and proper format
to prove your answer.
2. In tomatoes, red fruit is dominant over yellow fruit. If a heterozygous plant is crossed with a yellow-fruited plant, what
would be the genotype and phenotype ratios of the offspring?
3. In fruit flies, sepia eye colour is recessive to the dominant red eye colour, and curved wings are recessive to the
dominant straight wings. If a double heterozygous parent is crossed with a fly which is heterozygous for eye colour but
has curved wings, what would be the phenotype ratios in their offspring?
4. Allan has blood type AB, and his wife Kate has blood type A. If Kate is heterozygous, what are the possible blood types
in their children, and what chance do they have for each type?
5. Lisa’s father has red-green colour blindness, but Lisa has normal colour vision. Lisa’s husband Peter also has redgreen
colour blindness. If this condition is caused by a recessive sex-linked gene, what are the chances of the boys, that they
will be colour blind? What are the chances of the girls, that they will be colour blind? What are the chances of the girls,
that they will be carriers but have normal vision?
6. Study the pedigree to the right.
a. What kind of inheritance pattern does this pedigree suggest?
- Could it be dominant? What would the parental
genotypes ( 1 & 2) have to be?
- Could it be recessive? What would the parental
genotypes (1 & 2) have to be?
b. If black shapes on this pedigree show individuals with blond hair
(recessive to dark hair), work out the genotypes for each
individual