Bacterial Genetics

Question 1

Why is uracil used in RNA rather than thymine

Answer 1

Thymine takes more energy to be produced and since RNA is short lived, this saves the body energy and time

Question 2

Define a gene

Answer 2

A sequence of DNA that specifies a particular protein

Question 3

Define a codon

Answer 3

Sequence of 3 triplet code
One codon= one amino acid

Question 4

Define non-sense codons

Answer 4

Stop codons ( ie TAA terminates synthesis of particular proteins

Question 5

What is the wobble hypothesis

Answer 5

. The first anti codon on the tRNA is not spatially bound meaning the the first nucleotide on the tRNA can bind to 2 others rather than one

• this reduces the need for energy as less

Question 6

How does the wobble hypothesis save energy

Answer 6

As the tRNA molecules can be used for multiple codons or uses

Question 7

What can uracil on a tRNA molecule recognise

Answer 7

A or G

Question 8

What can guanine on a tRNA molecule recognise

Answer 8

U or C

Question 9

What are mutations

Answer 9

A change in the nucleotide sequence

Question 10

What’s an example of a beneficial mutation

Answer 10

Antibiotic resistance

Question 11

What is a beneficial mutation also known as

Answer 11

Selectable mutation (usually stable as it’s been passed down from mother cell to daughter cell

Question 12

What is the wild type mutation

Answer 12

It’s isolated from the environment/ nature

Question 13

What is a mutant type

Answer 13

Derived from the wild type, but caries a mutation

Question 14

What are the 2 mechanisms of mutations

Answer 14

Spontaneous and induced

Question 15

What is spontaneous mutation

Answer 15

Occasional random errors,
- point and frame shift

Question 16

what is induced mutation

Answer 16

Caused by environmental factors
- radiation (x-rays, gamma rays)
-exposure to mutagens

Question 17

What are some impacts of mutations

Answer 17

Can alter gene products
- can prevent gene function

Question 18

What is point mutation

Answer 18

A single base pair substitution in the DNA
( can be silent, missense or nonsense

Question 19

If a point mutation occurs and the result is the same amino acid what is the effect on the phenotype

Answer 19

There is no change

Question 20

If a point mutation occurs and the result is a different amino acid what is the effect on the phenotype

Answer 20

Changes the phenotype

Question 21

If a point mutation occurs and the results in a stop codon what is the effect on the phenotype

Answer 21

Changes due to the pre mature stop codon

Question 22

What is a frame shift mutation

Answer 22

Caused by a shift in the reading frame

Question 23

Explain the frame shift mutation - insertion

Answer 23

When a base is inserted somewhere in the sequence

Question 24

Explain the frame shift mutation - deletion

Answer 24

When a nucleotide base is deleted from the sequence

Question 25

What is the significance of mutations in bacteria

Answer 25

It’s what gives them their antibiotic resistance

Question 26

What is horizontal gene transfer

Answer 26

Movement of DNA between cells that are not directly related - DNA is incorporated into the recipient cell chromosome by recombination - or remain independent (plasmid)

Question 27

What is a plasmid

Answer 27

The circular piece of DNA s that Carrie’s extra genes

Question 28

Define transformation

Answer 28

Free DNA released from one cell and is taken up by another

Question 29

Define transduction

Answer 29

DNA transfer is mediated by a bacteriophage

Question 30

Define conjugation

Answer 30

DNA transfer request cell to cell contact

Question 31

If a cell takes up free DNA what is it then known as being

Answer 31

Competent

Question 32

What are the main 3 steps in transformation

Answer 32

1. Competent bacteria reversible bind DNA to their surface using a DNA binding protein 2. The protein assists in the uptake of ssDNA by helping it through the gram negative membrane 3. When the ssDNA enters the cell, competence specific proteins bind to the donor DNA to protect against degrading nucleases 4. DNA is integrated into the recipient chromosome by recombination

Question 33

Define generalised transduction

Answer 33

Any gene from the donor chromosome is transferred to a recipient

Question 35

Define specialised transduction

Answer 35

Selective transfer of a small, specific section of the donor chromosome to a recipient

Question 36

What are the 2 different cycles within generalised transduction

Answer 36

The lytic cycle and the lysogeny cycle

Question 37

What are transposons

Answer 37

Small pieces of DNA that can move/ jump around the chromosome or transfer from bacterium

Question 38

Do transposons always have a palindromic sequence its ends

Answer 38

Yes