Transcript CHANGES IN DNA CAN PRODUCE VARIATIONS

CHANGES IN DNA CAN
PRODUCE VARIATIONS
• DNA sequences can change (mutation)
• Mutations can cause genetic disorders (like
sickle cell anemia & cystic fibrosis)
• Cancer is a genetic disorder that affects the
cell cycle
DNA sequence can change
• Each human cell, with 46
chromosomes, has 6
billion base pairs in its
DNA.
• 99.9% of DNA in cells of
2 different humans is
same. Just 0.1% variation
in DNA makes you
unique & different from
others. (about 1 base in
every thousand).
• Only 5% of the billions of
base pairs of DNA are in
the GENES that code for
RNA and proteins
Differences in genes affect
height, color of eyes, hair,
skin, etc. Skin color comes
from protein (melanin). The
more melanin their skin
cells are programmed to
make, the darker their skin
color
DNA sequence can change
• Exposure to ultraviolet radiation, x-rays, & toxins
can damage DNA. Any change in DNA is called
a MUTATION.
• Cells have different ways to repair mistakes
(through enzymes).
• If a mutation occurs in a gene (the 5% of DNA
that’s the coding region) the wrong amino acid
may be placed in the amino-acid chain.
3 possible outcomes if mutation
occurs in a gene (coding region)
• MUTATION
CAUSES NO
EFFECT: there are 2
sets of DNA (1 from
each parent) so if 1
gene isn’t working,
the other may still
code for enough of
the protein to let the
cell function normally
• EFFECT OF
MUTATION IS
MINOR: a change in
the genes may only
produce a slight
change in appearance
(the amount of
melanin produced for
skin or hair color)
Possible outcome if mutation
occurs in coding region of DNA
• EFFECT OF MUTATION
IS GREAT: can be good
(plant has increased
resistance to disease) or
bad, causing genetic
disorder or disease.
• If mutation occurs in the
95% of DNA that doesn’t
code , no effect will
occur; it is neutral
MUTATIONS CAN CAUSE
GENETIC DISORDERS
• Genetic disorder results from mutations that
affect the normal functioning of a cell.
• Some are inherited (passed on from parent to
offspring; like Tay-Sachs, Sickle-cell , and cystic
fibrosis)
• Others are results from mutations within a
person’s own lifetime (cancers)
• Sometimes a “tendency” for getting a disease
(like diabetes, glaucoma, alzheimers) is inherited
and a person’s behavior can bring on or prevent
the disease.
GENETIC DISORDERS
• Sickle Cell disease occurs from a mutation where
one amino acid is replaced by another. Since it is
recessive, both alleles must be inherited to cause
it (abnormally shaped red blood cell decreasing
oxygen and damaging tissue).
• Sickle cell protects against malaria, so allows
people to survive with it and pass it on (occurs in
Africa, parts of India and Middle East).
• A PEDIGREE (diagram of family relationships
that include 2 or more generations) can show
how the sickle cell allele is passed on through
generations of a family.
Cancer is a genetic disorder that
affects the cell cycle
• Cancer is a group of disorders, all characterized
by uncontrolled division of cells.
• Cancer cells spread quickly & invade other
tissues; become “immortal” dividing indefinitelywhile normal cells have a definite life span and
die.
• Most cancers due to mutations to DNA over a
person’s life. Some from mistakes during
replication, but many from harmful chemicals
(carcinogens).
• Cancer involves series of mutations; some people
inherit 1 step in the series or a “tendency” for it.