microbiology exam 3

DNA helicase

unzips & unwinds DNA molecules

DNAa

initiator protein, initiates formation of replication bubble, binds ar origin & opens up the double helix

topoisomerase

prevents supercoiling of DNA strands ahead of the replication bubble

DNA polymerase I

removes RNA primers & replaces them with DNA

DNA polymerase

enzymes that synthesizes daughter strands during DNA replication

leading strand is replicated

continuously

lagging strand is replicated

discontinuously

type of bond that links the nitrogenous bases together in DNA double helix

hydrogen

start codon

AUG

Which researcher's work in the late 1920s provided early evidence that DNA was the genetic material of cells by using *Streptococcus pneumoniae*?

Fred Griffith

enzyme that catalyzes DNA synthesis

DNA polymerase

In E. coli, DNA replication stops when the replisome reaches the

the ter site on DNA

The consequence of having a linear chromosome in eukaryotes is that

there must be a mechanism to replicate the ends of the chromosome

The advantage of having multiple origins of replication for a eukaryotic chromosome is that

replication is faster

The "end replication problem" occurs

in cells with linear chromosomes

Eukaryotic chromosomes are _______ than bacterial chromosomes.

larger

format of DNA in eukaryotic chromosomes

linear

Eukaryotic DNA is packaged by wrapping around structural proteins called ________

histones

Initiation of replication for large eukaryotic chromosomes occurs at

multiple origins of replication

Eukaryotic origins of replication are marked by a cluster of proteins known as the

origin recognition complex

How are the four subunits of DNA polymerase α-primase organized

Two catalyze DNA synthesis and two catalyze RNA synthesis

There is no sequence or structural similarities between eukaryotic and bacterial DNA polymerases.

true

DNA polymerases have been sorted into seven families on the basis of their

3D structure & amino acid sequence

The end of a linear DNA chromosome complexed with proteins is called a

telomere

SSB proteins

single stranded binding proteins- keep strands of DNA separated

replisome proteins

topoisomerases, helicases, SSB proteins, primase, DNA polymerase

enzyme that relieves DNA tension

topoisomerase

enzyme that adds RNA primer

primase

Synthesis of the daughter DNA strand from the leading strand template occurs in

5’ to 3’ direction

guanine pairs with ____ ____ __using__ ____non covalent hydrogen bonds

cytosine, 3

adenine pairs with _______ __using__ _____ non covalent hydrogen bonds

thymine, 2

How many DNA polymerases have been discovered in *E. coli*?

5

Together, the primase and several accessory proteins make a complex known as the

primosome

genome

all the genetic information that defines an organism

chromosomes

structures containing DNA/genes

structural gene

produces a functional RNA, which encodes a protein

DNA control sequence

regulates the expression of a structural gene, includes promoters and binding sites

purines

adenine and guanine

pyrimidines

cytosine and thymine

2 types of gene transfer

vertical transmission and horizontal transmission

vertical transmission

from parent to child

horizontal transmission

from one cell to another

genetic code

a set of rules that determines how DNA is converted to an amino acid sequence

gene

basic physical and functional unit of heredity

plasmid

extrachromosomal DNA

DNA consists of 3 sturctures

nitrogenous base, deoxyribose sugar, phosphate

nucleotides are connected to each other by _________________

5’-3’ phosphodiester bonds

bacteria pack their DNA into a series of loops collectively called _____________

nucleoid

positive supercoil

DNA is overwound

negative supercoil

DNA is underwound

most DNA in nature have __________ supercoils

negative

enzymes that change DNA supercoiling

topoisomerases

DNA gyrase is a type _____ topoisomerase

2

type 1 topoisomerase

cleaves 1 strand of DNA, relives or unwinds supercoils

type 2 topoisomerase

cleaves both strands of DNA, needs ATP to introduce negative supercoils

2 kinds of extrachromosomal DNA interact with bacterial genomes

horizontally transferred plasmids and genomes of bacteriophages

conjugation

horizontal gene transfer mechanism requiring cell to cell contact

frederick griffith discovered ________ in bacteria

transformation

oswald avery showed that the transforming substance is:

DNA

rosalind franklin used _______ ____________ __to prove that DNA is__ ___ _ ______________

x-ray crystallography, double helix

james watson, francis crick, and maurice wilkins discovered what about DNA?

complementary bases and antiparallel nature

how do plasmids replicate?

autonomously

replication of cellular DNA in most cases is ___________ __&__ _________________

semiconservative and bidirectional

semiconservative DNA replication results in

daughter cell receives 1 parental and 1 newly synthesized strand

polymerases can only synthesize DNA in this direction

5’-to’3’

primary replication enzyme

DNA polymerase III

DnaB

DNA helicase

DnaC

helicase loader

DNA gyrase

relieves DNA supercoiling

DNA ligase

joins Okazaki fragments

energy for replication is supplied by

nucleotides

restriction endonucleases

cleave DNA at specific recognition sites

restriction endonucleases were cloned into __________

plasmids

bioinformatics

analyze a microbe’s genomes

PCR

polymerase chain reaction

PCR components

DNA sample, primers, nucleotides, Taq polymerase, mix buffer, PCR tube

PCR process

denaturing, annealing, extension

Taq DNA polymerase

heat resistant enzyme

metagenomics

uses modern genomic techniques to study microbial communities directly in nature

3 stages of DNA replication

initiation, elongation, termination

initiation occurs at the __________

origin (oric)

elongation occurs at the __________ ___________

replication forks

termination occurs at the _____________

terminus (ter)

found in mRNA & code for single amino acids

codons

template strand of DNA is read in _________ direction & synthesized in ___________ direction

3’-to-5’, 5’-to-3’

the recognition/binding site for RNA polymerase

promoter

shine dalgarno sequence is important for:

initiation of translation

coding region ends with ________ _________ & is immediately followed by the ___________ _____________

stop codon, trailer sequence

the trailer sequence contains a _______ _________ used to stop transcription

terminator sequence

ribozymes

special ribonucleases, remove spacers between coding regions after transcription

DNA transcription

DNA template is used to create a complementary RNA sequence

mRNA

messenger RNA, carries the message for protein synthesis

tRNA

transfer RNA, carries amino acids during protein synthesis

rRNA

ribosomal RNA, components of ribosomes

polycistronic mRNA

contains directions for more than 1 polypeptide catalyzed by a single RNA polymerase, multiple gene codes on 1 mRNA

bacterial RNA polymerases consist of _______ different proteins

5

sigma factor

helps the core enzyme recognize the start of genes (promoter), no catalytic activity

holoenzyme

core enzyme+sigma factor

sigma factor in e coli

sigma 70

down mutations

cause decreased transcription