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Microbial Genetics A. Structure of DNA Microbial Genetics A. Structure of DNA

Microbial Genetics A. Structure of DNA - PowerPoint Presentation

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Microbial Genetics A. Structure of DNA - PPT Presentation

1 Discovered by James Watson and Francis Crick in 1953 2 Stores genetic information for the production of proteins 3 Composed of nucleotides A A nucleotide is composed of a nitrogenous base ID: 932053

microbial dna rna genetics dna microbial genetics rna strand genetic strands polymerase codon iii segment process template cell bases

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Slide1

Microbial Genetics

A. Structure of DNA

1.

Discovered

by James Watson and Francis Crick

in 1953

2.

Stores

genetic information for the production of proteins

3.

Composed

of nucleotides

A)

A

nucleotide is composed of a nitrogenous base,

sugar,

and phosphate

Slide2

Microbial Genetics

1)

The

4 bases of DNA are adenine, guanine,

thymine,

and cytosine

2)

Sugar

– deoxyribose

3)

Phosphate

– PO

4

B)

Bases

attach to 1’ carbon

C)

Hydroxyl

(-OH) group on the 3’ carbon

D)

Phosphate

group on 5’ carbon

Slide3

Microbial Genetics

4.

Nucleotides

arranged in chains (strands)

A

) The ends of each strand are identified by the number of the carbon nearest to that end

5.

Bases

are held together by H

+

bonds

A) Base Pairing Rules

1) A with T

2) G with C

6. DNA is a complementary,

antiparallel

, double helix

Slide4

Slide5

Microbial Genetics

B. DNA Replication

1. Semi-Conservative Replication

A)

Results

in 2 molecules; each with 1 original strand and 1 new strand

B)

Uses

multiple enzymes:

1) DNA helicase – unwinds the double helix

a)

Breaks

H

+

bonds between bases

Slide6

Microbial Genetics

2) DNA Polymerase III – builds new strands

a)

Cannot add

nucleotides without one already

being present

(cannot start from scratch)

i

)

Requires

an

RNA primer

(a) S

mall

section of RNA that initiates DNA replication

(

i

)

Created

by RNA primase (can start from scratch)

Slide7

Microbial Genetics

b)

Can

only add new nucleotides to the 3’ end of an already existing chain

i

)

Therefore

the enzyme must read the original in a 3’ to 5’

direction and the new

DNA is built in a 5’ to 3’

direction

3) DNA Polymerase I – removes & replaces the RNA

primer(s)

with DNA

4) DNA ligase – joins together DNA fragments

Slide8

Microbial Genetics

C. DNA Expression

1. Transcription-Translation

A) Process by which information is taken from DNA and used to make proteins

2. Transcription

A)

Process

by which RNA is created from a DNA template

Slide9

Microbial Genetics

B) RNA polymerase “reads” the template DNA strand and creates a complementary RNA strand

1)

It

recognizes

promoter

and

termination

regions on the DNA template

3. Translation

A)

Process

by which a polypeptide strand is created from a mRNA template

B)

Occurs

in the ribosome

Slide10

Microbial Genetics

C)

Ribosome

begins “reading” the mRNA strand until it reaches the start codon (AUG)

1)

Codon

– three-nucleotide sequence that represents one amino acid

D)

tRNA

brings in the appropriate amino acid for the AUG codon

E) The next codon is read and another amino acid comes in forming a peptide bond with the previous one

Slide11

Microbial Genetics

F) This continues until the ribosomes reaches a stop (nonsense) codon on the mRNA

1)

Can

be UAA, UAG, or UGA

G) The new protein is released to the cell for use or release

Slide12

Microbial Genetics

Genetic Engineering

A. Tools & Techniques

1. DNA strand properties

A) Strands denature

(separate) at

near-boiling temperatures

B) Strands

renature

(reform) as

the strands

cool

Slide13

Microbial Genetics

2. Enzymes

A) Restriction endonucleases

1

) Capable of recognizing specific sequences and clipping the DNA at that location

2)

Used to splice pieces of DNA into plasmids and chromosomes

Slide14

Microbial Genetics

B) DNA Ligase

1) Used to rejoin DNA fragments

C) DNA & RNA polymerases

1) Used to make new strands of DNA or RNA (respectively)

Slide15

Microbial Genetics

D)

Reverse transcriptase

1) Uses an RNA template to create a strand of DNA

2) Can be used to help sequence RNA or examine DNA with the “junk” segments removed

Slide16

Microbial Genetics

3. Visualization

A) Electrophoresis

1)

Uses an electrical current and a gelatin-like medium to create

a visual pattern of DNA

fragments

Slide17

Microbial Genetics

4.

Oligonucleotides

A) Smaller segments of DNA created for research purposes

B) Most eukaryotic DNA is too large to study as a whole;

oligonucleotides

allow it to be studied in pieces and then information is consolidated to observe the whole genome

Slide18

Microbial Genetics

C)

Oligonucleotides

can also be sequenced using a sequencer

1) Can sequence 500-10 million

bp

segments at a rate of about 1000

bp

/day

Slide19

Microbial Genetics

5. Polymerase Chain Reaction (PCR)

A) Allows one to create millions of copies of a specific segment of DNA

B

) Most often know in advance the segments to be

copied

C) Requires:

1) A sample of the original DNA with the segment to be

copied

Slide20

Microbial Genetics

2) The appropriate endonucleases to extract the desired segment

3

) The appropriate RNA primer to initiate replication of that segment

4

) DNA polymerase III to make copies of that segment

5

) A thermal cycler to heat and cool the DNA so it can denature and renature

multiple

times

Slide21

Microbial Genetics

B. Recombinant DNA

1. R

ecombination

A)

The

transfer of DNA from one organism to another

1)

Results

in a new genetic strain different from the donor and original recipient

2)

Normally

involves the transfer of plasmids

Slide22

Microbial Genetics

3

)

The

recipient organism must accept the DNA into its genetic make-up, express it,

and

pass it on to its offspring for the transfer to be

successful

4) Can occur naturally or artificially

Slide23

Microbial Genetics

B) 3 mechanisms of natural transfer

1) Conjugation

a) Involves a pilus

b)

Pilus

forms a bridge between the 2 organisms and a replicated plasmid is transferred

Slide24

Microbial Genetics

c)

Only

certain bacteria are able to produce a pilus but that trait is also transferred through this process

d)

Generally

limited to organisms of the same

genus

Slide25

Slide26

Microbial Genetics

2) Transformation

a) A cell “picks up” a piece of DNA from the environment usually from a lysed cell

b

)

Allows

a cell to get genetic material from an entirely different

species

Slide27

Slide28

Microbial Genetics

3) Transduction

a) Involves infection by bacteriophage

b) The phage carries genetic material from its previous host cell into the new host

Slide29

Slide30

Microbial Genetics

C) Genes can also be introduced artificially

1

) Transfection – process of artificially introducing genes into

organisms

Slide31

Slide32

Microbial Genetics

a)

Transfected

orgs. may be patented

b) Can be microbes, plants, or animals

i

) Bacteria

(a) Plays a major role in agriculture

(

i

) Can act as insecticides

Slide33

Microbial Genetics

ii) Viruses

(a) Often used to transmit the gene into another organism

(

i

) Vector – a microbe or virus that transmits material (wanted or unwanted) into a host organism

(b) Gene therapy, experimental vaccines, and pathogenic testing all use

transfected

viruses

Slide34

Microbial Genetics

iii) Plants

(a) Can introduce a number of new characteristics

(i) Herbicide resistance

(ii) Built-in insecticide

(iii) Microbial resistance

Slide35

Microbial Genetics

iv) Animals

(a) Serve many valuable purposes

(

i

) Production of human hormones,

antibodies,

and enzymes

(ii) The study of human disorders

(iii) Healthier meat products

(iv) Replacement tissues and organs

(v) Nearly all early research involving human genetic therapy