Download 12-4 Mutations

11/6/2014
12-4 Mutations
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 Mutation
 How


- change in genetic material
do they occur?
Spontaneous mutations - mutations occurring
during replication (mitosis/meiosis)
Mutagen - chemical or physical agent that
causes a mutation
 Gene
mutation - changes in a single gene
 Chromosomal
mutation - changes in
whole chromosomes (affects many genes)
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Gene Mutations
 Point
Mutations - Changes in one or a few
nucleotides
 Include:
substitutions, insertions, and
deletions
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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
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Frameshift Mutations
that shifts the “reading” frame of
the genetic message by inserting or deleting
a nucleotide
 Mutation
 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.
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Chromosomal Mutations
 Changes
in # or structure of chromosomes
 May even change # of copies of some genes
 5 Types:

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
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off and attaches to another
Chromosomal Mutations
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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!
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Polydactyly
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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
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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 - failure of chromosome
pairs to separate during meiosis (making of
gametes – sex cells)

Can cause some gametes to gain an extra
chromosome and others to lose one


Monosomy - A chromosome having no
homologue (matching chromosome)
Trisomy - Having 3 copies of a given
chromosome in each somatic (body) cell
(normal number: 2 copies)
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Normal Male
Karyotype
Normal Female
Karyotype
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Turners Syndrome
1 in 5,000 births
45 chromosomes
(X only)
#23 Monosomy
Nondisjunction
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Turners Syndrome
96-98% do not survive to birth
No menstruation
No breast development
Broad shoulders and neck
No hips
Cri-Du-Chat Syndrome
1 in 216,000 births
46 chromosomes
XY or XX
#5 Deletion of upper
arm of chromosome
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Cri-Du-Chat Syndrome
Moon-shaped face
Heart disease
Mentally retarded
Malformed larynx
Normal lifespan
Aniridia-Wilms Tumor
Syndrome
1 in 500,000 births
46 chromosomes
XY or XX
#11 Deletion of upper arm
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Aniridia-Wilms Tumor
Syndrome
Mental retardation
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
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Thirteen Q Deletion Syndrome
Mentally retarded
Deformed face
No thumbs
Heart disease
Short lifespan
Prader-Willi Syndrome
1 in 15,000 to 1 in 25,000
46 chromosomes
XY= 97%
XX= 3%
#15 Deletion of lower arm
on paternal chromosome
(Angelman’s syndrome =
15 q deletion of maternal
chromosome)
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Prader-Willi Syndrome
Small hands and feet
Slow mental development
Respiratory problems
Obesity
Short lifespan
Very flexible
Poor muscle tone
Short stature
Eighteen Q Deletion Syndrome
1 in 40,000 births
46 chromosomes
XY or XX
#18 Deletion of lower arm
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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
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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
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Four-Ring Syndrome
Cleft palate
Club feet
Testes don’t descend
Short lifespan
Down Syndrome
Down Syndrome
Trisomy
1 in 31,000 births
1 in 1,250 births
46 chromosomes
XY=97%
XX=3%
47 chromosomes - XY or XX
#14/21 Translocation
#21 Trisomy Nondisjunction
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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
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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
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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)
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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
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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
h t
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