DNA Replication, Protein Synthesis, Mutations
Review Guide
2/21/2013 3:58:00 AM
I. DNA Replication
A. Scientists- they helped discover DNA’s structure and shape
i. Griffith 1928- determined dead bacteria could transform living
bacteria
ii. Avery, McCarthy, and MacLeod 1941- determined that DNA
was transforming the bacteria
iii. Hershey & Chase 1952- Radioactively labeled proteins and
DNA of viruses and determined that it was the DNA that spread
the virus not the proteins
iv. Rosalind Franklin 1952- X ray diffraction of DNA to
determine it is crossed. Got an image then died from radiation
exposure.
v. Watson and Crick 1953- “Double Helix bro!!!”, made a model
and won the noble peace prize
B. DNA Structure- Deoxyribonucleic Acid
i. Double Helix
ii. Made of Nucleotides
a. Pentose Sugar(deoxyribose)
b. Phosphate
c. Nitrogenous Base(Adenine , Thymine, Guanine,
Cytosine; A and T; C and G) C an T are Pyrimidines and
A and G are purines. C and G have three hydrogen pairs
while A and T have two
iii. Anti- Parallel- There is a 5’ side and a 3’ side. Still parallel but
going in opposite direction.
C. DNA Replication- Semiconservative; See PowerPoint
i. Semiconservative- There is an old strand and a new strand.
The DNA unwinds and new Nitrogenous bases are added to
make a complementary new strand
ii. Helicase- enzyme that’s job is to unzip the DNA to form two
old strands. Breaks hydrogen bonds
iii. RNA primer- this gets attached by RNA polymerase or RNA
primer to make a free 3’ end so that the DNA polymerase can
attach and do its thing
iv. Leading Strand- DNA polymerase 3 goes from the 5’ to 3’
direction and so the leading strand is continuously being
synthesized as the helicase unwinds the DNA then DNA
polymerase 1 replaces the primer and all is good
v. Lagging Strand- This strand has to wait for the helicase to
unzip. Because this goes 3’ to 5’ and RNA primer has to be
continuously attached to open a 3’ side. DNA polymerase 3
then makes a complementary strand. This all happens in
okazaki fragments and then ligase comes and attaches them.
Synthesized discontinuously has to wait for helicase to unzip
vi. Telomeres- short repeated sequences at the end of DNA
(mammalian cells generally have 50 repeats) each time DNA
replicates, part of the telomere sequence is cut off and when
they are gone, the cell can no longer divide and dies. Cancer
cells have telomerase and can continue to divide forever.
(Credit Grier)
II. Protein Synthesis- 2 steps: Transcription and
Translation
A. RNA Structure- Ribonucleic Acid
i. Single Strand of nucleotides
a. Pentose Sugar (ribose)
b. Phosphate
c. Nitrogenous Bases- Adenine and Uracil; Guanine and
Cytosine. NO THYMINE
d. Difference from DNA- there is an OH on the 2’ carbon
on the ribose instead of the H on the Deoxyribose
B. RNA- 3 types
i. mRNA- messenger RNA and the brings code from the DNA to
the ribosomes in cytoplasm
ii. tRNA- transfer RNA and that transfers the amino acids to the
correct sequence in the ribosome
iii. rRNA- ribosomal RNA and that makes ribosomes
C. Transcription
i. Definition-Taking DNA and making mRNA
ii. TATA Box- sequence of DNA of As and Ts that acts as
promoter for RNA polymerase and to attach and begin
transcription
iii. RNA Polymerase- enzyme that makes mRNA by attaching a
complementary RNA base strand to the strand of DNA
iv. DNA terminator- sequence of DNA that tell RNA polymerase
when to stop
v. 5’ Cap- modified Guanine that tells the ribosome where to
attach
vi. Poly A Tail- is 150- 200 Adenines that protect the mRNA in
the cytoplasm
D. mRNA processing- mRNA has to be made into mature RNA
i. Introns have to be removed; don’t code for anything; nuclease
takes out the introns
ii. Exons- parts that are “expressed” in the protein; ligase
attaches them
E. Translation: Taking mRNA and making it into protein. The amino
acid MET starts each proteins
i. Codon- mRNA is read in a group of three nitrogenous bases
called codons that each code for a separate amino acid
ii. tRNA- made of nucleotides. On the tRNA is an amino acid and
on the other side is an anti-codon that is complementary to the
codons of the mRNA all of this takes place in the ribosomes
iii. Ribosomes- have two parts and there are three sights
a. A site- add tRNA/ amino acid
b. P site- Peptide side or protein side
c. E site- exit (used tRNA exits the ribosome)
iv. Amino Acid formation- the tRNA brings the amino acid to the
complementary codon on the mRNA and they combine in long
chains and then an end codon comes and the chain is realeased
F. Protein Foldingi. Proteins can’t function unless they fold
ii. Proteins fold because of hydrophobic and hydrophilic
interactions want to stick together and they arrange them
selves to that.
iii. Primary Structure- amino acid chain
iv. Pleated Sheet or Alpha Helix- many primary structures get
folded into this and
v. Tertiary Sheet- many pleated sheets or alpha helixes are made
into this mass jumble of protein
vi. Quaternary Fold- final product and is made up of tertiary
sheets. The final product is a jumble of proteins
G. Repressible Operon- regulates genes and stops protein production
i. Trp Operon- represses trp production
a. Repressible operon- you can stop it
b. When trp operon is present, it binds with an inactive
repressor making it active
c. Repressor then attaches to operator region
d. Stops production of trp production since already
available in body
H. Inducible Operon- lac operon
i. Lac Operon- induce lactase; you can turn it on; gene is usually
off; lactase- enzyme that breaks down lactose
a. When lactase is present it binds with repressor and
turns it off; make the active one inactive
b. Repressor cant attach to operator region
c. Begin production of lactase since repressor is inactive
I. cAMP and Lac Operon; see power point
i. no lactose so no lactase being produces
ii. No lactose; no glucose process doesn’t work
iii. Glucose and Lactose present: process is induced but not many
lactase is produced because cell prefers to break down glucose
iv. No Glucose so high amount of cAMP. This kicks lactase
production into overdrive to break down lactose
III. Mutations: Any change to DNA; can be good
A. Mutagen- things that cause mutations such as pesticides, smoking
and radiation
B. Polyploid- organism that has extra sets of DNA like strawberries
C. Chromosomal Rearrangements
i. Deletion- portion of chromosomes deleted
ii. Duplication- Portion of chromosome is doubled
iii. Inversion- portion of chromosome is inverted
iv. Translocation- piece of one goes to the other
D. Gene Mutation- the base is substituted for another letter. Changes
amino acid but person live normal
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2/21/2013 3:58:00 AM
2/21/2013 3:58:00 AM