Cellular Control

Question 1

Define Gene

Answer 1

A length of DNA that codes for one (or more) polypeptides

Question 2

Define Polypeptide

Answer 2

A polymer consisting of a chain of amino acid residues joined by peptide bonds

Question 3

Define Genome

Answer 3

The entire DNA sequence of that organism. This consists of about 3 billion nucleotide base pairs.

Question 4

Define Protein

Answer 4

A large polypeptide - usually 100 or more amino acids. Some proteins consist of one polypeptide chain and some consist of more than one polypeptide chain.

Question 5

Define Transcription

Answer 5

The creation of a single stranded mRNA copy of the DNA coding strand.

Question 6

What is a triplet code?

Answer 6

It is a sequence of 3 nucleotide bases which codes of one amino acid.

Question 7

What is meant by the genetic code being a degenerate code?

Answer 7

All amino acids, except methionine have more than one code that codes for them.

Question 8

How does the gene sequence stop the transcription of amino acids?

Answer 8

Certain codes do not code for amino acid but indicate the sequence to stop so the polypeptide stops being made.

Question 9

Where are proteins assembled?

Answer 9

In the cytoplasm at ribosomes

Question 10

What is the first stage of protein sysnthesis?

Answer 10

Transcription

Question 11

What are the steps in transcription?

Answer 11

A strand of DNA is used as a template (the template strand).
This strand unwinds and unzips by dipping into the nucleolus where the hydrogen bonds break.
Activated RNA nucleotides bind to the exposed template strand (catalysed by the enzyme RNA polymerase).

Question 12

What are the steps in transcription?

Answer 12

A strand of DNA is used as a template (the template strand).
This strand unwinds and unzips by dipping into the nucleolus where the hydrogen bonds break.
Activated RNA nucleotides bind to the exposed template strand (catalysed by the enzyme RNA polymerase).
This mRNA strand is therefore a copy of the coding strand (the strand that used to be attached to the template strand).
The mRNA passes out of the nucleus through a pore in the nuclear envelope.

Question 13

Define Translation

Answer 13

The assembly of polypeptides (proteins) at ribosomes.

Question 14

Define Translation

Answer 14

The assembly of polypeptides (proteins) at ribosomes.

Question 15

What is the primary structure of a protein?

Answer 15

It is the order of the amino acids in the length of the chain. This is determined by the order of bases on the mRNA.

Question 16

What is the tertiary structure of a protein?

Answer 16

It is the 3D structure of the protein, determined by the primary structure. This is what allowed a protein to function. It is help together by hydrogen bonds, ionic bonds and hydrophobic interations between the R groups.

Question 17

What is the tertiary structure of a protein?

Answer 17

It is the 3D structure of the protein, determined by the primary structure. This is what allowed a protein to function. It is help together by hydrogen bonds, ionic bonds and hydrophobic interations between the R groups.

Question 18

Describe the structure of tRNA

Answer 18

Lengths of RNA (made in the nucleus) folded into a hairpin shape. It has 3 exposed bases which can bind to an amino acid, and an anticodon (with the same 3 base pair sequence) which can attach to a complementary codon temporarily.

Question 19

Describe the assembly of a polypeptide

Answer 19

Molecule of mRNA binds to a ribosome.
2 codons are attached to the small subunit and exposed to the large subunit of the ribosome.
tRNA molecule with methionine attaches to the first codon (AUG).
Second tRNA molecule binds to second exposed codon.
Peptide bond forms between the adjacent amino acids catalysed by an enzyme in the small subunit.
Ribosome moves along the mRNA reading the next codon where the complimentary tRNA molecules attaches.
The first tRNA molcule is able to detach from the amino acid and pick up another amino acid.
The polypeptide keeps growing until a stop codon is read.

Question 20

Describe the assembly of a polypeptide

Answer 20

Molecule of mRNA binds to a ribosome.
2 codons are attached to the small subunit and exposed to the large subunit of the ribosome.
tRNA molecule with methionine attaches to the first codon (AUG).
Second tRNA molecule binds to second exposed codon.
Peptide bond forms between the adjacent amino acids catalysed by an enzyme in the small subunit.
Ribosome moves along the mRNA reading the next codon where the complimentary tRNA molecules attaches.
The first tRNA molcule is able to detach from the amino acid and pick up another amino acid.
The polypeptide keeps growing until a stop codon is read.

Question 21

Define Mutation

Answer 21

A change in the amount of, or arrangement of, the genetic material in a cell.

Question 22

Define Chromosome Mutations

Answer 22

Mutations which involve changes to parts of or whole chromosomes.

Question 23

Define DNA Mutations

Answer 23

Changes to genes due to changes in nucleotide base sequences.

Question 24

What name is gives to substances which can cause mutations? Examples?

Answer 24

Mutagens. These include tar (from tobacco smoke), UV light, X-rays and gamma rays.

Question 25

What are point mutations?

Answer 25

A mutation where one base pair is replaced by another. Also called substitutions.

Question 26

What are insertion/deletion mutations?

Answer 26

Where one or more base pairs are inserted or deleted from a length of DNA. Also called frameshift.

Question 27

What are insertion/deletion mutations?

Answer 27

Where one or more base pairs are inserted or deleted from a length of DNA. Also called frameshift.

Question 28

Define Allele

Answer 28

An alternative version of a gene. It is still at the same locus on the chromosome and codes for the same polypeptide but the alteration to the DNA base sequence may alter the protein’s structure.

Question 29

What is a silent mutation?

Answer 29

A mutation where the chance in base pair sequence has no change to the overall amino acid sequence, and so does not affect the protein.