Download Genetics ppt

1
How did the
study of
Genetics
begin?
Clip
Genetics
is the branch
of biology that deals with
heredity. A great deal of
what we know about
genetics began with the
work of a monk named
Gregor Mendel, who
experimented with sweet
pea plants in the 1800s.
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 Mendel
studied
the patterns of
inheritance in
pea plants.
 He chose seven
traits to follow.
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

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Mendel needed to
make sure he had
plants that always
gave the same
offspring-called true
breeding.
He “self-pollinated”
plants until he got
seeds that always
gave the same
offspring.
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


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He took a purple
flower plant and
crossed it with a
white flower plant?
He called these the
parent generation
(P generation)
What do you think
the offspring
looked like?
Pollen
X
F1
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POLLEN
F2
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2. Something is being passed from
parent to offspring. He called these
“Factors”
3. Sometimes you can see “it” and
sometimes you can’t see “it”.
4. If you can see it- it is dominant.
1. If it’s there and you can’t see itit’s recessive.
5. There are two versions of these
“FACTORS”.
6. To show the two version we use a
capital letter for the dominant (S)
version of the trait and a lower
case for the recessive version (s)
of the trait.
ADD TO NOTES: Each Version is
called an Allele.
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Each chromosome has many genes, but
the alleles may be different
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Alleles are different versions of the same gene.
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Common Physical Human TraitsDifferent Alleles
Trait
Dominant
Recessive
Chin cleft
Absent (C)
Present (c)
Dimples
Present (D)
Absent (d)
Free (F)
Attached (f)
Almond (A)
Round (a)
Straight (S)
Upward slant
(s)
Eyebrow
position
Connected (Y)
Not connected
(y)
Eyebrow
shape
Bushy (B)
Fine (b)
Long (L)
Short (l)
Round (R)
Square (r)
Present (P)
Absent (p)
Curly (H)
Straight (h)
Tongue rolling
Can roll (T)
Can't roll (t)
Widow's peak
Present (W)
Absent (w)
Earlobe shape
Eye shape
Eye position
Eyelash length
Face shape
Freckles
Hair
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Activity
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We have two
copies of all
of our
chromosomes
Why?
These are
called
Homologous
Chromosomes
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Karyotype
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DNA codes for Proteins
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


A segment on the chromosome that
codes for a protein.
People have two copies of each gene, one
copy inherited from the mother and the
other copy inherited from the father.
There are many versions of each genealleles
Remember:
Genes come in pairs.
**One from your mother
**One from your father.
If the two alleles in
the pair are
identical, then the
condition called
homozygous. The
term “purebred”
is sometimes
used.
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
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If the 2 alleles are
different, the
condition is called
heterozygous.
The term “hybrid” is
sometimes used to
refer to
heterozygous.
What the genes/alleles
are …RR.…Rr
What the
organism looks
like……
Red…..White
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Predicting possible
outcomes of a genetic
cross.
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How did you
end up with
the traits
and genes
that you
got?
During
meiosis, each
egg or sperm
only gets one
copy of each
chromosome.
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Meiosis
Review
Animation
Geneticist use punnett squares to
determine the probability of a
combination of alleles.
 For example: If a heterozygous
black rabbit is crossed with a
heterozygous black rabbit, what
are the chances the offspring
will be black?

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•Geneticist use punnett squares to determine the
probability of a combination of alleles.
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Genotype
Phenotype
B=Black
b= Brown
Genotypes?
Phenotypes?
•Example: If a
heterozygous
black rabbit is
crossed with a
heterozygous
black rabbit,
what are the
chances the
offspring will
be black?
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Claymation Clip
 Genetic
Activity …..page 6
In humans, a widow’s peak is dominant over a
continuous hairline. Mary’s father has a
widow’s peak, but Mary and her mother
have a continuous hairline. What is the
genotype of Mary’s father?
A HH
B Hh
C hh
D cannot be determined
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Mendel’s
Laws
States that
the dominant
allele will
prevent the
recessive allele
from being
expressed.
•The recessive allele will appear when
it is paired with another recessive
allele in the offspring.

•Remember: Genes Come in Pairs!
Law of Segregation
(separation) states that
gene pairs separate
when gametes (sex
cells) are formed
•Each gamete has only
one allele of each
gene pair. (haploid)
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gene pairs separate
Goes
through
Meiosis
Mendel’s
Laws
A a
b B
S Phase
AA
aa
bb
BB
Makes
a copy
A
A
a
a
b
b
B
B
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Law of
Independent
Assortment
states that
different
pairs of
genes
separate
independentl
y of each
other when
gametes
are formed.
Mendel’s
Laws
Example:
Just because you get the gene for
brown hair does not mean you will
get the gene for blue eyes.
Animation
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1.
2.
3.
4.
5.
A trait is a characteristic an individual
receives from its parents.
Genes carry the instructions responsible for
the expression of traits.
A pair of inherited genes controls a trait.
One member of the pair comes from each
parent.
Alternative versions of genes are known as
alleles.

1.
2.
3.
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Inherited traits are transmitted by genes which occur
in alternate forms called alleles
Principle of Dominance - when 2 forms of the same
gene are present the dominant allele is expressed
Principle of Segregation - in meiosis two alleles
separate so that each gamete receives only one form
of the gene
Principle of Independent Assortment - each trait is
inherited independent of other traits (chance)
Peas in a pod- Genetics Clip
Earlobe shape is a human trait. Some people have
free earlobes while others have attached
earlobes. Two parents with free earlobes have
four children. Three children have free
earlobes and one child has attached earlobes.
If these parents have another child, what is
the probability that the child will have
attached earlobes?
A 25%
B 50%
C 75%
D 100%
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With codominance, a cross between
organisms with two different
phenotypes produces offspring
with a third phenotype in which
both of the parental traits appear
together.
DO NOT blend together.
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

Both phenotypes
are expressed at
the same time.
Example: Blood
Types
Genotype
IOIO
Phenotype
Type O
IAIO
IAIA
I BI O
I BI B
Type A
Type A
Type B
Type B
IAIB
Type AB
There are 3 alleles
for blood typemultiple alleles
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Many traits are
controlled by
more than
one gene.
Ex: Skin Color
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Traits associated with
particular sexes are called
sex-linked or X-linked traits.
Examples of
Sex-linked
Traits:
•Red-green
colorblindness
•Hemophilia
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

Occurs when particular alleles are inherited
jointly.
They tend to be inherited together, for
example, red hair and freckles.
1st 22 are Autosomes, the last pair
(XY) are sex chromosomes)
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Pedigree
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




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How many boys? __________________
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How many Girls? __________________
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How many generations? _______________
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How many with the disorder? ____________
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How many marriages are shown? ____________
1.
How many
generations?
2. How many
carriers?
3. How many
affected
males?
4. How many
affected
females?
5. Autosomal or
sex-linked?
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Autosomal-Dominant
What can you tell by the pedigree?
Dominant or recessive?
Autosomal or sex-linked?
SEX-LINKED
What can you tell by the pedigree?
Dominant or recessive?
Autosomal or sex-linked?
SEX-LINKED
What can you tell by the pedigree?
Dominant or recessive?
Autosomal or sex-linked?
Autosomal
Dominant or recessive?
-Dominant
Autosomal or sex-linked?
NO
carriers
when
Dominant.
Autosomal
-Recessive
Carriers
when
recessive.

Pedigree Practice-Smart board
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



Progressive,
degenerative disease
that causes certain
nerve cells in your brain
to waste away.
Experience
uncontrolled
movements, emotional
disturbances and
mental deterioration.
No cure. Fatal. ages:3060
Dominant Allele
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


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Sex-linked trait
Gene for color vision
located on the X
chromosomes.
Males are more
likely to have
colorblindness
because they have
only one X
chromosome
The individual with normal color vision will see a 5
revealed in the dot pattern. An individual with
Red/Green (the most common) color blindness
will
see
a
2
revealed
in
the
dots.
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3
copies of chromosome #21.
• Sister chromatid DO
NOT separate
during Meiosis.
• (or homologues fail to separate )
• Nondisjunction
• Also called:
Trisomy 21
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• Sister chromatid DO NOT separate during
Meiosis.
• Or homologues fail to separate during Meiosis.
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Cystic Fibrosis




CF is caused by a
recessive allele on
chromosome #7.
More than 1,000
different mutations
in the CFTR gene
have been identified
Deletion of 3 bases.
Affects the body's
respiratory and
digestive systems.
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Cystic Fibrosis

1 in 29 Caucasian Americans
have the allele.



Asian & African-less likely to have.
More than 10 million Americans carry the
cystic fibrosis gene
Treatments:
Pancreatic enzyme replacement
therapy to allow proper food
digestion
 Bronchodilators (also used by
people with asthma) that help
keep the airways open
 Inhaled antibiotics to kill the
bacteria that cause lung
infections
 Chest physical therapy, in which
the patient is repeatedly clapped
on the back to free up mucous in
the chest

Gene therapy ?????? Currently in
clinical trials
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People who carry the tendency
to have sickle cell anemia are
less likely to die from malaria.
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Mis-shaped
blood cells.
Mis-shaped
blood cells.
•Most
commonly
affects
AfricanAmericans.
•About 1 out of
every 500
AfricanAmerican
babies born in
the United
States has
sickle cell
anemia.
Interesting
fact:
Unlike
normal red
blood cells,
which can
live for 120
days,
sickleshaped cells
live only 10
to 20 days.
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
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

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Progressively destroys nerve cells (neurons) in the
brain and spinal cord.
Harmful quantities of a fatty acids accumulate in
the nerve cells of the brain.
Caused by insufficient activity of an enzyme
called beta-hexosaminidase A that catalyzes the
biodegradation of acidic fatty materials
More common in people of Ashkenazi (eastern and
central European) Jewish heritage
Fatal
Gene Therapy
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What is nondisjunction?
A. failure of chromosomes to separate during
meiosis
B. failure of the cytoplasm to divide properly
C. the insertion of a gene into a different
chromosome
D. the deletion of a gene from a chromosome
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Which of the following shows how
information is transformed to make a
protein?
A DNA RNA  protein
B gene  chromosome protein
C cell respiration  ATP  protein
D ATP  amino acid  protein
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Information on mRNA is used to make a
sequence of amino acids into a protein by
which of the following processes?
A replication
B translation
C transcription
D transference
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Pea plants have seeds
that are either round or
wrinkled. In this cross,
what will be the
phenotypic ratio of the
offspring?
A
B
C
D
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50% RR and 50% Rr
25% RR, 50% Rr, and 25% rr
50% round seeds and 50% wrinkled seeds
100% round seeds
What is a source of
genetic variation?
A mutation
B adaptation
C replication
D transcription
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In Mendel’s experiments with
a single trait, the trait that
disappeared in the first
generation
and reappeared in the next
generation is called the
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A homozygous trait
B dominant trait
C recessive trait
D heterozygous trait
What
pattern
of
inherita
nce is
this?
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What
would one
gene say to
another?
Cloning