1. MENDELIAN GENETICS
AND HUMANS

2. MENDELIAN GENETICS AND HUMANS
Human Traits
Mid-digital hair – dominant
Tongue rolling – dominant
Widow's peak – dominant
Earlobes – dominant
Hitchhiker's thumb less than 45° - dominant
Relative finger length
An interesting sex influenced (not sex-linked) trait relates to the relative lengths of the
index and ring finger. In males, the allele for a short index finger (S) is dominant. In
females, it is recessive. In rare cases each hand may be different. If one or both index
fingers are greater than or equal to the length of the ring finger, the recessive genotype
is present in males and the dominant present in females.

3. MENDELIAN GENETICS AND HUMANS
Human Blood Groups
Let the allele for blood type be represented by “I”
IA = Type A (dominant)
codominant
IB = Type B (dominant)
i
= Type O (recessive)

4. MENDELIAN GENETICS AND HUMANS
Human Blood Groups
IA = Type A (dominant)
IB = Type B (dominant)
i
= Type O (recessive)
Blood Types
Genotype Antigen (phenotype) Antibody
A
IAi or IAIA
Type A
Anti-B
B
IBi or IBIB
Type B
Anti-A
AB
IAIB
Type AB
None
O
ii
Type O
Anti A, Anti B

5. MENDELIAN GENETICS AND HUMANS
Human Blood Groups
What are the genotype and phenotype ratios of the offspring
between a Type AB male and Type O female?
Parent genotypes: IAIB x ii
IA
i
i
IB
I Ai
I Bi
I Ai
I Bi
Therefore:
F1 genotypes
1 IAi : 1IBi
F1 phenotypes
1 Type A : 1 Type B

6. MENDELIAN GENETICS AND HUMANS
Human Blood Groups
Is it possible for a Type A father and a Type B mother to
produce Type O children?
Let’s assume the parents are
homozygous IAIA and IBIB
Parent genotypes: IAIA x IBIB
Parent gametes: IA IA x IB IB
IA
IA
IB
I AI B
I AI B
F1 genotypes
100% IAIB
IB
I AI B
I AI B
F1 phenotypes
100% Type AB blood
Therefore:
None of the children have O-type blood.
So let’s assume the parents are both heterozygous

7. MENDELIAN GENETICS AND HUMANS
Human Blood Groups
Is it possible for a Type A father and a Type B mother to
produce Type O children?
Let’s assume the parents are
heterozygous IAi and IBi
Parent genotypes: IAi x IBi
Parent gametes: IA i x IB i
IA
i
IB
I AI B
I Bi
i
I Ai
ii
Therefore:
F1 genotypes
25% IAIB
25% IBi
25% IAi
25% ii
F1 phenotypes
25% Type A, 25% Type B, 25%
Type AB, and 25% Type O
So it IS possible!!!

8. MENDELIAN GENETICS AND HUMANS
Inheritance Patterns
Autosomal recessive:
Involves a recessive allele on
a non-sex chromosome
Autosomal dominant:
Involves a dominant allele
on a non-sex chromosome
X-linked recessive:
Involves a recessive allele on
the X-chromosome
X-linked dominant:
Involves a dominant allele
on the X-chromosome
Y-linked: Involves an allele
on the Y-chromosome

9. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Progeria
Inheritance Pattern:
-Autosomal dominant
Physical Effects:
-Premature aging,
prematurely old
-Few exceed 13 years old
-90% die from complications
from atherosclerosis
How does an autosomal
dominant allele not affect
the parent?
Allele appears from mutation in
gamete

10. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Huntington disease
Inheritance Pattern:
-Autosomal dominant
Physical Effects:
-Progressive brain disorder
causing uncontrolled
movements and loss of
cognition
-May live for 15-20 years after
onset of symptoms
-Trouble eating, swallowing,
talking, etc.

11. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Tay Sachs Disease
Inheritance Pattern:
-Autosomal recessive
Physical Effects:
-Nerve cells destroyed in brain
and spinal cord
-Symptoms appear 3-6 months
after birth
-Loss of motor control and
atrophy of muscles, seizures
-Death

12. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Phenylketonuria (PKU)
Inheritance Pattern:
-Autosomal recessive
Physical Effects:
-Permanent intellectual
disability, seizures
-Symptoms appear a few
months after birth
-May have a “musty” odour

13. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Albinism
Inheritance Pattern:
-Autosomal recessive
Physical Effects:
-Lack of melanin in skin, hair,
and/or eyes
-May have vision problems
-Sensitivity to UV light

14. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Familial
hypercholesterolemia
(FH)
Inheritance Pattern:
-Autosomal dominant
Physical Effects:
-Very high levels of cholesterol
in blood
-Buildup of excess cholesterol
in various bodily tissues
-High risk of atherosclerosis

15. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Sickle cell anemia
Inheritance Pattern:
-Autosomal recessive
Physical Effects:
-Shortness of breath, fatigue,
delayed growth and
development in children
-May experience painful
episodes of anemia resulting in
organ damage

16. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Hemophilia A
Inheritance Pattern:
-X-linked recessive
Physical Effects:
-Excessive bleeding from minor
cuts
-Extensive bruises

17. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Colour blindness
Inheritance Pattern:
-X-linked recessive (red-green
and blue colour defects)
-Autosomal recessive (blueyellow)
Physical Effects:
-Inability to perceive various
colours

18. MENDELIAN GENETICS AND HUMANS
Human genetic disorders
Duchenne muscular
dystrophy
Inheritance Pattern:
-X-linked recessive
Physical Effects:
-Muscle weakness, delayed
motor development in children
-Wheelchair dependence by
adolescence
-Enlargement and weakening
of the heart