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IN: Message Activity
Genetic Mutations
Human Genetics
Animal mutations
I. Mutations – permanent
changes to the nucleotide base
sequence of DNA;
Chromosomes have extra or
missing genetic material
II. Results of DNA Changes
A. Increased genetic
variation of offspring
B. Harmful - Cause cancer
C. Helpful – Create
antibiotic resistant
bacteria (bad for us
good for bacteria)
D. Neutral – many
occur on introns
(non-coding segment
of DNA) so they are
not expressed as
proteins
Antibiotic Discs
III. Two Categories of Mutations
A. Germline Mutations
a.
b.
c.
d.
Occur during meiosis
Affect sex cells
Passed from parent to offspring
Too many or not enough chromosomes
Ex. Down Syndrome
B. Somatic Mutations
a. Take place in body cells
b. Not passed to offspring
c. Localized to a single or small group of cells
Ex. Skin cancer from UV radiation exposure
IV. Where in the DNA do mutations occur?
A. Gene Mutations - occur within the
sequence of one gene.
B. Chromosome Mutations – occur when
chromosome structure changes
V. Gene Mutations (2 types)
A. Point Mutations – substitutions occur in a
single base pair
a. Silent Mutation –base pair substitution does
not change amino acid sequence
Ex: CUU ( Leucine ) to CUC ( Leucine )
b. Missense Mutation –base pair substitution
changes amino acids sequence
Ex: AGU (Serine) to AGA (Arginine)
c. Nonsense Mutation –base pair substitution
changes to a stop codon
Ex: AGA (Arginine) to UGA (Stop)
Silent
Normal Hb
Sickle
cell Hb
One base pair
substitution causes
hemoglobin to have the
wrong shape.
Sickle-cell Disease
is caused by a
missense mutation.
Diseases Caused by
Point Mutations
• Cystic fibrosis
• Cancer
• Neurofibromatosis (tumors form
on the nerves anywhere in the
body)
• Progeria (early aging)
time.
B. Frameshift Mutations
1. A single base pair in the
DNA is deleted or
added.
2. Every codon after the
deleted or added base
would be different.
3. Alters the reading
frame of mRNA
triplets
4. Makes the DNA
meaningless and
results in a short,
nonfunctional protein
Frameshift
Diseases
Syndrome with facial
deformity, skeletal
anomalies, and mental
retardation
video
VI. Chromosome Mutations
A. Deletion: removal of a
chromosomal segment
B. Duplication: repeats a
chromosomal segment
C. Inversion: segment reversal in a
chromosome
D. Translocation: movement of a
chromosomal segment to
another non-homologous
chromosome
Name the
Mutation
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THE DOG BIT THE CAT.
THE DOB ITT HEC AT.
Deletion with
Frameshift
THE DOG BIT THE CAT.
THE DOG BIT THE CAR.
Point
The fat cat ate the wee rat.
The fat tar eew eht eta tac.
Inversion
VII. Causes of Mutations
A. Spontaneous (chance):
1. Base pairing error during DNA replication
2. Errors during meiosis
B. Mutagen - environmental factor that
damages DNA
Ex: UV sunlight (cancer), cigarette tar, asbestos,
X-ray, radioactive isotopes, etc.
VIII. Irregular Chromosome Number
A. Caused by Nondisjunction
a. = Failure of chromosomes to separate
correctly during of meiosis
b. Result is extra or missing chromosomes
What are these two pictures called?
KARYOTYPE = Shows chromosomes paired by
size, shape, and appearance in metaphase.
IX. Nondisjunction Diseases/Syndromes
A. Monosomy (one missing chromosome)
a. Nearly all monosomies are fatal
b. Examples:
1. Turner syndrome (XO female) - 45
chromosomes instead of 46
2. Cri du chat = partial deletion of
chromosome 5
Turner Syndrome
Genetic disorder that
consists of a broad
spectrum of features that
vary in individuals, but
usually have the
common findings of short
stature (average adult
height: 4 feet 8 inches)
and loss of ovarian
function. The loss of
ovarian function usually
leads to infertility and
inhibited sexual
development.
Turner Syndrome affects 60,000 females in the United States. This
disorder is seen in 1 of every 2000 to 2500 babies born, with about 800
new cases diagnosed each year.
B. Trisomy = One extra single chromosome is
present
a. Many, but not all, are fatal
b. Examples: (47 instead of 46)
1.
Klinefelter’s Syndrome = XXY male
(rare cases (48,XXXY) or (49,XXXXY)
2. Jacob syndrome = XYY males
3. Triple X Syndrome = XXX females
4. Down Syndrome = extra 21st
chromosome
Klinefelter Syndrome
Low Testosterone
Infertility
Incomplete Masculinization
Female Body Hair Distribution
Decreased Libido
Low Energy
Developmental Delays
Learning Disabilities
Normal or High IQ
Social Interaction Difficulties
ADHD
Impulse Control Disorder
Depression
Low Self Esteem
Male inherits an extra X
chromosome. This means
they have two X
chromosomes and one Y
(written 47,XXY).
Individuals with Klinefelter
syndrome are male
because they have at least
one copy of the Y
chromosome.
About 1 in 500 to 1 in 1000
males is born with XXY
chromosomes. It is the most
common chromosome change
in men with very low or
absent sperm counts.
Jacob’s Syndrome XYY
Most boys who have the
extra Y chromosome will
go through life without
having been diagnosed.
Occurs in
only 1 out
of every
1,000
births
Extra Y chromosome is in
inherited from the father
Triple X syndrome
(trisomy X or 47,XXX)
• Characterized by an
additional X chromosome
• Most females with triple
X syndrome have normal
sexual development and
are able to conceive
children
Triple X
• Tall stature
• Small head
• Vertical skin folds in
inner corners of the eyes
• Delayed development of
motor skills, speech and
language
• Learning disabilities,
such as dyslexia
• Weak muscle tone
This condition occurs in about 1 in 1,000 newborn girls. Five to 10 girls with triple
X syndrome are born in the United States each day.
Down Syndrome Trisomy 21
►Physical signs:
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Decreased muscle tone
Excess skin at the nape of neck
Flattened nose
Separated joints between the bones of
the skull
Single crease in the palm of the hand
Small ears and mouth
Upward slanting eyes
Wide, short hands with short fingers
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Impulsive behavior
Poor judgment
Short attention span
Slow learning
OUT:
Compare and contrast gene mutations and
chromosome mutations using a Venn Diagram:
Gene
mutations
Chromosome
mutations