Download Document

II. Human Heredity
The family of the future
A. Sex Chromosomes vs. Autosomes
1) Sex Chromosomes: determine a person’s gender.
*Female = XX
*Male = XY
2) Autosomes: All 44 other chromosomes (not sex chromosomes).
3) During reproduction, there is a 50/50 chance of getting a boy or girl.
a) A gamete carries 22 autosomes and one sex chromosome.
* Egg cells carry only X chromosomes
* Sperm may carry either X or Y chromosomes
X
X
X
XX
XX
Y
XY
XY
XX
B. Sex Linked Genes
1. Some genes that carry genetic traits/diseases are
found on the X chromosome (usually recessive)
ex. Colorblindness
2. Females can be Carriers of the recessive allele:
Heterozygous for the trait -they don’t have the
disorder, but can pass the recessive allele onto
offspring
3. Males have only one X chromosome, so they are more
likely than females to have a sex-linked disorder.
ex. Hemophilia
XHXH = Normal Female
XHY = Normal Male
XHXh
XhY = Male with
Hemophilia
= Carrier (Female)
XhXh = Female with Hemophilia
ex. Colorblindness
XCXC = Normal Female
XCY = Normal Male
XCXc = Carrier (Female)
XcY = Colorblind Male
XcXc = Colorblind Female
Red-Green Colorblindness
XcY x XCXc
Xc
Y
XC
XC Xc
XC Y
Xc
Xc Xc
Xc Y
50% chance of
having a colorblind
child
XCY x XcXc
XC
Y
Xc
XC Xc
Xc Y
Xc
XC Xc
Xc Y
50% chance of
having a colorblind
child
C. Pedigree Charts
1) Shows the phenotypes of a specific trait for family members over
several generations (genotypes may also be determined).
2) Used to generate a family genetic history that may be used to predict
the occurrences of certain traits (usually disorders).
3) Key:
= Female without trait
Horizontal lines = marriages / mating
= Female with trait
= Male without trait
= Male with trait
Vertical Lines = offspring
F2 generation
F1 generation
P generation
Fill in the genotypes of each individual in the pedigree
below. The chart shows the frequency of widows peak, a
dominant trait (allele: A, a).
Aa
?
aa
aa
Aa
aa
aa
Aa
Aa
AA or Aa
Aa
Aa
aa
4) Examples:
F2 generation
F1 generation
P generation
1. Attached Earlobes (recessive trait):
*alleles: A, a
aa
?
Aa
aa
Aa
Aa
aa
Aa
Aa
Aa
aa
Aa
?
?
?
4) Examples:
2. Colorblindness (sex-linked trait):
*allele: C
F2 generation
F1 generation
P generation
Carrier female
XY
XCX
XY
XY
XCY
XX
XX
XCX
XCY
XY
XCY
XCX
XX
XY
XY
D. Karyotype
1) a picture of an individual’s chromosomes used to
analyze them.
Check this out.
I could go for
a twinkie right
about now.
Nice.
Blood Groups and Blood Transfusions
•Blood grouping is due to the presence of certain protein molecules called antigens
and antibodies
Antigen: Located on the surface of red blood cell (RBC) membranes.
Types: A antigen and B antigen
Antibody: Located in the blood plasma – bind to antigens that are foreign to the body.
•Therefore, a person whose blood contains A antigen will not produce A antibody
but will produce B antibody
Agglutination: Occurs when antibodies bind to antigens causing cells to clump together.
* This is done so that white blood cells may engulf and destroy multiple foreign cells
at once.
* This may lead to clogged vessels and agglutinated cells may break, leaking toxic
hemoglobin into the body.
* This condition may be fatal.
Blood types include:
A
B
AB
O
Alleles for blood types include: IA , IB , i
• IA and IB alleles are codominant
• The i allele is recessive and therefore, a person must be homozygous (ii)
to express this blood type.
IA
IB
i
IB
i
IAIB
IB
IBIB
IAi
I Bi
IA
i
IAIB
IAi
IBi
ii
Phenotypes: AB, A, B
Genotypes:
Hybrid AB (codominant)
Hybrid A
Hybrid B
Homozygous B
Phenotypes: AB, A, B, O
Genotypes:
Hybrid AB (codominant)
Hybrid A
Hybrid B
Homozygous recessive O
Who’s Baby Is It???
A baby’s ID tag was lost!
Two sets of parents claim the baby.
Baby: type O
The Smiths
Mr. Smith: type AB
Mrs. Smith: type O
The Jones’
Mr. Jones: type A
Mrs. Jones: type B
The Rh Factor
•Rh is another antigen that may be present on the surface of red blood cells.
Rh positive
If it is present in a person’s blood, that person is said to be ____________.
Rh negative
If it is not present, the person is said to be _____________.
•Rh antibodies do not occur naturally in the plasma of a person with Rh- blood.
However, the antibodies may be produced if introduced to the Rh antigen
through transfusion.
•Transfusions:
OK
Rh- to Rh+ = ______________
Agglutination
Rh+ to Rh- = ______________
•Universal Donor: O•Universal Recipient: AB+
http://nobelprize.org/educational_games/medicine/landsteiner/
Phenotype
(blood type)
Genotype
Antibodies
in plasma
Anti-B
You’re
a
sissy.
I do not discriminate!
A
IAIA or IAi
Safe Transfusions
To
From
A, AB
A, O
B, AB
B, O
Me neither!
B
IBIB or IBi
AB
IAIB
None
AB
A, B, AB, O
ii
Anti-A
Anti-B
O
Anti-A
universal
donor
A, B, AB, O
universal
recipient
O
4) Examples:
F2 generation
F1 generation
P generation
1. Attached Earlobes (recessive trait):
*alleles: A, a
4) Examples:
F2 generation
F1 generation
P generation
2. Colorblindness (sex-linked trait):
*allele: C
Phenotype
(blood type)
A
B
AB
O
Genotype
Antibodies
in plasma
Safe Transfusions
To
From