Haploid Number (N): The number of kinds of chromosomes
Ploidy: The number of copies of each kind of chromosomes
• Haploid (1N): one copy of each kind of chromosome
• Diploid (2N): two copies of each kind of chromosome
• Polyploid : more than two copies of each kind of chromosome [eg. triploid (3N), tetraploid (4N) etc.]
Gene: A DNA sequence or sequences encoding a functional product
Mutations: A change in the DNA sequence of gene that differs from the most common, normal or wild-type. A mutation can alter an organism’s
phenotype if the change in the DNA sequence alters the protein sequence. Mutants in which gene function is completely lost are called: knock-
out mutants, null mutants or loss-of-function mutants
• G – First Gap
• S – DNA synthesis
Chromosomes are copied
• G2– Second Gap
Preparation for division
• M – Mitosis
• Chromosomes can be viewed using a microscope
• Chromosomes are easily visible during Metaphase
• Chromosomes are viewed in cells halted at metaphase At this stage, all chromosomes have been copied!!!!
• Genes are linearly arranged along chromosomes.When a chromosome is copied, the copy will contain the same alleles for each gene in the
• Heterozygous: adh,ADH Homozygous: adh,adh
Why Are the Tropics Warm and the Poles Cold?
• Areas of the world are warm if they receive a large amount of sunlight per unit area; they are cold if they receive a small amount of sunlight
per unit area.
• Earth’s shape dictates that regions at or near the equator receive more sunlight per unit area than regions that are closer to the poles
Why Are the Tropics Wet?
• Areas along the equator receive the most moisture; locations at about 30 degrees latitude north and south of the equator are among the driest
• A major cycle in global air circulation, called a Hadley cell, is responsible for this patternAir heated by the strong sunlight along the equator
expands and rises. Warm air can hold a great deal of moisture because warm water molecules tend to stay in vapor form instead of
condensing into droplets.