Download Grade 11 Genetics Answers

SBI 3UI Unit 3 Review: Genetic Processes
Try these questions:
1. Which phase of meiosis is shown here?
d)
metaphase II
2. Which of the following processes contributes to genetic variation?
c) crossing over
3. What is the predicted phenotypic ratio of the offspring from a dihybrid cross between two individuals
that are heterozygous for both traits?
b) 9:3:3:1
4. What is the goal of therapeutic cloning?
a) to produce identical cells to treat disease
5. What are haploid and diploid cells? Where is each cell type found?
• Haploid: have half the normal chromosome number; found in sex cells
• Diploid: have the normal chromosome number; found in somatic (body) cells
6. Describe what the terms dominant and recessive mean. How are they used to describe the forms of
a trait at the genotype level and at the phenotype level?
• Dominant: if an organism has a single copy of the dominant allele, that trait will show up. In the
genotype, dominant alleles are represented by capital letters; in phenotype, it is a description of
the trait (ex. freckled)
• Recessive: an organism needs two copies of the recessive trait in order to have it. In the
genotypes, recessive alleles are represented by small letters; in phenotype it is a description of
the trait (ex. non-freckled)
7. What is the difference between a gene and an allele?
• Gene is a trait (ex. hair colour); allele is one of the forms of that trait (ex. blonde, brunette,
redhead)
8. Determine the probability of a hemophiliac child being born when neither the father nor mother has
hemophilia, but the mother’s father has hemophilia. Is there any chance that their daughters will be
affected? Why or why not?
H
H h
• Father: X Y; Mother: X X (hemophilia is a sex-linked recessive trait)
• Punnett square will show that 50% of sons will be affected by hemophilia and 50% of daughters
will be carriers (but will not have hemophilia)
9. From the following blood types, determine which baby belongs to which parents. Explain your
choices.
• Baby 1 – blood type O (belongs to the Jones family because both Mr. and Mrs. Jones could have
a type O allele, which is recessive, to give their baby)
• Baby 2 – blood type B (belongs to the Guttierez family
because only Mrs. Guttierez has a B allele to give to
her baby)
10. This pedigree traces a genetic disorder in a family. Is this
a dominant or recessive inheritance pattern? Explain why,
and show the genotypes and phenotypes of all the
individuals in the pedigree.
• Dominant. If it was recessive, individual #7 would
have to be affected, because both of his parents would
have only recessive alleles to pass on to him.
• #1: Aa; #2: Aa
• #5: A-; #6: A-; #7: aa
•
•
•
#3: aa; #4: Aa
#8: aa; #9: A#10 – 12: aa
11. Variability and diversity of living organisms result from the distribution of genetic
materials during the process of meiosis. Crossing over and independent
assortment play an important role in distribution of genetic material. Draw
labeled diagrams to show how.
• Crossing over: swap of genes between mom & dad chromosomes means
child can get a mixture of mom & dad’s genes
• Independent assortment: Mom’s and dad’s
chromosomes don’t always travel into sex
cells in the same way, so different sex cells
can produce different traits in offspring
12. Stem cell research has led to many ground-breaking discoveries, as well as thought-provoking
controversies. Describe some of the controversy surrounding stem cell research and how new
research has managed to reduce the controversy.
• Very effective stem cells (those that can be turned into any type of cell) come mainly from fetal
cells – some people believe that using these cells is murder
• New research allows the use of adult stem cells to develop into a variety of different cell types, so
fetal stem cells are not as important
13. How can having your genetic profile determine pose both potential risks and benefits? Does this
development of genetics research suggest a need for new social and political policies?
• Risks: risk of losing your right to privacy – genetic history may be used against you in the
workplace or by insurance companies
• Benefits: may make you aware of a condition you didn’t know you were susceptible to so you can
take preventative measures earlier
14. A long-haired cat and a short-haired cat have a litter of kittens. The litter has both short-haired and
long-haired kittens. If the allele for short hair is dominant to the allele for long hair, determine the
genotypes of the parents. Explain your answer.
• Short haired cat must be heterozygous (Ss) and long-haired cat is homozygous (ss) so that some
kittens are Ss (long hair) and others are ss (short hair)
15. In mice, the allele for black fur is dominant to the allele for brown fur, and the allele for deafness is
recessive to the allele for normal hearing. If a mouse that is heterozygous for both traits is crossed
with a homozygous black mouse carrying the deafness allele, determine the probability of producing
a deaf black mouse.
• BbDd x BBdd - Big ol’ Punnett Square:
BD
Bd
bD
bd
Bd
BBDd
BBdd
BbDd
Bbdd
• Probability of a deaf black mouse: 50%
16. Tim and Christine have freckles (a dominant trait hat is not sex-linked), but their son Michael does
not. Use a Punnett square to show how this situation is possible. Tim and Christine are expecting
another baby. What is the probability of this child having freckles?
B
b
B
BB
Bb
b
Bb
Bb - Michael
• Probability of a child having freckles: 75%