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Chapter 17
Neurospora

Auxotrophy
Enzyme
Mutant
Transcription
Translation

RNA polymerase

Nascent RNA
Primary transcript
mRNA

rRNA
tRNA

snRNA
siRNA
miRNA
Ribosome
Genetic Code

RNA processing
RNA splicing
Spliceosome
5’cap

A bread mold that Beadle and Tatum used to identify the enzymes in the
metabolic pathway that corresponded to genes which had been mutated
and were no longer working
...

The inability to synthesize a particular organic compound required for
growth
A protein that catalyzes a reaction by lowering the activation energy
required to start a reaction
...

Copying a DNA template strand onto a complementary mRNA transcript
using RNA polymerase (purpose: to make protein coded by certain genes)
Translating processed RNA into a polypeptide by a ribosome and tRNA;
involves adding an amino acid carried by tRNA (identified by aminoayl tRNA
synthetase) to the A site of the ribosome, then translocated to the P site by
the large subunit, and then exited through the E site in the large subunit of
the ribosome to make a protein
...
Pries DNA strands apart (exposing about 20 at a time)
...
RNA polymerase II is one of 3 types of RNA polymerase in
the nucleus, and it is used to transcribe mRNA that is translated into
protein
...

The original copy of nucleotide bases prior to further processing and caps
(in nucleus)
Messenger RNA; complementary to the template DNA strand and
transported into the cytoplasm for translation, allowing for expression of
genes encoding proteins that will be used by the cell
Ribosomal RNA; used for catalyzing reactions and forming the structure of
the ribosome (makes up majority of cell RNA)
The translator in translation; identifies with 1-3 amino acids using
synthetase and adds to the growing polypeptide by placing them at the P
site of a ribosome during translation

Made of large and small subunits; used in translation; lives in rough ER;
made in nucleosome
A combination of 3 nucleotide bases (a triplet or codon) and the amino
acids that each one corresponds to
...

The addition of the 5’ cap, then the 3’ cap
...

Removal of introns by the spliceosome
Cleaves intron sections and connects the exons on either side
A modified Guanine molecule added to 5’ end of mRNA for processing

Poly-A tail
Polyadenylation
Intron
Exon
SNRNP
Open reading frame
5’UTR
3’UTR
codon
Anticodon
Aminoacyl tRNA
synthetase
central dogma
reading frame
Transgenic animal
Promoter

TATA box
Transcription factor
Wobble

A site
P site
E site
SRP
SRP RNA
Tay Sachs Disease
Sickle Cell Anemia

Silent Mutation
Missense Mutation
Nonsense Mutation
Frameshift Mutation

Mutagen

A long chain of 50-250 adenine bases added after the 5’ cap to the 3’ end of
the mRNA being processed
AAUAA sequences that triggers the release of the mRNA strand before
release into cytoplasm
...

A non-coding section of mRNA that is taken out before translation
A coding section of mRNA that gets translated into protein
The start codon until the stop codon
Follows the 5’ cap and precedes the start codon
...

A triplet of nucleotides on either strand of DNA that do NOT overlap and act
as genetic instructions for polypeptide chains
A triplet of nucleotides corresponding to the mRNA codon
An enzyme that identifies the correct amino acid to add to the growing
polypeptide chain in translation
DNA – RNA – protein (Francis Crick, 1956)
The correct grouping of nucleotide bases on an mRNA strand; they must be
read 5’ to 3’ and in groups of 3
...

The sequence on DNA that makes up the binding place for RNA Polymerase
II to begin transcription
...

Example: TATA box
A crucial promoter for RNA transcription
Proteins that help RNA polymerase attach BY BINDING TO THE PROMOTER
The 3rd nucleotide in the CODON is less important because it does not
usually change the amino acid the codon associates with
...
These
are almost always BAD and often result in a stop codon being placed where
there wasn’t one before, and that will result in an incomplete protein
Anything that causes a mutation

Ames Test

A test with bacteria to tell how mutagenic a chemical is; you get lots of
colonies if it is very mutagenic, only a few if it is fairly mutagenic, and none
if it isn’t mutangenic
...
What organism did Beadle and Tatum use in their research? What made it so amenable to their
research aims? Why did some of their mutants grow with some substances while others didn’t? What
did this tell them about the relationship between genes and enzymes?
Neurospora crassa, a type of bread mold
...
After bombarding the neurospora with x-rays to mutate the
genetic information, they created mutants that were defective for a certain enzyme within the
metabolic pathway
...
The enzyme that catalyzed the production of that supplement was the one that was
defective; adding the supplement allowed the rest of the pathway to continue
...
They proved that by
altering genes they would also alter enzymes, which would then alter phenotype
...
What is the central dogma of molecular biology? What exceptions does it have that we studied in
class?
DNA to RNA to protein
...

3
...
We need triplet codons
in order to get the 64 possible combinations that form 20 amino acids in order for us to create proteins
based on our genetic information
...

The 3 stop codons are UAA, UGA, and UAG, which do not add amino acids but instead tell tRNA to add a
water molecule to a growing polypeptide chain in order to trigger its release from the ribosome
...
You should be able to spot an open reading frame within a nucleic acid and be able to translate it into
protein given the genetic code
...
How were mononucleotides, dinucleotides, and trinucleotides used to decipher the genetic code?

6
...
What does
that say about the genetic code?
The genetic code is generally UNIVERSAL; meaning that genes can be inserted into a different species
and still produce the protein that they would have produced in the original species
...
What are the stages of eukaryotic transcription? What is the enzyme that carries it out? In which
direction does this enzyme function? How does the enzyme know which nucleotide to put where? From
where does the energy for polymerization come? What differences are there between prokaryotic and
eukaryotic transcription?
mRNA is transcribed, then it is processed, both in the nucleus
...
Then it is transported to cytoplasm for translation
...
The primary
difference between prokaryotic and eukaryotic transcription is the separation of transcription and
translation in eukaryotes that isn’t present in prokaryotes
...
What is a promoter? What is the relationship between promoters and transcription factors? Where
does RNA synthesis begin? Where does it end?
The promoter is a sequence on the DNA that 1) determines the template strand and 2) acts as a binding
spot for RNA Pol II, allowing it to initiate transcription with the help of transcription factors (which bind
to the promoter to help the polymerase attach)
...
The STOP signal is the
polyadenylation sequence (AAUAAA) in the pre-mRNA which signals proteins to bind immediately
...
When the enzymes
catch up to the polymerase, it disassociates
...
What is the RNA called when it is first made? What modifications are done to it to make it into an
mRNA? What are the functions of these modifications?
It is called pre-mRNA, or the Primary Transcript
...
The 3’ and 5’ caps at both ends have
multiple functions; 1
...
2
...
3
...

10
...
What is the difference between an intron and an exon? Which is left in the mRNA? Which is cut out?

12
...
What is the relationship between exons and protein domains?

14
...
What is a stem loop structure in an RNA? How is one formed? Do they have biological functions?

16
...
What is an aminoacyl tRNA synthase? How many are there? What do they do, and how do they do
it? What is their function in protein synthesis?

18
...
How is translation initiated? What factors must be present for this to occur? Which codon always
initiates translation? Which amino acid does it encode?

20
...
How many ribosomes translate a given mRNA? What are the differences between prokaryotic and
eukaryotic transcription and translation?

22
...
What is the difference between a silent and a missense mutation? What is the causative mutation in
sickle cell anemia? Why does this mutation cause this disease?

24
...
What is a mutation? What agents can cause them? What is the Ames test and how does it work?
What is the relationship between mutagens and carcinogens? Are all carcinogens mutagenic?



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