SAC 1 REVISION

Question 1

Subunits of DNA

Answer 1

Nucleotides

Question 2

Structure of DNA

Answer 2

Anti-Parallel Double Helix

Question 3

Role of tRNA

Answer 3

Transfer RNA molecules supply specific amino acids to the growing polypeptide chain at the ribosome. Complementary base pairing between tRNA anticodons and mRNA codons ensure the synthesis of the correct primary structure

Question 4

What is the primary structure of proteins

Answer 4

Sequence of amino acids in a polypeptide chain

Question 5

Units of RNA

Answer 5

Phosphate group, Ribose sugar, Nitrogenous base

Question 6

Explain RNA processing

Answer 6

Introns are spliced out and removed and the exons join back together. A methyl cap is added to the 5’ end and a poly(A) tail is added to the 3’ end

Question 7

Describe translation

Answer 7

Translation involves the synthesis of a polypeptide chain at a ribosome as it reads a specific sequence of mRNA codons. At each codon, a tRNA molecule with a complementary anticodon enters the ribosome to add a specific amino acid to the growing polypeptide chain

Question 8

What do the 3’ and 5’ ends represent

Answer 8

The 5’ and 3’ mean ‘five prime’ and ‘three prime’, which indicates the carbon numbers in the ribose component of each nucleotide. The 5’ carbon is attached to the phosphate group of the nucleotide and the 3’ carbon sits at the ‘sugar’ end of the nucleotide

Question 9

Regulatory genes

Answer 9

A regulatory gene codes for a transcription factor that binds to a repressor protein, which changes its 3d conformation and detaches from the operator sequence of the gene

Question 10

Types of secondary structure

Answer 10

Alpha Helices, Beta pleated sheets and Random coils

Question 11

What is the tertiary structure

Answer 11

The tertiary structure refers to the way a polypeptide chain folds and coils to form a complex 3D functional conformation

Question 12

What happens in prokaryotes in high Tryptophan levels

Answer 12

Tryptophan molecule binds to a repressor protein and changes its 3D conformation. Activated repressor protein binds to the operator region of gene preventing the RNA polymerase from binding to the promotor sequence, preventing transcription

Question 13

Function of mRNA

Answer 13

Messenger RNA carries the genetic instructions of DNA (from a gene) to the ribosomes in order that the ribosomes synthesise the correct polypeptide chain

Question 14

What happens in terms of Attenuation in high Tryptophan levels

Answer 14

The leader sequence is transcribed with high tryptophan levels. When ribosomes read the leader mRNA transcript, they do not pause at trp codons. A terminator hairpin loop forms on the mRNA and the ribosome detaches from the short mRNA transcript, which causes RNA polymerase to detach from the DNA, preventing transcription from being completed

Question 15

Proteome

Answer 15

All the proteins that can be translated by an organism at a specific time

Question 16

Function of RNA polymerase

Answer 16

RNA polymerase attaches to the promotor sequence and breaks hydrogen bonds to unwind DNA. It then re=ads the template strand in the 3’ to 5’ direction producing a copy of pre-mRNA

Question 17

Name the molecule of inheritance

Answer 17

Deoxyribonucleic acid

Question 18

DNA base sequences code for

Answer 18

Specific polypeptide chain

Question 19

Nucleotides contain

Answer 19

Phosphate group, Pentose sugar, Nitrogenous base

Question 20

Name the purines

Answer 20

Adenine and Guanine

Question 21

Name the pyrimidines

Answer 21

Cytosine, thymine, uracil

Question 22

Are purines single or double ringed

Answer 22

Double

Question 23

DNA nucleotides contain

Answer 23

Phosphate group, Deoxyribose sugar, Nitrogenous base

Question 24

RNA nucleotides contain

Answer 24

Phosphate group, Ribose sugar, Nitrogenous base

Question 25

What DNA strand contains the genes

Answer 25

Template strand

Question 26

Genotype

Answer 26

The allele combination of an individual

Question 27

What are the temperatures and words used in steps of PCR?

Answer 27

94 (denature) , 55 (anneal) , 72 (extend)

Question 28

Outline the 3 steps of PCR (polymerase chain reaction)

Answer 28

1. DNA is heated to 94 degrees where the DNA is unzipped and DENATURED due to the broken hydrogen bonds.
2. The 2 single stranded DNA strands are cooled to 55 degrees, where primers ANNEAL to the 3’ end of the DNA strands.
3. It is reheated to 72 degrees, where Taq polymerase used the primers as a guide to where it should begin extending the singular DNA strands. It uses complementary base pairing to EXTEND the strands and synthesis 2 double strands.

This process is continued for as many times as needed.

Question 29

Why do we use PCR?

Answer 29

PCR helps create millions of copies of DNA in a short amount of time. This is used mainly for Gel electrophoresis, since you need at least 20 pieces of evidence to convict someone of a crime.

Question 30

What can CRISPR do to a gene?

Answer 30

Changed genome. It can add new nucleotides to change a gene, it can also remove nucleotides which can make it a non functioning gene. It can also edit nucleotides by replacing them to edit a faulty gene.

Question 31

What is a name of a plasmid which is altered?

Answer 31

A transformed plasmid

Question 32

Why do scientists add virus resistant genes into the plasmid?

Answer 32

It can see which bacteria has taken up the plasmid at the bacterias who are exposed and die haven’t taken up the plasmid whereas those resistant are bacteria which have taken up the transformed plasmid.

Question 33

What is DNA ligases role in plasmid altering?

Answer 33

DNA ligase create phosphodiester bonds between the human gene and the original plasmid gene to make sure the human gene stays in the plasmid.

Question 34

Why do scientists add a glow gene into transformed plasmids?

Answer 34

Scientist add a glow gene as it helps detect if the plasmid is present in the bacteria. Once the scientists put the bacteria in the petri dish, the bacteria will glow if the plasmid is present.

Question 35

When does the polypeptide chain go through the rough ER and the Golgi?

Answer 35

It goes through them when the polypeptide chain will be transported out of the cell and into the body. When the cell needs the protein for itself, the cell will use free ribosomes to synthesis the protein and be kept in the cell.

Question 36

What gives the rough Er its rough texture?

Answer 36

The ribosomes attached around the outside.

Question 37

Why is it smaller fragments of DNA can travel through the gel quicker?

Answer 37

The smaller fragments can travel through the pores of the gel more easily, compared to the larger fragments which lag behind.

Question 38

what is the role of Cas9 in gene editing?

Answer 38

It unwinds DNA and cuts at both strands at a specific target sequence

Question 39

what is the role of sgRNA in gene editing?

Answer 39

It guides the cas9 to the target sequence on the DNA as it is complementary to the target sequence

Question 40

What are the two ways CRISPR can edit genes?

Answer 40

1. By gene knocking in (gene editing) where a new DNA sequence is inserted into the DNA. eg. replacing a faulty gene sequence with correct sequence to restore normal gene functioning
2. By gene knocking out (gene silencing) where errors from the repair mechanisms used to mend broken DNA cause the insertion or deletion of bases. This changes how the sequence is read. eg. used to silence a faulty gene

Question 41

what are the benefits of CRISPR?

Answer 41

it enables scientists to precisely and easily edit genes at a low cost. The process is also very quick in comparison to other gene editing tools.