Exam Style Questions DNA

Question 1

What is meant by:

a homozygous genotype

Answer 1

both alleles are dominant / recessive

so both ALLELES (for a gene) are the same

Question 2

a heterozygous genotype

Answer 2

there is one dominant and one recessive allele
two alleles (for a gene) are different

Question 3

Why is this type of cell division important in producing cell C or cell D?

Answer 3

halves the number of chromosomes [1]; ensures the embryo have the correct/double/diploid set of chromosomes [1]

Question 4

Why is MITOSIS important for an organism?

Answer 4

growth [1]; cell replacement or tissue repair [1]; asexual reproduction/cloning [1]

Question 5

Where in a cell will you find DNA?

Answer 5

Nucleus/chromosome [1 mark]

Question 6

What does each gene code for?

What is a gene?

Answer 6

a sequence of amino acids/ protein [1 mark]
A gene is a small section of DNA on a chromosome that codes for a specific sequence of amino acids, to produce a specific protein.

Question 7

Define the term genome

Answer 7

the entire genetic material of an organism [1 mark]

Question 8

Describe how the Human Genome Project has helped establish a classification relationship between 2 species. [2 marks]

Answer 8

DNA from both species sequenced [1];
DNA compared for similarities and differences [1]; the higher the number of similarities the more closely related the species [1]

Question 9

State 2 other uses of the Human Genome Project

Answer 9

looking at migration patterns in humans [1]; understand inherited diseases [1]; finding treatments for diseases [1]
[2 marks]
trace human migration patterns from the past

Question 10

What word is used to describe ‘a small section of a DNA molecule that controls the synthesis of a protein’? [1 mark]

Answer 10

Gene/allele [1]

Question 11

In a cell, where are proteins synthesised?

[1 mark]

Answer 11

ribosomes [1]

Question 12

Describe how proteins are synthesised from a chain of bases in DNA. Use the diagram to help you answer this question. [3 marks]

Answer 12

amino acids make up a protein [1]
(protein is) particular combination/sequence of amino acids [1]
bases work in threes/triplets [1]
each triplet/group of 3 bases code for one amino acid [1]

Question 13

Mistakes sometimes occur when DNA molecules are copied during cell division.
Suppose that one of the bases, base A, was substituted by a C base.
What might be the effect of this change in structure of the protein?
[1 mark]

Answer 13

protein would not function properly [1]

Question 14

Couple 1 and 2 know there is a risk that their next baby could have cystic fibrosis.
Embryos can be screened for the allele that causes cystic fibrosis. Many people
support the screening of embryos, but others do not.
Suggest one reason why many people support the screening of embryos for the
cystic fibrosis allele.
[1 mark]

Answer 14

Reduce number of people with cystic fibrosis (in population) or reduce healthcare cost or expensive to have baby with cystic fibrosis or help to prepare financially / emotionally etc

Question 15

Suggest one reason why many people are against the screening of embryos for
the cystic fibrosis allele.
[1 mark]

Answer 15

expensive
possible damage / risk to embryo / fetus / baby
(may) have to make ethical / moral / religious decisions

Question 16

Embryos can be screened for genetic disorders.
Many people would favour the use of embryo screening for cystic fibrosis but not
for polydactyly.
Compare the issues involved in the use of embryo screening for cystic fibrosis
and for polydactyly.
You should use your knowledge and understanding of the process and the two
conditions.
[6 marks]

Answer 16

Award a maximum of 2 marks for each category below:
pros:
• reduce number of people with cystic fibrosis (in
population)
• reduce health-care costs
• allows decision / emotional argument,
eg allows people to make choices about termination
cons:
• possible damage / risk to embryo / fetus / baby
• possible harm / risk to mother
• (may) have to make ethical / moral / religious decisions
for polydactyly:
• cures ‘disfigurement’
• but condition not life threatening
• so risks to foetus / mother unjustified

Question 17

DNA is a polymer. TRUE OR FALSE?

Answer 17

True

Question 18

the ORDER of the bases is important because

Answer 18

it determines the order that amino acids are assembled to produce a specific protein

Question 19

structure of DNA

Answer 19

two complementary strands of nucleotides forming a double helix
phosphate –> deoxyribose sugar –> base

Question 20

what does a nucleotide consist of?

Answer 20

sugar phosphate group, and one of 4 different bases (A,G,C,T)

Question 21

what is a gene

Answer 21

small section of DNA that codes for a particular amino acid sequence, to make a specific protein

Question 22

how many bases code for an amino acid

Answer 22

3

Question 23

what is the function of non -coding DNA

Answer 23

switch genes on and off and control their expression

Question 24

What are alleles

Answer 24

different forms of the same gene

Question 25

What is a recessive allele

Answer 25

allele that needs to be present twice to be expressed

Question 26

What is a dominant allele

Answer 26

allele that only needs to be present once to be expressed

Question 27

where in the cells are proteins made

Answer 27

on the ribosomes

Question 28

what type of allele causes polydactyl

Answer 28

dominant allele

Question 29

what type of allele causes cystic fibrosis

Answer 29

recessive allele

Question 30

how many chromosomes do normal human body cells have?

Answer 30

23 pairs