Extra Practise mono & di copy



Extra Practise mono & di copy
Genetics - Practice!
Make an appointment card with 4
Appointment #1
The allele for hornless cattle is dominant to the
allele for cattle with horns. Occasionally, a
calf with horns appears in a herd of hornless
A black colour true-breeding cow is bred with a
brown colour true-breeding bull. All of the
offspring have black hair.
a. Which colour is dominant?
b. What are the genotypes and phenotypes of
the parents?
c. What are the genotypes & phenotypes of the
A certain breed of cattle in England produces
good meat when a particular gene is
heterozygous. That same gene is lethal when it
is homozygous recessive.
How would a farmer produce the best meat
without losing any cattle?
Appointment #2
Osteogenesis imperfecta (OI), also known as
brittle bone disease, results in extremely fragile
bones that tend to break for no apparent reason.
1. What inheritance pattern does OI display?
2. Identify the genotypes of all members of this
The pedigree below traces the appearance of a
cleft chin in a family.
1. Based upon this small pedigree, would you
determine that cleft chin is dominant or
recessive? Explain.
2. Identify the genotypes of the individuals.
Huntington’s disease is a terrible genetic disease
that is caused by a dominant allele. The disorder
presents itself when a person is in their 40s and
affects their neurological function often killing the
person within a decade.
a. Why do you think that most genetic disorders
are caused by recessive alleles and not
b. Why can Huntington’s continue to persist in
Appointment #3
In corn, the allele for purple kernels is dominant
to the allele for yellow kernels, and smooth
texture is dominant to wrinkled.
Determine the likely genotypes of the parents if
offspring consisted of 46 wrinkled purple, 54
smooth yellow, 153 smooth purple kernels, and
15 wrinkled yellow kernels.
In fruit flies, long wings are dominant to short
wings. Also grey body colour is dominant to
black body colour. Flies that are heterozygous
for both traits are crossed, and 256 offspring
are produced.
Predict how many of the offspring would be
long-winged & grey, long-winged & black,
short-winged & grey, and short-winged &
In humans, dark hair is dominant to blond hair,
and curly hair is dominant to straight hair. A
blond haired woman who is homozygous curly
has children with a man who is heterozygous
brown and curly.
a. What are the parents genotypes?
b. What is the probability that they will have a
child that is blond with straight hair?
b. What is the probability that they will have a
child that is blond with curly hair?