Chapter 4 - DNA and protien synthesis

Question 1

give two ways in which the structure of tRNA differs from structure of mRNA

Answer 1

• tRNA has an amino acid binding site
• tRNA has hydrogen bonds between base pairs
• tRNA three exposed bases

Question 2

explain what is meant by an allele

Answer 2

different form of a gene

Question 3

explain how DNA replicates

Answer 3

hydrogen bonds break, semi conservative replication occurs. as a result the nucleotides line up forming a sequence and the linking of the dna nucleotides is controlled by the enzyme DNA polymerase.

Question 4

why is dna helicase important in dna replication?

Answer 4

seperates the strands so nucleotides can attach

Question 5

explain why the replication of dna is described as semi conservative

Answer 5

the original strand is conserved and one new complementry strand is made using the old strand as a template for replication

Question 6

What is dna?

Answer 6

A polynucleotide (made up of lots of nucleotides joined together)
- deoxyribonucleic acid contains genetic info with instructions to grow and develop.

Question 7

What is a nucleotide?

Answer 7

Made up of a deoxyribose sugar, a phosphate group and a nitrogenous base. (each nucleotide has the same sugar and phosphate but base can vary)

Question 8

what are the four possible bases?

Answer 8

adenine and guanine (purines)

cytosine and thymine (pyrimidines)

Question 9

what are the differences between dna and rna

Answer 9

• sugar in rna nucleotides are ribose sugar not deoxribose
• nucleotides form a single polynucleotide strand not double
• uracil (a pyrimidine) replaces thymine as a base. [uracil always pairs with adenine in RNA]

Question 10

describe protein synthesis.

Answer 10

sections of DNA are copied into RNA, the RNA leaves the nucleus and joins with ribosome and synthesises a protein