I. Genes
a. Definition
? Segments of DNA molecules
? A nucleotide sequence
b. Functions
? Control of hereditary traits
? Sequence coding for a polypeptide which maybe an enzyme, or a part of an enzyme, which in turn is responsible for a certain phenotype or trait.
c. The Human Karyotype
? Ordered arrangement of chromosomes arranged in homologous pairs
? The chromosome complement of a cell or organism characterized by the number, size and morphological features of each chromosome
II. Types of Human Genetic disorders
a. Human Chromosomal Abnormalities
1. Nondisjunction
? Occurs when homologous chromosomes fail to segregate during meiosis
? Produces gametes with three chromosome pairs (trisomy) or only one chromosome of a normal pair (monosomy)
? Involves any chromosomes, including the sex chromosomes
? Causes serious genetic disorders
Ex: Down's syndrome- trisomy 21
Edward's syndrome- trisomy 18
Patau syndrome- trisomy 13
2. Klinefelter's syndrome, XXY
? Results when an abnormal sperm, containing both X and Y-chromosomes, fertilizes a normal egg with one X-chromosome
? Can also result when an XX egg is fertilized by a Y sperm
? Offspring has genotype XXY
? Occurs in 1 in 1000 born males
? Ha ...