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When DNA was discovered, it was found to be __.
acidic, rich in phosphorus, & a very large molecule
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The first evidence in discovering DNA was associated with genetic material came from __
experiments with bacteria
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Describe the results of the experiment with the virulent bacteria/avirulent bacteria.
It was found that when heat-killed virulent bacteria was mixed in with avirulent bacteria, the mouse dies. This is due to the thick capsule gene being passed on from the virulent to the avirulent bacteria.
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The conversion of living harmless bacteria into the virulent bacteria is called __
transformation
Transforming Principle = genetic material
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Why was protein once thought to carry genetic material before more information on DNA was found?
Proteins have different structures & a lot of variation compared to DNA
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How was DNA found to be the genetic material and not RNA or proteins?
- When the mouse was given protease or ribonuclease (to digest proteins or RNA), this did not prevent the transformation from avirulent to virulent, so the mouse still died. But when given Deoxyribonuclease (digests DNA), transformation did not occur and the mouse lives. This shows that DNA was the molecule that carried the virulent gene.
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Describe how pure DNA isolation was further proof of DNA being the genetic material.
- When pure DNA from a pathogenic (S) cell was isolated and added to a nonpathogenic (R) cell, this produced a pathogenic (S) cell after recombination and cell division.
- CapS = gene responsible for generation of a capsule, giving a smooth appearance
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How were virus genes proven to be made of DNA?
DNA and proteins (capsid part) of phages were labeled with 32P (phosphate) & 35S (methionine) and attached to bacteria. After agitating and centrifuging, infected bacteria absorbed 70% 32P from DNA, meaning that it was mostly DNA that entered the bacteria.
It has also been shown that it is possible to isolate the whole DNA component of some of the viruses & enter it to host cells. The host cells then will generate many complete viruses.
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DNA is a __ containing __
- long polymer;
- phosphate, sugar molecules (deoxyribose), & 4 nitrogenous bases (adenine, guanine, thymine, cytosine)
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Each base of DNA is attached to __ of a deoxyribose (__ bond) with a phosphate bound to __ of deoxyribose (__ bond).
- carbon 1; glycosidic; carbon 5; ester
- (same structure for RNA except with ribose)
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Subunits of DNA are linked by __ bonds
3' to 5' phosphodiester
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Watson & Crick identified DNA structure as a __
complementary double stranded helical polymer
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The 2 strands of DNA are held together by __ bonds
hydrogen
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Base pairs occur in DNA in a __ ratio.
1:1
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Base pairing is due to the formation of __ bonds between A & T, and C & G nucleotides in the 2 strands of DNA
hydrogen
(The order of nucleotides in the parental DNA can determine the order of nucleotides in the daughter DNA due to this base pairing.)
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In __ DNA synthesis was performed by using cell free bacterial extract. Then, __ was identified
vitro; DNA polymerase (enzyme that polymerizes DNA)
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DNA polymerization requires __
- the building blocks of DNA in the form of high energy molecules containing 3 phosphates, dATP, dTTP, dGTP, dCTP;
- and a DNA template
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DNA polymerase I (DNA Pol I) polymerizes the DNA strand by attaching the __ to the __ making __ bonds. The addition of each nucleotide releases __
phosphate of 5' end of the new nucleotide; 3'OH of the previous nucleotide in the chain; phosphodiester; pyrophosphate (PPi)
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Polymerization requires the presence of a __ to determine the order of nucleotides in the newly synthesizing DNA strand.
DNA template
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DNA polymerase synthesizes DNA from __
the parental DNA directly. (No other intermediate molecule such as protein is needed.)
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The produced DNA had __ ratios of the 4 nucleotides as the parental template DNA
the same (conserving the content of info)
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The __ scheme requires the separation of 2 strands during DNA polymerization.
semiconservative
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How was the semiconservative scheme discovered to be the correct one for DNA replication? (Meselson-Stahl experiment)
- Bacteria grown in 15N > 14N & harvested the cells after 1 & 2 generations. DNA was isolated and density gradient centrifugation was performed. After transfer to the regular media, there was only 1 band of DNA after 1 generation indicating a 15N-14N hybrid. There were 2 bands (15N-14N & 14N-14N) after 2 generations. These results indicate DNA replication is semiconservative.
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Genetic info is originated from the __
sequence of DNA & order of nucleotides
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RNA
intermediate molecule needed to carry the message of DNA to the production of proteins
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Genes are transcribed into __
RNA
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enzymes that perform transcription
- RNA polymerases
- (transcribe RNA from DNA)
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__ are needed to specifically bind to each amino acid for protein synthesis. (have specific binding to RNA as well)
adaptor molecules
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rRNA
- in the ribosomes of cytoplasm
- makes up more than 85% of cellular RNA
- very conserved among organisms with similar GC ratios
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mRNA (messenger RNA)
- make up a small percentage of total RNA within the cell
- varieties of this type of RNA in the cell (variable in size & composition)
- coded by DNA (sequence similar to DNA)
- interacts with ribosomes for protein synthesis
- Many ribosomes can bind to one mRNA (polysome)
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tRNA (transfer RNA)
- Amino acids, before incorporation into proteins, bind to these small RNA molecules.
- the adaptor molecules needed for the flow of info from RNA to protein
- On one side of a tRNA, there is a specific sequence for interaction with mRNA and on the other side of a tRNA, an amino acid is bound.
- different tRNAs for different amino acids
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RNA polymerase needs a presence of __
DNA & nucleotides ATP, UTP, GTP, CTP
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__ is used as a template for transcription
1 strand of DNA
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The Pulse Chase assay shows __
that RNA is synthesized in the nucleus & then localized in the cytoplasm.
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the idea of co-linearity
The sequences of nucleotides should determine the sequence of amino acids within the encoded protein.
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All amino acids can be coded with __ nucleotides.
3
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A __ is a polymer of amino acids linked one by one by __ bonds
polypeptide; peptide
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Polypeptides have a __ end & a __ end
amine (N terminal); carboxyl (C terminal)
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Ribosomes recruit __ (containing info) and __ (that translate the codons into amino acids) and __ the amino acids into specific proteins (polypeptide).
mRNA; aminoacyl-tRNAs; polymerize
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Gene expression occurs through __
- transcription of a gene to RNA &
- translation of an mRNA to a protein
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Proteins are synthesized from the __ terminal to the __ terminal
N; C
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How was the direction of translation determined?
There are more radioactive amino acids at the start of translation which is closer to the N terminal.
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Mutation is a change within the __
original DNA sequence
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A mutation may change one or more __. Depending on the mutation, it may cause a mild, moderate, or severe change in __
- amino acids coded by a gene;
- the function of the coded protein
- (Varieties of mutations may happen in a gene causing different effects.)
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chromosome
a genetic structure made of long DNA molecules & the proteins associated with the DNA
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genes
parts of the DNA molecule of each chromosome
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The order of nucleotides in a gene codes for __
a particular protein or a particular function
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