Chromosomes & DNA:
 In the human species (homo sapiens), there are 46 chromosomes, or
23 pairs of chromosomes. The last pair, pair 23, is the pair that
determines your sex, male (xy) or female (xx).
 Chromosomes are made up of DNA (Deoxyribonucleic Acid), which
is referred to as a double-helix ladder because it is shaped like a
twisted ladder (staircase).
 Your DNA is your unique blueprint for life and is what makes you,
YOU!
 Chromosomes contain  genes, which contain  a series of
nitrogen bases.
 The 4 nitrogen bases are also called, nucleotides, and consist of:
 Adenine = A
 Thymine = T
*Bases A & T always pair together.
(A & T University)
 Guanine = G
 Cytosine = C
*Bases G & C always pair together.
(Guilford College)
*These are the “rungs” on the ladder*
 D = Deoxyribose
 P = Phosphates
 A single gene can have several hundred or thousand bases.
 A gene is a code for a particular trait, such as eye color or dimples
(Your genetic code).
 The order of genes codes for proteins.
 Proteins determine the size, shape, and color of many traits.
 Proteins are made of amino acids (different chemicals
linked together).
 3 nitrogen bases (nucleotides) code for 1 amino acid (ATA or
TTA).
 3 nitrogen bases  1 amino acid  proteins = GENE