DNA replication And Protien Synthesis

Question 1

What is the structure of a nucleotide?

Answer 1

Phosphate group

Pentose sugar

Nitrogenous base

Question 2

Give examples of co-enzymes

Answer 2

NAD
FAD
NADP

Question 3

What is the structure of DNA?

Answer 3

2x polynucleotide chains
Arranged in a double helix

One strand antiparallel to the other 5’ ——3’ and 3’——5’

Sugar phosphate back bone (formed via condensation reaction between sugar and phosphate groups) held together by an Ester bond

Nitrogenous bases
Adenine
Thymine
Cytosine
Guanine 
(Hydrogen bonds between the bases A=T and C=G)

Complementary base pairing

Question 4

What is the nucleosome?

Answer 4

Complex between histone proteins and DNA helix

Question 5

What are start and stop codons?

Answer 5

Start codons tell RNA polymerase where to begin transcription of DNA

stop codons tell RNA polymerase where to stop transcription of DNA

Question 6

What are exons

Answer 6

Sequences on genes that code for an amino acid (coding sections of DNA)

Question 7

What are introns?

Answer 7

Non coding sections of DNA sequences found within genes

Question 8

How is DNA converted into a protein?

Answer 8

DNA

Transcription to RNA

Translation to protein

Question 9

What is the genome?

Answer 9

All of the DNA within a cell

Question 10

What are chromosomes?

Answer 10

Molecules of DNA

Question 11

What are the stages in the cell cycle?

Answer 11

Interphase (90% of cell cycle)

Mitosis/ meiosis

Cytokinesis

Question 12

What are the stages of interphase?

Answer 12

G1- cell grows and organelles replicate

S- DNA replication occurs

G2- mitochondria and chloroplast DNA replication

Question 13

Why is DNA a stable molecule?

Answer 13

Sugar Phosphate backbone protects the chemical organic bases inside the double helix

Hydrogen bonds between the base pairs form bridges making the molecule stable

Question 14

What is the function of DNA?

Answer 14

Contains hereditary material

Responsible for passing genetic information from cell to cell

Question 15

What is semi conservative replication?

Answer 15

DNA makes exact copies of itself by using each strand of the DNA molecule as a template for the next.
New copies of DNA therefor posses one original and one new strand of DNA

Question 16

What is the process of DNA replication

Answer 16

1. DNA unwinds via DNA gyrase
2. DNA is unzipped (hydrogen bonds between the base pairs are broken) via DNA helicase
3. Primers attach to the DNA strand allowing DNA polymerase to start synthesising new strands.
4. Free activated nucleotides align and hydrogen bond to the template strands
5. DNA polymerase catalysed the addition of the bases in the 5’ to 3’ direction
6. DNA polymerase also catalyses the addition of bases on the antiparallel strand
7. Fragments joined together by DNA ligase
8. DNA is replicated semi conservatively

Question 17

What does the semi conservative replication of DNA ensure?

Answer 17

The genetic continuity between generations

Question 18

What did James Watson and Francis crick propose the DNA model to be?

Answer 18

A double helix

Question 19

Why is DNA universal?

Answer 19

All organisms have the same amino acids which get formed via DNA codons

Question 20

Why is DNA degenerate?

Answer 20

More than 1 triplet code can code for an amino acid

Question 21

Why is DNA non overlapping?

Answer 21

The code is always read in a triplet at a defined start and end point.

Hence why an indel mutation may cause a frameshift

Question 22

What is the process of transcription?

Answer 22

1. DNA gene unwinds and unzips via DNA ligase
2. RNA polymerase catalyses temporary bonding between RNA nucleotides and the DNA bases
3. The complementary base pairs of DNA and RNA hydrogen bond forming a strand of pre-mRNA

Question 23

Why is transcription needed?

Answer 23

DNA is long and fragile

DNA is also stored in the nucleus and translation for proteins occurs in the cytoplasm but DNA is too large to leave through nuclear pores.

Easier to control the rate of translation

Question 24

What is the structure of RNA?

Answer 24

Phosphate group

Pentose sugar (ribose)

Nitrogenous base:
Adenine 
Uracil
Cytosine
Guanine

Question 25

What happens to the pre-mRNA to concert it to mRNA ready for translation?

Answer 25

Pre-mRNA gets spliced in the nucleus of the cell.

Introns are removed and exons are joined together forming mRNA

This leaves the nucleus via the nuclear pore

Question 26

What is the process of translation?

Answer 26

1. After mRNA has left the nucleus via the nuclear pore, a ribosome binds to be the mRNA start codon in he cytoplasm of a cell
2. A tRNA molecule with the complementary anticodon moves to the ribosome and binds to the mRNA molecule. The tRNA molecule carries a specific amino acid.
3. This process repeats as the ribosome moves along the mRNA molecule but only 2 tRNA molecules can bind at any one time.
4. The 2 amino acids in the adjacent tRNA molecules are joined via a peptide bond using an enzyme and ATP hydrolysis to provide energy.
5. The ribosome moves to the third codon and another tRNA molecule binds as the first one leaves (released from its amino acid and therefore is free to collect another)
6. The process repeats until the ribosome reaches a stop codon
7. The newly formed polypeptide (primary structure of a protein) requires chaperone proteins to fold the protein into its shape.

Question 27

What is the structure of a tRNA molecule?

Answer 27

Clover shaped

Has a complementary anitcodon to mRNA codons

Carries a specific amino acid

Question 28

What is the function of a tRNA molecule?

Answer 28

Carry/transfer amino acids to ribosomes for synthesis.