Genetics Biology Worksheet ANSWERS

QUESTION EIGHT: GENETICS
There are many genes used by pedigree cat breeders to get a range of
colours, fur length and body shapes. Several genes can control coat
colour in cats.
One of these produces the Agouti pattern, where each hair has a black tip
but bands of light and dark towards the hair root. This causes a cat to
have a striped appearance. This pattern is dominant, and denoted by the
letter A. The recessive allele for this trait gives plain black hairs.
(a)
A breeder wishes to have a pure breeding group with the Agouti
coat colour. He has a group of the Oriental breed pictured above,
some of which are black and some of which are Agouti.
Discuss how he would go about developing a pure breeding
Agouti group. Include punnet square(s) in your answer.
In the future it may be possible for breeders to simply sell copies of a
cloned Agouti cat rather than rely on selective breeding. Cloning involves
taking a cell from the parent and making an identical copy of the parent.
The genetic characteristics of the animals obtained by these two breeding
techniques will be different.
(b) Discuss the reasons for the differences in the genetic characteristics
of the cats produced by selective breeding and cloning. In your
answer you should:
Consider the type of cell division
involved in each breeding technique.
Variation (or lack of it) in the offspring
ANSWERS EIGHT: GENETICS
(a) For Achievement your answer should have ONE correct statement.
Eg:
He needs to do a test/back cross to find AA cats to breed together / AA are pure
breeding for agouti (a)
Breed agouti with black to find out which are AA
AND punnet/s (a)
For Merit your answer should explain process of test / back cross (m)Eg:
He needs to do a test/back cross to find AA cats to breed together/AA are pure
breeding for agouti. This means breeding the agouti with the black, if any black
kittens result, the agouti parent must be Aa and not pure breeding (m)
OR
appropriately annotated punnets ie
Punnet 1 – all agouti
A A
a Aa Aa
a Aa Aa
Punnet 2 – ½ agouti. ½ black
A a
a Aa aa
a Aa aa
For Excellence your answer should discuss the process of test cross to
establish pure breeding group (e) Eg:
The breeder first needs to find the AA agouti cats to breed from. By breeding the
agouti cats he has with the black ones, he can see this as AA x aa will only
produce Aa agouti kittens as in punnet 1. Quite a large number are needed to
ensure no black kittens will result. If a single black kitten is born, the agouti
parent must be Aa as in punnet 2, it must have given an a allele. When the
breeder is certain he has AA individuals he can breed only these, as all offspring
will be AA true breeding agouti, as no recessive alleles are present.
AND
Correct Punnett squares.
(b) For Achievement you need to describe a difference between cloning
and selective breeding or describe the processes of cloning and
selective breeding. (a) Eg
Cloning is a mitotic division but selective breeding is meiosis. OR
Cloning means there is no variation in the offspring whereas in selective breeding
there is variation in offspring. OR
Only one parent contributes all the genes/ genetic material / chromosomes in
cloning but two parents do in selective breeding.