Unit 4- DNA + protein synthesis =)

Question 1

What is a gene ? (1)

Answer 1

a sequence of DNA bases that codes for a polypeptide

Question 2

What are the 3 characteristics of a genetic code ?

from spec

Answer 2

1. universal
2. non-overlapping
3. degenerate

Question 3

What is the genome ?

Answer 3

complete set of genes in a cell

Question 4

What is proteome ?

Answer 4

full range of proteins that a cell is able
to produce

Question 5

Outline one difference in transcription between eukaryotic and prokaryotic cells.

Answer 5

• P: direct production of mRNA from DNA
• E: production of premRNA– spliced–> mRNA

Question 6

What is the fixed position occupied by a gene on a DNA molecule called ? (1)

Answer 6

Locus

Question 7

Describe how a gene is a code for the production of a polypeptide.
Do not include information about transcription or translation in your answer. (3)

Answer 7

• base sequence
• in triplets
• determines seq. of a.a. – primary structure

Question 8

Define the term exon. (1)

Answer 8

• base seq. coding for polypeptide

Question 9

Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule. (2)

Answer 9

• condensation
• between phosphate & deoxyribose
• by DNA polymerase

Question 10

State three differences between DNA in the nucleus
of a plant cell and DNA in a prokaryotic cell. (3)

Answer 10

Plant (EK) vs PK:
1. associated w/ histones vs x
2. linear vs circular
3. introns vs x
4. x plasmids vs plasmids
5. longer vs shorter

Question 11

Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome. (2)

Answer 11

• DNA that does not code for polypeptides/ a.a./ tRNA
• between genes

Question 12

.

Answer 12

1. in introns
2. some triplets code for the same a.a.

Question 13

Describe two differences between the structure of a tRNA molecule and the structure of an mRNA molecule. (2)

Answer 13

tRNA vs mRNA:
1. clover leaf shape vs linear/ has H bonds vs x
2. has a.a. binding site vs x
3. has anticodon vs codon
4. mRNA has ↑ nucleotides
5. diff mRNAs have diff lengths vs all tRNAs are similar/ same length

Question 14

Describe and explain a difference in the structure of pre-mRNA and mRNA molecules. (2)

Answer 14

• mRNA has fewer nucleotides, x introns
• ∵ spliced

Question 15

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation. (3)

Answer 15

1. tRNA brings specific a.a. to ribosome
2. anticodon on tRNA binds to codon on mRNA
3. a.a. joined to each other in condensation (using ATP) (–> peptide bond)

Question 16

Describe how mRNA is produced from an exposed template strand of DNA.
Do not include DNA helicase or splicing in your answer. (3)

Answer 16

1. free RNA nucleotides line up by complmentary base pairing
2. RNA polymerase joins them
3. by forming phosphodiester bonds

Question 17

AMY1 is a gene for amylase.
Multiple copies of the AMY1 gene is an adaptation to a high-starch diet.
Use your knowledge of protein synthesis and enzyme action to explain the advantage of this adaptation. (3)

Answer 17

• ↑ transcription ↑ mRNA
• ↑ translation ↑ enzymes
• faster reactions

Question 18

Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are postioned in the genome. (2)

Answer 18

• DNA that x code for proteins
• in between genes

Question 19

Describe the role of ATP in the process of translation in protein synthesis. (2)

Answer 19

• releases energy
• peptide bond formed between a.a.

Question 20

Give four structural differences between a DNA molecule and an mRNA molecule. (4)

Answer 20

DNA vs mRNA:
1. deoxyribose vs ribose
2. thymine vs uracil
3. long vs short
4. double stranded vs single stranded
5. H bonds vs x H bonds

Question 21

Suggest one advantage of showing the genetic code as base sequences on mRNA, rather than triplets on DNA. (1)

Answer 21

ribosomes use code on mRNA to assemble polypeptides

Question 22

Suggest the role of stop mRNA codons. (2)

Answer 22

• stops translation
• detachment of polypeptide chain from ribosome