Transcript 4. HONORS 2013 Human Genetics - Pedigree Charts, X

1. Write the possible
gametes in the following
parent: AaBbCc (notice:
one allele per gamete for
each genes: ABC, Abc,
…)
2. Repeat your answer
considering the position
of the genes on the
chromosomes:
Assort Independently:
A and C; B and C
Do NOT assort Independently:
A and B - they are on the same
chromosome.
This will affect the
ratios between the
phenotypes in F2
generation…
John
Isabelle
Sandy
Liz
Lucy
Dan
Joshua
Sue
Luke
Phil
marriage
What is the relationship between:
Dan-Sue; Luke-Joshua; Phil-Isabelle;
children
Liz-Dan; Joshua-Sandy?
John
Isabelle
Sandy
Liz
Lucy
Dan
Joshua
Sue
Luke
Phil
unaffected
affected
carriers
Copy the pedigree.
Is the disorder carried by a
dominant or recessive allele?
Explain your answer, add
(Question 5)
genotypes
Copy the pedigree.
Is the disorder carried by a
dominant or recessive allele?
Explain your answer.
Answer: The disorder is
Recessive, since it ‘skipped a
generation’. ‘Normal’ parents
must be heterozygous carriers.
Autosomal Vs. Sex-linked Disorders:
Sex-linked disorder = Gene is on a
sex chromosome (mostly on the X)
Autosomal disorder = Gene is
on any of the other 1-22
chromosomes.
Dominant vs. Recessive Disorders:
Dominant disorder = carried by
the dominant allele.
Recessive disorder = carried by
the recessive allele.
Women are XX, men are Xy
Several Genetic disorders are
inherited in genes that are
located on the X chromosome.
Predict: Who do you expect
will show these disorders
more often, females or males?
Explain.
Sex-linked
Inheritance
Definition:
Sex-linked genes are located on
the sex chromosomes, usually
on the X chromosome.
So, why is this important?
Dystrophin
(Duchenne MS)
Clotting Factor
(Hemophilia A)
Color Receptor
(Red/Green)
“Royal” Disease - Hemophilia
Adiel (1986-1999)
46XX
46XY
Female
Male
A recessive X-linked disorder has
a better chance to show in males.
Example: Color Blindness.
C = normal c = colorblind
x
C
c
C
Cross: 1) X X x X Y
x
C
C
c
2) X X x X Y
1)
c
X
C
c
X X
x
C
X Y
C
X
Y
C
c
X X
c
XY
x
XC XC XC X C Y
Daughters: 0% color-blind
Sons: 50% chance to be color-blin
2)
C
X
C
C
X X
x
c
XY
C
X
Y
C
c
X X
C
X Y
x
XC XC Xc X C Y
Daughters: 100% To be a carrier
Sons: 0% chance to be color-blind
In Conclusion:
1) X-linked Disorders are more
common amongst males.
Reason:_________________
2) Can a colorblind man pass the
disorder to his son?
Answer:___________________
http://www.kcl.ac.uk/teares/gktvc/
vc/lt/colourblindness/plate1.htm
About Sickle Cell Anemia
•Caused by a mutation in the
gene for Hemoglobin, which
delivers oxygen in the blood.
•Symbols:
A
H = Normal hemoglobin.
HS = Mutated hemoglobin.
- The same symbols are used for
the corresponding alleles.
Red
Blood
Cells
Sickled
Normal
Why does this happen?
Normal (with
Mutated (with
Valine)
Glutamic Acid)
Traffic
Jams by
sickled
cells
Add punnet square for sickle
cell with HA and HS, and with
corresponding phenotypes.
Abundance of the S Allele in Malariainfested regions.
Normal and Sickle
hemoglobin proteins
migrate differently in a
gel: normal is more
negative.
What kind of
hemoglobins are for
each persons 1, 2 and
3?
(Alleles: H is normal
and Hs is sickled)
A rare unknown disorder causing
deafness was found to be common in
one family.
In a genetic test of this
family, the mutated and
normal proteins were
1.
analyzed.
Is the disease recessive
or dominant? Explain.
affected
not affected
2. 3.
4.
Some disorders we learned
about are very harmful, even
deadly.
Why, then, do they still exist in
the population?