Bacterial Genetics

Question 1

All living cells maintain their genetic information in chromosomes made of double stranded DNA.
Genome- all of the genetic material in the cells of an organism.

Answer 1

Bacterial genome

Question 2

1. Code for protein: gene expression/ transcription & translation.
2. Inheritance: DNA replication
3. Self-regulation: turns genes on and off to maintain homeostasis for survival

Answer 2

Jobs of DNA

Question 3

Organic macromolecules called nucleic acids.
Nucleic acids are built from nucleotides
Each nucleotide has a phosphate, sugar and base.
Constant- phosphate & sugar
Variable- base= code

Answer 3

DNA structure

Question 4

5’ end - end with phosphate sticking end
3’ end- where new nucleotide can be added

Answer 4

DNA structure

Question 5

Make 2 identical copies of DNA to pass to new bacterial cells (binary fission)
Semi conservative
Requires : DNA nucleotides, energetic (anabolic) and enzymes

Answer 5

DNA replication

Question 6

enzyme called helicase unwinds DNA & splits it apart at origin of replication.

Answer 6

Replication process: step 1 - initiation

Question 7

Results in replication bubble with a fork at each end.
There is a leading and lagging strand on each side of the bubble.
Leading end- is copied continuously
Lagging end- is copied in chunks (works backwards)

Answer 7

Replication process step 2

Question 8

Enzyme called primase adds an RNA primer to each strand of DNA.
The leading strand only gets primed once.
The lagging strand is primed for each chunk.

Answer 8

Replication process step 3

Question 9

Helicase continues to open DNA
DNA gyrase untangles the DNA as the fork opens
DNA polymerase adds nucleotides to the RNA primers on the 3’ of the primer
*on leading strand this occurs continuously

Answer 9

DNA replication : elongation

Question 10

DNA polymerase 1 removes the primes and replaces them with DNA nucleotides

Answer 10

Elongation on lagging strand

Question 11

Continues in opposite directions until the DNA polymerase runs into each other.
Comes together at termination sequence

Answer 11

DNA replication: termination

Question 12

To express, or produce proteins that a cell needs at a given time.
A section of DNA codes for a necessary protein is copied (transcription) onto mRNA.
The code on the mRNA is translated into a protein at a ribosome with the help of tRNA.

Answer 12

Gene expression

Question 13

RNA is necessary for gene expression:
1. mRNA is a copy for a gene/recipe card
2. rRNA folds up to make ribosomes/reading
3. tRNA carries amino acids to ribosome according to the mRNA code

Answer 13

Ribonucleic acid

Question 14

Occurs in cytoplasm in bacteria.
Job: RNA polymerase makes a copy of expressed gene in the form of RNA.
Genes are switched on or switched off.
•the promoter region is ready to RNA polymerase when a protein coded for by that gene is needed the cell (switched on)

Answer 14

transcription

Question 15

Location: bacterial ribosomes
Reading to make a protein

Answer 15

Initiation of translation

Question 16

1. tRNA binds to exposes codon
2. New amino acid attached to polypeptide chain
3. Ribsome shifts one codons over on the mRNA

Answer 16

Elongation of translation

Question 17

Small loops of DNA with a few genes.
May enter or leave a bacterial cell without changing the species- horizontal gene transfer.
Contain small # of genes - these can include genes for toxins, antibiotic resistance

Answer 17

Plasmids

Question 18

What are two ways bacteria generate genetic diversity?

Answer 18

1. Random gene mutation
2. Horizontal gene transfer

Question 19

Random
Any changes in base sequences during DNA replication can occur
Bacteria reproduce quickly & generate these more often
can be- lethal, neutral and benefit bacteria

Answer 19

Mutations

Question 20

Mistakes in DNA replication
Physical agents- X-rays and UV radiation
Chemical agents- mutator strains, superoxide radicals & reactive O2 molecules

Answer 20

Causes of mutations

Question 21

1. Point mutation
2. Insertion/deletion
3. Inversion

Answer 21

Types of mutations

Question 22

Neutral
When a single nucleotide is changed in a DNA sequence

Answer 22

Point mutation

Question 23

Involves the + or - of one more more molecules

Answer 23

Insertion/ deletion

Question 24

Occurs when a fragment of DNA is flipped in orientation in relation to the DNA on other side

Answer 24

Inversion

Question 25

Also called lateral transfer
A donor cell contributes a part of genome to recipient cell.
Donor & recipient cells can be different species or even different genus

Answer 25

Horizontal gene transfer

Question 26

1. Conjugation
2. Transformation
3. Transduction

Answer 26

Types of horizontal gene transfer

Question 27

Recipient cell takes DNA from environment
Transforming agent is DNA
Competent cells

Answer 27

Transformation

Question 28

Genetic material is carried between bacteria by a bacteriophage
•lysogenic life cycle
Ex: responsible for the transfer of toxins to some cells

Answer 28

Transduction

Question 29

Cells stay alive
Requires the physical contact between 2 cells
Mediated by conjugation pili

Answer 29

Conjugation

Question 30

Switching genes on or off
75% of genes are expressed at all times.
•continuously transcribed and translated
Operons

Answer 30

Regulation of gene expression

Question 31

section of DNA, only in prokaryotes
Consists of promoter and series of genes that are part of a related cell function.
Some controlled by an operator - where a repressor protein binds to stop transcription.
Promoter- where the RNA polymerase binds.

Answer 31

Operons

Question 32

Cells that take in DNA from their environment

Answer 32

Competent cell