3.8 The control of gene expression

Question 1

Addition mutation

Answer 1

When a nucleotide is added to a segment of DNA
Results in frame shift

Question 2

Deletion mutation

Answer 2

When a nucleotide is removed to a segment of DNA
Results in frame shift

Question 3

Substitution mutation

Answer 3

When a nucleotide is switched out for a different nucleotide in a segment of DNA
Doesn’t result in frame shift

Question 4

Inversion mutation

Answer 4

When multiple nucleotides are reversed in order
Doesn’t result in frameshift

Question 5

Duplication mutation

Answer 5

When multiple nucleotides are duplicated within the DNA segment
Can result in frame shift

Question 6

Translocation mutation

Answer 6

When nucleotides are transferred to another part of the DNA sequence
Can result in frame shift

Question 7

What can increase number of mutations

Answer 7

Mutagenic agents

Question 8

What is a mutation

Answer 8

Changes to a base sequence in DNA

Question 9

How can a mutation result in a different/dysfunctional protein

Answer 9

1. Change in base sequence
2. Change in primary structure
3. Different hydrogen bonding in secondary structure as different binding sites
4. Different binding in tertiary structure by H bonds/disulfide bridges/ionic bonds
5. Different/dysfunctional protein

Question 10

Properties of DNA

Answer 10

Non-overlapping - each base only read once and is part of only one triplet
Degenerate - Multiple triplets code for the same amino acid
Universal - All organisms share same 4 nucleotides (A,T,C,G)

Question 11

Stem cell definition

Answer 11

A cell that can divide by mitosis an unlimited number of times and can become differentiated

Question 12

Totipotent cells

Answer 12

Stem cells that can differentiate into any body cell + embryonic cells. Found in mammalian embryo

Question 13

Pluripotent cells

Answer 13

Stem cells that can differentiate into any body cell. Found in mammalian embryo

Question 14

Multipotent cells

Answer 14

Stem cells that can differentiate into multiple different cells. e.g Found in bone marrow

Question 15

Unipotent cells

Answer 15

Stem cells that can differentiate into only one type of cell. e.g. cardiomyocytes

Question 16

How are Induced pluripotent stem cells produced

Answer 16

From adult somatic cells, using an appropriate transcription factor

Question 17

How do cells specialise

Answer 17

Only certain parts of the DNA is translated.
Controlled by transcription factors

Question 18

Oestrogen

Answer 18

1. Lipid soluble so diffuses through phospholipid bilayer
2. Binds to receptors on transcription factor in cytoplasm
3. Causes DNA binding site on TF to be altered
4. TF enters nucleus
5. TF binds to promoter region of DNA - activating transciption

Question 19

What is DNA amplification

Answer 19

When a fragment of DNA is replicated

Question 20

PCR steps

Answer 20

1. Requires DNA fragment, primers and nucleotide
2. Heat to 95 degrees to break hydrogen bonds
3. Reduce temperature so primers bind to DNA
4. Increase temp, DNA polymerase joins nucleotides
5. Repeat

Question 21

Epigenetics definition

Answer 21

involves heritable changes in gene function, without changes to the base sequence of DNA

Question 22

Two epigenetic changes

Answer 22

1. Increased methylation - supresses gene transcription, prevents binding of TF’s
2. Decreased acetylation - increases positive charge of histone, so they bind more tightly to the DNA, TF’s can no longer access DNA

Question 23

How does RNAi inhibit translation of mRNA

Answer 23

1. Complimentary to mRNA base sequence
2. Bind to mRNA
3. Break it down
4. Prevent its translation

Question 24

Cancer definition

Answer 24

Uncontrolled cell division

Question 25

Role of tumour suppressor genes

Answer 25

Slow down/regulate cell division

Question 26

Role of protooncogenes

Answer 26

Produces proteins that stimulate cell division Cause apoptosis

Question 27

How can increased oestrogen concentration cause cancer

Answer 27

More TF's bind to DNA More transcription More cell division - uncontrollable

Question 28

How do oncogenes cause cancer

Answer 28

Abnormal methylation Protooncogenes become hyperactivated Cause uncontrolled cell division No programmed cell death (apoptosis)

Question 29

How do mutated tumour suppressor genes cause cancer

Answer 29

Abnormal methylation Tumour suppressor genes not translated Cell division not regulated Uncontrollable cell division

Question 30

Applications of genome projects

Answer 30

Identification of antigens for vaccines Human genome project Identifying genetic diseases Tracing ancestry

Question 31

Why is it harder to translate the genome of more complex organisms into the proteome

Answer 31

Non-coding DNA Regulatory genes

Question 32

What is recombinant DNA technology

Answer 32

Involves the transfer or DNA from one organism/species to another. This can be translated as DNA is universal

Question 33

3 methods of producing DNA fragments

Answer 33

- Reverse transcriptase - Restriction enzymes - Gene machine

Question 34

What does in vitro mean

Answer 34

In glass

Question 35

What does in vivo mean

Answer 35

In life

Question 36

Role of reverse transcriptase in producing DNA fragment

Answer 36

1. Extract desired mRNA from virus/bacteria 2. Reverse transcriptase catalyses the production of DNA to mRNA

Question 37

Role of restriction endonucleases in producing DNA fragment

Answer 37

Restriction endonucleases cut gene from DNA Same enzyme cuts host DNA Ligase joins sticky ends together

Question 38

In vitro

Answer 38

1. Isolation - 3 methods 2. Insertion 3. Transformation - 4. Identification 5. Growth/cloning

Question 39

Gene machine

Answer 39

1. Protein amino acid sequence 2. mRNA codons 3. DNA triplet code 4. Computer produces synthetic gene

Question 40

Insertion (step 2)

Answer 40

1. Add a promoter region and a terminator region 2. So that RNA polymerase/TF can attach and transcribe base sequence 3. Insertion of DNA fragment into a vector 4. Vector transports DNA fragment to host cell

Question 41

Transformation (step 3)

Answer 41

Transforming the bacteria by introducing the recombinant plasmid

Question 42

Identification (step 4)

Answer 42

Fluorescent die Radioactive marker

Question 43

Growth/cloning (step 5)

Answer 43

Allow bacteria to divide

Question 44

What is a DNA probe

Answer 44

Single stranded section of DNA that has complimentary base pairing with target gene

Question 45

Why are DNA probes made in same amounts

Answer 45

They can be amplified using PCR

Question 46

Uses of DNA probes

Answer 46

Indicate where harmful alleles are by using a radioactive material of fluorescent dye Prevent genetic diseases Screen patients for heritable conditions, drug responses or health risks.

Question 47

Gel electrophoresis

Answer 47

The negatively charged DNA fragments move through the pores in the gel, towards the positively charged electrode Smaller DNA fragments are able to move at a faster rate through the pores and so they travel a further distance The fragments separate according to size and charge, producing bands in the gel

Question 48

What are VNTRs

Answer 48

Variable Number Tandem Repeats. Short sequence of nucleotides repeated a variable number of times. The probability of two people having the same VNTRs is very low.

Question 49

Recombinant DNA definition

Answer 49

DNA that has been formed artificially

Question 50

USes of genetic fingerprinting

Answer 50

Forensics Medical diagnosis Animal/plant breeding

Question 51

The scientists used a radioactively labelled DNA probe to show that the cells of tobacco plant leaves contained the SUT1 gene. Describe how they would do this. Do not include PCR in your answer.

Answer 51

1. Extract DNA and add restriction endonucleases/restriction enzymes; 2. Separate fragments using electrophoresis; 3. (Treat DNA to) form single strands 4. The probe will bind to/hybridise/base pair with the SUT1/gene; 5. Use autoradiography (to show the bound probe);

Question 52

Why is DNA treated to form single strands for testing

Answer 52

So that the DNA probe can bind

Question 53

What is meant by a non-coding base sequence?

Answer 53

Does not code for amino acid/tRNA/rRNA

Question 54

Explain the role of reverse transcriptase in RT-PCR.

Answer 54

Produces DNA using RNA

Question 55

Why is the gene machine used over enzyme catalysed reactions

Answer 55

It is much faster

Question 56

Suggest and explain how the viruses became able to infect other species of frog.

Answer 56

1. Mutation in the viral DNA 2. Altered (tertiary structure of the) viral attachment protein 3. Allows virus to bind to receptors of other species