SBI 3U REVIEW SHEET – GENETICS
1.
Terms you should know:
hybrid
Punnet Square
allele
purebred
incomplete dominance
F1 generation
Gregor Mendel
P generation
multiple alleles
codons
nitrogen bases
cell cycle
cytokinesis
haploid
diploid
monohybrid
dihybrid
gene
dominant
heterozygous
recessive
homozygous
F2 generation
DNA structure
nucleotides
mitosis
anaphase
telophase
crossing over
non-disjunction
2. Imagine a disease controlled by a dominant allele.
Babies born with this disease die before they are born.
What implication does this have (e.g. dominance when
the allele kills those who carry it)? With respect to this
allele, what would your genotype be? The genotypic
ratio of the class?
3. How are mitosis and meiosis different? Similar? What is
the purpose of the extra division in meiosis?
4. With the treatment of diseases such as haemophilia,
more people bearing these genes are surviving to
reproductive age. What will happen to the numbers of
recessive disease-carrying alleles in the human
population as a result of this? Explain.
Problems
1. In rabbits, short hair is dominant over long hair. If a
heterozygous short-haired rabbit is crossed with a longhaired rabbit, what percentage of the F1 generation will
be long-haired?
2. In sheep, a white coat is dominant to a black coat. A
white ram (male sheep) is mated with 3 ewes (female
sheep). Ewe A, which is black, gives birth to a white
lamb. Ewe B, also black, gives birth to a black sheep.
Ewe C, which is white, gives birth to a black sheep.
What are the genotypes of the four parents?
3. In humans, brown eyes are dominant to blue and the
ability to float in mid air is recessive to the inability to
float. A blue eyed man who cannot float (but is
heterozygous for that trait), and a woman with brown
eyes (homozygous) who can float, are planning on
having a family. The woman would really like a child
that has blue eyes and can float
a) What is the probability that she will get her wish?
b) State the genotypic and phenotypic ratio of the offspring.
4. In turtles, thick shell is dominant over thin shell, and the
ability to tango is dominant over inability to dance the
tango. A female turtle that has a thin shell and is
homozygous for ability to dance the tango is mated to a
trait
sex chromosome
genotype
phenotype
sex-linked characteristic
probability
gamete
co-dominance
meiosis
interphase
prophase
centriole
spindle fibres
epigenetic
polygenetic
male turtle that has a thick shell and cannot dance the tango.
You know that the male turtle’s mother had a thin shell.
a) Give the genotype and phenotype of the parents.
b) What is the probability of producing thick-shelled, tangodancing turtles?
c) Give the genotypic and phenotypic ratio of the F1
generation.
5. In chocolate rabbits, the allele for type of chocolate is a
type of incomplete dominance. Purebred bunnies can be
dark chocolate or white chocolate, but people have seen some
light brown “milk” chocolate bunnies. If a dark chocolate
bunny is mated with a milk chocolate bunny what are
genotypic and phenotypic ratios of the F1 generation.
6. In bees, the alleles for body colour display co-dominance.
When a yellow-bodied bee is crossed with a black-bodied
bee, the offspring are all striped black and yellow.
a) If a baby bee is striped, what are the possible genotypes and
phenotypes of its parents?
b) If a baby bee is black, then what are the possible genotypes
and phenotypes of its parents?
7. A woman with blood type O and a man with blood type AB
have 8 children. How many of them will have type O like
their mother? AB like their father? Type A? Type B?
8. John with blood type A and Julie with blood type B have
children. If John’s mother and Julie’s father both had type
O blood, what is the genotypic and phenotypic ratio of their
children?
9. In rats, the ability to talk is a recessive, sex-linked (X) allele.
a) Show the cross between a talking male and a non-talking
(homozygous) female. Of the offspring, how many
males/females can talk?
b) Show the cross between a speechless male and a talking
female who is heterozygous for the trait. Give the
genotypic and phenotypic ratios for F1.
Unit Review p179-183