· Chromosomes
A chromosome is a long, rod-shaped structure composed of DNA and proteins. The single DNA molecule contains many genes
·A gene is a region of DNA that controls hereditary characteristics
· 1 chromosome = 1 strand of DNA
o Chromosome numbers
· Each species has a specific number of chromosomes in each cell
(Except sex cells)
· Humans have 46 chromosomes
o Types of chromosomes
· Sex chromosomes
· Chromosomes that determine the sex of an organism
· In humans
o Normal Female- XX
o Normal Male- XY
§ Pair 23
· Autosomes
· All chromosomes in an organism that aren’t sex cells
§ Pairs 1-22
· Organisms receive one copy of each autosome from each parent
Pair of homologous chromosomes
Two copies are called homologous chromosomes

This is an example of a pedigree. The shaded areas are affected offspring. A pedigree is like a family tree.

Sister Chromatids

· Pedigree
· Used by genealogists
· Shows all possible phenotypes for an individual
· Genetic Disorders
o Mutations
· Can occur in an entire chromosome or a single nucleotide
· Fatal mutations
· Mutations that occur and the child will most likely die before birth.
· Single allele mutations
· Achondroplasia
· Cataracts
· Polydactyly
· Albinism
· Sickle cell anemia
· Multifactoral
· Hard to treat
· Hard to research
· Chromosomal Abnormality
· Pieces of the chromosome are either: deleted, duplicated, inserted, or translocated.
o Example: down syndrome.