Past Mock Questions

Question 1

Distinguish between DNA profiling and genetic screening

DNA profile

Answer 1

DNA profiling is a method of making a unique pattern of bands from the DNA of a person, which can then be used to compare with the DNA profile of another person

Question 2

Distinguish between DNA profiling and genetic screening

Genetic screening

Answer 2

Genetic screening means testing DNA for the presence of absence of a particular gene or an altered gene

Question 3

On what basis are DNA fragments separated by during gel electrophoresis

Answer 3

They are separated based on size

Question 4

Why are DNA fragments stained after electrophoresis?

Answer 4

To make them more visible and easier to see

Question 5

To which group of bases does Guanine belong to?

Answer 5

Purines

Question 6

Name the type of bonding that exists between strands of the DNA double helix

Answer 6

Hydrogen bonds

Question 7

What causes the double helix of DNA to unwind?

Answer 7

Enzymes

Question 8

Explain the function of the enzyme RNA polymerase

Answer 8

Causes a sequence of RNA bases to join together to form messenger RNA i.e. it joins nucleotides together to form mRNA

Question 9

In which part of the cell does transcription occur?

Answer 9

Nucleus

Question 10

In which part of the cell does translation occur?

Answer 10

Cytoplasm

Question 11

Why is it necessary for a protein to fold?

Answer 11

A protein only becomes functional once its folded into its correct shape

Question 12

What group of biomolecules provide the nitrogen needed to make the nitrogenous bases contained in DNA?

Answer 12

Protein

Question 13

Name one of the purine bases found in DNA

Answer 13

Adenine or guanine

Question 14

In the DNA molecule what base does adenine bond to?

Answer 14

Thymine

Question 15

In the DNA molecule what base does guanine bond to?

Answer 15

Cytosine

Question 16

Explain the importance of complementary base bonding in DNA

Answer 16

The bonding between complementary base pairs hold two strands of DNA in a double helix shape

Question 17

In RNA what does R stand for?

Answer 17

Ribose

Question 18

Name the type of RNA molecule made during the process of transcription?

Answer 18

Messenger RNA (mRNA)

Question 19

In which structure of the cell does transcription occur?

Answer 19

Nucleus

Question 20

Describe the relationship between messenger RNA (mRNA) and the DNA molecule
(2)

Answer 20

The mRNA molecule has complementary bases to those on the DNA strand from which it was transcribed

Thymine is replaced with uracil on the mRNA molecule

Question 21

What is the final step in protein formation which gives it it’s function?

Answer 21

The protein must be folded into it’s correct shape

Question 22

Explain the importance of heredity to living organisms

2

Answer 22

Heredity is the passing on of features from parents to offspring by means of genes

Heredity is also called genetic inheritance

Question 23

Explain the phrase gene expression

Answer 23

Gene expression is the way in which the genetic information in a gene is decoded in the cell and used to make a protein

Question 24

Explain why it is important that the correct sequence of bases is maintained during DNA replication

Answer 24

If the correct sequence of bases is not maintained then the production of an incorrect amino acid will result

Question 25

Apart from the nucleus, name one other organelle where DNA may be found

Answer 25

Chloroplast | Mitochondrion

Question 26

Explain what is meant by junk DNA

Answer 26

Junk DNA or non-coding DNA is DNA that does not cause the production of a protein

Question 27

To which base does uracil bond?

Answer 27

Adenine

Question 28

Explain the difference between the terms genetic screening and genetic engineering (Genetic screening)

Answer 28

This means testing DNA for the presence or absence of a particular gene or an altered gene

Question 29

Explain the difference between the terms genetic screening and genetic engineering (genetic engineering)

Answer 29

Genetic engineering is the artificial manipulation or alteration of genes

Question 30

Explain why it is necessary to break down the cell walls during DNA profiling

Answer 30

The cells are broken down to release their DNA

Question 31

During DNA profiling, how is the DNA cut into sections?

Answer 31

Using restriction enzymes

Question 32

Give an example of heredity | 2

Answer 32

Humans inherit features such as number of fingers, the production of nails and the ability to form tears Plants inherit features such as the number of petals, the colour of petals and the shape of leaves

Question 33

Name the five carbon sugar found in DNA

Answer 33

Deoxyribose

Question 34

Indicate any one way that RNA and DNA differ | 1/3 differences

Answer 34

DNA - contains the sugar deoxyribose - bases are AT GC (thymine) - double stranded (double helix) RNA - contains ribose - bases are AU GC (Uracil) - single-stranded

Question 35

Give one reason why a genetic screening may be carried out | 2

Answer 35

To test for the present or absence of a specific gene i.e. the gene for albinism or cystic fibrosis To test for the presence of abnormal or altered genes

Question 36

What does the m stand for in mRNA?

Answer 36

Messenger

Question 37

During protein synthesis, transcription occurs. What organelle does the mRNA travel to when it leaves the nucleus?

Answer 37

Ribosome

Question 38

How many bases code for an amino acid?

Answer 38

3

Question 39

Name one other type of RNA other than mRNA that is involved in protein synthesis

Answer 39

tRNA - transfer RNA

Question 40

Where in the cell is tRNA located

Answer 40

Cytoplasm

Question 41

Name one other type of RNA other than mRNA or tRNA

Answer 41

rRNA - ribosomal RNA

Question 42

Where in the cell is rRNA located?

Answer 42

Ribosome

Question 43

How does mRNA pass out of the nucleus?

Answer 43

Through nuclear pores

Question 44

How does mRNA attach itself to a ribosome?

Answer 44

The mRNA strand forms weak bonds with rRNA

Question 45

What does the letter t stand for in tRNA?

Answer 45

Transfer

Question 46

How does the tRNA know at exactly what position on the mRNA to deposit the amino acid it is carrying?

Answer 46

It binds with the complementary bases on mRNA

Question 47

Name the organelle where protein synthesis takes place

Answer 47

Ribosomes

Question 48

Explain the term triplet | 2

Answer 48

Also called a codon A sequence of three bases in DNA or RNA that act as a code for an amino acid

Question 49

State the role of triplets in protein synthesis

Answer 49

Each codon/triplet codes for an amino acid

Question 50

Describe the role played by mRNA in protein synthesis | 6

Answer 50

mRNA is a complementary strand to the DNA mRNA contains a start codon and a stop codon as well as many other codons specifying amino acids The mRNA moves from the nucleus to the cytoplasm The mRNA strand carries instructions for the production of a protein from DNA The mRNA bond forms a weak bond with rRNA tRNA will then bind with mRNA until the stop codon is reached

Question 51

Describe the role played by tRNA in protein synthesis | 2

Answer 51

tRNA has a complementary anticodon to mRNA codon tRNA carries an amino acid to the ribosome

Question 52

Name one component of a nucleotide other than a base pair

Answer 52

Sugar - deoxyribose | Phosphate

Question 53

Give a brief account of the stages involved in DNA profiling | 4

Answer 53

DNA is released from cells DNA is cut into fragments of different lengths using restriction enzymes DNA fragments are separated according to size by electrophoresis The patterns produced by the fragments are compared or analysed

Question 54

What is a gene?

Answer 54

A section of DNA that causes the production of a protein

Question 55

Name the two purine bases

Answer 55

Guanine | Adenine

Question 56

Give an application of DNA profiling

Answer 56

Forensic science - identifying a suspect Medicine- identifying the paternity or maternity of a person