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A Level Biology > 8A Mutations and Gene Expression > Flashcards

8A Mutations and Gene Expression Flashcards

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1
Q

Substitution mutation

A

One or more bases are swapped for another

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2
Q

Deletion mutation

A

One or more bases are removed

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3
Q

Addition mutation

A

One or more bases have been added

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4
Q

Duplication mutation

A

One or more bases are repeated

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5
Q

Inversion mutation

A

A sequence of bases has been reversed

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6
Q

Translocation mutation

A

A sequence of bases is moved from one location to another in the genome. Can be same or different chromosome

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7
Q

Hereditary mutations

A

If a gamete containing a mutation for a genetic disorder is fertilised the mutation will be present in the fetus

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8
Q

Mutagenic agent

A

Increase the rate of mutations

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9
Q

How can different mutagenic agents work?

A 
Act as a base (changing base sequence of DNA) 
Alter base (cab delete or alter base)
Change the structure of DNA- causes problems during DNA replication
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10
Q

Acquired mutations

A

Mutations that occur after fertilisation

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11
Q

Tumour

A

A mass of abnormal cells

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12
Q

What makes a cancer?

A

A tumour that can invade and destroy surrounding tissue

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13
Q

What do tumour suppressor genes normally do?

A

Slow cell division by producing proteins that stop cells dividing or cause them to self destruct

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14
Q

Apoptosis

A

Cells self destruct

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15
Q

What happens if a mutation occurs in a tumour suppressor gene?

A

The gene will be inactivated. Protein that suppresses cell division won’t be made, so cells are allowed to divide uncontrollably, resulting in a tumour

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16
Q

What to proto-oncogenes usually do?

A

Stimulate cell division by producing proteins that make cells divide

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17
Q

What happens if a mutation occurs to a proto-oncogene?

A

The gene becomes overactive, produces more of the protein, so cells divide uncontrollably resulting in a tumour

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18
Q

What is a mutated proto-oncogene called?

A

An oncogene

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19
Q

Malignant tumour

A

Cancerous- grow rapidly and invade and destroy surrounding tissue
Cells can break off the tumours and spread to other parts of the body in the bloodstream or lymphatic system

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20
Q

Benign tumours

A

Not cancerous- grow slower and are covered in fibrous tissue the stops the cells invading other tissues

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21
Q

How do benign tumours pose a risk?

A

Can develop into malignant tumours and can cause blockages, putting pressure on organs

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22
Q

Name six ways that tumour cells can differ from normal cells

A

Nucleus is darker and rounder or can have more than one nucleus
Irregular shape
Don’t produce all the proteins needed to function properly
No antigens on surface
Don’t respond to growth regulating processes
Divide via mitosis more frequently

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23
Q

What two mutations can cause the growth of a tumour?

A

Abnormal methylation

Increased exposure to oestrogen

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24
Q

How does hypermethylation lead to the development of a tumour?

A

Methylation = adding a methyl group
Of tumour suppressor genes
Genes are not transcribed, so translation doesn’t occur, so the proteins they produce to slow cell division aren’t made. This means cells can divide uncontrollably

25
Q

How does hypomethylation lead to the development of a tumour?

A

Of proto-oncogenes.

Causes them to become oncogenes and produce the proteins needed for cell division at a more rapid rate

26
Q

How does oestrogen lead to the development of a tumour?

A

Oestrogen can stimulate breast cells to divide and replicate- more cell divisions = more chance for mutations to occur
Can stimulate division- cells become more cancerous
Introduce mutations directly into DNA of certain breast cells

27
Q

Stem Cells

A

Unspecialised cells that can develop into other types of cell

28
Q

Where are stem cells found?

A

embryos and adult tissue such as bone marrow

29
Q

Totipotent stem cells

A

Can mature into any cell in the body (including cells that make up the placenta)- only present in the first few stages of an embryo

30
Q

Pluripotent stem cells

A

Can become any cell in the body except placenta cells - embryonic

31
Q

Multipotent stem cells

A

Available from adult tissue- can differentiate into a few types of cell (e.g white and red blood cells can be developed from stem cells in bone marrow)

32
Q

Unipotent stem cells

A

Available from adult tissue- can only differentiate into one type of cell

33
Q

How do stem cells become specialised?

A

All stem cells contain the same genes but not all are expressed during development
mRNA is therefore only transcribed from the specific genes, and then translated into proteins
The proteins produced causes changes to occur in the cell that are difficult to reverse, so once a cell has specialised, it stays specialised

34
Q

What are cardiomyocytes?

A

Heart muscle cells

35
Q

How are cardiomyocytes made from unipotent stem cells?

A

Unipotent stem cells in the heart can replace old or damaged cardiomyocytes

36
Q

What are the tree main sources of stem cells?

A

Adult stem cells
Embryonic stem cells
Induced Pluripotent stem cells

37
Q

What are Induced Pluripotent Stem Cells?

A

Cells created by scientists in a lab
Made to express certain transcription factors in order to swtch on/ off certain genes
A way to do this is by infecting adult cells with a specially modified virus

38
Q

What is the transcription of genes controlled by?

A

Transcription Factors

39
Q

Where do transcription factors move from in eukaryotes?

A

The cytoplasm to the nucleus

40
Q

Where do transcription factors bind to?

A

Specific DNA sites called promoters

41
Q

Where are promoters found?

A

Near the start of the target gene

42
Q

What are activators?

A

Transcription factors that stimulate or increase the rate of transcription

43
Q

What are repressors?

A

Transcription factors that inhibit or decrease the rate of transcription

44
Q

How is oestrogen used as a transcription factor?

A

Binds to a transcription factor called an oestrogen receptor, forming an oestrogen- oestrogen receptor complex. The complex moves from cytoplasm to the nucleus and binds to a specific Dna site near the star of the target gene. The complex acts as an activator

45
Q

What is an example of stimulating transcription?

A

Helping RNA polymerase to bind to the start of the target gene

46
Q

What is an example of inhibiting transcription?

A

Preventing RNA polymerase from binding

47
Q

What is RNAi?

A

Double stranded RNA molecules stop mRNA from target genes being translated into proteins

48
Q

What are the molecules involved in RNAi?

A

siRNA and miRNA

49
Q

Where does siRNA work?

A

During translation

50
Q

Describe the function of siRNA

A

mRNA transcribed and leaves nucleus for cytoplasm. In cytoplasm, double stranded siRNA associates with proteins and unwinds, producing two single strands. One strand is selected, the other is degraded
The single strand of siRNA then binds to the target mRNA as their base sequences are complementary
The proteins associated with the siRNA cut the mRNA into fragments so that it can no longer be translated
The fragments then move to a processing body, where it is degraded

51
Q

Do plants have siRNA?

A

No, they only have miRNA

52
Q

What is the function of miRNA in mammals?

A

Less specific than siRNA as it is not fully complementary to the target mRNA, so it can target more than one mRNA molecule.
The double strand of miRNA is broken down into two single strands by enzymes, then one single strand associates to proteins (the other is degraded)
The miRNA-protein complex physically blocks the translation of the target mRNA. The mRNA is then moved to the processing body where it can either be stored or translated

53
Q

Epigenetic control

A

The attatchment/ removal of a chemical groups to or from DNA or histone proteins, which determine whether a gene is switched on or off

54
Q

Epigenetic marks

A

The chemical groups that are removed/ attached to DNA or histone proteins

55
Q

In simple terms, describe how epigenetic marks work?

A

They alter how easy it is for enzymes and other proteins needed for transcription to interact and transcribe the DNA

56
Q

Why can the expression of some genes be passed on to offspring?

A

Epigenetic marks may still be present through generations, so the offspring can be affected by environmental changes that affected their parents or grandparents

57
Q

Describe the process of increased methylation

A

Methyl group attaches at a CpG site (cytosine and guanine are next to each other. Increased methylation changes the DNA structure so that the transcriptional machinery can’t interact with the genes

58
Q

Describe the process of decreased acetylation of histones

A

When acetyl groups are removed, the chromatin becomes highly condensed and genes can’t be transcribed because the transcriptional machinery can’t physically access them

59
Q

What enzyme is responsible for removing the histone group?

A

Histone deacetylase

A Level Biology (10 decks)

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