Nester's Microbiology: A Human Perspective: The Blueprint of Life, from DNA to Protein Flashcards


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1

Central Dogma of Molecular Biology

the flow of information from DNA to RNA to protein; main idea of microbiology

2

First arrow of Central Dogma of Molecular Biology

DNA Replication

3

DNA replication

DNA is copied before cell division; not mitosis

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Second arrow of Central Dogma of Molecular Biology

Transcription

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Transcription

DNA instructions are copied to RNA

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Third arrow of Central Dogma of Molecular Biology

Translation

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Translation

RNA instructions are read and used to build proteins

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Ribosomes

where proteins are assembled out of amino acid monomers

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Messenger RNA (mRNA)

produced by transcription, it is a copy of the instructions in DNA for making protein; the blueprint

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Ribosomal RNA (rRNA)

subunits used to make ribosomes; made up of 2 subunits; function as the spot where proteins are made

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Transfer RNA (tRNA)

holds one specific type of amino acid and adds it to the newly forming protein; brings in amino acid anticodons to match mRNA; 20 different amino acids; upside down clover-leaf

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Binary fission

cell division in bacteria; not mitosis; bacterial cell dividing in half; 2 daughter cells are identical to each other and identical to parent cell

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What are the enzymes associated with DNA Replication?

Helicase and Replisome

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Helicase

enzymes that unzips DNA; separates two sugar phosphate backbones; forms replication fork

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What are the three enzymes of the Replisome?

Primase, DNA Polymerase, DNA Ligase

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Primase

crates a small piece of RNA that acts as a primer

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DNA Polymerase

reads, copies and builds DNA; only reads in 3' to 5' direction; creates a leading strand and lagging strand

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Leading strand

template strand that is read continuously from 3' to 5'; makes one continuous piece of new DNA

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Lagging strand

template strand that is read discontinuously from 3' to 5' prime; makes several fragments of new DNA

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Okazaki fragments

DNA fragments on lagging strand

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DNA Ligase

enzyme that joins the Okazaki fragments together into one piece; makes lagging strand one continuous chain

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When is DNA Replication over?

When the entire chromosome has been copied

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Semiconservative

DNA Replication yields two chromosomes; each one made of one old template DNA strand and one new DNA strand; contains one old sugar phosphate backbone and one new sugar phosphate backbone; still identical

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Bidirectional

Prokaryotic DNA Replication copies their DNA in directions of circular chromosome; clockwise and counter-clockwise

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ORI

Origin of replication; spot on circular chromosome where replication begins; all bacterial cells have a different ORI

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Primer

attaches to 3' end of unzipped DNA; gives DNA polymerase a place to attached; both unzipped backbones need a primer to give a locations for the DNA polymerases to attach

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How does DNA Polymerase make a new strand of DNA?

By matching the template strand with complimentary base pairing; A with T, G with C

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Gene

section of DNA that has the instructions for making one protein

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Gene expression

using the instructions from DNA to build protein

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What are the two parts of gene expression?

Transcription and Translation

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Transcription

copying DNA's instructions into mRNA

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Translation

using the mRNA as an instruction guide for how to assemble proteins

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Sense strand

plus strand of unzipped DNA

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Missense strand

minus strand of unzipped DNA

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What strand is used as the template for mRNA?

Missense strand; ensure that the mRNA that is made is in a sense form

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Monocistronic

transcribed piece of mRNA carries the instructions from one gene; humans have this type of mRNA

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Polycistronic

transcribed piece of mRNA carries the instructions from more than one gene; bacteria have this type of mRNA

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Three processes of Transcription, also in Translation

Initiation, Elongation, Termination

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Initiation of Transcription

upstream of the gene to be transcribed; short section of DNA called the promotor where RNA polymerase will bind to the DNA

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Sigma factor

portion of the RNA polymerase that recognizes and binds to the promoter; falls off after transcription starts

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Elongation of Transcription

RNA polymerase reads the minus strand of DNA from 3' to 5'; makes a piece of mRNA by complementary base pairing

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Termination of Transcription

ends transcription; segment of DNA downstream from the gene called the terminator

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Terminator

where RNA Polymerase falls off/ lets go of DNA

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Ribosome

site of protein synthesis

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Codon

set of three nucleotides that code for one amino acid

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AUG - Start Codon

Methionine

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Ribosomal subunits of prokaryotic cells

30S/50S = 70S

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Ribosomal subunits of eukaryotic cells

40S/60S = 80S

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Initiation of Translation

two subunits of the ribosome come together

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Three positions on the ribosome

Acceptor site (A), Peptidyl site (P), Exit site (E)

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Acceptor site

where the first codon will bind

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Peptidyl site

where amino acids that will be joined together by dehydration synthesis

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Exit site

where the mRNA and tRNA are about to exit the ribosome

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Elongation of Translation

when a tRNA molecule comes in and matches up with codon in the A site; peptide bonds between the two amino acids at the P site; exits at the E site

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Termination of Translation

happens when last codon of an mRNA molecule is a stop codon that does not code for a protein; 3 possible stop codons

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Post transcriptional modificiations

changes that are made to the mRNA molecule after transcription but before translation begins; Eukaryotic cells

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Cap

added to the 5' end of the mRNA; stabilizes the transcript

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Poly A tail

added to the 3' end of the mRNA; A stands for adenine; increases the life of transcript so it does not degrade in cytoplasm

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Splicing

where introns and removed and exons joined together

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Introns

sections of mRNA that do not code for protein; don't contain instructions for protein

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Exons

section of mRNA that do code for a protein; have to be glued together

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Regulation of Gene Expression

Necessary for based on environment, energy preservation, turning on and off Transcription/Translation

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Regulatory proteins of Gene Regulation

Repressors and Activators

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Repressors

regulatory protein that blocks transcription; binds to promotor and stops transcription

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Negative control of gene expression

turns off process of protein production; binds to a section of DNA and blocks RNA Polymerase from reading the DNA; no mRNA is made; allosteric molecules

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Allosteric molecules

they can change shape to become active or inactive

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Activators

regulatory protein that helps transcription occur; helps RNA polymerase bind to the promoter; allosteric molecules

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Positive control of gene expression

turns on process of protein production; used when RNA polymerase does not bind to the promoter well

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Quorum sensing

when organisms sense the density of cells within their own population; allows cells to activate genes that are only useful when expressed by a critical mass

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Operon

set of regulated genes transcribed as a single mRNA molecule, along with the sequences that control its expression

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Regulon

separate operons controlled by a single regulatory mechanism

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Global control

simultaneous regulation of numerous genes

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Constitutive

enzymes that are synthesized constantly; genes that encode these enzymes are always active

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Inducible

enzymes not routinely produced at significant levels; synthesized when needed

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Repressible

enzymes produced routinely, but synthesis can be turned off when they are not required; synthesizes amino acids when needed

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Inducer

attaches to the repressor to change its shape so that it can no longer attach to the operator; with repressor unable to bind to DNA, RNA polymerase transcribes gene

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Corepressor

corepressor-repressor complex binds to operator and blocks transcription

78

Activator-binding site

binding enhances the ability of RNA polymerase to initiate transcription at the promoter.

79

lac operon

encodes proteins involved with the transport and degradation of lactose and is only turned on when glucose is not available but lactose is

80

CCR

Carbon catabolite repression; regulatory mechanism in which a carbon compound prevents the production of inducible enzymes needed for metabolism of a different carbon source