Mutations - Somers Public School District
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Transcript Mutations - Somers Public School District
Mutations
What Are Mutations?
Changes in the
nucleotide sequence of
DNA (big or small)
May occur in somatic
cells (aren’t passed to
offspring)
May occur in gametes
(eggs & sperm) and be
passed to offspring
Are Mutations Helpful or
Harmful?
Mutations happen
regularly
Almost all mutations are
neutral
Chemicals & UV radiation
cause mutations
Many mutations are
repaired by enzymes
Are Mutations Helpful or
Harmful?
Some type of skin
cancers and leukemia
result from somatic
mutations
Some mutations may
improve an organism’s
survival (beneficial)
Types of Mutations
Chromosome Mutations
May Involve:
Changing the
structure of a
chromosome
The loss or gain
of part of a
chromosome
Chromosome Mutations
Six types exist:
Deletion
Inversion
Translocation
Insertion
Duplication
Aneuploidy by
nondisjunction
Deletion
Due to breakage
A piece of a
chromosome is lost
Disorders due to
chromosome deletions:
Cri du Chat – deletion of short arm
of 5
1p36 Deletion Syndrome-deletion
of short arm of 1
Angleman Syndrome- deletion of
short arm of maternal 15
Prader-Willi syndrome- deletion of
short arm of paternal
15
Inversion
Chromosome segment
breaks off
Segment flips around
backwards
Segment reattaches
Disorders caused by
inversions:
If they are “balanced”
they cause no
phenotype
If they are
“unbalanced” they
usually are associated
with a deletion and
several effects
Duplication
Occurs when a
gene sequence is
repeated
Translocation
Involves two
chromosomes that
aren’t homologous
Part of one
chromosome is
transferred to
another chromosome
and swapped with a
region of that
chromosome
Translocation
Disorders caused by
translocations
“Robertsonian” usually show
no phenotypes but often
problems during meiosis
leading to miscarriages in
developing fetus.
Common to have
Robertsonian traslocation of
13 and 14.
If translocation of long arm of
21 and long arm of 14-Down’s
Some cancer cells have
translocations (leukemia,
sarcoma)
Insertion
• A piece of one
Chromosome gets
Inserted into
Another
Chromosome
• Effect depends
on what was
Inserted and wheree
Nondisjunction
Failure of chromosomes to
separate during meiosis
Causes gamete to have too many
or too few chromosomes
Disorders:
Down Syndrome – three 21st chromosomes
Turner Syndrome – single X chromosome
Klinefelter’s Syndrome – XXY chromosomes
Some Aneuploid
Chromosomal Disorders
Patau Syndrome
Edward Syndrome
Klinfelter’s Syndrome
Turner Syndrome
Super Male Syndrome
Super Female
Syndrome
Down’s Syndrome
Normal Male
2n = 46
20
Normal Female
2n = 46
21
47, XY, +13
serious eye, brain,
circulatory defects
as well as cleft
palate. 1:5000 live
births. Children
rarely live more
than a few months.
Patau Syndrome
Cleft Palate
Edward Syndrome
almost every organ system affected
1:10,000 live births. Children with full
Trisomy 18 generally do not live more
than a few months.
Male, Trisomy 21 (Down’s)
2n = 47
28
Female Down’s Syndrome
2n = 47
29
Down’s Syndrome
Down’s Syndrome
Characteristics
•
•
•
•
•
•
•
•
One in 733 births
Slow cognitive ability and growth
Small chin
Round face
Almond shaped, often upslanting eyes
Heart defects
Gastric reflux disease
Thyroid problems
Klinefelter’s Syndrome
2n = 47
32
Kleinfelter’s Syndrome
Turner’s Syndrome
2n = 45
34
Turner’s syndrome
Chromosome Mutation
Animation