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biology year 2 > 8a mutations and gene expression > Flashcards

8a mutations and gene expression Flashcards

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1
Q

What are mutations?

A

Changes to a base sequence of dna

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2
Q

What are the 6 types of mutations (name) ?

A

Substitution
Deletion
Addition
Duplication
Inversion
Translocation

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3
Q

What is a substitution mutation?

A

One or more bases swapped for another

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4
Q

What is a deletion mutation?

A

One or more bases removed

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5
Q

What is an addition mutation?

A

One or more bases added

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6
Q

What is an inversion mutation ?

A

A sequence of bases reversed eg ATGCCT becomes ATCGGT

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7
Q

What is a translocation mutation ?

A

A sequence of bases is moved from one location in the genome to another by movement within the same chromosome or movement to a different chromosome

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8
Q

How can a mutation cause a change in the polypeptide formed ?

A

Changes tertiary structure
Active site changes
Stops substrates from being able to bind
Enzyme can no longer catalyse reaction

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9
Q

What is a hereditary mutation?

A

If a gamete contains a mutation for a type of cancer or genetic disorder the mutation will be present in the new fetus formed

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10
Q

What is a degenerate mutation and effect ?

A

Same amino acids are coded for by more than one DNA triplet so it might not cause a change in polypeptide

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11
Q

What is a frameshift mutation?

A

Triplet code read in a different way when an addition, deletion and duplication mutation are present

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12
Q

What are mutagenic agents?

A

Things that increase rates of mutations eg UV, radiation, chemicals

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13
Q

How do mutagenic agents change the rate?

A

Acting as a base
Altering bases
Changing the structure of DNA

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14
Q

What is an acquired mutation?

A

Occur in individual cells after fertilisation

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15
Q

What are tumours ?

A

Uncontrollable cell division

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16
Q

What are the two types of genes that control cell division?

A

Tumour suppressor genes

Proto oncogenes

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17
Q

What does a tumor suppressor gene do ?

A

Slow cell division by producing proteins that stop cells dividing or cause self destruction

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18
Q

What is the effect of a mutation on tumor suppressor genes?

A

The gene will be inactivated so the protein it codes for isnt produced and the cell divides uncontrollably

Mutation (in tumour suppressor genes);
Tumour suppressor genes are not transcribed/expressed
Amino acid sequence/primary structure altered
(Results in) rapid/uncontrollable cell division;

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19
Q

What does a proto oncogenes do?

A

stimulate cell division by making proteins that make cells divide

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20
Q

What is the effect of a mutation on proto oncogenes?

A

Gene becomes overactive so they divide uncontrollably

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21
Q

What is the name of a mutated proto oncogene?

A

Oncogene

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22
Q

What are the 2 types of cancers?

A

Benign

Malignant

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23
Q

What is the difference between the two types of cancers?

A

Malignant
- cancers
- rapidly grow
- invade and destroy surrounding tissue

Benign
- not cancerous
- grow slower and often covered in fibrous tissue that stops cells invading other tissues
- cause blockages and puts pressure on organs

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24
Q

How do tumour cells differ from normal cells ?

A

Nucleus is larger
Irregular shape
Don’t produce all proteins needed to function
Different antigens on surface
Don’t respond to growth regulating processes
Divide by mitosis more frequently

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25
Q

What are the two causes of tumour growth?

A
  • Abnormal methylation of DNA
  • Increased exposure to oestrogen
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26
Q

How does abnormal methylation cause tumour growth?

A

By it occurring too much (hypermethylation) or too little (hypomethylation)

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27
Q

What is hypermethylation and how does it relate to tumour growth?

A

Tumour suppressor genes are hypermethylated so the genes are not transcribed - so the proteins they produce to slow cell division are not made

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28
Q

What is hypomethylation and how does it relate to tumour growth?

A

Protooncogenes causes them to act as oncogenes increasing protein production that encourage cell division

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29
Q

What is the role of oestrogen in breast cancer?

A
  • stimulate certain breast cells to divide and replicate
  • their rapid replication could be further assisted by oestrogen helping tumours form quickly
  • oestrogen can introduce mutations directly into DNA of breast cells
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30
Q

What are the 2 risk factors for cancer?

A

Genetic
Environmental

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31
Q

How can you prevent cancer?

A

Screen for mutation in the DNA
More sensitive tests done so more accurate diagnosis

32
Q

How can you treat and cure cancer ?

A
  • drugs that can bind to protein receptor suppressing divison and tumour growth
  • blocking enzymes that are involved in dna repair
  • radiotherapy
  • surgery
  • gene therapy
33
Q

what are stem cell?

A

They are unspecialised stem cells that can divide to become new specialised cells

34
Q

What are some specialised cells?

A

Nerve
Muscle

35
Q

Where are stem cells found ?

A

embryo - stem cells to become specialised

adult tissues - stem cells to be replaced

36
Q

What are totipotent cells and when are they present ?

A

Stem cells that can mature into any type of body cells and are present in the first few cell divisions of an embryo

37
Q

What are pluripotent cells ?

A

They can still specialise into any cell in the body but lose the ability to become the cells that make up the placenta

38
Q

What is the difference between multipotent and unipotent cells?

A

Multipotent are able to differentiate into a few different types of cells

Unipotent can only differentiate into one type of cell

39
Q

How does a cell become specialised ?

A
  1. Genes are expressed
  2. mRNA transcribed and translated into proteins
  3. Proteins modify the cell
  4. Cell becomes specialised for a particular function
40
Q

What is the name of the heart muscle cell

A

cardiomyocyte

41
Q

What type of stem cell can replace old cardiomyocytes ?

A

Unipotent stem cells

42
Q

What is a bone marrow transplant and what diseases has it treated ?

A

Bone marrows contain stem cells that can become specialised to form any type of blood cell

Replace the faulty bone marrow that produce abnormal cells

leukaemia, lymphoma, sickle cell anaemia

43
Q

How does stem cell therapy help spinal cord injuries ?

A

Replace damaged nerve tissue

44
Q

How does stem cell therapy help heart disease?

A

Replace damaged heart tissue

45
Q

How does stem cell therapy help bladder conditions?

A

Grow whole bladders, which are implemented to replace diseased ones

46
Q

How does stem cell therapy help respiratory diseases ?

A

Donated windpipes can be stripped to simple collagen structure and covered with tissue generated by stem cells

47
Q

What are the 3 sources of stem cells and what do they do ?

A
  1. Adult stem cells - found in bone marrow to specialise into limited range if cells
  2. Embryonic stem cells - created using IVF
  3. Induced pluripotent stem cells - reprograming adult stem cells to become pluripotent so they can express a series of transcription factors
48
Q

In IPS what is the way transcription factors can be introduced to adult cells?

A

By infecting them with a specially modified virus

The virus has the genes coding for transcription factors within dna

When virus infects the genes are passed into adult cells dna so it can produce the transcription factors.

49
Q

What are the ethical considerations to do with stem cells ?

A
  • getting stem cells created by IVF raises issues because the procedure destroys embryos
  • that adult stems cells can not specialize like embryonic
50
Q

What are the benefits of stem cell therapy ?

A
  • save lives as allows organs to grow for those awaiting transplant
  • make stem cells genetically identical to a patients own cells which can be used to grow some tissue
  • improve quality of life
51
Q

What is transcription?

A

When a gene is copied from DNA into messenger RNA

52
Q

What are transcription factors?

A

These are protein molecules that control the rate of transcription of genes

53
Q

What does the transcription factor bind to in the nucleus?

A

Promoters which are specific dna sites

54
Q

What are the activators?

A

These are transcription factors that stimulate or increase the rate of transcription

55
Q

What is the role of activators ?

A

They help RNA polymerase bind to start of the target gene and activate transcription

56
Q

What is repressors?

A

Inhibit or decrease the rate of transcription by binding to the start of target gene preventing RNA polymerase from binding, stopping transcription

57
Q

How does oestrogen affect transcription?

A

It binds to a transcription factor called an oestrogen receptor forming an oestrogen-oestrogen receptor complex

58
Q

Where does the oestrogen-oestrogen receptor complex bind and move too?

A

Moves from the cytoplasm into the nucleus where it binds to specific dna sites near the start of the target gene.

59
Q

What does the oestrogen-oestrogen receptor complex act as?

A

The complex can act as an activator of transcription eg helping rna polymerase bind to start of the target gene

60
Q

What is RNAi?

A

RNA interference is where small double stranded RNA molecules stop mRNA from target genes being translated into proteins

61
Q

What are the molecules involved in RNAi?

A

siRNA ( small interfering RNA )
miRNA ( microRNA)

62
Q

What are the steps for how RNAi works ? (siRNA and miRNA in plants)

A
  1. Once mRNA has been transcribed, it leaves the nucleus for the cytoplasm
  2. In the cytoplasm double stranded siRNA associates with several proteins and unwinds
  3. One of the resulting single strands of siRNA is selected and the other strand broken down
  4. The single strand of siRNA binds to target mRNA.
  5. The base sequence of siRNA is complementary to base sequence in sections of target mRNA.
  6. The proteins associated with the siRNA cut mRNA into fragments
  7. Fragments move to processing body and are degraded.
63
Q

What is the role of the miRNA in mammals?

A
  1. When miRNA is first transcribed it exists as a long folded strand –> processed into a double strand–> 2 single strand
  2. One strand associates with proteins and binds to target mRNA in the cytoplasm
  3. Now instead, the miRNA complex physically blocks translation of target mRNA
  4. The mRNA is then moved into a processing body where it is stored or degraded
64
Q

How does epigenetic control work?

A

Determines whether a gene is switched on or off by attachment or removal of chemical groups to or from DNA or histone proteins

65
Q

What does the epigenetic marks alter?

A

How easy it is for enzymes and other proteins needed for transcription to interact with and transcribe DNA

66
Q

What are the 2 ways to control gene expression?

A

Increased methylation of DNA
Decreased acetylation of histones

67
Q

What is increased methylation of DNA ?

A

When a methyl group is attached to the DNA coding for a gene

  1. The group attaches at a CpG site (cytosine - phosphodiester - guanine)
  2. This changes DNA structure so that the transcriptional machinery cant interact with the gene = SWITCHED OFF
68
Q

What is histones?

A

Histones are proteins that DNA wraps around to form chromatin

69
Q

What happens when histones are acetylated?

A

The chromatin is less condensed so transcriptional machinery can access DNA so genes can be transcribed

70
Q

What affects the access of DNA?

A

Whether chromatin is highly condenses or less condensed therefore affecting whether it can be transcribed

71
Q

What happens when acetyl groups are removed from histones?

A

The chromatin becomes highly condensed and genes in the DNA cant be transcribed because the transcriptional machinery cant physically access them

72
Q

What enzymes are responsible for removing acetyl groups?

A

Histone Deacetylase

73
Q

How does epigenetics cause Fragile X syndrome ?

A

Mutation on the X chromosome where the sequence CGG is repeated many times so there are more CpG sites –> more methylation –> switches off so lack of protein –> disease

74
Q

How does epigenetics cause Angelman Syndrome ?

A

Deletion of region 15

mainly on maternal allele

gene switched off by methylation –> motor and delay problems

75
Q

How does epigenetics cause Prader willi syndrome?

A

loss of functions on gene of chromosome 15

occurs when deletion occurs on paternal chromosome

maternal gene silenced by methylation so can not compensate

76
Q

How do you treat Epigenetic diseases?

A

Drugs to stop DNA methylation

Decreased acetylation of histones –> inhibit histone deacytylase enzymes

77
Q

What is the phenotype?

A

Result of organisms genotype and interaction of its genotype with the environment

biology year 2 (11 decks)

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