This document discusses human genetics and genetic disorders. It covers inheritance and human variation, including dominant and recessive traits. Quantitative traits like skin and eye color are influenced by both genetic and environmental factors. The document also discusses genetic diagnosis through amniocentesis and common genetic disorders such as autosomal dominant, autosomal recessive, and those linked to the X chromosome like color blindness and hemophilia. Pedigree charts are presented as a way to track inheritance of genetic traits across generations.

1. UNIT 6: HUMAN GENETICS

2. INDEX
1. Inheritanceand HumanVariation
2. Diagnosis of GeneticDiseases
3. HumanGenetic Disorders

3. 1. Inheritance and Human
Variation
The
characteristics
of the
individuals
depend on two
factors:
Genetic traits
Genotype
Inherited
Environmental
factors (food,
lifestyle habits…)
Phenotype
Usually not
transmissible

4. Types of traits
Quantitative
Skin colour
Eyes colour (they
have a range of
possible
expressions)
Qualitative Examples of quantitative traits: skin and eyes colour

5. Qualitative traits in human
beings
Dominant
allele
Recessive
allele
Curly hair Straight hair
Ability to roll
the tongue
Inability to roll
the tongue
Thick lips Thin lips
Long eyelash Short eyelash
Detached
earlobes
Attached
earlobes
Blood group A
and B
Blood group 0
Blood group
Rh+
Blood group
Rh-
Straight and curly hair

6. The ABO system establishes four blood groups (A, B, AB and O) according
to the presence or absence of certain proteins, called A and B, in the
membrane of the red blood cells.
Antibodies react against specific antigens destroying them.

7. Phenotypes Group A Group B Group AB Group 0
Genotypes AA BB AB 00
A0 B0
Alleles A and B are codominant.
Alleles A and B are dominant over allele 0, whichis recessive

8. Rh System
Rhesus factor is another antigen which can be present (Rh+) or not (Rh-) in
the red blood cells.
Rh+ is dominant
Rh- is recessiv
http://www.nobelprize.org/educational/medicine/bloodtypinggame/gamev2/index.html
Page 109 activity 3, 4, 5, 9
Phenotypes Rh+ Rh-
Genotypes Rh+Rh+ Rh-Rh-
Rh+Rh-
Erytroblastosis fetalis: http://education-portal.com/academy/lesson/rh-blood-
group-rh-factor-erythoblasotis-fetalis.html
AB- group
Test tubes containing the corresponding antibody
The blood typing game

9. A double homozigous 0+ woman decides to have a baby with a A- man, whose father was 0-.
What is the probability to obtain an A- baby?
00Rh+Rh+ x A0Rh-Rh-
From the father
ARh- 0Rh-
0Rh+ A0Rh+Rh- 00Rh+Rh-
Sol.: 0% (none of the babies will be Rh negative)

10. 2. Diagnosis of Genetic Diseases
Amniocentesis
Foetus cells from the amniotic fluid are extracted with a needle. The DNA is
analysed and possible chromosom or metabolic disorders are detected

11. Recommendation for
amniocentesis
Couples already with
a child with a
chromosome
anomaly
Parents’ family with
genetic disease
Pregnant women
over 35 years old

12. 3. Human Genetic Disorders
Autosomal dominant (A)
Autosomal recessiv (a)
Linked to the X chromosome
Daltonism, haemophilia

13. 4. Some examples of Pedigree Charts

14. • At least 3 generations
• Phenotype coloured
• Indicate genotypes
• Indicate type of allele
• Include cousins
Autosomal dominant