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