Genes And The Triplet Code

Question 1

Explain how a change on the sequence of DNA bases could result in a non- functional enzyme

Answer 1

• change in 1’
• cause change in ionic/H/D
• change in 3’
• change active site
• no E-S complexes

Question 2

How does organic bases help to stabilise the structure of DNA?

Answer 2

• H bonds b/t base pairs to gold 2 strands together
• many H bonds provide strength

Question 3

An advantage of showing the genetic code as base sequences on mRNA, rather than triplets on DNA

Answer 3

-ribosomes use mRNA to make polypeptides

Question 4

Why is the genetic code describes as degenerate?

Answer 4

• more than one triple codes for the same aa

Question 5

Which part of the cell cycle are gene mutations most likely to occur?

Answer 5

• interphase
• where DNA replication occurs

Question 6

Why is the genetic code described as non-overlapping?

Answer 6

-same base isn’t used in different codons

Question 7

What are introns?

Answer 7

-non-coding section of DNA
-removed after transcription
-splicing forms mRNA

Question 8

Why is a small proportion of genes transcribed in any human cell?

Answer 8

-most genes aren’t needed
-genes transcribed only when needed

Question 9

Why is it an advantage to mitochondria + chloroplasts to have own DNA?

Answer 9

-has genes for respiration/photosynthesis
-don’t need to move enzyme from cytoplasm

Question 10

What is a gene?

Answer 10

• section of DNA that codes for sequence of aa in polypeptide

Question 11

What is locus?

Answer 11

• location of gene on strand of DNA

Question 12

Compare chloroplast DNA with nucleus DNA (3)

Answer 12

-Ch: shorter , N: longer
-Ch: circular, N: linear
-Ch: no histones, N: histones