GenTech Unit 2 DNA
Transcript GenTech Unit 2 DNA
Major Cell Activities Include:
– Cell Respiration
DNA Replication This unit
Protein Synthesis three
Pre-Notes, Background Info:
• Nucleic acids
A. Store & transmit
B.DNA & RNA
repeating units called
DNA double helix
Pre-Notes, Background Info:
Nucleotides consist of:
1. a sugar
2. a phosphate group
3. one nitrogen base
I. DNA (Deoxyribonucleic Acid)
A. Found in almost all living cells –in the
nucleus of eukaryotes (3 Feet/Cell)
B. 2 primary functions
1. Control protein (enzyme) production (ie.
ATPase)-These enzymes then control
chemical reactions in cells.
2. Duplicate itself for new cells that are
C.Forms of DNA
1. Chromatin –Partially unwound
when? (Normal Situations)
2. Chromosome – tightly wound
DNA (Cell division)
D. Structure of DNA
1. Consists of two long strands that spiral
2. Each strand is a chain of nucleotides
3. Three parts to each nucleotide
a. 5 carbon sugar (deoxyribose)
c. Nitrogen base (4 different kinds of bases)
Nucleic acids are polymers of nucleotides.
sugar + phosphate + nitrogenous base
4.All nucleotides have same
sugar and phosphate
5. Four different kinds of nitrogen bases
a. Adenine – purine – double ring molecules
b. Guanine – purine – double ring molecules
c. Thymine – Pyrimidines – single ring
d. Cytosine – pyrimidines –
single ring molecules
Segment of DNA
6. Double Helix – Spiral ladder
a. Sides of the ladder = 5 carbon
sugar and phosphates
b. Rungs of the ladder = nitrogen
bases bonded together from
Rosalind Franklin’s X-ray Photo (1951)
7. Hydrogen bonds form between purines and
pyrimidines creating “steps” of ladder
a. Adenine + Thymine = 2 hydrogen bonds
=2 hydrogen bonds
=3 hydrogen bonds
Cytosine + Guanine= 3 hydrogen bonds
E. DNA Replication
-each cell must get same DNA copy when
1. DNA helicase (enzyme) attaches to DNA
2. Helicase moves along DNA breaking
hydrogen bonds- “unzips” DNA into two
3. Each strand now has unpaired nitrogen
4. Free floating nucleotides in the nucleus
form hydrogen bonds with unpaired
5. DNA Polymerase (enzyme) bonds
together nucleotides by connecting
Deoxyribose(Sugar) to phosphate
6. Ligase (enzyme) repairs DNA
7. Final result = 2 exact copies of DNA
* Each copy = 1 “old” strand and 1
8. Replication occurs at many (1000’s) of
sites along DNA – speedy process
9. Replication very accurate – 1 error per
10. Nitrogen bases:
a. Adenine (A) bonds with Thymine (T)
b. Cytosine (C) bonds with Guanine (G)
If unzipped old segment = C-C-A-T-G-A-G-T
What will the new segment be?
II. RNA (Ribonucleic Acid)
A. Structure of RNA
*Different than DNA in 3 ways
1. RNA is a single strand – DNA = Double
2. RNA has ribose sugar – DNA =Deoxyribose
3. RNA has Uracil instead of Thymine
DNA nitrogen bases
RNA nitrogen bases
B.3 types of RNA
*All made in the nucleus and
travel to the ribosomes
1. Messenger RNA (mRNA)
a. Single straight strand
b. Transmits DNA information
c. Serves as template (pattern)
for making proteins
2. Transfer RNA (tRNA)
a. Single folded strand
b. Complimentary bases pair up
c. Also involved in protein synthesis
3. Ribosomal RNA (rRNA)
a. Globular form
b. Part of ribosome structure
C. Transcription – process of making RNA
1. Protein enzyme called RNA
polymerase binds to DNA.
2. RNA polymerase separates portion of
DNA into two separate strands.
3. Free floating nucleotides in nucleus
match their nitrogen bases with
bases of “unzipped” DNA.
DNA base code
Complimentary RNA = G-C-U-A-U
4. RNA polymerase forms bonds
(hydrogen) between nitrogen
5. Polymerase connects
nucleotides by bonding sugars
6. Enzyme releases new RNA
strand when it reaches “stop
sign” on DNA.
III. Protein Synthesis – ribosomes
make proteins using information coded in RNA
1. Many amino acids linked by peptide
2. 100’s to 1000’s of AA’s per protein
3. 20 different AA’s
4. Sequence of AA’s determine
structure and function of each
B. Codon – a group of 3 sequential
nitrogen bases of an mRNA molecule.
1. 64 different combinations = 64
-How many codons?
3. Each codon codes for:
a. 1 of the 20 amino acids
b. Start or stop codons
-Region of tRNA that consists of
bases which are complimentary to
codon bases of mRNA
D. Translation – putting amino acids
(AA’s) together to build protein
from information encoded in mRNA
1. mRNA and tRNA transcribed from
DNA in nucleus.
2. This RNA exits the nucleus through
3. mRNA travels to ribosomes.
4. Free floating AA’s are brought
to ribosomes by tRNA.
5. Protein always starts with
methionine (aug) AA
6. A second AA on tRNA enters
ribosome. Codon and anticodon
pair up and peptide bonds form
*This process of linking AA’s continues
until ribosome reaches a stop codon on
What are the stop codons?
A. Plasmids: circular double-stranded DNA
1. Separate from chromosomal DNA
2. Contain genes which code for less essential traits
(ex. Adaptive traits)
3. Common in bacteria
A. Recombinant DNA
– This is the union of
DNA from 2 different
A. Restriction endonuclease (RE): enzymes in
cells which cleave (cut) DNA into pieces
– We can use this enzyme to cut and splice genes
A. Procedure of recombinant DNA technology
Isolate desired gene from a donor cell
Cut out desired gene using RE
Extract plasmid from bacterium using lysozyme
Using RE cut out DNA segment from plasmid
creating sticky ends
5. “paste” desired gene “sticky” ends into plasmid
6. Insert recombinant plasmid into healthy
7. Allow bacteria to multiply (cloning) by incubating
8. Bacteria will transcribe and translate new gene,
producing desired proteins
9. What are some desired proteins?
Hemoglobin Protein Molecular Formula:
Glycine (typical AA): C2H5N1O2
Some Products Made Using Biotechnology
Human growth hormone is used to treat dwarfism. It previously took the pituitary glands from over 50 cadavers to
make one dose.
Human Insulin is used to treat diabetes.
Tissue plasminogen activator dissolves blood clots in heart attack victims.
Clotting factor VIII will soon be available. Most cases of hemophilia are due to the absence of this factor.
Human lung surfactant is used in premature infants with respiratory distress syndrome.
Atrial natriuretic hormone can be used to treat hypertension.
Bovine growth hormone (bGH) increases milk production in cows by about 10%.
A vaccine for hepatitis B is now produced using biotechnology.
Vaccines for chlamydia, malaria and HIV are being developed.
Vaccines for hoof-and-mouth disease and scours (a form of dysentery) have been developed for farm animals.
Bacteria have been produced that inhibit the formation of ice crystals. These bacteria have been released onto crop
plants to protect them from frost damage.
A bacteria species that normally colonize corn roots have been given a gene that enables it to produce an insect-killing
Bacteria are being developed that do a better job at breaking down oil.
Bacteria have been developed that are capable of removing some kinds of toxins from the air and water.
Bacteria have been engineered to extract metals from low-grade ore (bioleaching).
there are 50 types of genetically engineered plants that resist insects, viruses, and herbicides.
A weed called mouse-eared cress has been designed to produce a biodegradable plastic called polyhydroxubutrate
Pharmaceutical companies are developing techniques to produce chemicals using animals. The drug is produced in the
milk of females. For example, goats have been developed to produce antithrombin III, used to prevent blood clots.
Clinical trials of this drug will begin soon.
A pig has been produced that can produce human hemoglobin. Artificial blood may soon be a reality.
B. DNA fingerprinting
1. Analysis of DNA sequences to