All my best wishes for you with a successful academic year!

1. Chapter 4 Modern Genetics
Section 1
Human Inheritance
By
Mr Hamdy Karim

2. Human Inheritance and Genetic Disorders
Polydactyly
Down SyndromeHemophelia
Progeria
Hypertrichosis
Sickle Cell Anaemia

3. Warm-up:
Below is an actual photo of a person's full set of chromosomes. Use
the picture below to answer the following questions in your notebook:
●How many chromosomes does each human have?
●How any chromosomes does the person below have?
●What might have caused this extra chromosome? (Hint: It happens during meiosis)
●How do you predict this might affect the person?

4. Human Inheritance
Review:
●Every living thing (organism) is controlled by it's DNA, which is
tightly bound in strands called chromosomes inside the nucleus
of each cell.
●Each individual trait (characteristic) of an organism is controlled by
a gene which is a part of a chromosome.
●Each gene is controlled by two allelles; one from mother, one from
father.
●Alleles are patterns of DNA that tell the body how to make certain
amino acids which form proteins.
●Proteins control how an organism looks and functions.

5. Human Inheritance
●Some traits are controlled by just one gene, two alleles.
A widow's peak for example.
●Multiple alleles are three or four forms of a gene that code
for a single trait. Our blood type is an example:
●Still other traits are controlled by multiple genes. Skin type,
eye color, hair color and many others are controlled by
multiple genes.

6. Sex Chromosomes
●Sex Chromosomes are 1 pair of the 23 pairs of chromosomes in
the body.
●Sex Chromosomes carry the genes that makes a person male
or female, but also carry genes which determine other traits.

7. Sex Chromosomes
●The 'Y' chromosome (male) is much smaller than the
'X' chromosome.
●Because the 'X' is bigger, it carries a lot more genetic information
than the 'Y'
●Sex-Linked Genes have alleles that pass from parent to child on
a sex chromosome.

8. Sex-Linked Genes
●A common sex-linked gene is colorblindness.

9. Is anyone unable to see the image in this circle?
If so, you have red-green colorblindness!
This is a sex-linked recessive trait.

10. Sex-Linked Genes
●This punnet square shows sex-linked genes for colorblindness.
●Only the X chromosome carries the gene, so if a male gets
a recessive Xc and a Y, he automatically has the disease.
●Females, however, can be carriers of the disorder with one
dominant XC and one recessive Xc, but only have the disorder if
she has both recessive: Xc Xc
●A carrier is a person who has one recessive and one dominant
allele for the trait.

11. Environment
●Environmental factors also determine how genes are expressed.
●A person can have genes to be really tall, but if they do not have
proper nutrition, they will not reach their optimal height.
●A person can even have genes which wire the brain to be good at
making music, but if they never try to play an instrument, they will
never know.
●This is why everyone should try everything at least once; you could
end up being really great at anything!

12. Genetic Disorders
●A Genetic Disorder is an abnormal condition that a person inherits
through their genes.
●Genetic disorders can be caused by either changes in the DNA,
or an extra, or a missing chromosome.

13. Types of Genetic Disorders
●Cystic Fibrosis is where the body produces abnormally thick mucus
in the lungs.
●It is caused by a recessive allele on one chromosome.
●The recessive allele is a mutation where strands of DNA are deleted.

14. Types of Genetic Disorders
●Sickle Cell Disease is where a person's blood cells are shaped
differently.
●The 'sickle' shape of blood causes it to clot in vessels and cause
blockage and carries less oxygen.
●The allele for the disease is codominant with the normal allele.
●A person with one recessive and one dominant allele will produce
half normal blood cells, half sickle.
●A person with two recessive alleles will produce only sickle cells.
Normal RBC Sickle-Cell RBC

15. Types of Genetic Disorders
●Hemophilia prevents blood clotting.
●It is a recessive sex-linked disorder, found on the X sex chromosome.
●It is dangerous because even small wounds can cause unnecessary
bleeding and even death through blood loss.

16. Types of Genetic Disorders
●Down Syndrome is a form of mental retardation and physical
abnormalities.
●It is caused by a duplicate 21st chromosome. Instead of two,
they have three 21st chromosomes.
●This occurs when the chromosomes fail to seperate during meiosis.

17. Pedigrees
●A Pedigree is a chart or “family tree” which maps genetic disorders
in a family.

18. Pedigrees
●Below is a sample of a pedigree from a family which carries
hemophilia.

19. Karyotypes
●A Karyotype is a picture of all the chromosomes in a cell.
●Modern scientists can take a blood sample from an unborn child to
an adult, create a karyotype by seperating chromosomes, and be able
to determine if any genetic disorders are present.
●A couple who wishes to have children can receive genetic counselling
where a doctor looks at both parents karyotypes to see if any
disorders will pass to offspring.