Review Sheet for Test 3 - Biology 1107                 Dr. Adams

Cell Division - Mitosis and Meiosis
Chromosomes (eukaryotic) composed of chromatin (DNA + protein); mature chromosomes
         (before cell division) have two chromatids, held together by a centromere
Karyotype - chromosomal make-up of cells: diploid (2 sets) and haploid (1 set) cells

MITOSIS (division of nucleus [genetic material]) and cytokinesis
Phases of cell division - Prophase, Metaphase, Anaphase, Telophase
what happens in each phase (see book and other handouts)
        Differences in mitosis between plants and animals (plants with no centrioles, synthesis of new 
             cell plate by vesicles from Golgi Apparatus; construction results in plasmodesmata)
        Single celled organisms can use this to reproduce asexually
    Cell Cycle - Cell division and interphase (G1, S [replication of DNA], G2)

MEIOSIS -- production of gametes (haploid cells) from diploid cells
     For meiosis (production of haploid gametes), requires two divisions:
         first division (diploid to haploid) is the reduction division
         second division (haploid to haploid) is like mitosis -- the equational division

    For both mitosis and meiosis, know centrioles, spindle fiber complex (microtubules),
         genes, homologous chromosomes, bivalents or tetrads, crossing over (during prophase I)

    Meiosis (gametogenesis) results in four functional sperm cells in males (human),but just one
         functional egg cell (and non-functional polar bodies) in females

(Alternation of generations - haploid and diploid parts of life cycle;gametophyte/sporophyte for plants)

Significance of sexual reproduction - production of variation; potential for natural selection
    Sources of variation:
        1.  Independent assortment of chromosomes in production of gametes
        2.  Crossing over
     3.  Recombination of chromosomes from two different individuals in formation of zygote

GENETICS -- perhaps most important to learn and be able to handle the terminology
Gregor Mendel (1860's) - Principles of Heredity

  1. Principle of Segregation
  2. Principle of Independent Assortment
  3. Principle of Dominance/Recessiveness

        Gene - specific base sequence at specific locus on a chromosomes; codes for a specific trait
- different possible base sequences for a gene (results in different expressions)
        Genotype/Phenotype (and their ratios)

Genetic Crosses: parental and filial (F1, F2, etc.) generations; Punnett Square
     CONCEPTS and potential genetics problems
Intermediate Inheritance: Incomplete dominance and Codominance     
    Multiple alleles for genes
Epistasis (masking) - gene interaction; modifier genes -- more than one gene influencing one trait
Polygenic Traits - additive effects of several genes at different loci on one trait (a continuation of
             the concept of epistasis)
    Pleiotropy - one gene influencing several traits
Environmental influences on phenotype
Linkage - genes on same chromosomes (do NOT assort independently)
     Mapping of genes on chromosomes (using frequency of crossing over)
Sex determination and sex linkage
     Autosomes and Sex chromosomes (X & Y); Holandric traits (on Y) and X-linked traits
     Homogrametic/Heterogametic sexes
Sex influenced an sex limited traits

Monhybrid, dihybrid, etc. crosses. I will demonstrate crosses involving dominance/recessiveness,
incomplete/codominance, epistasis, mapping, X-Linked traits.  I will also present a mathematical
method of determining ratios instead of using exclusively Punnett Squares to figure expected ratios.

DNA - the Genetic Material
    Discovery of DNA as the genetic material
         Know the experiments of Griffith; Hershey and Chase
Structure of DNA - Proposed by Watson and Crick, using information from:
     Chargaff (Chargaff's rule):  in any DNA,  amt. of A = amt. of T & amt. of G = amt. of C
        Franklin and Wilkins (x-ray crystallography):  dimensions of DNA include 2.0, .34 and 3.4 nm
    DNA (and RNA) composed of nucleotides, each of which are composed of three components:
         1. Phosphate
            2.  5-carbon sugar (deoxyribose/ribose for DNA/RNA) 
                        these two parts attach to form phosphate-sugar backbones of nucleic acids
         3.  Nitrogenous bases:  stick off to side from backbone.  Two types:
                 purines (double-ringled) - adenine and guanine
                 pyrimidines (single-ringed) - thymine (uracil in RNA) and cytosine
DNA is a double helix, held together by hydrogen bonds (two between A & T, three
             between G & C)
Opposite sides of the helix run in opposite directions (5' - 3')

DNA replication (in S of interphase) - semiconservative; always in the 5' - 3' direction
     Enzymes involved: helicase, DNA polymerase, DNA ligase -- KNOW function of each
        Many origins of replication, all must begin with an RNA primer

Leading strand/Lagging strand (with Okazaki fragments)

    Packaging of DNA in chromosomes: Chromatin
        Euchromatin -- extended (active) chromatin; Heterochromatin -- condensed (inactive) chromatin
         Histone (core of nucleosomes) and non-histone proteins