Protein syn and Mutation

Question 1

Describe mRNAs structure

Answer 1

single strand
linear
no hydrogen bonds
consists of many codons
no amino acid binding site

Question 2

Outline the process of transcription

Answer 2

hydrogen bonds between DNA bases broken by DNA helicase and strands separate.
Only one DNA strand acts as a template.
Freee RNA nucleotides form hydrogen bonds with template strand by complementary base pairing.
Uracil base pairs with adenine on DNA
RNA polymerase joins adjacent RNA nucleotides by forming phosphodiester bonds

Question 3

What is a gene mutation

Answer 3

A change in DNA base sequence of Chromosome

Question 4

Outline the process of translation

Answer 4

mRNA leaves the nucleus and attaches to ribosomes
tRNA enter the ribosome and their anticodons bind to complementary mRNA codons
Each tRNA brings a specific amino acid
The amino acids on adjacent tRNAs are joined by peptide bonds, with the use of ATP
The tRNA is released after the amino acid is joined to polypeptide.
THe ribosome moves along the MRna to form the polypeptide

Question 5

What is deletion of insertion mutation

Answer 5

deleted or added - cause a frameshift, so all Codons after the mutation are changed

Question 6

What is a chromosome mutation

Answer 6

non disjunction - chromsomes dont separate during anaphase in meiosis

Question 7

How can mutations occur

Answer 7

happen spontaneously during DNA replication
Rate of mutation increased by mutagenic agents (e.g. Ionising radiation and Chemicals)

Question 8

What chromosome mutation is Down syndrome

Answer 8

Trisomy of chromosome 21, when the chromosomes don’t separate in anaphase (non -disjunction)

Question 9

What id the genome

Answer 9

is the complete set of genes in a cell

Question 10

What determines the sequence of amino acids in a protein

Answer 10

the sequence of bases in DNA, read as triplets, determines the sequence of Amino acid in protein

Question 11

What is a substitution mutation

Answer 11

substituted - may have no effect (degenerate code) change an amino acid and so the tertiary structure or introduce a stop codon

Question 11

Describe tRNA strcutre

Answer 11

single strand
clover leaf shaped
held in shape by hydrogen bonds
has a single anticodon
has an amino acid binding site

Question 12

How is transcription different in prokaryotes

Answer 12

no introns so no splicing

Question 13

What is the proteome

Answer 13

proteome is the full range of proteins that a cell is able to produce

Question 14

mRNa strcutre

Answer 14

Single strand
Linear
No hydrogen bonds
Consists of many codons
No amino acid binding site

Question 15

Describe how mRNA is formed by transcription in eukaryotes.

Answer 15

)  1. Hydrogen bonds (between DNA bases) break;
Ignore DNA helicase.
Reject hydrolysing hydrogen bonds.
2. (Only) one DNA strand acts as a template;
3. (Free) RNA nucleotides align by complementary base pairing;
For ‘align by complementary base pairing’, accept ‘align to complementary bases’ or ‘align by base pairing’.
4. (In RNA) Uracil base pairs with adenine (on DNA)
OR
(In RNA) Uracil is used in place of thymine;
Do not credit use of letters alone for bases.
5. RNA polymerase joins (adjacent RNA) nucleotides;
Reject suggestions that RNA polymerase forms hydrogen bonds or joins complementary bases.
6. (By) phosphodiester bonds (between adjacent nucleotides);
7. Pre-mRNA is spliced (to form mRNA)
OR
Introns are removed (to form mRNA);

Question 16

Describe how a polypeptide is formed by translation of mRNA.

Answer 16

) 1. (mRNA attaches) to ribosomes
OR
(mRNA attaches) to rough endoplasmic reticulum;
2. (tRNA) anticodons (bind to) complementary (mRNA) codons;
3. tRNA brings a specific amino acid;
4. Amino acids join by peptide bonds;
5. (Amino acids join together) with the use of ATP;
6. tRNA released (after amino acid joined to polypeptide);
7. The ribosome moves along the mRNA to form the polypeptide;

Question 17

What is the proteome of a cell?

Answer 17

) (The proteome is the full) range of / number of different proteins that a cell is able to produce (at a given time);
OR
(The proteome is the full) range of / number of different proteins the genome / DNA is able to code for;

Question 18

Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA).

Answer 18

) 1. mRNA does not have hydrogen bonds / base pairing, tRNA does;
OR
mRNA is linear / straight chain, tRNA is cloverleaf;
2. mRNA does not have an amino acid binding site, tRNA does;
Accept mRNA cannot carry an amino acid, tRNA can
3. mRNA has more nucleotides;
Accept mRNA is longer or converse
4. (Different) mRNAs have different lengths, all tRNAs are similar / same length;
5. mRNA has codons, tRNA has an anticodon;

Question 19

Starting with mRNA in the cytoplasm, describe how translation leads to the production of a polypeptide.
Do not include descriptions of transcription and splicing in your answer.

Answer 19

) 1. mRNA associates with a ribosome / ribosome attaches to mRNA;
Idea of association is required
2. Ribosome moves to / finds the start codon / AUG;
3. tRNA brings / carries (appropriate / specific) amino acid;
Must be explicitly stated and not inferred.
4. Anticodon (on tRNA complementary) to codon (on mRNA);
5. Ribosome moves along to next codon;
OR
Ribosome ‘fits’ around two codons / can fit two tRNAs;
Must be explicitly stated and not inferred.
6. (Process repeated and) amino acids join by peptide bonds / condensation reaction (to form polypeptide);
OR
(Process repeated and) amino acids joined using (energy from) ATP (to form polypeptide);

Question 20

Describe how mRNA is produced in a plant cell.

Answer 20

) 1. The DNA strands separate by breaking the H bonds;
OR
H bonds broken between (complementary) (DNA) bases;
2. (Only) one of the strands/template strand is used (to make mRNA/is transcribed);
3. (Complementary) base pairing so A ⟶ U, T ⟶ A, C ⟶ G, G ⟶ C;
4. (RNA) nucleotides joined by RNA polymerase;
5. pre-mRNA formed;
6. Splicing / introns removed to form mRNA;
1. Ignore ‘hydrolysis’ of bonds
1. Accept DNA “unzips” by breaking the H bonds
6. Accept ‘non-coding’ sections for introns

Question 21

Messenger RNA (mRNA) is used during translation to form polypeptides.
Describe how mRNA is produced in the nucleus of a cell.

Answer 21

) 1. Helicase;
2. Breaks hydrogen bonds;
3. Only one DNA strand acts as template;
4. RNA nucleotides attracted to exposed bases;
5. (Attraction) according to base pairing rule;
6. RNA polymerase joins (RNA) nucleotides together;
7. Pre-mRNA spliced to remove introns.