8A- Mutations and Cancer.

Question 1

What is a mutation?

Answer 1

Any change to the base nucleotide sequence.

Question 2

What are the types of mutations?

Answer 2

Substitution

Deletion

Addition

Duplication

Inversion

Translocation

Question 3

What is substitution?

Answer 3

One or more bases are swapped.

Question 4

What is deletion?

Answer 4

One or more bases are removed.

Question 5

What is addition?

Answer 5

One or more bases are added.

Question 6

What is duplication?

Answer 6

One or more bases are repeated.

Question 7

What is inversion?

Answer 7

A sequence of bases is reversed.

Question 8

What is translocation?

Answer 8

A sequence of bases is moved from one location in the genome to another.

Question 9

How might mutations affect an enzymes ability to catalyse a reaction?

Answer 9

A mutation in the polypeptide that makes up an enzyme may change the shape of the enzyme’s active site.

This may stop the substrates from being able to bind to the active site, leaving the enzyme unable to catalyse the reaction.

Question 10

How do some mutations cause genetic disorders?

Answer 10

Inherited disorders can be caused by abnormal genes or chromosomes.

Some mutations increase the likelihood of developing certain cancers. Eg, BRCA 1

Question 11

How to mutations affect gametes?

Answer 11

If the gametes contain a mutation for a genetic disorder or a type of cancer when they are fertilised it may be present in the new foetus.

This is hereditary mutations because they’re passed on to the offspring.

Question 12

Which mutations do not always affect the order of amino acids?

Answer 12

Substitutions

Inversions

Question 13

Which types of mutations always cause a frame shift?

Answer 13

Addition

Duplication

Deletion

Question 14

How do mutagenic agents increase the rate of mutation?

Answer 14

1) Acting as a base.
2) Altering bases.
3) Changing the structure of DNA.

Question 15

How do mutagenic agents act as a base?

Answer 15

Chemicals called base analogs can substitute bases during replication.

This changes the base sequence.

Eg. 5-bromourscil substitutes for thymine, but it pairs with guanine, leading to a substitution mutation, one base is swapped for another.

Question 16

How do mutagenic agents alter bases?

Answer 16

Some chemicals delete and alter bases.

Eg. Alkylating agents can add an alkyl group to guanine, causing it to pair to thymine.

Question 17

How to mutagenic agents cause a change in the structure of DNA?

Answer 17

Some types of radiation affect the structure of DNA.

This leads to problems during replication.

Eg. UV radiation can cause adjacent thymine bases to pair together.

Question 18

What are acquired mutations?

Answer 18

Mutations that occur after fertilisation.

Question 19

How do mutations in genes cause uncontrolled cell growth?

Answer 19

Mutations in genes that control cell division could cause uncontrolled cell growth.

This results in a tumour, a mass of abnormal cells.

Question 20

What are the two genes that control cell division?

Answer 20

Tumour suppressor genes.

Proto-oncogenes.

Question 21

How do tumour suppressor genes work?

Answer 21

It can be inscribed if a mutation occurs in the DNA.

Tumour suppressor genes usually slow cell division by producing proteins that stop cells dividing or to self destruct.

If a mutation occurs the protein isn’t produced, allowing a tumour to form.

Question 22

How do proto-oncogenes work?

Answer 22

The effect of proto-oncogenes can be increased if a mutation occurs in the DNA.

Once mutated it’s called a oncogene.

Proto-oncogenes usually stimulate cell division by producing proteins.

If a mutation occurs in the gene it can become overactive. This causes cells to divide uncontrollably, resulting in a tumour.

Question 23

What are malignant tumours?

Answer 23

These are cancers.

They grow rapidly and invade other tissues.

It spreads via the bloodstream or lymphatic system.

Question 24

What are benign tumours?

Answer 24

These are not cancerous.

They grow at a slower rate.

They’re usually covered by fibrous tissues that stop it breaking off.

It only causes issues if it causes blockages.

Benign tumours can become malignant.

Question 25

How are tumours different to other cells?

Answer 25

They may have an irregular shape.

The nucleus is larger and darker and there could be more than one.

They don’t produce all the proteins necessary.

They have different antigens.

They divide by mitosis more frequently than other cells.

Question 26

How can abnormal methylation cause tumour growth?

Answer 26

Methylation means adding a methyl group.

It controls whether a gene is transcribed or translated.

If a tumour suppressor gene is hyper methylated, the genes are not transcribed, so the proteins to slow down cel division aren’t made.

Hypo methylation causes oncogenes, increasing the producition of the proteins that encourage cell division.

Question 27

How does increased oestrogen may contribute to some breast cancers?

Answer 27

It may increase the risk of developing breast cancer.

It may stimulate breast cells to divide and replicate so naturally increases the chance with each replication.

If it encourages the speed of replication, cancer cells already existing may form more quickly.

Oestrogen may introduce mutations directly into the DNA.

Question 28

How do we prevent cancer?

Answer 28

If we know that mutation to look for we can screen for it. Eg, BRCA 1.

If we know there is a risk mastectomies can reduce the risk.

More sensitive tests can be developed, which leads to earlier diagnosis.

Question 29

What are the treatments and cures for cancer?

Answer 29

He treatment is different for different mutations.

If we know which specific mutations cause it, we can develop drugs to effectively target them.

Some cancers require a more aggressive treatment, we need to know which ones these are.

Gene therapy can replace the faulty genes.

Eg replace inactive tumour suppressor genes.