Chapter 8

Question 1

Mutation

Answer 1

a change in the nucleotide sequence of a cell’s DNA that is the passed on to daughter cells

Question 2

Why is mutation a problem

Answer 2

If the DNA sequence i s changed, then the mRNA sequence is altered, which can result in incorrect protein synthesis

Question 3

Types of mutations

Answer 3

Substitution
Deletion
Insertion
Thymine dimers

Question 4

Substitution

mutation

Answer 4

One or more nucleotides are randomly replaced with different nucleotides.

Question 5

Example of substitution

Answer 5

superoxide ion and hydrogen peroxide can change guanine so it will pair with adenine

Question 6

Deletion

mutation

Answer 6

one or more nucleotides are randomly removed and not replaced (or nucleotide becomes unreadable)
AKA frameshift mutation

Question 7

Example of Deletion

Answer 7

ethidium bromide dye adds small molecules to a base so it is skipped during transcription or replication

Question 8

Insertion

mutation

Answer 8

One or more nucleotides are randomly added.

AKA frameshift mutation

Question 9

Types of frameshift mutations

Answer 9

Insertion

Deletion

Question 10

Thyamine dimers

mutation

Answer 10

Bonding of two adjacent thymine bases

-Double helix is distorted enough that enzymes do not work properly for transcription and replication

Question 11

What causes thyamine dimer mutation

Answer 11

Caused by exposure to UV light

Question 12

Outcomes of Mutations

Answer 12

• Death- most mutations are detrimental
• Benefit - sometimes mutations are beneficial
• No change - mutation doesn’t change the protein or affects a part of the chromosome that isn’t important

Question 13

Natural Selection

Answer 13

if one bacteria cell has an advantage (example antibiotic resistance) over another bacteria in the same population; it will be able to survive longer and reproduce more often.
-Can become most common type of bacteria in a population

Question 14

What causes mutations?

Answer 14

Spontaneous Mutation

Induced Mutation

Question 15

Spontaneous mutation

Answer 15

random changes during normal cell processes

- Rare (1/10,000 to 1/ 1,000,000 replications for a single gene)

Question 16

Induced mutation

Answer 16

changes from influence outside of a cell.

-Mutagens - physical or chemical agent that can change genetic material; increases risk of mutation by 10 to 1000x

Question 17

Examples of induced mutations

Answer 17

Ethidium Bromide
Superoxide ion
Hydrogen peroxide

Question 18

Repair of substitution, insertion and deletion mutations

Answer 18

1. Proofredding by DNA polymerase as DNA synthesis occurs

2. Mismatch repair - other proteins and enzymes detect and removed mismatched nucleotide

Question 19

Repair of Thyamine dimers

Answer 19

Photoreactivation

Excision repair

Question 20

Photoreactivation

thyamine dimer repair

Answer 20

Enzyme photolyse uses energy to break bonds in thyamine dimers

Question 21

Excision repair

thyamine dimer repair

Answer 21

1. Protein trimer (two Uvr A and one Uvr B) scan for damage
2. Uvr C makes cuts around the damaged DNA
3. Uvr D (helicase) releases the cut DNA piece
4. DNA polymerase and DNA ligase fill in the missing part

Question 22

SOS repair

Answer 22

• When DNA is too damaged to be repaired by other mechanisms

- approx 16 proteins including 1 type of DNA polymerase that does not proofread itself

Question 23

disease resulting from faulty repair systems

Answer 23

Xeroderma pigmentosa

Question 24

Gene Transfer

Answer 24

Genes are transfered between bacteria in three ways

1. Transformation
2. Transduction
3. Conjugation

Question 25

Transformation

Answer 25

- uptake of "naked DNA" | - Only competent cells will take in new DNA

Question 26

What is "naked" DNA

Answer 26

a fragment of DNA not in a cell or virus

Question 27

Types of Competency | Transformation

Answer 27

Natural competency - may be environmentally influenced | Artificial competency - from electric current or chemicals

Question 28

Example of Transformation

Answer 28

Avery and Griffith 1944 DNA transformed non-virulent Pneumococci into virulent form. Also showed that DNA is molecule of inheritance and not proteins

Question 29

Transformation process

Answer 29

1. DNA receptor molecule bind naked DNA 2. Nucleases degrade one strand of DNA 3. Only one DNA strand enters cell 4. New strand integrates into recipient cell's DNA 5. Replaces a similar part of recipient DNA

Question 30

Transduction

Answer 30

Bacterial viruses (bacteriophages or phages) transfer DNA from one bacteria to another

Question 31

Transduction process

Answer 31

1. Phages inject their DNA into bacteria 2. Bacteria DNA cut into pieces 3. Phage DNA replicated and new phage protein coats are made 4. Sometime bacteria DNA can enter phage instead of phage DNA 5. New phages are released that carry bacteria DNA called transducing particles

Question 32

Generalized Transduction Process

Answer 32

- Transducing particle attaches to bacteria - Bacteria DNA injected into host bacteria and is integrated into host chromosome - replaced host DNA is degraded

Question 33

Conjugation

Answer 33

- Transfer of DNA through sex pili that joins two cells | - Plasmids and chromoses can be transferred in conjugation

Question 34

Transformation= Transduction= Conjugation=

Answer 34

``` Transformation= naked DNA Transduction= viruses Conjugation= pilus + plasmid ```

Question 35

Plasmid

Answer 35

Very small, circular pieced of DNA - free floating in cell with a few to 1000 genes - can replicate - not essential, but helpful

Question 36

Conjugative plasmids

Answer 36

Plasmids that include sequences to begin transfer and to make pili 1. Resistance Plasmids 2. Fertility plasmids

Question 37

Resistance plasmids

Answer 37

R plasmids - contain genes for resistance to antimicrobial medication and to heavy metals - Broad host range

Question 38

Fertility plasmids

Answer 38

F plasmids - if F plasmid is present a bacteria cell can perform conjugation - bacteria with F plasmid are F+ and those without are F-

Question 39

Plasmid Transfer (Conjugation)

Answer 39

- When F plasmid is transferred the recipient cell become F+ | - Plasmid is replicated as it is transferred so both cells have the F plasmid

Question 40

Chromosome transfer (conjugation)

Answer 40

- Involves Hfr cells (High frequency recombination) - Have genes from F plasmid in the chromosomal DNA - When F plasmid genes are transferred part of chromosomal DNA can also be transferred - Recipient cell is still F- because whole F plasmid is not transferred - New chromosomal DNA will survive only if integrated into recipients DNA

Question 41

Transposons

Answer 41

- segments of DNA that can move from one part of the cell's DNA to another part in the same cell - Genes on transposon and on part of the affected DNA are disrupted

Question 42

Jumping Genes

Answer 42

Barbara McClintock 1950 - Transposons in corn kernels moved around unpredictably and changed color of the corn kernels - McClintock recieved Novel Prize in 1983

Question 43

MRSA developed vancomycin resistance from...

Answer 43

conjugation and transposons