Protein Synthesis

Question 1

What is a gene?

Answer 1

A sequence of nucleotides bases found in DNA that codes for one or more polypeptides

Question 2

What is a DNA dictionary

Answer 2

A grid showing the base triplets on the DNA reference Strand that code for each amino acid

Question 3

What do genes code for

Answer 3

Polypeptides which have structural roles such as keratin and collagen,and metabolic rolls such as channel proteins, enzymes, antibodies and haemoglobin.

Question 4

How is the sequence of amino acids in a polypeptide chain determined simply?

Answer 4

By the sequence of nucleotides bases on the Gene

Question 5

How many different types of nucleotides bases are found in DNA and what are the ?

Answer 5

Four different types A, T, C, G

Question 6

What kind of code do we call the genetic code and why is it called this?

Answer 6

The genetic code is a triplet code which means three bases code for one amino acid. This results in 64 different triplet codes

Question 7

Why is the genetic code described as degenerate ?

Answer 7

Because most amino acids have more than one code (codon - meaning a collection of 3 bases….?) As there are only 20 amino acids used in protein synthesis. Some codons correspond to stop codes which indicate the end of the polypeptide chain

Question 8

What does the term non overlapping mean in regard to the genetic code?

Answer 8

It means each triplet is read separately and no triplet is used for the same Gene

Question 9

What does the term universal mean in regard to the code?

Answer 9

It means the triplet code is widespread and universal for all organisms and viruses.

Question 10

What are prokaryotic genes like in terms of continuous and non continuous genes?

Answer 10

genes are usually continuous, lacking non-coding sequences (introns)

Question 11

What are eukaryotic genes like in terms of continuous and non continuous genes?

Answer 11

The genes are usually discontinuous genes with coding exons and non-coding introns

Question 12

What does Gene expression mean

Answer 12

Transcription and translation

Question 13

What does the enzyme RNA polymerase do

Answer 13

It catalyses the formation of the mRNA molecule by: forms new hydrogen bonds , forms the RNA’s sugar phosphate backbone and catalyses the free nucleotides joining onto the template.

Question 14

What does the term non-template Strand mean?

Answer 14

A coding Strand

Question 15

What does the term ribonucleotide mean?

Answer 15

It’s another name for the free nucleotides

Question 16

5’ and 3’?

Answer 16

This refers to the carbons in the shape. Transcription occurs 3’ to 5’ off the DNA strand, forming an RNA molecule that is 5’ to 3’

Question 17

Comparison of tRNA and mRNA

Answer 17

Made of the same sugar and mRNA bases but tRNA structurally forms a different shape.

Question 18

Comparison of DNA vs tRNA and mRNA

Answer 18

DNA has T, not U.

DNA has a different sugar- deoxyribose, not ribose

Question 19

What does DNA helicase do ?

Answer 19

It works the same way as the direction of transcription, breaking hydrogen bonds.

Question 20

What do pre mRNA and mature mRNA mean?

Answer 20

pre mRNA is the result of transcription and is still in the nucleus. Mature mRNA is the result of pre mRNA having undergone post transcriptional modification - just exons left. Mature mRNA is what leaves the nucleus. Both are single stranded.

Question 21

What happens in post transcriptional modification?

Answer 21

Introns (non-coding triplets/codons) are spliced out by an enzyme. This is initiated by primers. Does not occur in prokaryotes. DNA ligase makes the remaining triplets join / ‘ligated’ together.

Question 22

What are introns

Answer 22

The non coding areas of a gene

Question 23

How does RNA polymerase know when to stop transcribing

Answer 23

There is a stop-transcribing sequence, at which point RNA polymerase leaves the DNA

Question 24

What do ribosomes consist of

Answer 24

rRNA and protein

Question 25

What happens to make the amino acid attach to a TRNA molecule

Answer 25

It is activated by ATP and then attaches to the specific trna molecule

Question 26

What is usually the start codon on Mr n a?

Answer 26

AUG

Question 27

Where can polypeptides be further modified and and potentially combined with other polypeptides to create complete protein?

Answer 27

Golgi body

Question 28

Define exon

Answer 28

A section of pre-mrna, transcribed from DNA, which will code of the protein

Question 29

Define intron

Answer 29

A section of pre-mrna, that is removed in post-transcriptional modification

Question 30

Define the one Gene one polypeptide hypothesis

Answer 30

This hypothesis suggests that there is a specific, separate Gene that codes to each polypeptide and that they exist on a one-to-one ratio basis.

Question 31

What are the three types of mutation?

Answer 31

Deletion, insertion, substitution

Question 32

Deletion

Answer 32

A base is lost or deleted

Question 33

Insertion

Answer 33

An extra base is added or inserted

Question 34

What is a frameshift mutation

Answer 34

Where the reading frame changes, changing the amino acid sequence from this point forward. It can be caused by deletion or insertion

Question 35

Substitution

Answer 35

Where one base is substituted for another. If a substitution changes the amino acid, it’s called a missense mutation . if the substitution does not change the amino acid, it’s called a silent mutation. If a substitution changes the amino acid to a stop it’s called a nonsense mutation

Question 36

Where are DNA fragments broken in regards to 5’ and 3’? (…?)

Answer 36

on the 5’ side…?

Question 37

What are pyrimidines?

Answer 37

cytosine and thymine

Question 38

What are purines?

Answer 38

adenine and guanine