Download DNA Student Lecture Notes

DNA Student Lecture Notes
CHAPTER 12
To understand genetics, scientists had to understand the __________________of each gene. If gene
structure can be identified, then understanding how genes are inherited can be understood. In 1928
Fredrick Griffith was trying to figure out how bacteria made people sick. He was looking at the
bacteria in pneumonia. He isolated 2 strains of bacteria, where each strain looked different on a Petri
dish. One strain _______________________, one strain didn’t. He killed off the harmful strain from
heat, but left the bacterial ‘body’.
1. Killed-harmful strain injected into mice = no death
2. Injected LIVE harmless strain into mice= no death
3. Dead harmful and live harmless= ____________________
*Results: The living harmless somehow received harmful material from the dead strain. This is
called _________________________________. Harmless was somehow transformed into harmful.
AVERY 1944
Avery repeated the experiment to try to figure out which __________________ in a cell is causing
pneumonia. His team ended up systematically killing all proteins in one trial, all fats and carbs, in
another trial, even killing RNA. Yet, the dead strain STILL transformed the non lethal strain. Avery
finally used an enzyme that destroyed the DNA of the bacteria. Only then was the dead strain was
unable to transform. This proved that _______ stores and transmits genetic information form one
__________________________ to the next.
HERSHEY- CHASE 1952 pg 289
They worked with _______________________. Viruses were considered non living because they
didn’t follow all the characteristics of life. One type of virus is called a bacteriophage. It infects
bacterial cells. These viruses are very, very small and contain only RNA or DNA. A bacteriophage will
attach to a specific cell (based on its shape) and inject its DNA or RNA into the cell. This viral DNA
enters the ________________________ and attaches to existing DNA. This cell now makes
______________________, rather than a regular cell. Before the cell bursts, it can have
____________________________ of new viruses produced in the cell.
Radioactive Markers.
Martha Chase and Hershey wanted to know if the shape of the virus protein or the DNA was entering
the cell. This would tell them if genes are in protein or in DNA. Proteins contain no phosphorus, but
DNA does. DNA contains no sulfur. When they looked at infected cells, they all contain
___________________________. This proved that DNA contains genetic material, and proteins do
not contain ___________________.
DNA does 3 critical things
1. Transfers genetic information to each ___________________________.
2. DNA must be copied with each cell _____________________________.
3. DNA has to function to make new ________________________.
DNA is made of: a sugar deoxyribose
A phosphate group
One of 4 nucleotides; Adenine, Guanine, Cytosine, Thymine (AGTC)
CHARGAFF concluded that A’s are connected to ___and that G is connected to ______
A-T, G-C.
ROSILAND FRANKLIN showed that DNA is twisted in shape, in helix, where the nitrogen bases are
in the middle. She looked at it through X-rays.
WATSON AND CRICK
Using Franklin’s x- rays, they constructed the first model
of the _________________ __________________. Their paper was one page long and they won
the Nobel Prize. Hydrogen bonds are what kept A bonded to T and G to C.
DNA Beads
How is your strand similar to your partners?
How is your strand different from your partners?
Compare your sequence to others.
How is it similar?
How is it different?
Chromosomes and DNA Replication
DNA molecules are very long. E coli (bacteria) have over 4 million base pairs. This is about the same
as you having 300 meters (3 football fields) of rope on your backpack. Eukaryotic cells have DNA
even more tightly packed. Now your backpack has 30 miles of rope. One microscopic skin cell has
enough DNA to stretch 1 _____________. To make this possible, to fit into the nucleus, the DNA is
tightly coiled and proteins called ___________________ hold them together.
During mitosis, the coils get tighter to form specific chromosomes. A nucleusome is DNA coiled to fit
into the nucleus. Each DNA strand folds around histone proteins. Then the coils coil around into
super coils, which form the nucleosome.
DNA Replication
Once the double helix was formed it was easy to see how it could be replicated. Part of the double
Helix can dismantle, by the breaking of the hydrogen bonds holding the _________________. In the
S phase of a cell cycle, the double helix unwinds, making two strands; Enzymes are a vital part of
DNA replication. Polymerase, Ligase, Helicase, are a few of the enzymes. DNA helicase unzips the
DNA by breaking the hydrogen bonds. Each strand is now the template for the other strand.
ATGCATGCATGCATGC
TACGTACGTACGTACG
(Original DNA Sequence)
A
T
G
CATGCATGCATGC
GTACGTACGTACG
(Unzipping, breaking hydrogen bonds)
C
A
T
After the DNA unzips, new individual nucleotides begin to attach to the old DNA strand with the help
of an enzyme called DNA polymerase. This enzyme also “proofreads” the old DNA template DNA.
Vitamin B-12 is used to help this enzyme. Ligase reattaches the hydrogen bonds, resulting in two
identical DNA strands.
A
T T
A G
C CATGCATGCATGC
G GTACGTACGTACG
TC
A A
T
ATGCATGCATGCATGC
TACGTACGTACGTACG
ATGCATGCATGCATGC
TACGTACGTACGTACG
(Unzipping, adding nucleotides)
(Original DNA Sequence)
(Replicated counter sequence)
(Replicated counter sequence)
(Original DNA Sequence)
Both strands are exactly the same.
pg. 300
Sometimes the entire DNA strand doesn’t need to be replicated, just a small portion, such as for the
production of a new ___________________________. This is when RNA will attach to the original
DNA strand. RNA is used for the purpose of __________________
___________________. RNA
is single stranded. RNA doesn’t have thymine. Instead of a “T” it has an Uricil, “U”. There are several
types of RNA; Messenger RNA (________), ribosomal RNA (_________), transfer RNA (_______).
Most of your DNA genes code for proteins. Proteins are made of __________ ____________.
These amino acids are assembled on ribosomal RNA.
Steps for protein synthesis
1. Part of the DNA unwinds
2. The enzyme RNA polymerase helps mRNA attach to unwound part of DNA. The mRNA makes
a copy of the DNA protein code.
3. The mRNA detaches from the DNA strand and the DNA double helix reforms, with the help of
DNA ligase.
4. Notice that the RNA strand is backwards.
DNA
mRNA
tRNA
ACCTGTCAA
UGGACAGUU
ACCUGUCAA (same as DNA)
CATGCATGC
GU ACGU ACG
(mRNA)
ATG
TGC
TACGTACGTACGACG
(Original DNA Sequence)
GUACGUACGU
tRNA with amino acid attached
CATGCATGC
GUACGUACG
(mRNA)
5. This tRNA also has an amino acid (the primary structure of a protein) attached to it.
Primary protein structure
How does the mRNA know where to attach and when to stop? Within the DNA, there are starting
regions (promoter) and stopping regions. The start regions have a code TAC. The stop codes
represent TGA, TAA, and TAG. This is how scientists know that some type protein was being coded
in the DNA, when they would see TAC followed later by stop code.
CCA AAC TGC GGA TACGGA GTC GGG TTA CTT CAC GAG AAA TTC TGA TGC GGA GTC
RNA editing 302
Within the DNA “TAC” and a stop code, there are extra parts that do not makeup the protein. The
RNA must edit, or cut these parts so that only the protein code is in the mRNA sequence. The parts
that are cut out are called introns. The parts that are left (the real code for a protein) are called
__________.
TAC TTC BLA BLA BLA CAA ACA UGA
mRNA AAG GUU UGU
tRNA UUC CAA ACA
The “BLA” must be cut out before it can code
The BLA, the _______ code, and the________ are not in the mRNA sequence because they do not
code for a protein.
Gene to protein, genetic code pg 302.
A protein is made of poly “many” peptide chain of amino acids. The simplest proteins have
thousands of amino acid chains. The tRNA has an amino acid attached to it. There are
______amino acids, and therefore 20 types of tRNA. The mRNA sequence which has the code to
make the amino acid chain is read in 3’s, and called a ________. UAU codes for the amino acid
tyrosine, UGG codes for tryptophan.
UCG-CAC-GGU
Serine – Histodine - Glycine
Amino acid chain
There are 64 codons, but 6 code for leucine.
Translation Factory- Making, of the primary protein
1.
2.
3.
4.
5.
6.
7.
8.
DNA unwinds
mRNA assembles on the DNA attaches to DNA strands
mRNA detaches, removes introns.
mRNA moves to a ribosome, called ribosomal RNA
transfer RNA begins to attach one at a time to the mRNA strand
tRNA leaves the amino acids when it detaches from the mRNA.
The amino acids chain (polypeptide chain) continues to grow until the last tRNA attaches.
the polypeptide chain goes to the endoplasmic reticulum to make its protein shape. It travels to
the Golgi to put its outer coating on.
9. the final protein is now functioning.
10. many proteins are enzymes that help the cell or organism function.
ALL JACKED UP- When DNA goes BAD- mutations
Mutations are changes in the DNA sequence, which affects genetic information. There can be gene
mutations or chromosomal mutations.
Many mutations involve just one change of a nucleotide. These are called __________ mutations.
Sickle Cell Anemia is a point mutation. The substitution of nucleotide causes red blood cells to be
crescent shaped instead of round. There is no cure for this disease.
Sickled RBC
Substitution: when one nucleotide is __________ with another.
Deletion: when one nucleotide is __________ from the sequence.
Insertion: when one nucleotide is ___________ to the sequence.
Normal
THE
Substitution: THE
FAT CAT
FAT CAT
ATE THE
ATE THE
RAT
BAT
Normal RBC
DNA
TAC GCA TGG AAT
.mRNA
AUG CGU ACC UUA
Amino Acid Met---Arg---Tro---Leu
mutated DNA
mRNA
Amino Acid
TAC GTA TGG AAT
AUG CAU ACC UUA
Met---His---Tro---Leu
A ____________________ mutation occurs when a nucleotide is added or deleted. Frameshift
mutations render the entire protein useless.
Normal
Insertion:
Deletion
THE FAT CAT ATE THE RAT
THO EFA TCA TAT ETH ERA T
TEF ATC ATA TET HER AT
Sometimes and entire ____________ can be added or deleted. These effects can be less harmful
that a frameshift mutation.
Normal
insertion codon
Deletion codon
THE
THE
THE
FAT CAT ATE THE RAT
BIG FAT CAT ATE THE RAT
CAT ATE THE RAT
________________________ happens when one codon is moved into a different location.
Normal
Translocation
Translocation
THE
THE
ATE
FAT CAT ATE THE
CAT ATE THE FAT
THE FAT CAT THE
RAT
RAT
RAT
Chromosomal Mutations pg308
This involves changes in the number of chromosomes or the removal or addition of parts.
Duplication involves doubling a chromosome or some part of a chromosome. People with Downs’
Syndrome have three chromosomes at the 18th or 21st homologous set.
Inversion involves pair of the chromosome break and reforming in the wrong spot.
ABCD
EFGHIJK
EFABC
GHIJK
Translocation This involves non-homologous pairs transferring chromosomal material. (example
chromosome 5 and 12 crossing over). This is not the same as Cross Over in Meiosis.