Transcript Human Inheritance

Human Inheritance
ABO Blood Groups and Genetic
Disorders
Slide #2
Important Vocabulary
1. Carrier: someone who is heterozygous for a trait
2. Multiple alleles: traits that have more than 2
possible alleles; still only inherit 2 alleles
3. Co-dominance: when two different alleles are
present and BOTH alleles are expressed.
4. Mutation: a change in an organism’s DNA;
changes how a gene functions
a. leads to 2 or more alleles for a given trait
Slide #3
Variations in Alleles
1. Variations in traits arise from mutations
2. Many mutations produce genes that don’t function
a. most of these mutations produce non-functioning
proteins
b. non functioning proteins can cause lethal genetic
defects
c. sometimes mutations produce proteins that have
different functions
Slide # 4
ABO Blood Groups
1. Multiple alleles
a. 3 different alleles; IA, IB, & i
b. 6 genotypes / 4 phenotypes
IA IA or IA i = Type A
IB IB or IB i = Type B
IA IB
= Type AB
ii
= Type O
2. IA and IB are co-dominant;
both are expressed if both
are present
Slide # 6
Guide to who can give and who can
receive in donating blood
Genetic Disorders are caused
by defective genes.
Defective genes arise from
mutations in DNA.
Slide # 7
Cystic Fibrosis
1. Mode of inheritance
a. recessive allele on
chromosome # 7
2. Symptoms:
a. thick mucus forms in
lungs & digestive tract
b. Affected people have
trouble breathing; contract
lung infections easily
c. Affected people live to be
about 30 years old
1 in 25 Caucasians in
US are carriers
1 in 2500 are affected
Slide # 8
Sickle-Cell Anemia
1. Mode of inheritance
a. recessive allele on
chromosome # 11
2. Symptoms
a. blood cells become
sickle shaped; don’t carry
oxygen
b. sickle shaped cells clog
blood vessels & cause
pain & swelling
c. Affected persons live to be
about 50
3. Carriers are resistant to
malaria
Normal
blood cells
live 120 days
Sickleshaped
blood cells
live 10-20
days
8 to 10% African
Americans are carriers
Slide # 9
Tay Sachs
1. Mode of Inheritance
a. recessive allele on
chromosome # 15
2. Symptoms
a. Fatty substance builds up
in nerve cells in brain
b. Gradual paralysis & loss of
nerve function
c. Affected children die by
age 4 or 5
3. Carriers resistant to
tuberculosis
11% of Jewish
population are carriers
Also common in
French-Canadians &
Cajuns
Slide # 10
PKU
1. Mode of Inheritance
a. recessive allele on
chromosome # 12
2. Symptoms
a. body does not break
down phenylalanine
b. high level of phenylalanine
interferes with nervous
system development; leads
to mental retardation
c. Easily treated by following
strict diet
d. all newborns tested for PKU
Foods farthest away
from the target must
be avoided.
Slide # 11
Huntington’s Disorder
1. Mode of inheritance
a. dominant allele on chromosome
#4
2. Symptoms
a. brain cells slowly break down;
causes jerking muscles, slurred
speech, difficulty swallowing,
loss of balance, reasoning &
memory loss, & eventually death
b. Symptoms usually begin at 3545 years of age
Sex-linked traits: Genes located
on the sex chromosomes.
Slide # 13
Important Vocabulary
1. Autosome: a regular body chromosome (# 1 - 22)
2. Sex chromosome: chromosome that determines
the sex of an individual; X & Y
a. XX = female
b. XY = male
c. The sex chromosomes are # 23
Slide # 14
Sex Linked Traits
1. Sex-linked trait: A trait that is determined by a
gene found on one of the sex chromosomes.
2. Occur more often in males because males only
receive one X chromosome (one copy of the
gene).
3. Fathers pass the X chromosome on to daughters
only.
4. Mothers pass an X chromosome on to sons and
daughters.
5. Females must receive 2 copies of the defective
gene to show the trait.
Slide # 15
Hemophilia
1. Mode of inheritance
a. recessive allele on X
chromosome
2. Main Symptom
a. blood fails to clot
properly
b. may bleed internally
– especially at the
knees and elbows
Hemophilia can be traced
through a pedigree of the
royal family.
Slide # 16
Color-blindness
1. Mode of Inheritance
a. recessive allele
on X chromosome
2. Symptoms
a. inability to distinguish
red and green colors
b. Normal life span