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DNA: History, Structure, & Function
Nucleic Acids
I. DNA (Deoxyribonucleic Acid)
A. Overview of Griffith’s 1928 Experiment
Two types of Streptococcus pneumoniae
a. rough (non-virulent)
b. smooth (virulent)
B. First experiment
1. Rough serum
2. Smooth serum
C. 2nd experiment
1. Rough serum heated
2. Smooth serum heated
D. 3rd experiment
1. Live rough + heated smooth
2. Conjugation caused “transformation”
dead
smooth
live
rough
Transformed
from rough
a. DNA = “transforming principle,”
changes what cells look like and do
b. Mendel’s “partikles” = genes = nucleic acids
II. Structure of DNA
A. DNA – Deoxyribonucleic Acid
B. Composed of :
1. Phosphate, which is connected to a …
2. Sugar (Deoxyribose), which is connected to…
3. One of four nitrogenous bases
a.
b.
c.
d.
Adenine
Thymine
Guanine
Cytosine
Complementary Bases
Complementary Bases
II. Structure of DNA
C. Nucleotide
1. One unit of phosphate, sugar, and
base
2. One nucelotide base is connected
to another, complementary one,
by hydrogen bonds
3. This is called a “base pair”
D. Codon
1. Group of 3 nucleotides in a row
2. Each codon codes for placement
of one amino acid in a protein
II. Structure of DNA
E. Genes
1.
Group of codons on a chromosome that generally cod
for the production of a protein.
2.
There are different kinds of genes
a.
b.
c.
d.
Promoters – Help other genes work better
Structural – Contain coding of proteins used outside
Regulatory – Turn others off and on (how many?)
Operational – Used in the cell to make “local” products
F. Chromosomes
1.
Long strands of DNA, each with many genes
2.
One chromosome has +/- 20,000 genes on it.
3.
A typical human cell has 46 chromosomes in it
II. Structure of DNA
G. The Nucleus
1. Location in the cell in which most DNA is
contained.
2. Some DNA is
also found in the
mitochondria, or
energy making
structures of the
cell.
III. Function and Properties of DNA
A. DNA Replication
A. DNA can copy itself, using
free-floating pieces of
nucleic acid as building
blocks
B. Occurs in mitosis and
meiosis
III. Function and Properties of DNA
B. Protein Synthesis Overview
1. Structural proteins are the big structural components
of tissue (e.g. muscle, epithelial, etc.)
2. Enzymes are proteins that serve as catalysts, aiding
chemical reactions in the body.
3. Amino acids are the building blocks of protein.
1. There are 20 important amino acids.
2. Proteins differ according to number of amino
acids and the sequence in which they are
arranged.
III. Function and Properties of DNA
B. Protein Synthesis Overview, continued
4. Two basic steps to Protein Synthesis
a. Transcription (copying the message)
1. DNA partially unwinds
2. Free-floating RNAs “click in”, copying
3. Completed strand of mRNA breaks off
b. Translation (transporting and interpreting)
1. mRNA travels to ribosome
2. mRNA attracts tRNA with amino acids on them
3. amino acid chains form proteins
4. tRNA and mRNA return to their jobs
III. Function and Properties of DNA
C. Understanding Protein Synthesis
1. DNA and RNA as a language
Grammar
Letters
Words
Sentences
Paragraphs
Example:
THEFATCATATETHEREDRATENDTHEFATRATSATANDSATEND
III. Function and Properties of DNA
C. Understanding Protein Synthesis
2. Protein Synthesis: a manufacturing business
Crazy Industrialist in his “compound”
Trusted Relative/Messenger
The Factory
The Factory Workers
The Raw Materials
The Finished Product
III. Function and Properties of DNA
D. Mutation – a change in the genetic code
1. Point mutations – individual base changes
a. Substitution
b. Insertion or Deletion
Examples:
THEFATCATATETHEREDRATENDTHEFATRATSATANDSATEND
THEFATCATATETHEREDBATENDTHEFATRATSATANDSATEND
THEFATCATATETHEREDBRATENDTHEFATRATSATANDSATEND
THEFATCATATETHEREDATENDTHEFATRATSATANDSATEND
2. Chromosomal mutation – major change
a. Translocation
III. Function and Properties of DNA
3. Effects of mutation
a. Nothing
b. Slight change in gene product
c. Change for the better or worse
d. Lethal
4. Some causes of mutations:
Radiation, chemicals, UV light, random error
Cell Division
I.
Introduction: Why do Cells Divide?
A. Reproduction, Growth, Repair, & Replacement
B. Unicellular and some multicellular organisms
rely on mitotic cell division for reproduction,
creating identical copies of the parent. Others
(prokaryotes) divide by binary fission.
C. In multicellular organisms, mitosis serves the
purpose of growth and repair.
D. The life cycle of a cell is called
the Cell Cycle
E. The two types of eukaryotic
division are mitosis and meiosis.
Prokaryotic
cell division
Mitosis and Meiosis
II. Meiosis versus Mitosis
A. Mitosis is responsible for making… in the….
B. Mitosis creates _____ daughter cells that are genetically…
C. Daughter cells in mitosis have the _____ # of chromosomes
D. Meiosis is responsible for making… in the…
E. Meiosis creates ___daughter cells that are genetically…
F. Daughter cells in meiosis have the ___# of chromosomes.
II. Mitosis
A. Interphase
1. DNA unwound (chromatin)
2. Nuclear membrane exists
3. Centrioles may be visible
4. DNA copies itself into chromatids
One 2N cell
Diploid
Two 2N cells
B. Early Prophase (prephase)
1.
2.
3.
4.
Mitosis begins here
Nuclear membrane dissolves
DNA winds to form
chromosomes
Centrioles move apart
C. Late Prophase
Chromatid
Dyad
Centromere
Chromatid
Chromosome
Spindle Fibers
D. Metaphase (Middle Phase)
1. Centrioles at poles
2. Spindle completely
formed
3. Each replicated
chromosome
(chromatid) becomes
attached to a spindle
fiber at the centromere
4. Dyads (chromosomes)
at equator
E. Anaphase
1. Chromatids separate and
begin moving to opposite
ends of the cell
2. The spindle fibers pull the
chromatids while pushing
against each other, elongating
the cell in preparation for
cytokinesis
F. Telophase
G. Cytokinesis
1. Nuclei reform
2. Cell plate or cleavage
furrow forms
3. Chromosomes unwind
Daughter Cell 1
Daughter Cell 2
Cleavage
furrow
III. Meiosis
Sex cell (gamete) formation: pollen , ovules,
sperm, ova
Gonads: anther, pistil, testes, ovaries
Reduction division
One 2N cell
Diploid
Four 1N cells
Haploid
B. Meiosis I: Early prophase
1. Basically like mitosis except
for synapse.
2. Synapse is when
homologous pairs of
chromosomes line up tightly
together.
3. Homologous chromosomes
are paired, one from mom
and the other from dad.
C. Meiosis I: Late prophase
1. Homologous pairs may do
crossing over.
2. Crossing over is the exchange of
genetic material between
homologous chromosomes.
3. Crossing over results in extra
genetic diversity
D. Meiosis I: Metaphase
1. Synapsed pairs
line up at equator,
on opposite sides
of the cell plate
2. This lining up is
random, and is
called independent
assortment.
E-F. Meiosis I: Anaphase - Cytokinesis
1. Basically identical
to mitosis, except
for…
2. Now it’s time to do
a reduction division
G. Meiosis II: Prophase - Anaphase
Proceeds as did mitotic prophase,
but… no new DNA synthesis occurs
H. Meiosis II: Early Telophase
I .Meiosis II: Late Telophase
Reduction
Division is
complete
Gametes / Conception
Hyaluronidase Hyaluronic acid
Sperm
Ovum
Nucleus
Cytoplasm
Zona Perllucida
Corona Radiata
Acrosome
Nucleus
Midpiece =
mitochondrial
sheath
flagellum
Conception
1. Sperm & egg meet
2. Acrosome releases enzymes
to burrow through the c.r &
z.p.
3. C.r. & z.p. form fertilization
membrane when the first
sperm nucleus gets into
cytoplasm
4. 2 pronuclei fuse to form the
zygote – morula – blastocyst fetus
Zygote
Morula
Blastocyst
Fetus
Baby
umbilical cord
placenta