This document discusses human genetics and genetic disorders. It explains that genes located on chromosomes control human traits and can cause disorders if mutated or in an abnormal number. Some examples of genetic disorders mentioned are cystic fibrosis caused by a recessive gene mutation, sickle cell anemia caused by a codominant allele, and Down syndrome caused by an extra 21st chromosome. Pedigrees and karyotypes are tools that can be used to study genetics and identify genetic disorders in families.

1. Human Inheritance and Genetic Disorders
Polydactyly Progeria
Hypertrichosis
Hemophelia Down Syndrome Sickle Cell Anaemia

2. 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?

3. 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.
Allelles 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.

4. 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.

5. 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.

6. Sex Chromosomes
The 'Y' chromosome (male) is much smaller than 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.

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

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

9. 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.

10. 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!

11. 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.

12. 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.

13. 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

14. 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.

15. 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.

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

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

18. 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
counseling where a doctor looks at both parents karyotypes to
see if any disorders will pass to offspring.