Download Are you just your DNA?

How does the
ENVIRONMENT
affect the traits of
organisms?
How does the environment
affect the traits of organisms?
 1. The environments influences the expression of
traits by chemically interacting with DNA in the
cell, or by limiting available resources the organism
requires to express the gene.
 Ex. The gene for the dark pigment in
coat color for Siamese cats is activated
by colder temperatures.
Because of this, only the coolest
parts of the body-- the feet, tail, and
face– express the dark color fur
Snowshoe Hare
 Brown in summer
 White in winter
My DNA does NOT
change every
season…the
temperature just
makes the pigment
in the hair come
out DIFFERENT
So I blend in with my
environment…harder for
predators to catch me for
dinner!!
 2. Environmental hazards can create genetic
mutations , turning off or altering the expression of
a gene. These hazards are called mutagens.
 Ex. Environmental toxins mimic human hormones such
as estrogen and inhibit the production of that hormone
by cells
Because they
cause
MUTATIONS!!
 Identical Twins are used to study the effect of
environment on gene expression. This is because
identical twins have identical genes but are often
exposed to different environments.
Causes and Effects
Disease/Cause
Lung/Mouth
Cancer &
Tobacco Use
Cause and Effect relationship
between the environment and the
expression of genetic traits
■Tobacco products contains toxins
and carcinogens
■Carcinogens can cause mutations in
the DNA leading to uncontrolled cell
division (cancer)
Disease/Cause
Cause and Effect relationship between the
environment and the expression of genetic
traits
Skin Cancer &
Sun Exposure
■Skin cancer is directly linked to sun
exposure because UV light mutates the DNA,
causing cancer
■Sunlight also destroys folate (folic acid)
when absorbed by skin. Folic acid is key to
DNA repairing its mutations.
■Folic acid deficiency is a contributor to skin
cancer but can be found in vitamins.
■Sun exposure gives us vitamin D, a vitamin
that helps prevent heart disease. However,
you only need 10 minutes of exposure a day
for this benefit…or you can take a vitamin!!
Disease/Cause
Cause and Effect relationship between the
environment and the expression of genetic traits
Diabetes &
Diet/Exercise
■Linked to diet and exercise
■It is possible to delay or prevent type 2 diabetes by
exercising and losing weight
Heart Disease
&
Diet/Exercise
■Different genes respond differently to changes in
diet and health choices
■So far, 40 or more genes have been identified that
are linked to cardiovascular health
Carriers
 What is a carrier?
 A person or organism that has inherited a genetic
trait or mutation, but does NOT have the genetic
disorder.
 They have only 1 copy of the ‘bad’ gene.
 They can pass the trait to their offspring.
Autosomal Genetic Disorders
 Occur when the gene defect is on one of the
first 22 pairs of chromosomes. –
THE AUTOSOMES
1. Huntington’s Disease
~Autosomal Dominant Gene
You only
need 1 copy
of the bad
gene!
~Breaks down certain areas
of the brain
~Symptoms begin mid to late 40’s
http://www.yo
utube.com/wa
tch?v=4HgFU
vVyHYQ
Sickle Cell Anemia
 2. Sickle Cell Anemia:
 Codominant autosomal gene
http://www.youtube.com/
watch?v=R4-c3hUhhyc
http://www.youtube.com/
watch?v=2CsgXHdWqVs
 Leads to misshapen red blood cells, which lead to
poor circulation and pain.
 Heterozygous (carrier) individuals are NOT
afflicted with sickle cell and they are resistant to
malaria
Cystic Fibrosis
 3. Cystic Fibrosis
http://www.youtub
e.com/watch?v=FM
AOEOmLoUE
 Recessive autosomal gene – must have TWO
copies of bad gene
 Leads to mucus build up in lungs and digestive
tract which may be fatal
Tay-Sach’s
 4. Tay-Sach’s
http://www.youtu
be.com/watch?v=
SeoPF74QSms
 Recessive autosomal gene
 Degenerates (breaks down) the central nervous
system, leading to premature death
PKU
 5. PKU (Phenylketonuria)
http://www.youtube.com/
watch?v=1_lSwuidmQg
 Recessive autosomal gene
 Leads to the inability to break down the amino acid
phenylalanine when ingested
 The phenylalanine builds up in the brain and leads to
decreased mental function
 If detected early, it can be controlled by diet
 Individuals with PKU cannot eat foods/drinks with
phenylalanine (breads, dairy, proteins, etc.)
Practice EOC Questions
 One of the parents of a child has PKU, which is caused
by recessive alleles. The other parent does not have the
PKU alleles. What is the chance that the couple will
have a child with phenylketonuria?
 0%
 50%
 75%
 100%
Practice EOC Questions
 Which cross would be represented as Aa x aa, where (A)
is a dominant allele and (a) is a recessive allele?
Cross
1
Parental Feather Colors Offspring Feather Colors
White x White
100% White
2
White x White
75% White, 25% Dark
3
White x Dark
50% White, 50% Dark
4
Dark x Dark
100% Dark
Practice EOC Questions
 If Jeanette is a carrier for sickle cell and has a baby with
Juan, who is also a carrier, what is the probability that
their child will be born with sickle cell
anemia?___________________
 What is the probability that their child will be a carrier?
___________________
http://www.edheads.org
/activities/dna/swf/index
.html
Practice EOC Questions
 Huntington’s disease is a dominant trait. What are the
chances that a child will develop Huntington’s disease if
both parents are heterozygous for the trait?
 A. 0 out of 4
 B. 1 out of 4
 C. 2 out of 4
 D. 3 out of 4
http://www.youtube.com/
watch?v=_IOIx__UJ5g
Practice EOC Questions
 Himalayan rabbits carry the C gene, which is required
for the development of pigments in the fur, skin, and
eyes. The C gene is maximally active from 15°C to 25°C
and inactive above 35°C . This gene expression produces
rabbits with a distinctive coat coloring. Why do the
Himalayan rabbits exhibit different colors of fur?
 A. The environment determines whether the gene
for fur pigmentation is expressed.
 B. The genetic makeup of the rabbits change.
 C. The rabbit’s color changed in order to attract a
mate.
 D. The rabbit’s cells undergo mitosis.