Unit 1- DNA And Protein Synthesis

Question 1

Is DNA and RNA a weak acid?

Answer 1

Yes

Question 2

What elements are in nucleotides?

Answer 2

CHNOP

Question 3

What components make up DNA?

Answer 3

• pentose sugar
• phosphate group
• nitrogenous base

Question 4

What is a pyrimidine?

Answer 4

Single ring carbon/nitrogen structure

Thymine and cytosine and uracil

Question 5

What is a purine?

Answer 5

A double ring carbon/nitrogen structure

Adenine and guanine

Question 6

How is the sugar phosphate backbone of DNA made?

Answer 6

Nucleotide polymerisation

• covalent phosphodiester bonds form between phosphate and deoxyribose
• condensation reaction

Question 7

Shape of DNA

Answer 7

• 2 polynucleotide strands run anti parallel forming a double helix
• hydrogen bonds form between the complementary base pairs

Question 8

What is a gene?

Answer 8

A section of DNA that codes for a specific protein
Or
A sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain

Question 9

What is gene expression?

Answer 9

The process by which the instructions in our DNA are converted into functional proteins (expressed)

Question 10

What are the 2 stages of gene expression in order?

Answer 10

Transcription

Translation

Question 11

What kind of cells have non-coding DNA?

Answer 11

Eukaryotes

Question 12

What are the non-coding sections of DNA known as?

Answer 12

• introns (interruption sequences), they are found inbetween exons in a gene
• satellite DNA, which are regions of non-coding DNA found between genes

Question 13

What is the purpose of non-coding DNA?

Answer 13

• structural (to help coil the DNA)
• some code for RNA but don’t code for a protein (not expressed)
• control functions (to regulate which genes are expressed)
• involved in DNA replication
• contains unused copies of genes

Question 14

What is the purpose of DNA polymerase in DNA replication?

Answer 14

Catalyses the formation of phosphodiester bonds between adjacent nucleotides

Question 15

What bonds are involved in DNA replication?

Answer 15

Covalent phosphodiester bonds

Hydrogen bonds

Question 16

Describe the process of DNA replication

Answer 16

• DNA helical unwinds and separates the 2 strands of DNA, breaking the hydrogen bonds between base pairs
• the nucleotides present in the nucleoplasm attach themselves to the bases on the old strands by complementary base pairing
• DNA polymerase joins the new nucleotides together by strong covalent P bonds forming sugar back bone
• the 2 strands wind up into a double helix
• the DNA molecules are identical to each other and the old DNA, each new one containing an old and new strand

Question 17

Where do the nucleotides that bind together to from the new polynucleotide strand come from?

Answer 17

Nucleoplasm

Question 18

What are replication forks?

Answer 18

A replication fork is simply the site of DNA replication, and as DNA is so large it will have many forks at the same time

Question 19

What are nicks in DNA strands?

Answer 19

Where a phosphodiester bond hasn’t formed between 2 adjacent nucleotides due to 2 forks meeting (2 DNA polymerase enzymes colliding and not finishing the job)

Question 20

How are nicks in DNA strands joined?

Answer 20

DNA ligase

Question 21

What is the purpose of DNA ligase in DNA replication?

Answer 21

• repairs nicks in DNA

- finds mismatched base pairs and replaces them with the correct base

Question 22

Why is the known method of dna replication known as semi conservative replication?

Answer 22

Each new DNA molecule contains one new and one old strand

Question 23

Differences between RNA and DNA? 4

Answer 23

RNA

• contains ribose sugar, instead of deoxyribose
• has base uracil instead of thymine
• single stranded
• shorter

Question 24

What is mRNA?

Answer 24

• messenger RNA
• Carries the code for a particular protein into the cytoplasm
• just long enough to contain 1 gene (1000 nucleotides)
• degrades straight after use

Question 25

Structure of tRNA:

Answer 25

Transfer RNA - looped clover shape - ends in the bases ACC, which bind to the amino acid - contains a triplet nucleotide sequence (anticodon) which is complementary to a codon on the mRNA

Question 26

What is rRNA?

Answer 26

Binds to proteins to form ribosomes, the site of translation | - 2 subunits and found in cytoplasm

Question 27

What does degenerate mean?

Answer 27

There is often more than 1 codon for an amino acid

Question 28

AUG is the codon for methionine, what is the significance of this amino acid?

Answer 28

This tends to be the start codon, so all proteins start with this amino acid

Question 29

What amino acids to the stop codons code for?

Answer 29

None, when the rRNA reads the stop codon the whole process stops, no more amino acids are bonded

Question 30

What does the term non-overlapping mean?

Answer 30

A sequence of six bases can only be read as 2 codons, eg AUGUAG only contains the codons AUG and UAG, not AUG,UGA...

Question 31

Where are proteins synthesised? And why?

Answer 31

In the cytoplasm, as this is where the ribosomes are

Question 32

What is another word for post transcriptional modification of mRNA?

Answer 32

Splicing

Question 33

What is splicing?

Answer 33

When non coding introns are removed from pre-mRNA

Question 34

Where does splicing occur?

Answer 34

In the nucleus