Proteinsynthesis - B8

Question 1

Describe the process of transcription.

Answer 1

1)helicase->break hydrogen bonds between bases
2)one strand acts as a template
3)free RNA nucleotides bind to complementary bases
4)uracil is used instead of thymine
5)RNA polymerase joins RNA nucleotides by a phosphodiester bonds(condensation)
6)pre-mRNA has it’s intron removed by splicing -> mRNA

This is all found in the nucleus - mRNA then leaves the nuclear pore and goes to ribosomes to be translated

Question 2

Why is DNA universal?

Answer 2

3 bases code for the same amino acids in all organisms e.g. AAA will code for phenylalanine in all organisms

Question 3

What does it mean if DNA is degenerate?

Answer 3

More than one triplet codes for the same amino acid

Question 4

What does it mean if DNA is non-overlapping?

Answer 4

Each base is only part of one triplet.

Question 5

What is the start codon for every gene?

Answer 5

AUG

Question 6

What are the stop codons?

Answer 6

UAA, UAG, UGA

Question 7

What is the function of the ribosome?

Answer 7

1)mRNA associates(binds) to ribosomes
2)allow tRNA with anticodons to associate
3)catalyses formation of peptide bond between amino acids
4)moves mRNA along to next codon

Question 8

Describe the process of translation.

Answer 8

1)mRNA associates with the ribosomes
2)ribosome find the start codon(AUG)
3)specific tRNA enters the ribosome carrying the specific amino acid
4)correct tRNA anticodon complementary to codon mRNA ->bind (temporarily) by complementary bases
5)ribosome moves along to next codon
6)process repeats and the ribosome catalyses peptide bonds to from a polypeptide-> condensation reaction

Question 9

What causes mutations?

Answer 9

Nothing causes mutations, but mutagens increase the chance of mutations

Question 10

What are mutagens?

Answer 10

Environmental factors that increase the occurrence of a mutation. E.g. UV light, x-rays, radioactivity, and some chemicals like substances found in cigarette smoke and caffeine.

Question 11

Define mutation.

Answer 11

A change which occurs in the nucleotide base sequence.

Question 12

What is a point mutation?

Answer 12

These occur when a single base pair is changed.

Question 13

What are the different type of point mutation?

Answer 13

3 types: substitution, addition and deletion

Question 14

What is a substitution mutation?

Answer 14

One base pair is swapped for another. This usually leads to a single, different amino acid being inserted during translation.

Question 15

What is an addition mutation?

Answer 15

An extra base pair is inserted into the DNA sequence ->every codon ‘down stream’ is different(frame shift)

Question 16

What is a deletion mutation?

Answer 16

A base pair is lost from the DNA sequence -> has a similar effect as an addition mutation

Question 17

What different effects can mutations have?

Answer 17

Mutations can be beneficial, have no effect, or the can be harmful

Question 18

What is a silent mutation?

Answer 18

When a mutation occurs in an intron or non-coding repeat.

There may be a different codon, but it is the same amino acid.

Mutations happen all the time, but we don’t notice as they’re in non-coding repeats.

Question 19

What is frame shift?

Answer 19

After the additional base, codons read differently ->different amino acids

Question 20

Which mutation(s) have a bigger effect on the polypeptide chain that should be produced?

Answer 20

addition and deletion