The Nature of Heredity

 The study of heredity and the variation of inherited characteristics  HEREDITY: the passing of traits from parents to offspring

 Genetic information is contained in a molecule of DNA  The modern DNA model has 3 parts: 1. Composed of pentose sugar, a phosphate group and one of four nitrogenous bases (Levene, 1920) 2.The proportion of nitrogenous bases are equal. (Chargaff, 1940) 3.DNA has a helix shape (Franklin, 1951)

 The backbone of DNA is composed of phosphate group and pentose sugar.  The nitrogenous bases pair up: ◦ Thymine-Adenine ◦ Cytosine-Guanine

 COMPLEMENTARY BASE PAIRING: pairing of the nitrogenous base of one strand of DNA with the nitrogenous base of another strand  You only need to know the nucleotide sequence for one strand

 GENE: a segment of a DNA molecule that codes for a particular trait  Found at a specific location on a chromosome  LOCUS: the location of a gene on a chromosome  CHROMOSOME: carries information for hundreds or thousands of different genes

ASEXUALSEXUAL  The production of offspring from a single parent  The genetic makeup of the offspring is identical to that of the parent  The production of offspring from the fusion of two sex cells  The genetic makeup of the offspring is different from that of either parent

 There are 3 stages to the cell cycle: ◦ INTERPHSE ◦ MITOSIS ◦ CYTOKINESIS

 The period between cell divisions, where the cell grows, DNA replicates and the cell prepares for mitosis.

 There are three parts to interphase: ◦ G 1 (First Gap) Phase: the cell is growing and preparing for replication ◦ S (Synthesis) Phase: duplication of genetic material ◦ G 2 (Second Gap) Phase: cell begins final prep for cell division

 The chromosomes in the nucleus form a mass of thread like structures called CHROMATIN  The replication of chromosomes results in a pair of SISTER CHROMATIDS

 The process by which a cell divides the genetic material in its nucleus into two identical nuclei  Used for:  Growth  Reproduction  Repair

 There are four phases of mitosis:  PROPHASE  METAPHASE  ANAPHASE  TELOPHASE

 Chromosomes shorten and thicken  Centrioles move to opposite poles of the cell  Spindle fibres form  Nuclear membrane starts to dissolve

 Spindle fibres move to align the chromosomes  Chromosomes are lined up at the equator of the cell

 The chromosomes move to opposite poles of the cell  The chromosomes are pulled by their centromeres

 Chromosomes are at opposite poles and start to unwind  Spindle fibres start to dissolve  Nuclear membranes reform

 The process in which a cell divides its cytoplasm in to two new INDENTICAL daughter cells  The same number and type of chromosomes in each cell

 The process of producing one individual that is genetically identical to another using a single cell or tissue  EXAMPLES:  “Dolly” the sheep  Genetically Modified Organisms  Pharmaceutical products

 Cancer is occurs when cells divide uncontrollably  There are two kinds of cancer tumors:  BENIGN: the cancer cells are not capable of spreading  MALIGNANT: the cancer cells are capable of spreading