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Biology A1 & A2 > 8A: Mutations and gene expression > Flashcards

8A: Mutations and gene expression Flashcards

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1
Q

Describe a substitution mutation

A

1 or more bases are swapped for another

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2
Q

Describe a deletion mutation

A

1 or more bases are removed

= frame shift

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3
Q

Describe an addition mutation

A

1 or more bases are added

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4
Q

Describe a duplication mutation

A

1 or more bases are repeated

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5
Q

Describe an inversion mutation

A

A sequence of bases is reversed

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6
Q

Describe a translocation mutation

A

A sequence of bases is moved from one location in the gene to another. This could be movement within the same chromosome or movement to a different chromosome

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7
Q

What does the order of DNA bases in a gene determine?

What may happen if there’s a mutation?

A

The order of bases in a gene determines the sequence of amino acids in a particular polypeptide. If a mutation occurs in a gene, the sequence of amino acids in a polypeptide that codes for it could be changed (= change in functionality)

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8
Q

What is a gamete?

A

A sex cell

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9
Q

What can genetic disorders be caused by?

A

Inherited disorders, e.g cystic fibrosis, can be caused by mutations (abnormal genes or chromosomes)

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10
Q

Some ______ can increase the likelihood of developing certain cancers.

A

Some mutations can increase the likelihood of developing certain cancers.

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11
Q

What will happen if a gamete containing a mutation for a genetic disorder is fertilised?

A

The mutation will be present in the new fetus formed - called hereditary mutations because they are passed onto the offspring

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12
Q

Why can some amino acids be coded for by more than one DNA triplet?

A

Because of the degenerate nature of genetic code

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13
Q

What 3 types of mutation will almost always change the amino acid sequence of a polypeptide? Why?

A

Additions, duplications and deletions. Because, they all result in a frame shift so that the triplet code is read in a different way

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14
Q

What are the base triplets that follow on from a mutation called?

A

They are said to be ‘downstream’ of the mutation.

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15
Q

Give 3 examples of mutagenic agents

A
  1. Radiation (UV, ionising)
  2. Some chemicals
  3. Some viruses
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16
Q

What are mutagenic agents?

A

Things that can increase the rate of mutations

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17
Q

What 3 ways can mutagenic agents increase the rate of mutation?

A
  • Acting as a base
  • Altering bases
  • Changing the structure of DNA
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18
Q

How do mutagenic agents ‘act as a base’?

A

Chemicals called base analogs can substitute for a base during DNA replication, changing the base sequence in the new DNA.

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19
Q

What are mutations that occur in individual cells after fertilisation called?

A

Acquired mutations

20
Q

How can mutations result in uncontrolled cell division?

A

If the mutation(s) occur in the genes that control the rate of cell division (mitosis)

21
Q

What is a tumour?

A

A mass of abnormal cells

22
Q

When are tumours called cancers?

A

If they invade and destroy surrounding tissue

23
Q

What are the 2 types of gene that control cell division?

A

Tumor suppressor genes and proto-oncogenes🙈

24
Q

What is the normal function of tumour suppressor genes?

A

They slow the rate of cell division by producing proteins that stop cells dividing or cause them to self-destruct (apoptosis)

25
Q

Describe how a mutation in tumour suppressor genes may result in a tumour.

A

The mutation may cause them to become inactivated, this means that the protein will not be produced and the cells will divide uncontrollably (the rate of cell division increases) resulting in a tumour.

26
Q

What is the normal function of proto-oncogenes?

A

They stimulate cell division by producing proteins that make cells divide

27
Q

Describe how a mutation in proto-oncogenes may result in a tumour.

A

The effect of a proto-oncogene can be increased if a mutation occurs, this stimulates the cells to divide uncontrollably (the rate of division increases) resulting in a tumour

28
Q

What is a mutated proto-oncogene called?

A

An oncogene

29
Q

Describe a malignant tumour

A

They are cancerous and grow rapidly, they invade other cells and destroy the surrounding tissues. Cells can break off and spread to other parts of the body in the bloodstream of lymphatic system

30
Q

Describe a benign tumour

A

They are not cancerous and usually grow slower than malignant tumours and are often covered in fibrous tissue that stops cells invading other tissues. They are often harmless but they can cause blockages that put pressure on organs. Some benign tumours can become malignant

31
Q

Describe how tumour cells are different to normal cells (6 ways)

A
  • Irregular shape
  • Larger and darker nucleus (sometimes more than one nucleus)
  • Dont produce all the proteins needed to function properly
  • Different surface antigen
  • Don’t respond to growth regulating processes
  • Divide by mitosis more frequently
32
Q

What does methylation mean?

A

Adding a methyl (-CH₃) group to something

33
Q

What does hypermethylation mean?

A

Too much methylation

34
Q

What does hypomethylation mean?

A

Too little methylation

35
Q

Describe what happens if tumour suppressor genes are hypermethylated.

A

The tumor suppressor genes are not transcribed - so the proteins they produce to slow cell division aren’t made
= Cells divide uncontrollably by mitosis and tumors develop

36
Q

Describe what happens if proto-oncogenes are hypomethylated.

A

Proto-oncogenes act as oncogenes - increasing the production of the proteins that encourage cell division
= stimulates cells to divide uncontrollably causing tumors to develop

37
Q

Increased exposure to oestrogen has been linked to some breast cancers.
Give 2 reasons why oestrogen might contribute to causing breast cancer.

A

1) Oestrogen can stimulate some breast cells to divide and replicate. More divisions = more likely mutations will occur, so increasing chance of cells becoming cancerous
2) Bc oestrogen stimulates cell division, this could also mean that if cells do become cancerous their replications would be faster = tumors would form quickly

38
Q

What type of hormone is oestrogen?

A

A steroid hormone

39
Q

What are 2 types of risk factors for cancer?

Give examples

A

Genetic - specific inherited alleles

Environmental - radiation, high fat diet, smoking

40
Q

Describe totipotent stem cells.

A

Totipotent cells can divide and produce any type of body cell.
- During development, totipotent cells translate only part of their DNA = cell specialisation.

41
Q

Where are totipotent stem cells found?

A

Totipotent cells occur only for a limited time in early mammalian embryos.

42
Q

Describe multipotent stem cells.

Give an example

A

Can differentiate into a few different types of cell

e.g red and white blood cells are formed from stem cells in bone marrow

43
Q

Describe unipotent stem cells.

Give an example

A

Can differentiate into one type of cell

e.g cardiomyocytes

44
Q

Describe pluripotent stem cells.

A

Pluripotent stem cells can divide in unlimited numbers and can be used in treating human disorders

45
Q

Where are pluripotent stem cells found?

A

Pluripotent cells are found in embryos

46
Q

How are induced pluripotent stem cells made?

A

iPS cells can be produced from adult somatic cells using appropriate protein transcription factors.

47
Q

Give 2 things stem cells can be used to treat

A

Leukemia and lymphoma

Biology A1 & A2 (19 decks)

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