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108 Cards in this Set

  • Front
  • Back
what are the three levels of structure and function of the genome
genome
chromosome
gene
The sum total of genetic material of a cell
genome
describe a chromosome
A discrete cellular structure composed of a neatly packed DNA molecule
describe eukaryotic chromosomes
DNA molecule tightly wound around histone proteins
Located in the nucleus
Vary in number from a few to hundreds
Can occur in pairs (diploid) or singles (haploid)
Appear linear
describe bacterial chromosomes
Condensed and secured by means of histone like proteins
Single, circular chromosome
what is A certain segment of DNA that contains the necessary code to make a protein or RNA molecule
gene
what kinds of genes code for proteins and RNA
structural genes
what do regulatory genes do?
control gene expression
sum of all types of gene expression
genotype
define phenotypes
how the expression of the genotype looks
do all of an orgs genes in their genotype manifest all the time?
no
what are the basic units of DNA
nucleotides
what are the three types of nucleotides
Phosphate
Deoxyribose sugar
Nitrogenous base
what types of bonds are formed between the deoxyribose sugar and phosphate?
covalent
each deoxyribose sugar attaches to _____ ______
two phosphates
where are the covalent bonds between the sugar and phospates on the deoxyribose?
One bond is to the 5’ carbon on deoxyribose
The other is to the 3’ carbon
what do the nitrogenous bases consist of?
purines and pyrimidines
what do the nitrogenous bases bond to?
the 1' position of the deoxyribose sugar and each other
what kinds of bonds form between the nitrogenous base and the deoxyribose sugar?
covalent bonds
what kinds of bonds form between the complementary nitrogenous bases?

describe these bonds
hydrogen bonds

Easily broken
Allow the molecule to be “unzipped”
Adenine always pairs with _______
thymine
Guanine always pairs with _______
cytosine
describe Antiparallel Arrangement
One side of the helix runs in the opposite direction of the other
One helix runs from 5’ to 3’ direction
The other runs from 3’ to 5’
describe The Overall DNA Replication Process
Requires the actions of 30 different enzymes
Separate the strands
Copy its template
Produce two new daughter molecules
what is DNA Replication?
DNA to DNA
what is transcription?
DNA to mRNA
what is translation?
mRNA to protein
Synthesis of DNA proceeds ___’ to _____’ adding new bases to a free _____’ _______group.
5' to 3'
3' OH groups
Each new DNA strand is made of :
1 parent and 1 daughter strand (see slide 20)
what unzips the DNA helix?
helicase
what synthesizes an RNA primer
Primase
what adds bases to the new DNA chain and proofreads the chain for mistakes/
DNA polymerase III
what removes the primer, closes gaps, and repairs mismatches?
DNA polymerase I
What is responsible for the final binding of nicks in DNA during synthesis repair
Ligase
what is responsible for supercoiling
gyrase
describe the origin of DNA replication
Denotes the of DNA synthesis
Rich in A and T
Held together by only two H bonds rather than three
Less energy is required to separate the two strands
describe the action of helicases
Helicases bind to the DNA at the origin
Untwist the helix
Break the hydrogen bonds
Results in two separate strands
what is the Enzyme responsible for for DNA synthesis in Prokaryotes
DNA Plymerase III
DNA polymerase Can only add a new base to an _____ _______
existing 3’ OH
what is the ability to “back up” and correct mistakes made during replication called?
exonuclease activity
Greatly reduces mutation rate
what is responsible for making an RNA primer that provides the 3' OH group for DNA Polymerase III?
RNA Primase
what removes RNA primers and replaces them with DNA
Also has exonuclease (proofreading activity)
DNA polymerase I
when and what do DNA ligases act?
When the forks come full circle and meet, DNA ligases move along the lagging strand
Anneal DNA fragments together into a continuos strand.
Heavily involved in the continuous production of the lagging strand
what is the central dogma of DNA transcription and translation
Genetic information flows from DNA to RNA to protein
Exceptions: RNA viruses and retroviruses
How does RNA differ from DNA?
Single stranded molecule
Helical form
Contains uracil instead of thymine
The sugar is ribose instead of deoxyribose
what does RNA polymerase do?
codes DNA into RNA
what are The Major Participants in Transcription and Translation?
mRNA
regulatory RNAs
RNA Polymerase (Codes DNA into RNA)
storehouse of raw materials
Only _______ is translated into a protein molecule
mRNA
what is the first stage of gene expression
transcription
A gene differs from another in its ______ __ _______
composition of triplets
what is a triplet?
Three consecutive bases on the DNA strand
Each triplet represents a code for what?
a particular amino acid
When the triplet code is transcribed and translated, it dictates the _________________in a polypeptide chain
type and order of amino acids
A protein’s primary structure determines its what?
characteristic shape and function
what ultimately determine phenotype?
proteins
DNA triplets are transcribed into a series of ________ by the ___________
codons
messenger RNA
Describe how Amino acids are formed
DNA triplets are copied into mRNA codons which code for the amino acids
what is the message in messenger RNA?
The mRNA codons and the amino acids they specify
what is it called when a particular amino acid can be coded for by more than a single codon
redundancy
what is it called when only the first two nucleotides are required to encode the correct amino acid
wobble

thought to permit some variation or mutation without altering the message
what is the start codon?
AUG
what are the three stop codons?
UAA
UAG
UGA
what is the second stage of gene expression?

where does it occurs
translation - mRNA codes for amino acids broght together on the ribosmes
what are the first three stages of translation?
initiation, elongation, termination
describe tRNA
Also a copy of a specific region of DNA
It is uniform in length (75-95 nucleotides long)
Cloverleaf shape
Bottom loop of the cloverleaf exposes a triplet (the anticodon) that designates the specificity of the tRNA and complements mRNA’s codons
For each of the 20 amino acids there is at least one specialized type of ______to carry it
tRNA
describe the what happens after transcription
after mRNA has been transcripted, it leaves the DNA transcription site
it is transported to the ribosomes in the cytoplasm
ribosomal subunits have sites to hold the mRNA and tRNA
describe the steps of protein synthesis at the ribosome
small subunit binds to the 5’ end of the mRNA
A sequence know as the Shine-Delgarno sequence in the mRNA binds the 16srRNA sequence - Large subunit docks with the small subunit, Start codon AUG initiates
With the mRNA message in place on the ribosome, the tRNAs the enter with their amino acids
The complementary tRNA carrying its corresponding amino acid, meets with the mRNA code, tRNA is released thru E site and leaves its amino acid
.
.
describe simply the sequence of events from DNA to protein.
DNA codes for mRNA
mRNA transferred to ribosome
tRNA carries in amino acids and meets with complementary codes of mRNA
tRNA leaves ribosome, leaving amino acid behind
the amino acids are bound into a polypeptide chain
which is released from the ribosome by release factors after the termination codon is reached (nonsense codons that don't code for a tRNA)
..
..
what enzyme is responsible for mRNA transcription?
RNA polymerase
Before it is released from the ribosome, the polypeptide chain starts to _____ _____ ____to achieve its biologically active ______ ______
fold upon itself

tertiary conformation
polypeptide chains Join with other proteins to form ______ ______of structure
quaternary levels
what is an operon?
Prokaryotes organize collections of genes into operons
Coordinated set of genes regulated as a single unit
what is an inducible operon?
Inducible- the operon is turned on by the substrate of the enzyme for which the structural genes code
what is a repressible operon?
Repressible- contain genes coding for anabolic enzymes; several genes in a series are turned off by the product synthesized by the enzyme
three things to know about protein synthesis
ribosomes are the site of p.s.
tRNA brings in amino acids
the anti codon on fRNA matches with an mRNA codon to determine which amino acid gets brought in.
what is the Best understood cell system for explaining control through genetic induction
the Lactose operon
three features of the lactose operon
the regulator
the promoter
the operator
describe the regulator
a gene that codes for a protein capable of repressing the operon (a Repressor)
describe the promotor
recognized by RNA polymerase
describe the operator
a sequence that acts as an on/off switch for transcription
what happens when there is no substrate (lactose)?
the Repressor will grab on to the gene strand and prevent RNA polymerase from working (negative feedback)
what happens when there is substrate
the presence of lactose turns the operon on - the repressor is bound to the lactose inducer, allowing more lactase to be produced to digest the lactose. (positive feedback)
the lactose operon is a model of ________ gene regulation
inducible
describe the repressible operon
Normally the operon is in the “on” mode and will be turned “off” only when the nutrient is no longer required
The excess nutrient serves as a corepressor needed to block the action of the operon
Example, arg operon
(negative feedback)
describe the arg operon
when you have enough arg. the arginine turns on the repressor - interacts with it to allow it to clamp onto the gene and stop the transcription
define mutation
when phenotypic changes are due to changes in the genotype
An alteration in the nitrogen base sequence of DNA
wild type
Wild type: an organism that exhibits a natural, non-mutated characteristic
mutant strain
Mutant strain: when a microorganism bears a mutation
what are the causes of mutations
Spontaneous mutation: random change in the DNA arising from errors in replication
Induced mutation: results from exposure to known mutagens
what are point mutations?
involve addition, deletion, or substitution of single bases
what are the 4 types of point mutations?
missense mutation
nonsense mutation
silent mutation
back-mutation
describe missense mutations
Missense mutation: any change in the code that leads to placement of a different amino acid
Can create a faulty, nonfunctional protein
Can produce a protein that functions in a different manner
Can cause no significant alteration inI protein function
describe nonsense mutation
changes a normal codon into a stop codon
describe a silent mutation
alters a base but does not change the amino acid and thus has no effect
describe a back-mutation
when a gene that has undergone mutation reverses to its original base composition
describe frameshift mutations
Frameshift mutations: mutations that occur when one or more bases are inserted into or deleted from a newly synthesized DNA strand
Changes the reading frame of the mRNA
Nearly always result in a nonfunctional protein
what are the three means of genetic recombination in bacteria
conjugation
transformation
transduction
describe conjugation
bacterial "sex"
requires cell to cell contact, usually through a pilus
f+ donor cell donates genetic material (plasmid copy) into the f- recipient cell.
describe transformation
living cell uptakes naked DNA from other dead cells
doesn't require cell to cell contact
describe trnsduction
virally mediated horizontal DNA transfer