1. Human Heredity

2. Human Chromosomes
A karyotype is a picture of matching pairs of chromosomes.
Two of the 46 chromosomes are sex chromosomes
The other 44 chromosomes are called autosomes.
Females are XX, and males are XY

4. Human Traits
A pedigree is a chart that shows relationships within a family (family tree)
We can use a pedigree to trace genetic disorders through generations of families

6. Blood Group types
Rh blood group is determined by a single gene with 2 alleles
Rh stands for “rhesus monkey” the animal in which the factor was discovered
(Rh+) is dominant (DD,Dd)
(Rh-) is recessive (dd)
ABO blood group has 3 alleles
A,B, are codominant, O is recessive

8. Autosomal Disorders in Humans
Recessive disorders:
Albinism: lack of pigment
Cystic fibrosis: excess mucus (infections, early death)
Galactosemia: accumulation of sugar in tissues (mental retardation)
PKU: accumulation of phenylalanine in tissues (mental retardation)
Tay-sachs disease: lipid accumulation in brain cells( mental deficiency, early death)

12. Autosomal Disorders in Humans
Disorders caused by dominant alleles:
Achondroplasia (dwarfism)
Huntingtons disease: mental deterioration
Hypercholesterolemia: excess cholesterol
Disorders caused by codominant alleles:
Sickle cell anemia: sickle shaped red blood cells, causes damage to many tissues

16. Sex-linked Genes
A sex-linked gene is a gene located on the X or Y chromosome
A sex chromosome is one of 2 chromosomes that determine an individuals sex
Males have only one X chromosome.
All X-linked genes are expressed in males, even if they are recessive

17. Examples of Sex-linked Disorders
Colorblindness- recessive sex-linked disorder
(1 in 10 males affected) rarer in females
Hemophilia- recessive disorder that affect s the blood’s ability to clot (1 in 10,000 males)
Duchenne Muscular Dystrophy- a sex-linked disorder that results in the progressive weakening and loss of skeletal muscle (1 0f 3000 males)

20. Chromosomal Disorders
Disorders caused by abnormal separation of chromosomes during meiosis
Nondisjunction- the most common error in meiosis, chromosomes fail to separate, the word means “not coming apart”
If nondisjunction occurs abnormal numbers of chromosomes may find their way into gametes, and a disorder of chromosome numbers may occur

21. Examples of Nondisjunction
Down syndrome occurs when an individual is born with 3 copies of a chromosome
This is known as “trisomy” (3 bodies)
The most common form of trisomy involves 3 copies of chromosome 21
1 of 800 babies is born with Down syndrome

24. Sex chromosome disorders
Turners syndrome- Female only inherits one X chromosome ( women are usually unable to have children)
Klinefelters syndrome- males born with an extra X, usually prevents males from reproducing (nondisjunction is the cause)
Interesting fact: There have been no reported instances of babies being born without an X chromosome