Transcript Chapter 6 - Mr.P Biology B at EKFC

Please Turn in the Following
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Punnett Square Practice.
Monster Genetics.
Pedigree Practice (albino).
Pedigree Extra-Credit.
Sex-Linked Inheritance
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Sex-linked genes-genes located on the sex
chromosomes X and Y.
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Most sex-linked genes are on the X
chromosome.
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Recessive disorders on the X chromosome
affect males more than females because
females can be carriers without having the
disorder.
Colorblindness
XBXB - Normal female
XBXb - Normal (carrier) female
XbXb – Colorblind female
XBY - Normal male
XbY - Colorblind male
Alternative Inheritance
Incomplete Dominance
 Genetic
condition in which neither allele is
completely dominant or recessive
 Example:
Snapdragons that are RR are
red. Those that are rr are white. If they
are Rr, then they are pink.
Incomplete Dominance
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Example:
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Parent 1 is red and Parent 2 is white.
Write genotypic and phenotypic ratios for the offspring.
Phenotypic
R
r
r
R
Rr Rr
Rr Rr
0Red : 4Pink : 0White
Genotypic
0RR : 4Rr : 0rr
Alternative Inheritance
Codominance
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Condition in which both alleles of a gene are
expressed equally.
 Example: Chickens
FB - Black Feathers
FW - White Feathers
A chicken that is FB FB will have all black
feathers and a chicken that is FW FW have all
white. But, a chicken that is FB FW will have
black and white feathers.
Codominance
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Example:
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Parent 1 has black feathers and Parent has black and
white feathers.
What is the probability that these parents will have
offspring with all white feathers?
FB
FB
FB
FBFB FBFB
FW
FBFW FBFW
0% will have all white
feathers.
In the 1950’s, a young woman sued film
star/director Charlie Chaplin for parental
support of her illegitimate child. Charlie
Chaplins’s blood type was already on record
as type AB. The mother of the child had type A
and her son had type O blood.
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The judge ruled in favor of the mother and ordered
Charlie Chaplin to pay child support costs of the
child. Was the judge correct in his decision based
on blood typing evidence?
A man is in an awful car accident. She
needs to have a blood transfusion. The
doctors determine that her blood type is
O. Her son volunteers to donate. A new
doctor forgets to check his blood type
before going through with the
transfusion. It turns out that he is blood
type B.
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What will happen to his mother?
Alternative Inheritance
Multiple Alleles
A
gene with more than 2 possible alleles.
 Example: In humans, there are 3 alleles
for ABO Blood Type.
Multiple Alleles
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Example: ABO blood group
 Three alleles IA, IB, and i
 IA & IB are codominant, both dominant over i.
Blood
Group
Alleles
A
IA IA or IAi
B
IB IB or IBi
AB
IA IB
O
ii
What do these letters tell us?
 IA IA
or IAi code for the A antigens on
blood.
 IB IB
or Ibi code for the A antigens on
blood.
 IAIB codes
for both the A and B antigens on
blood.
 ii
doesn’t code for an antigen.
What is an antigen?
Antigens and Antibodies.
Practice Problem
 If
I am A, what antigen does my blood
have?
 What antibodies will I produce?
 Who can I receive blood from?
 Who can I donate to?
More Practice.
Blood Type Genotype(s Antigen
)
Present
A
B
AB
O
Antibody
Present
Receive
From
Donate To
More Practice.
Blood Type Genotype(s)
Donate To
A
IA IA or IAi
Antigen
Present
A
Antibody
Present
B
Receive
From
A and O
A and AB
B
IB IB or IBi
B
A
B and O
B and AB
AB
IA IB
A and B
None
AB
O
ii
None
A and B
A, B, AB,
O
O
A, B, AB,
O
Blood Type Example
 Parent
1 is heterozygous Type A. Parent
2 is homozygous Type B.
 What is the probability that they will have a
child with blood type B?
IA
i
50% for Type B child
IB
IA IB
IB i
IB
IA IB
IB i