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AQA A Level Biology > Control Of Gene Expression > Flashcards

Control Of Gene Expression Flashcards

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1
Q

What is a mutation?

A

A change to the nucleotide sequence of DNA

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2
Q

When do spontaneous mutations happen?

A

During DNA replication (interphase)

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3
Q

What is a mutagenic agent?

A

Something that increases the rate of mutations above normal

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4
Q

What is a base analog?

A

Something that can substitute for a normal nucleotide base

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5
Q

What type of mutation does a base analog cause?

A

A substitution mutation

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6
Q

What does radiation do to DNA?

A

Changes the structure of it

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7
Q

What are the types of mutations?

A
  • Substitution - Addition- Deletion- Inversion- Duplication- Translocation
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8
Q

What happens in a substitution mutation?

A
  • One base is swapped for another
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9
Q

What can a substitution mutation do to the amino acids translated for?

A
  • Can have no effect because DNA is degenerate - Can change one amino acid
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10
Q

What can cause a substitution mutation?

A

Some chemicals are able to react with DNA and change its structure

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11
Q

What happens in an addition mutation?

A

An extra base is added

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12
Q

What happens in a deletion mutation?

A

A base is removed

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13
Q

What can addition and deletion mutations cause?

A

A frame shift

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14
Q

What happens if a frame shift occurs?

A

All the following DNA triplets will be affected

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15
Q

What happens in an inversion mutation?

A

A sequence of DNA is reversed

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16
Q

What can an inversion mutation cause?

A
  • No change (palindromic)- Change to one or a few amino acids- No frame shift (nothing added or removed)
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17
Q

What is a duplication mutation?

A

One or more bases are repeated

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18
Q

What can a duplication mutation cause?

A

A frame shift

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19
Q

What is translocation?

A

When a sequence of DNA is removed from one part of the genome and moved to another part of the genome (can be the same or a different chromosome)

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20
Q

What is a mutation?

A

A change to the base sequence of DNA

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21
Q

Why can a mutation result in no change to the amino acid sequence?

A
  • Amino acids are coded for by more than one triplet of DNA- DNA is degenerate
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22
Q

What happens if a mutation results in a change to one DNA triplet?

A
  • Changes the transcription and translation - Different amino acid made- Changes the primary structure of the protein- Changes the hydrogen/ionic bonding- Changes the tertiary structure of the protein
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23
Q

What effect will a frame shift have on the resultant protein?

A
  • Changes the sequence of all the following triplets- Changes all the following amino acids- Changes the primary structure- Changes the hydrogen/ionic bonding- Changes the tertiary structure
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24
Q

What mutations can result in a frame shift?

A
  • Additions- Deletion- Duplication
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25
Q

What are stem cells?

A

Cells that can divide and differentiate to become different types of cell and can divide for the organisms whole life

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26
Q

What are totipotent stem cells?

A
  • Stem cells that can differentiate into any type of specialised cell- Can for placental cells
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27
Q

Where are totipotent stem cells found?

A

Vey early mammalian embryos

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28
Q

What are pluripotent stem cells?

A
  • Stem cells that can differentiate into many types of specialised cell- Cant make placental cells
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29
Q

Where are pluripotent stem cells found?

A

Adult and embryo cells

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30
Q

What are multipotent stem cells?

A

Stem cells that can differentiate into a few types of specialised cell

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31
Q

What is an example of multipotent stem cells?

A

Bone marrow can differentiate into red blood cells or white blood cells

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32
Q

What are unipotent stem cells?

A

Stem cells that can differentiate into one type of specialised cell

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33
Q

What is an example of unipotent stem cells?

A

Heart unipotent cells can make cardiomycytes only

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34
Q

How does cell specialisation happen?

A
  • All cells contain 100% of an organisms DNA- Conditions within cells control which genes are expressed (transcribed and translated) into proteins- Transcription factors change the internal environment of the cell and affect the expression of other genes- Cells become specialised
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35
Q

What happens once a cell becomes specialised?

A

It cannot be reversed

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36
Q

What are IPS cells?

A

Induced pluripotent stem cells made by treating unipotent stem cells with transcription factors that make them become pluripotent

37
Q

How are IPS cells made?

A
  • Modified virus as a vector- Virus inserts transcription factor genes from pluripotent cells into the DNA of unipotent stem cells- Transcription factors are expressed
38
Q

How are embryonic stem cells obtained?

A
  • Embryos made in a lab by IVF- Pluripotent stem cells removed after a few days- Embryo destroyed
39
Q

How are adult stem cells obtained?

A

Taken from adults in an operation e.g. the removal of bone marrow

40
Q

Why are adult stem cells less useful for medicine

A

Adult stem cells are multipotent therefore less useful for medicine as they cannot for every type of cell

41
Q

What can stem cells do?

A

Differentiate to form any type of specialised cell

42
Q

What can stem cells . e used for?

A

Replacing faulty or damaged genes

43
Q

What does bone marrow contain?

A

Multipotent stem cells that can differentiate into red and white blood cells

44
Q

What can you do if someone has faulty bone marrow?

A

Replace their bone marrow with a donors bone marrow which will form new healthy cells

45
Q

Why would someone have faulty bone marrow?

A

Genetic disorder or leukemia

46
Q

How can stem cells be used to grow new organs?

A
  • IPS cells used- No donor needed- IPS organs will have the same antibodies preventing rejection
47
Q

What are the advantages of stem cells?

A
  • Save lives- Improve quality of life- Prevent suffering
48
Q

What are the ethical issues surrounding stem cells?

A
  • Stem cells are taken from IVF embryos which could develop into a fetus if implanted- Some people believe from fertilisation a zygote has the right to live- Use unfertilised eggs that are triggered to divide
49
Q

What is a transcription factor?

A

A protein that controls the rate of protein synthesis by switching some genes on and some genes off

50
Q

What is a promoter region?

A

Short sequence of DNA at the start of a gene (the bit that RNA polymerase/ DNA polymerase attaches to)

51
Q

What does an activator do?

A

Help RNA/DNA polymerase bind to DNA

52
Q

What does a repressor do?

A

Prevent RNA/DNA polymerase bind to DNA

53
Q

How do activators and repressors work?

A
  • Transcription factor moves from the cytoplasm into the nucleus- Binds to the promoter regions- Controls whether gene is or isn’t transcribed
54
Q

What is an example of controlling transcription factors?

A
  • Oestrogen is a steroid hormone- If it is present it will bind to an oestrogen receptor to form an oestrogen-oestrogen receptor complex
55
Q

How can transcription factors be turned on or off?

A

By second messengers e.g. cAMP

56
Q

What do tumour suppressor genes and proto-oncogenes do?

A

Control the rate of mitosis and therefore the expression of genes

57
Q

What is cancer?

A

Uncontrolled cell division

58
Q

What do proto-oncogenes do?

A

Make proteins that increase the rate of mitosis

59
Q

What is an oncogene?

A

A mutated proto-oncogene

60
Q

What can happen to oncogenes?

A

They can be over expressed

61
Q

What do tumour suppressor genes do?

A

Make proteins that slow down the rate of mitosis or speed up the rate of apoptosis

62
Q

What happens if there is a mutation to a tumour suppressor gene or a proto-oncogene?

A

The resultant synthesised protein may be non-functional that may cause uncontrolled cell division

63
Q

What is epigenetics?

A

Changes to gene expression caused by environmental factors (without changing the base sequence of DNA)

64
Q

What does epigenetics do?

A
  • Controls gene expression by preventing transcription- Can be inherited between generations- Helps organisms respond to environmental factors
65
Q

What is an example of epigenetics?

A

If pregnant mice are exposed to famine their off spring will be better adapted to low nutrients

66
Q

What is the methylation of DNA?

A
  • More Methylation Terminates Transcription- Methyl groups can attach to DNA at CpG sites- Methylated CpG sites prevent transcription enzymes attaching- Methyl groups can be removed by enzymes
67
Q

What is the acetylation of DNA?

A
  • Less Acetylation Terminates Transcription- Acetyl groups force histones to be more spread apart - DNA is less coiled- Allows transcription enzymes to attach- Enzymes can remove acetyl groups to prevent transcription
68
Q

What can SiRNA and MicroRNA do?

A

Control gene expression by preventing translation

69
Q

What is SiRNA?

A

Small interfering RNA

70
Q

How does SiRNA work?

A

1 - Short double stranded RNA2 - Combines with proteins to form an SiRNA - protein complex 3 - SiRNA - protein complex single stranded 4 - SiRNA has a complimentary base sequence to target mRNA 5 - SiRNA - protein complex breaks down the mRNA into pieces 6 - Prevents translation7 - mRNA pieces are recycled

71
Q

What does MicroRNA do?

A

1 - MicroRNA combines with a protein to form a MicroRNA - protein complex 2 - MicroRNA - protein complex binds to mRNA by complimentary base pairing3 - Prevents translation by blocking the ribosome from attaching4 - mRNA can be stored for later or recycled

72
Q

How are the ways MicroRNA and SiRNA different?

A

MicroRNA is less specific that SiRNA and MicroRNA can work on multiple mRNA strands

73
Q

How can gene expression (transcription) be controlled?

A

Methylating DNA

74
Q

In what two ways can tumours be effected by methylation?

A

Tumours can be hypermethylated or hypomethylated

75
Q

If a tumour is hypermethylated, which gene is said to have mutated?

A

Tumour supressor gene

76
Q

If a tumour is hypomethylated, which gene is said to have mutated?

A

Proto-oncogene

77
Q

What are the two types of tumour?

A

Benign and malignant

78
Q

What is a benign tumour?

A
  • Enclosed in a membrane- Slow growing- Harmless- Can become malignant if the membrane ruptures
79
Q

What is a malignant tumour?

A
  • Fast growing- Destroys tissue- Can easily break apart and spread in the blood/lymph
80
Q

How can oestrogen cause breast cancer?

A
  • Oestrogen can bind to a protein to form the oestrogen - oestrogen receptor complex- Increases rate of cell division- Increases rate of mutations- Can lead to cancer
81
Q

How can tumours be identified?

A
  • Mitosis (more cells dividing)- Nuclei (large, odd shapes, multiple)- Cell shape (irregular)- Function (loss of normal function)- Arrangement (disorganised)
82
Q

What is the genome?

A

The complete set of genetic material (genes and non coding DNA) that an organism has

83
Q

What is the proteome?

A

The complete set of proteins that an organism can make

84
Q

What is a current sequencing project?

A

Human genome project (sequence a whole human genome)

85
Q

What is the current sequencing method used to sequence the human genome?

A

High thouroughput pyrofrequency- Faster- Cheaper- Automated

86
Q

Why can we predict the amino acid sequence of simple prokaryotes but not large eukaryotes?

A

Simple organisms are made up of very few regulating genes and contain little non-coding DNA whereas in complex organisms we have regulating genes, the ability to turn genes on/off, lots of non-coding DNA so it is hard to determine our proteins from our DNA

87
Q

What are the uses of genome projects?

A
  • Understanding evolutionary relationships (phylogeny)- Medicine
88
Q

How are genome projects useful in medicine?

A

Understand the antigens to develop new vaccines

AQA A Level Biology (13 decks)

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