Mutations

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• Mutations
• any change in the nucleotide sequence of DNA
• can be single nucleotide or large section
• (ie. many nucleotides) of a DNA molecule

• Types of mutation
• substitutions (changes)
• insertions (additions)
• deletions

Not every mutation will influence the amino acid
sequence, therefore not Every mutation will have
an effect on phenotype. Why???
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Mutations
- any change in the nucleotide sequence of DNA
Normal hemoglobin DNA
Mutant hemoglobin DNA
mRNA
mRNA
Sickle-cell hemoglobin
Normal hemoglobin
Glu
Val
Figure 10.21
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Types of Mutations

• Mutations within a gene

• two general categories
• 1.result in changes in the amino acids in proteins

mRNA
Protein
Met
Lys
Phe
Gly
Ala
(a) Base substitution
Met
Lys
Phe
Ser
Ala
Figure 10.22a
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• Insertions and deletions

2.Change the reading frame of the genetic message
mRNA
Protein
Met
Lys
Phe
Gly
Ala
(b) Nucleotide deletion
- Disastrous effects
Met
Lys
Leu
Ala
His
Figure 10.22b
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Genotype determines phenotype
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Mutagens

• Mutations may result from

• Errors in DNA replication
• Physical or chemical agents called mutagens

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• Although mutations are often harmful

• They are the source of the rich diversity of
  genes in the living world
• They contribute to the process of evolution by
  natural selection

Figure 10.23
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VIRUSES GENES IN PACKAGES

• Viruses sit on the fence between life and nonlife

They exhibit some but not all characteristics of
living organisms

• 3 categories of viruses
• - bacterial
• - plant
• - animal

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Bacteriophages

• Bacteriophages, or phages

• Attack bacteria

Head
Tail
Tail fiber
DNA of virus
Bacterial cell
Figure 10.25
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• How phages infect bacteria and reproduce

Bacterial chromosome (DNA)
Phage DNA
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Cell lyses, releasing phages
1
Many cell divisions
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Lysogenic cycle
Lytic cycle
2
6
Prophage
3
5
New phage DNA and proteins are sythesized
Phage DNA inserts into the bacterial chromosome
by recombination
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Plant Viruses

• Viruses can also infect plants

Protein
RNA

• Can stunt growth and diminish plant yields
• Can spread throughout the entire plant

Figure 10.27
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Animal Viruses

• Molecular genetics helps us understand viruses

• Virus studies help establish molecular genetics

Membranous envelope
RNA
Protein coat
Protein spike
Figure 10.28
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HIV, the AIDS Virus

• HIV is a retrovirus

Envelope
Protein

• A retrovirus is an RNA virus that reproduces by
  means of a DNA molecule
• It copies its RNA to DNA using an enzyme called
  reverse transcriptase

Protein coat
RNA (two identical strands)
Reverse transcriptase
(a) HIV
Figure 10.30a
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• How HIV reproduces inside a cell

Reverse transcriptase
Viral RNA
Cytoplasm
1
Nucleus
Chromosomal DNA
DNA strand
2
3
Provirus DNA
Double-stranded DNA
4
5
Viral RNA and proteins
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(b) The behavior of HIV nucleic acid in an
infected cell
Figure 10.30b
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• AIDS is

• Acquired immune deficiency syndrome
• The disease caused by HIV infection
• Treated with the drug AZT

(c) HIV infecting a white blood cell
Figure 10.30c
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EVOLUTION CONNECTIONEMERGING VIRUSES

• Many new viruses have emerged in recent years

• HIV
• Ebola
• Hantavirus

(a) Ebola virus
Go back and look at very first lectures from the
semester on evolution and HIV
(b) Hantavirus
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• How do new viruses arise?

• Mutation of existing viruses
• Spread to new host species

Figure 10.32
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Friday Whats all this about bird flu?