What is a mutation?
Changes in the genetic material
(DNA). A feature of DNA.
Mutations can occur in two
different types of cells:
1. Somatic (body) cells
2. Gamete (sex) cells
Mutations that occur in somatic
(body) cells usually result in killing
that body cell only.
An exception to this is if the
mutation occurs to the DNA that
controls regulation of the cell
cycle. This can result in cancer.
• Somatic mutations usually do
NOT affect future individuals.
• Somatic mutations can NOT be
passed on to the next
generation.
Mutations that occur in gamete
(sex) cells means that every cell
of the developing fetus/baby
will have that mutation.
• Gamete mutations usually do
affect the individual with some
genetic disorder.
• Gamete mutations can be
passed on to the next
generation.
There are two types of
mutations that can occur in
gamete cells:
1. Gene Mutations
2. Chromosomal Mutations
CHROMOSOMAL MUTATIONS
• Multiple congenital anomalies
(deformities)
• Occur during pregnancy,
present at delivery
• Usually not inherited
5 types of Chromosomal
Mutations:
1.
2.
3.
4.
5.
Deletion
Duplication
Inversion
Translocation
Non-disjunction
Deletion
Involves the loss of part of a
chromosome.
Interstitial Deletion
Deletion
• TWO TYPES OF
DELETIONS:
• End missing (terminal)
• Piece within
chromosome missing
Terminal deletion of p 5
(interstitial)
Cri du Chat Syndrome =
Cry of the Cat
Maternal
15q11-13
•“Happy puppet
syndrome”
•Low IQ
•Abnormal gait
•Inappropriately happy
Deletion of Paternal 15q11-13
Deletion of Paternal 15q11-13
Duplication
Involves the production of extra
copies of parts of the
chromosome.
Duplication
• 4 copies of the top of chromosome 22
• Mental retardation in all babies
•Over sized babies
•Over sized organs
•Too much mitosis!
•Insulin-like growth
factor not turned off
because two paternal
alleles for chromosome
11p
Inversion
Reverses the direction of parts of
a chromosome.
Inversion
• Around the
centromere
• Above or below the
centromere
Inversion
Also an inversion
Translocation
When one part of a
nonhomologous chromosome
breaks off and attaches to
another chromosome.
Translocation
A Robertsonian translocation
All essential genetic material is
present so the children appear
normal
Most common birth defects with
unbalanced translocations of 11 and
22 are cleft palate, heart defects, ear
anomalies, and male genital defects.
Point Mutations
• This type of mutation takes place when 1 or
more bases is changed for another base on
the strand of DNA.
• This changes what protein is produced and
could change how something functions.
Errors in Chromosomal
Separation
Non-disjunction
Means “not coming apart”.
When homologous
chromosomes fail to separate
properly during anaphase 1 of
meiosis.
• Results in abnormal numbers of
chromosomes.
• Trisomy means a person has an
extra copy of a chromosome.
• Monosomy means a person is
missing a copy of a
chromosome.
Normal female
Normal male
Trisomy means a person has an
extra copy of a chromosome
•3 of chromosome 21
Non-disjuction: Trisomy
• Chromosome 18 does
not separate properly
during meiosis.
• This gives the child
three parts of
chromosome 18.
• Also called Trisomy
18
Edward’s Syndrome
•1/3000 births
•Mental Retardation
•Failure to thrive
•Heart defect
•Overlapping fingers
•Low set, fawn-like ears
• three of chromosome 13 present
•
•
•
•
These individuals are males.
Little body hair is present.
Typically tall.
Some development of breast tissue
normally seen in females.
• May or may not have evidence of mental
retardation.
Monosomy means a person is
missing a copy of a chromosome.
• These individuals are female
• Underdeveloped ovaries
• Individuals are sterile and lack expected
secondary sexual characteristics
• Short stature, webbed/bull neck, broad
chest
• Mental retardation typically not evident.
Turner’s Syndrome Baby
Turner’s Syndrome age 12
•Only one X chromosome present
• Karyotyping
• Fluorescent (FISH)