Biology Questions

QUESTION ONE: DNA AND VARIATION
Genes determine many of the features of organisms, such as the
colour of the flowers on a plant.
A gene is a part of a DNA molecule.
The type of plant shown in the photograph below can have red or
white flowers.
QUESTION TWO: SEXUAL REPRODUCTION
Meiosis is a particular form of cell division that produces male and
female gametes.
(a)
Describe what gametes are and explain why they are needed
for sexual reproduction.
Meiosis contributes to genetic variation.
Red flowers are due to a dominant allele and white flowers are due
to a recessive allele.
Discuss how information in DNA gives organisms (like the plant
above) their individual features, such as red and white flowers. In
your answer, you should:
explain the difference between a gene and an allele
draw a labelled diagram to show the relationship between a gene
and an allele and the structure of a DNA molecule
explain how the base sequence on DNA determines a particular
feature (eg, flower colour) and different forms (variations) of that
feature (eg, red and white flowers)
(b)
Discuss how meiosis contributes to genetic variation, and why
genetic variation is important in a population. In your answer,
you should:
describe what is meant by genetic variation
explain how the process of meiosis leads to genetic
variation
explain why genetic variation is of benefit to a population
You could draw labelled diagrams to support your answer.

QUESTION THREE: MONOHYBRID CROSSES
The allele for a cleft chin (D) is dominant over the allele for a
smooth chin (d).
The pedigree diagram below shows the chin types in a family.
(c)
Individuals A and B, as shown on the pedigree diagram,
decide to have another child. They draw a Punnett square to
find what type of chin their child might have.
Explain why the result predicted by the Punnett square may
not accurately tell them what type of chin their child will have.
In your answer, you should:
draw a Punnett square to show the cross between
individual A and individual B
determine the probabilities of the child having a cleft chin
and having a smooth chin
explain why the ratio of children born into the family with
cleft and smooth chins may not match the probabilities.
(a)
(b)
Explain how evidence in the pedigree diagram shows that the
cleft chin allele (D) is dominant over the smooth chin allele (d).
In your answer, you should:
Describe what the term dominant allele means
draw a Punnett square(s) to show your reasoning.
Explain why the genotype of male A in generation 2 of the
pedigree diagram must have the genotype Dd.

QUESTION FOUR: SURVIVAL
Mutations can occur in DNA during cell division.
Explain whether a mutation could be inherited if it occurred in a skin
cell of an individual. In your answer, you should:
describe what a mutation is
explain what determines whether a mutation is able to be
inherited or not.
QUESTION SIX: VARIATION
A population of plants, species A, living in a certain area shows a
lot of variation in its leaf size, from very small to very large as
shown in the graph below.
Leaf size of plants of species A
QUESTION FIVE: GENETICS
Explain how two parents who don’t show a particular characteristic
can have a child who does show that feature.
In your answer include:
The nature of the characteristic
What causes a feature to be expressed (shown)
What is different (genetically) between the parents and the child
Leaf size affects the ability of a plant to absorb sunlight and make
food. Plants with larger leaves can live in areas with lower light
levels.
A new plant, species B, starts growing in the same area as
species A. Species B plants grow taller than species A plants,
which reduces the light available to plants growing below species
B.
Discuss how variation in leaf size occurs in the starting population
of species A and explain how this might help species A to survive
when species B starts growing in the same area.
In your answer, you should consider:
what causes variation within a population
the effect of reduced light on different individuals of plant
species A

QUESTION SEVEN: GENETICS
Cloning involves making an exact copy of an organism. Selective
breeding involves the breeding together of organisms that possesses
highly desirable characteristics.
Compare and contrast selective breeding and cloning.
Your answer should include
How the offspring compare to their parents
Their relative advantages and disadvantages
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

QUESTION NINE: BREEDING
A chicken farmer discovers a chicken which has four legs.
a) Explain what must have happened for the chicken to be born with
four legs
The farmer raises chickens to sell to a fried chicken restaurant. He gets
paid for each leg he supplies.
b) Discuss what he would have to do to get a pure breeding strain of
four legged chickens. Assume the allele for four legs is dominant
(L) and show punnett squares with your answer. A complete
answer would mention any possible negative side effects as well)
QUESTION TEN: GENETICS
Read the following article and then answer the questions that
follow it.
The mistake that turned out to be worth a
fortune!
Back in 1930, nature made a “boo-boo”. This mistake led to
a ram (male) lamb in an otherwise normal flock growing up
with a fleece more like hair than wool. Dr F. W. Dry
researched the new ram by introducing it into his breeding
experiments. This success story has an intriguing twist to it.
Dr Dry initially found that the hairiness was a dominant
genetic factor. So instead of trying to breed it out, he later
realised that it was a superior replacement for the resilient
wool New Zealand always had to import. As a result, he was
able to produce a flock of a new breed of sheep called the
Drysdale.
a) Explain how the first hairy ram could have come to be born.
b) Discuss the steps Dr Dry would have taken to start with the
one hairy ram and end up with a flock of pure breeding hairy
male and female sheep

QUESTION ELEVEN: GENETICS
The kiwifruit species need both female and male plants to be close
to each other for it to reproduce. The kiwifruit has 58 chromosomes
in a body cell.
(a) Using the information above describe how meiosis in kiwifruit
occurs.
(b) Explain how meiosis causes a random assortment of genes
from the parent plant.
QUESTION TWELVE: GENETICS
A mutation in an egg cell of a fish gave rise to a new DNA
sequence.
(a) Describe how the change in the DNA sequence could
produce a new allele.
(b)
C A T G C T G A C T G C A
G T A A G A C T G A C G T
Above is a strand of fish DNA which contains a mutation.
(i) Identify the mutation in the above sequence.
(ii)
(iii)
Explain why this is a mutation.
As a result of this mutation fish were able to resist
pollution in a stream. Discuss whether this mutation
may be passed along to future generations and what
this may mean for this fish species.
(c) An orchard is infected with the disease BSA which attacks
kiwifruit vines. Discuss why some infected plants will survive.

QUESTION THIRTEEN: GENETICS
A pure breeding homozygous dominant short haired Siamese cat
is mated with a long haired recessive cat.
QUESTION FOURTEEN: PEDIGREE TREES
(a)
Long-haired Siamese
Define pure breeding.
Short-haired Siamese
(b) Complete the Punnett square for the cross described above
and state the genotype and phenotype of the offspring (kittens).
Use the letter L and l.
(c) A breeder wishes to have an equal mixture of both long
haired and short haired Siamese kittens to sell. Explain how she
could best ensure that this occurs.
The above diagram shows a pedigree tree for a family affected by cystic fibrosis.
This is a recessive genetic disease which affects the entire body.
(a) Explain how (in general terms) the genotypes of individuals can be
determined from a pedigree tree.
(b)
(c)
(i)
Using the letters D and d state the genotypes of the following individuals:
Generation I male (No. 1):
Generation II female (No. 2):
Generation III female (No. 2):
Carry out a cross to determine the probability of the male (3) and female
(4) in Generation II having another child affected with cystic fibrosis.
(ii) Explain how you determined the genotypes of male (3) and female (4).

QUESTION FIFTEEN: SEX DETERMINATION
A couple has four children, all girls. What are the chances that there
next child will be a boy? Explain your answer.
In your answer you should talk about:
What chromosomes are needed for a boy to be born
Which chromosomes are provided by each parent