Transcript Unit 5: Genetics

Unit 5: Genetics
Learning Goal 5: Examine
problems that arise from
miscoded DNA and
chromosome conditions.
Mutation
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A Mutation occurs when
a DNA gene is damaged
or changed in such a way as to alter the
genetic message carried by that gene.
A Mutagen is an agent of substance that
can bring about a permanent alteration to
the physical composition of a DNA gene
such that the genetic message is changed.
Types of Mutations
Types of Mutations
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Point Mutation: Gene mutations involving
changes in one or a few nucleotides.
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Substitution: One base is changed to
another.
• This only affects one amino acid.
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Frameshift Mutations: Changes that shift
the “reading frame” of the genetic message.
• This may change every amino acid after that point.
• This occurs if a nucleotide is added or deleted.
Types of Mutations
Types of Mutations
Types of Mutations
Chromosomal Mutations
 Changes
in the
number or structure
of chromosomes.
Chromosomal Mutations
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Deletion: Involves the loss
of all or part of the
chromosome.
Duplication: produce extra
copies of parts of the
chromosomes.
Inversion: Reverse the
direction of parts of the
chromosomes.
Translocation: Occurs
when part of one
chromosome breaks off and
attaches to another.
Significance of Mutations
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Most mutations are neutral.
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Meaning that they have little or no effect on the
expression of genes or the function of the proteins for
which they code.
Mutations that cause dramatic change in the protein
structure are usually harmful.
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Some are beneficial.
They lead to variations in populations
Karyotype
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A picture of chromosomes grouped in order
of pairs.
Cystic Fibrosis
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Cystic fibrosis is a
genetic disorder that
affects the respiratory
and digestive
systems.
Sickle Cell Disease
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Sickle cell disease is a
disorder that affects the red
blood cells, which use a
protein called hemoglobin to
transport oxygen from the
lungs to the rest of the body.
Huntington’s Disease
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Huntington's Disease (HD) is a brain
disorder that affects a person's ability
to think, talk, and move.
Alzheimer’s Disease
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Alzheimer's is a disease that causes
dementia, or loss of brain function. It
affects the parts of the brain that deal
with memory, thought, and language.
What Are BRCA1 And BRCA2 Genes?
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In the 1990s, mutations in two genes, BRCA1 (BReast CAncer
1) and BRCA2 (BReast CAncer 2), were shown to be involved
in inherited breast cancer. It is estimated that 40 percent to 90
percent of families with an inherited form of breast cancer have
a defective copy of the BRCA1 or BRCA2 gene.
BRCA1 and BRCA2 are called "tumor suppressor genes"
because they make proteins that help prevent the cells from
forming tumors. If one of these genes is changed through a
mutation, the protein may not do its job, making it easier for a
tumor to develop. Women who inherit a mutated copy of either
the BRCA1 or BRCA2 gene have an
increased chance of developing
breast cancer. In addition, there
may be an increased risk for other
cancers.
Hemophilia
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Hemophilia is an inherited
bleeding, or coagulation,
disorder.
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Persons with hemophilia
lack the ability to stop
bleeding because of the low
levels, or complete absence,
of specific proteins, called
“factors,” in their blood that
are necessary for clotting.
Hemophilia
Turner Syndrome
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Turner syndrome is
caused by a missing or
incomplete X chromosome.
People who have Turner syndrome develop
as females.
The genes affected are involved in growth
and sexual development.
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sex organs don't mature at adolescence
sterility
short stature
Down Syndrome
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Down syndrome is a
developmental disorder
caused by an extra copy of
chromosome 21 (which is why the disorder
is also called "trisomy 21").
Having an extra copy of this
chromosome means that each
gene may be producing more
protein product than normal.
Children with Down Syndrome develop
slower, may have heart and stomach
illnesses and vary greatly in their degree
of intelligence
Klinefelter Syndrome
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Klinefelter syndrome is a
disorder that affects only males.
Males normally have an X chromosome and
a Y chromosome (XY).
Males who have
Klinefelter syndrome
have an extra X
chromosome
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XXY, XXYY, XXXY
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Sterility
Breast enlargement
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XYY Syndrome
“super male”
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This condition occurs in about 1 in 1,000 newborn
boys. Five to 10 boys with 47,XYY syndrome are
born in the United States each day.
Most males with 47,XYY syndrome have normal sexual
development and are able to father children.
47,XYY syndrome is associated with an increased risk of
learning disabilities and delayed development of speech
and language skills.
Delayed development of motor skills (such as sitting and
walking), weak muscle tone (hypotonia), hand tremors or
other involuntary movements (motor tics), and behavioral
and emotional difficulties are also possible.
These characteristics vary widely among affected boys
and men.
XYY Syndrome
“super male”
•Normal male traits
•Often tall and thin
•Associated with antisocial and
behavioral problems
Triple X syndrome
also called trisomy X or 47,XXX,
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characterized by the presence of an
additional X chromosome in each of a
female's cells.
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.
Triple X syndrome
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Physical Symptoms
-Taller than average
-Increased width
between eyes
-Skin fold at inner
eyelid
-Smaller head size
-Porportionatly tinier
chin
Developmental
Symptoms:
-Learning disabilities
-Speech & language
delays
-Poor coordination
-Awkwardness
-Clumsiness
Trisomy 18
Edwards Syndrome
Caused by extra chromosome
at chromosome 18.
 It is three times more common
in girls than boys.
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Fifty percent of infants with this
condition do not survive beyond
the first week of life. Some children
have survived to the teenage years,
but with serious medical and
developmental problems.
Trisomy 18
Edwards Syndrome
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Symptoms
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Clenched hands
Crossed legs (preferred position)
Feet with a rounded bottom (rocker-bottom feet)
Low birth weight
Low-set ears
Mental deficiency
Small head
Small jaw
Underdeveloped fingernails
Undescended testicles
Unusual shaped chest
Trisomy 13
Patau Syndrome
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Trisomy 13 occurs when extra DNA from chromosome 13 appears
in some or all of the body's cells.
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The extra material interferes with normal development.
Trisomy 13 occurs in about 1 out of every 10,000 newborns. Most
cases are not passed down through families (inherited). Instead,
the events that lead to Trisomy 13 occur in either the sperm or the
egg that forms the fetus.
The syndrome involves multiple
abnormalities, many of which are
not compatible with life. More than
80% of children with trisomy 13 die
in the first month.
Trisomy 13
Patau Syndrome
Symptoms
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Cleft lip or palate
Clenched hands (with outer fingers on top of the inner fingers)
Close-set eyes -- eyes may actually fuse together into one
Decreased muscle tone
Extra fingers or toes
Hole, split, or cleft in the iris
Low-set ears
Mental Retardation,severe
Scalp defects (missing skin)
Small eyes
Small head
Small lower jaw