Mutations

1

• 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

2
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
3
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
4

• 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
5
Genotype determines phenotype
6
Mutagens

• Mutations may result from

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

7

• 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
8
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

9
Bacteriophages

• Bacteriophages, or phages

• Attack bacteria

Head
Tail
Tail fiber
DNA of virus
Bacterial cell
Figure 10.25
10

• How phages infect bacteria and reproduce

Bacterial chromosome (DNA)
Phage DNA
4
Cell lyses, releasing phages
1
Many cell divisions
7
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
11
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
12
Animal Viruses

• Molecular genetics helps us understand viruses

• Virus studies help establish molecular genetics

Membranous envelope
RNA
Protein coat
Protein spike
Figure 10.28
13
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
14

• 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
6
(b) The behavior of HIV nucleic acid in an
infected cell
Figure 10.30b
15

• 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
16
EVOLUTION CONNECTIONEMERGING VIRUSES

• Many new viruses have emerged in recent years

• HIV
• Ebola
• Hantavirus

(a) Ebola virus
(b) Hantavirus
17

• How do new viruses arise?

• Mutation of existing viruses
• Spread to new host species

Figure 10.32
18

• Chapter 11 Control of the Gene
• what makes all the cell in your body different
• cloning

19

• Shortly after you drink a milk shake, bacteria
  living in your large intestine turn on certain
  genes. A cell can express some genes and
  others that are in its genome.

• How cells determine and the mechanisms a cell
  uses to express
• some genes and not others
• gene regulation or regulation of
  gene expression

• Gene expression refers to the process of
  transcription and translation to make
• a protein

20
FROM EGG TO ORGANISM HOW AND WHY GENES ARE
REGULATED

• Four of the many different types of human cells

(a) Three muscle cells (partial)
(b) A nerve cell (partial)

• They all share the same genome
• What makes them different?

(c) Sperm cells
(d) Blood cells
Figure 11.2
21
BIOLOGY AND SOCIETY BABYS FIRST BANK ACCOUNT

• In recent years umbilical cord and placental
  blood has been collected at birth

Figure 11.1
22
Fertilized Egg
How??
Fully developed, Multicellular organism
23

• A process called cellular differentiation occurs

• Certain genes are turned on and off
• Gene expression is regulated
• Cells become specialized in structure and function

http//embryology.med.unsw.edu.au/Movies/Movies.ht
mEmbryoGrowth
24
The Genetic Potential of Cells

• Differentiated cells

• All contain a complete set of DNA
• May act like other cells if their pattern of gene
  expression is altered

25

• In gene expression

• A gene is turned on and transcribed into RNA
• Information flows from genes to proteins,
  genotype to phenotype

• The regulation of gene expression plays a central
  role in development from a zygote to a
  multicellular organism

26
Eye lens cell (in embryo)
Pancreascell
Nerve cell

• Even though cells of an organism have the same
  genes (genotype)
• Patterns of gene expression in specialized human
  cells

Glycolysis enzyme genes
Crystallin gene
Insulin gene
Hemoglobin gene
Key
Active gene
Inactive gene
Figure 11.3
27
Where do stem cells come from?
Why are stem cells medically important?

• Totipotent stem cells
• Pluripotent stem cells

28

• Umbilical cord and placental blood is rich in
  stem cells

• Stem cells can develop into a wide variety of
  different body cells

Stem Cell
liver
heart
brain
blood
bone
29
Cloning
Cloning 1) Reproductive 2) Therapeutic
(involves stem cells)
How are cloning and stem cell research related?
30
Reproductive Cloning

• Scottish researchers cloned the first mammal in
  1997 using a technique called nuclear
  transplantation

• Other organisms have since been produced using
  this technique, some by the pharmaceutical
  industry

(a) Piglets
(b) Banteng
31

• The procedure that produced Dolly is called
  reproductive cloning

Reproductive cloning
Donor cell
Nucleus from donor cell
Implant embryo in surrogate mother
Clone of donor is born
Therapeutic cloning
Remove nucleus from egg cell
Add somatic cell from adult donor
Grow in culture to produce an early embryo
Remove embryonic stem cells from embryo and grow
in culture
Induce stem cells to form specialized cells for
therapeutic use
Figure 11.6
32
Eunucleation of egg
Transfer of new nucleus
33
Therapeutic Cloning and Stem Cells

• Therapeutic cloning

• Produces embryonic stem cells (ES cells)

• Can give rise to specific types of differentiated
  cells

34
Liver cells
Cultured embryonic stem cells
Nerve cells
Heart muscle cells
Different culture conditions
Different types of differentiated cells
Figure 11.8
35

• Adult stem cells

• Generate replacements for nondividing
  differentiated cells
• Are unlike ES cells, because they are partway
  along the road to differentiation

36

• In 2001, a biotechnology company announced that
  it had cloned the first human embryo

Figure 11.9