Download Did you ever get a message from a friend that was in code

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Did you ever get a message from a friend that was in code?
How did you figure out what the message said?
Like a secret code, DNA also involves the match of a code with a key, and the translation of the
code results in something useful!
Molecular Genetics
Chapter 12
I.
A. Discovery of the Genetic material
1. Introduction
a. 1900’s, scientists search for the chemical involved in Mendelian genetics.
b.
2. Griffith (1928)
a.
Streptococcus pneumonia
-S strain has smooth outer sugar coat on cell (caused disease)
-R strain had no coating and rougher looking (no disease)
b.
!
c. Figure 2 p. 327-experiment
d. Set the stage to identify the transforming factor (DNA)
3.
a. Isolated the macromolecule which transformed bacteria into a different
strain
b. Scientists still have not concluded that the genetic material is a protein
or DNA
4.
a. Provided definitive evidence that DNA was the transforming factor.
b. They used bacteriophages (virus which infects bacteria) to prove
that DNA was the genetic material.
c.
~Fig. 3 p. 328
~Used radioactive Phosphorus
-not found in normal protein
would be radioactive
~
-Sulfur found in protein
-Proteins and not DNA would be radioactive
d.
~Results-the viral DNA was injected into the cell and
provided the genetic information needed to produce new viruses.
-powerful evidence that DNA is the genetic material.
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B.
1. Nucleotides
a. Structure of all nucleotides
-Sugar (5-Carbon sugar)
-Nitrogenous base
b. DNA nucleotides
-Phosphate group
-Nitrogenous bases
Adenine, Thymine, Guanine and Cytosine
c.
-Ribose sugar
-Phosphate group
Adenine, Uracil, Guanine and Cytosine
2.
a. discovered that the amount of Adenine is close to Thymine
and the amt of Guanine is close to the amount of Cytosine.
b. Figure 5 p. 329
c.
Adenine pairs with Thymine
Guanine pairs with Cytosine
d. in RNA
A-U, G-C
3.
a. what was the exact structure of the two nucleic acids
b. Rosalind Franklin –chemist
Francis Crick-physicist
James Watson-biologist
4.
a. X-ray of molecule showed shape
figure 6 p. 330
b. Franklin gave Watson and Crick the final piece of the puzzle of
the shape of the DNA molecule
c.
5. Watson and Crick (Figure 7) 1953
DNA has
a.
Two outside strands consisting of alternating deoxyribose and
phosphate.
b.
Cytosine pairs with Guanine and held together with H-bonds
c.
Adenine pairs with Thymine and held together with H-bonds.
6.
a. similar to a twisted ladder
-sides of ladder = sugar and Phosphates
-rungs of ladder = base pairs
b. Purines=
Pyrimidines=thymine and cytosine
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c. The ORDER of the nucleotides holds the CODE to make the
gene for a trait.
7. Orientation
a. Each point of the 5-carbon sugar is numbered.
b.
c. Sugar/phosphate runs either 5’ to 3’ or 3’ to 5’
d.
5’ = five-prime carbon on the left
3’ = carbon is on the right of the sugar
e.
Both strands run opposite to each other.
f.
Ex. Two pencils facing in opposite directions.
C.
1. Prokaryotes
a. DNA is in the cytoplasm
b.
2. Eukaryotes
a. DNA organized into individual chromosomes
-51 million to 241 million Base pairs
-141 million laid out would be about 5 cm (2 inches)
b.
-coil, coil, condense, coil…around histones to form
nucleosome (genes)
-chromatin makes chromosomes
c. Figure 9 p. 332
Genes are specific sequences of DNA in a chromosome, and they code for a protein.
II.
Chromosomes appear doubled in prophase..
A.
Semiconservative Replication
DNA-chromosomes doubling
1.
Defined-parental (original) strands of DNA separate, serve as templates
(pattern), and produce new DNA.
-one strand (side) of DNA is the parent strand
-one strand (side) of DNA is new
2.
a. unwinding
b. base pairing
c.
3. UNWINDING
a. DNA helicase (enzyme) breaks the bonds between the nitrogen
bases (ATGC)---unzips the molecule
b. Double stranded DNA is now 2 single strands
c.
4. BASE PAIRING
a. Free nucleotides in the cell fit in and match up with the correct
nitrogenous base to create another strand.
b. Free nucleotides are added to the 3’ end of the new strand.
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c. One strand begins at the end and works towards the original unwinding
DNA fork. This is continuous until the end of the DNA split.
d. The other strand elongates away from the replication fork
-Made in discontinuous small segments called Okazaki fragments
-Enzymes attach this strand together so it is continuous at
the end of replication
5.
B.
a. Figure 12 p. 335
b. DNA strands join together by enzymes making H-bonds
Comparing DNA replication in eukaryotes and prokaryotes
1.
E
a.
DNA unwinds in many separate areas.
b.
Many areas of replication are occurring along the large eukaryotic
chromosome at the same time.
-appears
2. Prokaryotic DNA replication
a.
b. replication occurs in two directions
DNA must be replicated before mitosis, meiosis, and reproduction can take place!
III. DNA,RNA,and Protein
DNA codes for RNA, which guides protein synthesis (making of a protein)
A.
C
1.
2.
3.
4.
Proteins function as structural building blocks for the cells and as enzymes
ALL living things, from bacteria to humans, make protein from instructions in
DNA
DNA is the recipe (gene) that is found on the chromosome in the nucleus.
The recipe gets to the ribosome (in the cytoplasm) by the RNA writing it
down in the nucleus and bringing it to ribosomes to be made.
B.
1.
2.
3.
Nucleic Acid
~One of two nucleic acids. DNA is the other nucleic acid.
S
a.
Ribose sugar
b.
Phosphate
c.
N
Types of RNA in a cell
a.
Messenger
-Job is to carry written recipe (code) for a protein from the nucleus
to the ribosome
-Can
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-Writes recipe from DNA in the nucleus and takes it to the ribosome
in the cytoplasm.
-Table 2 p. 336
b. R
-Job is to help supervise making a protein at the ribosome and to
help make new ribosomes.
c. T
-Job is to travel throughout the cell and pick up the correct
ingredients for making the protein.
-Reads the code given by mRNA and picks up the correct amino acids
and bring them back to the ribosome to make the protein.
MAKING A PROTEIN:MAKING A CAKE
Cell=House
Nucleus=Family room
Ribosome=Kitchen (makes things)
mRNA= you
rRNA=supervisor in kitchen
tRNA=many children
DNA=Cookbook (in family room)
Codon=(secret code for an ingredient-aa)
Amino Acids=ingredients for cake
B.
Protein Synthesis (making a protein)
1.
T
a.
Process of writing down (coding) the recipe (gene) for making a
protein and carrying that recipe to the ribosome in the cytoplasm.
b.
S
-DNA unzips where recipe that is needed. (open cookbook)
-mRNA writes down (in backward code) the recipe from DNA
-mRNA carries the recipe (code) to the rRNA in the ribosome.
c. Detailed steps
-DNA unzips where recipe is located for the needed protein
-RNA polymerase (enzyme) attaches to the site and manufactures
mRNA
-mRNA moves along the DNA in the 3’ to 5’ direction.
-__________________=strand of DNA that is read by RNA
polymerase
-Nontemplete strand=strand of DNA not being read by RNA
-mRNA detaches from DNA template strand, travels through nuclear
pores in the nuclear membrane and into the cytoplasm.
d. RNA
-Scientist found that RNA code was much shorter than the original
DNA code
-Discovered that DNA has sequences NOT used in the recipe called
i_______________________________
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-The coding sequences that remain in the final mRNA are called
_______________.
-Some eukaryote cells make a pre-mRNA which is edited before
leaving the nucleus as mRNA.
2.
a. Process of reading the recipe (code) for making a protein and putting the
recipe together. The end product is the protein.
b.
The
-Proteins are made with __________different amino acids
-there must be 20 different codes in the DNA for each amino
acid
~CODON= ____________________________ FIGURE 14 P. 338
~There are codes for start and stop.
c.
Process of _________________
-mRNA at the ribosome is interpreted (read) by tRNA
-tRNA travels with the anticodon (opposite of codon)
to find the correct Amino Acid in the cell.
-tRNA brings the amino acid back to the ribosome where it is put
together to make the correct protein.
-Protein is made (polypeptide chains—poly=many, peptides bonds
=___________________________
Figure 14 p. 338
Determine the possible sequences that would produce the amino acid chain;
Start—serine—histidine—tryptophan—stop
Does protein synthesis ‘cost’ the cell energy?
IV. Gene
Gene expression is regulated by the cell, and mutations can affect this expression.
A.
Prokaryote
1.
Gene Regulation = the ability of an organism to control which genes are
transcribed in response to the environment.
2.
__________-a section of DNA that contains the genes for the proteins
needed for a specific metabolic pathway.
a.
Acts as an on/off switch _____________________________
b.
Tryptophan and lactose needed to function properly
c.
Types _______________________
-trp operon
~represses _________________
~makes prokaryote inactive
-lac operon
~turns on _________________
~makes prokaryote active
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B.
Eukaryote ___________________________________
~Eukaryote cells must control what genes are expressed at different times in the
organism’s lifetime.
~Eukaryotes are more complex than prokarytoes so they have a more complex
control system for turning off/on genes.
1.
Controlling ___________________________
2.
Hox genes ___________________________
a.
Crucial during development of a fertilized egg to an organism.
b.
Cells move from mitosis to differentiate (change) into different
cells.
c.
Important to determine the body plan of an organism.
d.
Controls the transcription of specific genes at specific times and in
specific locations
e.
One mutation in the Hox genes may cause legs to grow where
antennae should be….. 
f.
Studying Hox genes helps scientists study how genes control the
body plan of organisms.
3.
________________________________
a.
RNA cut/damaged and cannot translate code for protein.
b.
Currently being studied as a possibility to treat cancer, diabetes, and
other diseases.
C.
Mutations Table 3 p. 346
1.
Defined- ______________________________________________
2.
Types of mutations
a.
Point mutations (substitution or missense mutation)
-change in just one base pair (codon) and messes up the genetic
order
Normal-THE BIG FAT CAT ATE THE WET RAT
Mutation-THE BIZ FAT CAT ATE THE WET RAT
b.
-Changes the codon for an amino acid to a STOP codon.
Normal-THE BIG FAT CAT ATE THE WET RAT
Mutation-THE BIG RAT
c.
-deletion of amino acids Normal-THE BIG FAT CAT ATE THE WET
RAT
Mutation- THB IGF ATC ATA TET HEW ETR AT
-insertion of amino acids
d.
-too many amino acids
Normal-THE BIG FAT CAT ATE THE WET RAT
Mutation-THE BIG ZFA TCA TAT ETH EWE TRA
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e. Expanding mutations
-tandem repeats of an amino acid with every division
THE BIG FAT CAT ATE THE WET RAT
THE BIG FAT CAT CAT ATE THE WET RAT
THE BIG FAT CAT CAT CAT ATE THE WET RAT
f. Large portions of DNA mutated
-drastic effects on organism
-big chunks of DNA can move to other chromosomes or lost
-ex. Fragile X syndrome
3.
Causes of mutations
a.
S__________________________________________
-you have a DNA proofreader that will fix most of these mistakes
-1 in 1 billion will NOT be fixed
b. __________________________
-defined-substances which cause mutations
-High energy radiation (x-rays) Causes free radicals to damage DNA.
-UV radiation from the sun Causes thymine to stick together and
disrupt DNA codes.
4. Body-cell v. sex-cell mutations
a.
-Most go unnoticed
-If it disrupts making a particular enzyme, may be fatal or make you
-This mistake is NOT passed onto to the offspring since it
is NOT in the sperm or egg.
b.
-The mutation IS passed onto the offspring.
-Depends on what type of cell in the offspring that is affected as to
how serious the mutation may be.
-making digestive enzyme mutation=very serious
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