Gene expression

Question 1

What is addition of bases?

Answer 1

-an extra base becomes inserted in the sequence which causes a frame shift to the right so the sequence is read diffferently
-if 3 bases are added there will not be a frame shifit but
the polypeptide will be different

Question 2

What is the duplication of bases?

Answer 2

• one or more bases are repeated

- this produces a frame shift to the right

Question 3

What is the inversion of bases?

Answer 3

-a group of bases becomes separated and rejoin at the same point but in the reverse order so the sequence is read differently and produces a different polypeptide

Question 4

What is the translocation of bases?

Answer 4

-a group of bases are separated from DNA on one chromosome and inserted into DNA on a different chromosome which produces a different phenotype

Question 5

What are the causes of mutations?

Answer 5

• gene mutations can arise spontaneously during DNA replication
• mutations can also occur due to mutagens like radiation and chemicals

Question 6

What is high energy ionising radiation?

Answer 6

• x-rays and ultra violet light
• these forms of radiation can disrupt the structure of DNA
• ultraviolent radiation disrupts DNA replication
• x-rays produce free radicals so that DNA polymerase wont work

Question 7

What are chemicals?

Answer 7

• chemicals can alter the structure of DNA or interfere with transcription
• tobacco smoke, can inactivate a tumour-suppressor gene
• by stopping guanine pairing with cytokine so DNA polymerase inserts any for the other bases

Question 8

What are the costs and benefits of mutations?

Answer 8

• it produces genetic diversity necessary for natural selection
• they are almost always harmful and produce an organism that is less well suited to its environment
• mutations can lead to distribution of normal cellular activities such as cell division which may cause cancer