Module 2

Question 1

What are Genes

Answer 1

Linear Sequence of Nucleotide of DNA

Determines Phenotype

Question 2

What does a nucleotide consists of:

Answer 2

Nitrogen containing molecule
Base
Sugar molecule
Deoxyribose
Phosphate

Question 3

Structure of DNA

Answer 3

2 nucleotide strands with bases connected anti-parallel by hydrogen bonds

Question 4

How how a Chromosomes formed and how do they differ between bacteria, eukaryotes and viruses

Answer 4

Tightly coiled genes

Bacteria - single circular chromosome
Eukaryotes - multiple chromosomes
Viruses - Single or double stranded nucleic acids rather than distinct chromosomes

Question 5

What are plasmids

Answer 5

Smaller piece of DNA that are found in some bacteria.

They contain additional information and replicate independently

Encodes for antibiotic resistance and/or enzymes

Question 6

What are proteins

Answer 6

Long chain of amino acids
Used in metabolism, growth and repair

The amino acids are held together by peptide bonds

Question 7

How is Protein Synthesised

Answer 7

Genetic information contained within the DNA need to be copied into mRNA (TRANSCRIPTION).
(this occurs with the enzyme RNA polymerase)

Question 8

rRNA

Answer 8

combines with ribosomes and acts as a site for protein synthesis

Combines with ribosomal proteins to form ribosomes

Question 9

mRNA

Answer 9

Synthesised on chromosomal DNA and carries information to site of synthesis (from gene)

Binds to ribosomes and creates a template for the correct sequence of amino acids to be joined together to form the right protein

Question 10

tRNA

Answer 10

Transfers amino acids to mRNA to the ribosome (site of synthesis)

Question 11

Mechanism of Protein Synthesis

Answer 11

Transcription occurs
mRNA acts as a template for protein synthesis
RNA polymerase binds at the promotor site
Nucleotides are arranged and ‘read’ in codons (sets of 3)
These codons are matched with an anticodon on the tRNA. (so that correct amino acids can be transported to the mRNA template)

Translation occurs
formation of a protein or polypeptides (from a chain of amino acids)

Question 12

Genotype

Answer 12

genetic information contained within the DNA

Question 13

Phenotype

Answer 13

Observable characteristics

Question 14

Mutations

Answer 14

permanent change in the sequencing of bases in DNA

This can alter the properties (can be good or bad)

Question 15

what are the 3 types of mutations

Answer 15

Point mutation
change of only 1 base (can be silent)

Frame-shift mutation
deletion or insertion of 1 or more bases, changing the codon

Nonsense codon
introduction of a premature ‘stop’ codon
Produces an incomplete polypeptide chain

Question 16

What are the 3 types of Horizontal Gene Transfer

Answer 16

Transformation
process where naked DNA passes from 1 bacterial cell to another changing the properties of the cell

Transduction
Transfer of DNA from 1 bacteria to another by a bacteriophage

When a bacterium is infected by a phage, the phage attaches to specific receptor sites on the outside of cells
IT then injects its DNA into the cell (just DNA)
The phage DNA is then synthesised assembling new phage particles
The phage enzymes breaks the bacterial chromosome
This is the LYTIC CYCLE

Conjugation
Uses 2 bacterial cells, the Donor and recipient to come in close contact with each other.
Forms a sex pilus (via a tubule structure that forms between them )
Transfers genetic material from 1 to the other in the form of PLASMIDS
Conjugation can lead to multiple changes at one unlike mutations