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12-4 Mutations
1
 Mutation
 Gene
= change in genetic material
mutation = changes in a single gene
 Chromosomal
mutation = changes in
whole chromosomes (affects many genes)
2
Gene Mutations
 Point
Mutations = Changes in one or a few
nucleotides
 Include:
substitutions, insertions, and
deletions
3
Types of Point Mutations
 Substitutions
= one base is changed to
another

Usually affects a single amino acid
 Insertions
= one base is inserted
 Deletions = one base is deleted


More dramatic changes
Cause frameshift mutations
• Changes all amino acids after the
point of change
4
Frameshift Mutations
 mutation
that shifts the “reading” frame of
the genetic message by inserting or
deleting a nucleotide
 May change every amino acid after that
point
 Frameshift mutations can alter a protein so
much that it is unable to perform its normal
functions.
5
6
Chromosomal Mutations
 Changes
in the number or structure of
chromosomes
 May
even change the number of copies of
some genes
7
5 Types of Chromosomal Mutations

Insertions = addition of part of a chromosome
 Deletions = loss of all or part of a chromosome
 Duplications = extra copies of parts of a
chromosomes
 Inversions = reverse direction of parts of a
chromosomes
 Translocations = part of one chromosome
breaks off and attaches to another
8
Chromosomal Mutations
9
10
Significance of Mutations
 Most

have little effect
Most mutations occur in portions of the DNA
that is not currently being used.
 Dramatic

changes = usually harmful
Producing defective proteins that don’t do
their job
 Mutations

= source of genetic variability!
Can be very good! Useful!
11
Polydactyly
12-5 Gene Regulation
A
typical gene includes start and stop
signals, with the nucleotides to be
translated in between.
 Regulatory Sites = determine if gene is on
or off.
14
Lac
Repressor in
E. coli
 Prokaryotic
cells
 Cells turn genes
on and off as
needed
15
Eukaryotic Gene Regulation
 Similar
but more complex than prokaryotes
 Many eukaryotic genes include a sequence
called the TATA box that may help position
RNA polymerase.
16
 Enhancer
sequences in DNA: Protein
binding area that can



enhance transcription by opening up tightly
packed chromatin
attract RNA polymerase
block access to genes
 More

complex because of cell specialization
Not all proteins are needed in every cell
17
Chromosomal Mutations
& their effects
Karyotype
A
picture of the chromosomes of an
individual (or a species), including
number, form, and size of the
chromosomes.
 Often used to diagnosis chromosomal
abnormalities.
Chromosomes

Humans have 23 pairs


22 pairs are autosomes
1 pair are sex chromosomes
• (women = XX, men = XY)
Chromosomes have a centromere that holds
the chromatids (two parts of the
chromosome) together.
 The top ½ of the chromosome is called the
“p” arm and the bottom ½ is “q”

Nondisjunction Disorder
Nondisjunction is the failure of chromosome
pairs to separate during meiosis (making of
gametes – sex cells)
 it can cause some gametes to gain an extra
chromosome and others to lose one
 Monosomy = A chromosome having no
homologue (matching chromosome)
 Trisomy =The condition of having three copies
of a given chromosome in each somatic (body)
cell rather than the normal number of two.

Normal Male
Karyotype
Normal Female
Karyotype
Turners Syndrome
1 in 5,000 births
45 chromosomes
X only
#23 Monosomy
Nondisjunction
Turners Syndrome
96-98% do not survive to birth
No menstruation
No breast development
No hips
Broad shoulders and neck
Cri-Du-Chat Syndrome
1 in 216,000 births
46 chromosomes
XY or XX
#5 Deletion of upper
arm of chromosome
Cri-Du-Chat Syndrome
Moon-shaped face
Heart disease
Mentally retarded
Malformed larynx
Normal lifespan
Aniridia-Wilms Tumor
Syndrome
1 in 50,000,000 births
46 chromosomes
XY or XX
#11 Deletion of upper arm
Aniridia-Wilms Tumor
Syndrome
Mentally retarded
Growth retarded
Blindness
Tumors on kidneys
Short lifespan
Thirteen Q Deletion
Syndrome
1 in 500,000 births
46 chromosomes
XY or XX
#13 Deletion of lower arm
Thirteen Q Deletion Syndrome
Mentally retarded
No thumbs
Short lifespan
Deformed face
Heart disease
Prader-Willi Syndrome
1 in 5,000,000 births*
(new info = 1 in 25,000)
46 chromosomes
XY= 97%
XX= 3%
#15 Deletion of lower
arm
paternal chromosome
(Angelman’s syndrome = 15 q
deletion of maternal
chromosome)
Prader-Willi Syndrome
Small bird-like head
Mentally retarded
Respiratory problems
Obesity
Short lifespan
very flexible
low muscle tone
Eighteen Q Deletion
Syndrome
1 in 10,000,000 births
46 chromosomes
XY or XX
#18 Deletion of lower arm
Eighteen Q Deletion Syndrome
Mentally retarded
Heart disease
Abnormal hands and feet
Large eyes
Large ears
Normal lifespan
Cat-Eye Syndrome
1 in 1,000,000 births
46 chromosomes
XY or XX
#22 Deletion of
bottom arm
Cat-Eye Syndrome
Fused fingers and
toes
Mentally retarded
Small jaw
Heart problems
Normal lifespan
Four-Ring Syndrome
1 in 10,000,000 births
46 chromosomes
XY or XX
#4 Inversion
Four-Ring Syndrome
Cleft palate
Club feet
Testes don’t descend
Short lifespan
Down Syndrome
1 in 31,000 births
46 chromosomes
XY=97%
XX=3%
#14/21 Translocation
Down Syndrome
Trisomy
1 in 1,250 births
47 chromosomes - XY or
XX
#21 Trisomy
Nondisjunction
Down Syndrome
Short, broad hands
Stubby fingers
Rough skin
Impotency in males
Mentally retarded
Small round face
Protruding tongue
Short lifespan
Edward’s Trisomy
Syndrome
1 in 4,400 births
47 chromosomes
XX=80%
XY=20%
#18 Trisomy
Nondisjunction
Edward’s Trisomy Syndrome
Small head
Mentally retarded
Internal organ abnormalities
90% die before 5 months of age
Jacob’s Syndrome
1 in 1,800 births
47 chromosomes
XYY
#23 Trisomy
Nondisjunction
Jacob’s Syndrome
?
Normal physically
Normal mentally
Increase in testosterone
Acne
Normal lifespan
Klinefelter Syndrome
1 in 1,100 births
47 chromosomes
XXY only
#23 Trisomy
Nondisjunction
(sometimes seen as
Kleinfelter)
Klinefelter Syndrome
Scarce beard
Longer fingers and arms
Sterile
Delicate skin
Low mental ability
Normal lifespan
Triple X Syndrome
1 in 2,500 births
47 chromosomes
XXX only
#23 Trisomy
Nondisjunction
Triple X Syndrome
Normally physically
Normal mentally
Tall
Fertile
normal lifespan

This is a cell after it has been broken open. A
photo is taken of this and then manipulated on a
computer. Each chromosome is cut out of the