Upon completion of this unit you will be able to:
1. List several characteristics which
the genetic material must possess.
2. List the components of a nucleotide.
3. Name and describe the five different
nitrogenous bases.
4. Explain how DNA molecules vary
in structure from one species to another; thus
producing variations in the proteins of different species.
5. Describe the bonding between the
nitrogenous bases in the DNA molecule.
6. Diagram the process of DNA replication
if given a "sense" strand of DNA.
7. Provide the functions of endonuclease,
exonuclease, polymerase and ligase.
8. Identify the different types
of RNA.
9. Diagram the process of DNA transcription
if given a "sense" strand of DNA.
10. Diagram the process of translation
(protein synthesis).
11. Compare and contrast DNA and RNA.
12. Describe how DNA controls the synthesis
of proteins in a cell.
13. Differentiate between frameshift
and point mutations.
14. List several causes of mutations
and how they might effect DNA.
15. Distinguish between somatic and
sex cells.
16. Explain how cancer is caused and
treated.
17. Relate the operon concept to
the regulation of gene activity and the functioning
of a living organism.
18. Define and discuss differentiation.
19. Discuss bacterial plasmids and
processes involved in recombinant DNA procedures.
20. List the importance of transduction
and transformation in bacteria.
21. Define locus, gene and chromosome.
22. Describe the chromosome theory.
23. Differentiate between haploid
and diploid cells.
Unit References:
Text Chapter 3 pgs. 56-59; Text Chapter 8
www.mhhe.com/enger12
An Online Biology Text Book
DNA From The Beginning
PBS - DNA Workshop
Unit 6: DNA The Hereditary Material/ Protein Synthesis
DNA- DeoxyriboNucleic Acid; reference library of "How-To" books
I Search for Genetic Material
A. Requirements for genetic material:
(Objective #1)
1. Must be able to store info used to control development and metabolic activities.
2. Must be stable so that it
can be replicated w/ high fidelity and passed generation
to generation
3. Must be able to undergo
mutation to generate variability (changes must
be inheritable)
4. Must be chemically
diverse
5. Must use stored info to direct synthesis of products necessary for operation of cell.
B. Early researchers believed protein
was genetic material because of its diversity.
1. Meischer- nuclein
2. Griffiths (1928) bacterial transformation, material passed
3. Avery and others- chemical
proof that Griffiths found DNA not protein
4. Hershey and Chase (1952)-
used virus and radioactive isotopes of sulfur
and phosphorous, Concluded:
DNA genetic material
5. Watson/Crick/Franklin (1953)-
structure of DNA, double helix w/ 4 nitrogenous bases
of differing sequences.
II. Structure of DNA (Objectives #2, 3) Text pg. 56-59, 144-147
Check Out
: DNA Structure Tutorial
Molecule of the Month - DNA
What Is A Genome?
A. DNA- deoxyribonucleic acid
1. Double Helix (zipper,
ladder, spiral staircase)
2. Helix consists of 2 complementary
chains of nucleotides
3. Nucleotide = 1 nitrogenous
base + 1 deoxyribose sugar + 1 phosphate
4. Nitrogenous bases: PURINES
PYRIMIDINES
Adenine (A) Thymine (T)
Guanine (G) Cytosine (C)
DOUBLE STRANDED HELIX
(Objective #5) Text pg 145
Hydrogen bonds
Covalent bonds
S- deoxyribose sugar
P- phosphate
B. RNA- RiboNucleic Acid
Text pg. 58, 146-147
1. uses ribose sugar rather
than deoxyribose
2. single stranded
3. Bases A, C, G, and U
(uracil, substitutes for thymine)
C. Chargaff's Rules- Complementary
Base Pairing (Objective #4, 5)
1. Base composition of DNA
differs from species to species
a. amount of DNA
b. sequences of bases
on DNA
2. In each species, however, the %A = %T and %C = %G
-further, 50% of bases were
purines (A & G) and 50% of bases were
pyrimidines (T &
C)
-therefore, A must
pair w/ T; C must pair w/G
D. DNA Replication - mitosis
(cell division) (Objective #6)
text pgs. 145-146
-Watson/Crick model suggests
replication by Complementary Base Pairing
-during replication each
parental DNA strand serves as a template ("blueprint")
for a new strand
-replication requires the
following steps:
1. DNA must unwind (helicase) and "unzip" (break hydrogen bonds)
2. Complementary nucleotides,
always present in nucleus, move into place by
complementary base
pairing
3. Nucleotides joined to reestablish
double strand: Steps #2, #3 carried out by DNA
Polymerase
4. When done, 2 completed,
identical, double stranded DNA molecules present
DNA Replication is Semiconservative-
each new double helix contains one parental strand and
one new strand; Meselson
and Stahl 1958- radioactive isotope N 15
E. Enzyme Activity
(Objective #7)
1. Polymerase- enzyme responsible
for addition of nitrogenous bases (nucleotides)
to newly forming
strands of DNA
a. Has proofreading
function that checks each pairing.
Check Out:
Molecule of the Month - DNA Polymerase
2. Exonuclease- can remove nucleotide
from end of chain
3. Endonuclease- break bonds
within chain (restriction enzymes)
4. Ligase- repairs nicks and
cuts within chain
F. Accuracy of Duplication
-estimated mistakes 1/10,000
base pairs
-actual 1/1,000,000,000
much better than estimated
due to action of polymerase proofreading
-if error does occur and
is not corrected, then a gene mutation has occurred.
II. PROTEIN SYNTHESIS-
(Objective #9, 10, 12) Text pgs. 147-155
-gene expression, cell activity; DNA
master code for protein synthesis
Problem: DNA in Nucleus -->
protein synthesis occurs in cytoplasm, how do
instructions get to
construction site?
DNA --> copy small piece --> remove
from nucleus --> take to ribosome --> let workers read
instructions and assemble --> protein
(gene product)
Check Out:
Beginner's Guide to Molecular Biology
Role of the Nucleus in Protein Synthesis
Molecule of the Month - Ribosome
DNA - RNA - Protein
Transcribe and Translate a Gene
(Objective #8)
A. RNA- RiboNucleic Acid; nucleotides
like DNA except:
1. Ribose rather than deoxyribose
sugar
2. Pyrimidines (cytosine
and uracil) RNA uses U rather than T
B. Part I: Transcription, making of
mRNA- messenger RNA
(Text pg 147-148)
-"Reads", copies or TRANSCRIBES
(transcription) DNA code, takes message (copy)
to cytoplasm
C. rRNA- ribosomal RNA; Ribosomes
-site of protein synthesis,
RIBOSOMES made of RNA
-site where code is translated
(decoded)
D. Part II Translation, using tRNA-
transfer RNA to translate
mRNA code
3 parts:
Initiation, Elongation, Termination
(text pgs 148-151)
-clover leaf shape- string of
paired and unpaired nucleotides
-translates code contained
on mRNA (Text 148-151)
1. every 3 bases in DNA (or mRNA copy) codes for one Amino Acid
2. tRNA translates and carries appropriate amino acid to ribosome
3. at ribosome tRNA deposits
amino acid coded for and A.A.chain (protein)
is created.
E. THE PROCESS: DIAGRAM FORM
(Text pgs 150-154)
DNA vs. RNA (Objective #11)
DNA
RNA
FUNCTION genes, controls
protein helper to DNA, involved in
synthesis
actual building (synthesis) of protein
SUGAR deoxyribose ribose
BASES A, C, T, G A, C, U, G
STRUCTURE double stranded;
single stranded
complementary
base
pairing;
helix
T A C A T G G G T C A T A T C
REPLICATE ---->
TRANSCRIBE --->
TRANSLATE ---->
MUTATIONS- (Objective
#13, 14) Text pgs.158-160 -
an inheritable change in a genetic
character resulting either from a change
in a gene at a specific point or an alteration of
chromosome structure.
Check Out:
The Beauty of Mutations
Genetic Parasites and a Whole Lot More
1. Point Mutation - a mutation that involves a single base pair. Usually a substitution.
-may result in no noticable change
or code for different protein (amino acid)
resulting in something
as serious as PKU or Sickle cell
-Spontaneous Mutations
Tautomeric shift- a
shift in the form of a nitrogenous base
2. Frame Shift- removal or
addition of a base pair, alterations effect everything after
the addition or deletion
EX. POINT MUTATION FRAME SHIFT MUTATION
THE CAT ATE THE RED HAT THE CAT ATE THE RED HAT
THE RAT ATE THE RED HAT THE ATA TET HER EDH AT (DEL C)
THE CAT ATE THE RED CAT THE CCA TAT ETH ERE DHA (ADD C
3. Causes- mutagens- environmental substances that cause mutations (text pg 171-173)
Radiation- Ionizing and X-ray ---> Break DNA, causes deletions and translocations
U.V. ---> alters DNA of surface cells (thymine dimers)
**cause primarily Frame Shift type mutations
Organic Chemicals: Pesticides
Cigarette
smoke (benzo(a)pyrine) and 9 others
automobile
exaust
Smoked
foods
Agent
orange/mustard gas - methylating/ alkylating groups added to DNA
**all cause mispairing
of bases (Point Mutation) usually a single nucleotide
substitution
(Objective #15)
-if mutation in somatic
cells (body cells) ---> cancer
-if mutation in gametes
(sex cells) ---> genetic defect in offspring
CANCER-
(Objective #16) Text pg
171-173 abnormal division of cells; when cells rebel!
Carcinogens- noxious chemicals,
radiation, virus
Check Out:
Oncolink
Your Cancer Risk
Introduction to Skin Cancer
-cause alterations in DNA which
cause cells to divide uncontrolably
(environmental/ self imposed)
-Oncogenes- stretches of DNA
capable of transforming normal body cells into
tumor cells.
-p53, Apoptosis
*cancer arises when genetic material
damaged in a manner that frees the cell from
normal constraints of
growth
TUMORS- clusters of cancer
cells; some grow fast, some grow slow
Benign ("kind")- growth
restricted to area of tumor
Malignant ("evil")- breaks
from original mass, enabling them to metastasize
(spread through body)
Treatment- center around removal
of tumor (early detection key)
1. Surgery- location
dependent
2. Chemotherapy- lowers
immune reactions and others
3. Radiation- effective
on rapidly dividing cells, however, . . . . .
4. Immune therapy-
build bodies own defenses
BACTERIAL DNA
(Objective #19, 20) - Pioneering Modern
Biotechnology
A. Transformation- Free DNA in
environment becomse incorporated in bacterial cells
(Griffiths, Avery)
-genetic change in one strain
of bacteria brought about by exposure to freshly killed
bacteria of another
strain
B. Transduction - genetic transfer
among bacteria involving the use of a virus
as the transmitting agent
1. plasmids used extensively
in DNA research; piece of DNA incorporated into existing
DNA
Gene Expression/
Regulation (text pg 152-157)
OPERON CONCEPT-
(Objective #17) part of each gene acts as a "switch" to either
turn "on" or "off" depending
on kind of cell or concentrations of gene products
(proteins)
*lac operon; pancreas- insulin
Promoter
Protein Coding Region
Termination Sequence
Regulatory regions
Using
DNA to our Advantage (chapter 11 text pgs 215-236)
DNA tech.; Gene splicing; Recombinant
DNA/ Transgenics
Human insulin: old ---> pancreas
of cattle/sheep; new ---> bacterial
Gene Therapy
Forensics
Check
Out :
The Gene Doctor
Use of DNA in Identification
Genetically Modified Organisms
To Know Ourselves
The Gene Hunters
Harvest of Fear
CHROMOSOMES- (Objective #21)
composed of genes; genes- ~450-1000
nucleotides (DNA)
gene --> mRNA --> protein -->
gene expression
Specific location on a chromosome
referred to as a gene locus
Chromosome theory-
(Objective #22) since there are more traits than there are
chromosomes, each chromosome
must carry many traits (genes)
**all cells contain an identical
copy of every chromosome (w/exception of egg
and sperm which have
1/2)
-however, not all cells have all genes "turned on"
(Objective #23)
Diploid- chromosomes found in
pairs (2N; N= chromosomes)
Human 2N number is 46
Dog 2N= 78
Haploid- single set of chromosomes,
characteristic of gametes (eggs and sperm)
Human haploid (1N) number
is 23
Maternal egg Paternal
sperm Zygote
1N +
1N ------> 2N
haploid = 23
haploid = 23 diploid = 46