2. Mutations
A mutation is a mistake made when the
cell is copying DNA
 If a gene in one cell is altered it is passed
on to every cell that develops.
 2 types
 Gene mutations-produce a change in a singe
gene
 Chromosomal mutations-produce changes in a
whole chromosome

3. Gene Mutations
 Point Mutations
 Involve changes in one or a few nucleotides
 Occur at a single point in the DNA sequence
 Occur during replication
 3 types
 Substitution
 Insertion
 deletion

4. Substitutions
 One base is changed to a different base
 Affect one amino acid
 Sometimes have no affect at all

5. Insertions and Deletions
A base is inserted or removed from the
DNA sequence
 Bases are still read in groups of 3 but now
those groupings shift in every codon that
follows the mutation

6. Insertions and Deletions
 Also called “framshift mutations” because
they shift the reading frame of the genetic
mutation
 Changes every amino acid after the point
of mutuation
 Can change a protein so much it alters its
function

7. Chromosomal Mutations
 Involves changes in the number or
structure of chromosome.
 These mutations can change the location
of genes on chromosomes and can even
change the number of copies of some
genes.
 4 types: deletion, duplication, inversion,
translocation

8. Deletion
 Loss of all or part of a chromosome

9. Duplication
 Produces
an extra copy of all or part of a
chromosome

10. Inversion
 Reverses
the direction of parts of a
chromosome

11. Translocation
 Partof one chromosome breaks off and
attaches to another

12. Effects of Mutations
 Genetic material can be altered by natural
events or by artificial means.
 The resulting mutations may or may not affect
an organism.
 Some mutations that affect individual
organisms can also affect a species or even an
entire ecosystem.

13. Mutagens
 Some mutations arise from mutagens,
chemical or physical agents in the
environment.
 Chemical Mutagens Examples: pesticides,
tobacco, smoke,environmental pollutants
 Physical:x-rays, ultraviolet
light,electromagnetic radiation
 If the mutagen interacts with DNA they
can produce mutations at high rates.

14. Harmful and Helpful
 Whether a mutation is negative or
beneficial depends on how its DNA
changes relative to the organism’s
situation.

15. Harmful Helpful
 Some cancers  new or altered
 genetic disorders. functions
 Sickle cell disease  polyploidy.
 Point mutation  An extra set of
chromosomes
 Larger and stronger
than diploid plants

16. Prokaryotic Gene Regulation
 Prokaryotes produce only those genes
needed to function by doing this
prokaryotes can respond to changes in
their environment
 DNA-binding proteins in prokaryotes
regulate genes by controlling transcription.

17. Prokaryotic Gene Regulation
 DNA-binding proteins in prokaryotes
regulate genes by controlling transcription.
 The genes in bacteria are organized into
operons.
 An operon is a group of genes that are
regulated together.

18. Lac Operon
 Lactose is made of Glucose and
Galactose
 A cell must bring lactose across its
membrane then break the bond
 Performed by a protein called the lac operon
 If lactose is the only food source it must
make proteins to break these bonds
 If on another food source it has no need
for these proteins

19. Promoters and Operators
 The operon has 3 genes
 On one side of these genes there are 2
regulatory genes
 Promoter- RNA polymerase binds here to begin
transcription
 Operator-DNA lac opressor (blocker) can bind
here to stop production

20. Turning Off
 When lactose is not present the lac
repressor binds to the O region blocking
transciption
 This switches the operon “off”

21. Turning On
 Lac repressor has a place for lactose to
bind
 When lactose is present it bonds to this
site and makes the repressor fall off
 RNA polymerase can now bind to the
promoter and begin transcription
 If lactose is present it is automatically
turned “on”

22. Eukaryotic Gene Regulation
 TATA Box
 Found just before a gene
 Marks the point just before a gene begins to
help guide RNA polymerase into the right
position

23. Transcription Factors
 Transcription factors regulate gene
expression at the transcription level
 Can control the expression of genes
 Examples:
 enhance transcription by opening up tightly packed
chromatin
 attract RNA polymerase
 block access to certain genes
 Multiple
factors must bind before RNA
polymerase can attach to the promoter

24. Cell Specialization & RNA Interference
 Complex gene regulation in eukaryotes is
what makes specialization possible.
 Small RNA molecules that do not belong
to any major group ( mRNA,tRNA,rRNA)
are found in the cell.
 These RNA molecules interfere with
mRNA and control gene expression

25. RNA Interference
 Blocking
gene expression by means of an
miRNA silencing complex is known as
RNA interference
 the small interfering RNA molecules fold into
double-stranded hairpin loops
 the “Dicer” enzyme cuts loops into microRNA
 miRNA pieces attaches to a cluster of proteins
called the silencing complex
 This destroys any mRNA containing a
sequence that is complementary to the miRNA

26. RNA Interference in pictures

27. Genetic Development
 differentsets of genes are regulated by
transcription factors and repressors.
 Gene regulation helps cells undergo
differentiation, becoming specialized in
structure and function.
 Homeotic genes, regulates organs that
develop in specific parts of the body.
 Lewis grew a fly with a leg in place of an
antennae!

28. Homeobox
 Homeobox genes code for transcription
factors that activate other genes that are
important in cell development and
differenetiation
 Code for legs and wings in fruit flies

29. Hox Genes
 Homeobox genes known as Hox genes determine the body plan of
an embryo
 They are arranged in the order in which they are expressed
 Anterior to posterior
 A mutation in these genes can change the order of the body or
what parts develop

30. Environmental Influences
 Temperature,salinity,and nutrient
availibility can influence gene expression
 Lac operon in e.coli
 Alligator Eggs
 Metamorphosis

31. Genome
 Fullset of genetic information that an
organism carries in its DNA.
 Shows us what makes us uniquely human

32. Karyotype
 Shows the complete diploid set of
chromosomes grouped together in pairs,
arranged in order of decreasing size.

33. Karyotype
 Biologists photograph the cells during
mitosis so the chromosomes are
condensed and easy to view
 Scientists then
cut out the
chromosomes and
arrange them

34. Chromosomes
 Humans have 46 chromosomes grouped
together in 23 pairs
 44 of the chromosomes are autosomal
chromosomes (autosomes)
 2 of the 46 chromosomes are sex
chromosomes
 Females have 2 x chromosomes
 Males have 2 y chromosomes

35. Interesting…..
 The human Y chromosome
is much smaller than the X
chromosome and contains
only about 140 genes, most
of which are associated with
male sex determination and
sperm development
 More than 1200 genes are
found on the X
chromosome, some of which
are shown.

36. Chromosomes
A sex linked gene is a gene located on a
sex chromosome
 Genes on the y chromosome are found only in
males and are passed directly from father to
son
 Genes on the x chromosome are found in both
sexes but tend to occur more often in males

38. Color Blindness
 Humans have 3 genes for colorblindness
all on the x chromosome
 A defective allele for any of these genes
results in color blindness for males about
1 in 12 males
 In order for this to be expressed in
females they need an effective allele on
both of their x chromosomes about 1 in
200

39. If one X chromosome is enough, how do
females cope with having 2?
 Mostof the genes in 1 x chromosome are
turned off
 This forms a dense area in the nucleus called a
Barr Body
X inactivation happens in other mammals
as well

40. Spotted Cats!
 In cats a gene that codes for
the color of spot is located on
the X chromosome.
 One x may have an allele for
orange spots, and one x may
have an allele for black spots
 In cells in some parts of the
body, one X chromosome is
switched off. In other parts of
the body, the other X
chromosome is switched off.
As a result, the cat’s fur has a
mixture of orange and black
spots.

41. Pedigree
 Analyzes the pattern of inheritance
followed by a particular trait
 Shows the relationship within a family
 Based on a pedigree, you can often
determine if an allele for a trait is dominant
or recessive, autosomal or sex-linked.

42.  This pedigree shows the inheritence of the
white forelock trait which is dominant
 Grandfather has the trait
 2 of his 3 children have the trait
 3 of the 5 grandchildren have the trait
 Since every child does not have the trait
Grandfather must be heterozygous
 The children and grandchildren without the
trait are homozygous recessive

43. Genetic Disorders
 The molecules present affect the traits we
display/have
 The genotype correlates to the phenotype
 Genetic Disorders are molecular
 DNA is altered, changing the sequence of
amino acids, this changes the proteins
produced, and directly affects the phenotype

44. Sickle Cell Anemia
 Defective allele for
beta globin
 This forces cells into
a distinct, rigid, sickle
shape
 The cells get stuck in
capillaries and can
damage tissues and
organs

45. Cystic Fibrosis
 Results from the deletion of just 3 bases
 Phenylalanine is missing from proteins,
 Phen. Normally lets Cl pass through
membranes
 Without Cl the body’s tissues malfunction
 Produces digestive problems,thick heavy
mucus, labored breathing

46. Cystic Fibrosis
 Recessive Trait
 Meaning you need to be homozygous recessive
to have CF

47. Huntington’s Disease
 Caused by a dominant allele for a protein
found in brain cells
 Causes a long string of the codon CAG
 Symptoms
 Mental deterioration
 uncontrollable movements
 Does not present until middle age
 The longer the string of CAG the earlier it appears