Microbio Exam 3

What is Replication?

DNA makes DNA

What is Transcription?

DNA makes RNA

What is Translation?

mRNA makes protein

What is Reverse Transcription?

RNA makes DNA

What is the Central Dogma (AKA Information Flow)?

DNA, RNA, Polypeptide (amino acids)

What is a Gene?

A unit of DNA that encodes for a single protein

What is a Chromosome?

Genes stung together into larger molecules

What is a Genome?

The complete set of an organism’s genes

Paired building blocks of DNA

A, T, G, C

Paired building blocks of RNA

A, U, G, C

What is the sugar molecule in DNA?

Deoxyribose

What is the sugar molecule in RNA?

Ribose

In DNA and RNA, which carbon does Phosphate attach to?

5’ Carbon

A,T pairing has how many H bonds?

2 H bonds

G, C has how many H bonds?

3 H bonds

The two complementary strands of DNA are _______ and run in the _____ direction of the backbone

Antiparallel, 5’ 3’

Chromosomal DNA exists in a _______ form so it can be packed inside a cell

Supercoiled

Supercoiling is catalyzed by the _______ enzyme

Topoisomerase

In prokaryotes, supercoiling is catalyzed by the _____ enzyme

DNA gyrase

Bacterial DNA is supercoiled to form what?

A Nucleoid

Eukaryal DNA are wrapped around ______ to form ______ inside the nucleus

Histones, Nucleosomes

What is an Operon?

A set of functionally related genes that will be transcribed together

What is an Intron?

Non-Coding DNA

What is an Exon?

Coding DNA

In prokaryotes, Chromosomes are what shape?

Circular

True or False: Archaea have Histones whereas Bacteria don’t

True

What is a Plasmid?

Short, double-stranded DNA

In Eukaryotes, Chromosomes are what shape?

Linear

What shape and size is the DNA inside Mitochondria and Chloroplast?

Circular, intermediate

Can Eukaryotes have Plasmids?

Rarely

What is the typical number of genes in a Prokaryotic cell?

3000-4000 genes

A human has how many genes?

20-25K genes

What % of human DNA is non-coding?

> 98%

What % of Prokaryotic DNA is non-coding?

~20%

True or False: A DNA sequence containing high % of G and C bases will

have a stronger association between the two strands than the

sequences with high A and T bases.

True

DNA replication is _________, resulting in one parental strand and one progeny strand

Semi-conservative

When does DNA replicate?

When cells are ready to divide

Where does DNA replication start at?

Ori

Prokaryotic chromosomes have how many Ori?

1

Eukaryotic chromosomes have how many Ori?

> 1

What binds to OriC to open double-stranded DNA to begin replication?

DnaA

What is the job of Helicase (DnaB)?

Unwinds double helix

What is the job of SSB protein?

Binds to ssDNA and prevents re-association of the ssDNA at the fork

What is the job of Primase (DnaG)

Binds and synthesizes short RNA primers

What is the job of DNA polymerase III?

Synthesizes DNA in 5’ → 3’ direction; forms phosphodiester bonds

What are the directions of the leading and lagging strands of DNA polymerase III?

Leading strand: 5’ → 3’ continuously, Lagging strand: 5’ → 3’ discontinuously

The discontinuous fragments are called what?

Okazaki fragments

Replication in circular DNA is __directional

Bi-directional

Replication is terminated when two replication forks meet at ______ site

Ter (termination)

What is the job of DNA Pol I?

Removes RNA primers and fills in nucleotides

What is the job of DNA Ligase?

Seals nicks in the backbone with phosphodiester bonds

What is a Telomere?

Repetitiveve, short, non-functional DNA fragments added to the 3’ end of eukaryotic DNA by the enzyme telomerase

In the Griffith Experiment, what is the Transforming Principle?

Allowing dead S cells to convert R cells into living S cells

What is Transformation?

The ability of bacteria to take up extracellular DNA

In the Avery, Macleaod, and McCarty experiment, which enzymes still allowed for R cells to transform dead S cells into living S colonies when treated with said enzymes?

Protease, RNase

What was the transforming agent of the Avery, Macleaod, and McCarty experiment?

DNA

What gene was passed that transformed R into S strains during the Avery, Macleaod, and McCarty experiment?

The gene for making the polysaccharide capsule

When was the Hershey-Chase experiment conducted?

1952, by Alfred Hershey and Martha Chase

What was the hypothesis of the Hershey-Chase experiment?

Because bacteriophage T2 is made of only protein and DNA, one substance must be the genetic material

What was the experiment conducted during the Hershey-Chase experiment?

Proteins were labeled with radioactive S, DNA with radioactive P → infect E. coli → centrifuge and separate capsids from cells → analyze location of radioactive molecules

What was the conclusion of the Hershey-Chase experiment?

DNA was the genetic material

When did the Franklin, Wilkins, Watson, and Crick experiments occur?

1953

What was the question asked by the Franklin, Wilkins, Watson, and Crick experiments?

What is the structure of DNA

What was the conclusion to the Franklin, Wilkins, Watson, and Crick experiments?

They developed the double-helix model of DNA

What is the forward and reverse direction of DNA strands?

Forward: 5’ → 3’, Reverse: 3’ → 5’

The strands of a DNA double helix are ________ and _________

Complimentary, Antiparallel

During bacterial initiation, what is the Origin of Replication?

oriC

What two kinds of repeats are found in oriC?

13-bp, 9-bp

Which protein is bacterial Helicase?

DnaB

Which protein delivers Helicase to the replication complex in bacteria?

DnaC

What structure forms after DNA strands separate?

A Replication Bubble with two replication forked ends

What do SSBs do during DNA replication?

They bind single-stranded DNA to keep the strands apart, preventing them from re-annealing and protecting them from degradation

What are the ter sites in bacterial replication?

Sequences opposite to oriC where replication stops

Which proteins bind to bacterial ter sites, and what do they do?

Tus proteins, which halt the replication forks

What enzyme separates newly created bacterial chromosomes from each other?

Topoisomerase II

True or fasle: bacterial chromosomes have telomeres

False

In eukaryotic initiation, which complex binds to the Autonomously Replicating Sequece (ARS)?

ORC

What proteins are recruited after ORC binds to ARS?

Cdt1, Cdc6, and the MCM complex

Which if the recruited proteins in eukaryotic initiation is the Helicase?

MCM

What are Telomeres?

Repeat sequences at the ends of linear chromosomes

What would happen if the replication process stopped at the completion of the incomplete lagging strand?

The chromosome would get shorter with each round of replication, eventually causing cell senescence or death

What removes the RNA primer at the end of every lagging strand?

Exonuclease

What kind of enzyme is Telomerase?

An RNA-dependent DNA polymerase

What does telomerase extend, and in which direction?

The 3′ end of the parental strand, 5′→3′

What is Translocation?

Telomerase shifts along the newly made repeat so it can add another one

What is the job of Primase?

It synthesizes short RNA primers, giving DNA polymerase a 3′ end to extend

What is the main DNA polymerase in bacteria?

DNA pol III

What is an Okozaki Fragment?

A short stretch of DNA made on the lagging strand, beginning with an RNA primer

Which enzyme removes RNA primers in bacteria?

DNA pol I, using its 5′→3′ exonuclease activity

What is the Primase used in eukarya?

DNA pol a

What is the Helicase used in eukarya?

Dna2

What is the replication enzyme used in eukarya?

DNA pol ϵ (leading), DNA pol δ (lagging)

What is responsible for the removal of primers in eukarya?

FEN1 [Rad2]

What is the function of mRNA?

Coding molecules translated into proteins

What is the function of tRNA?

Involved in translation, charged with amino acids

What is the function of rRNA?

Structural components of ribosomes

What is a Promoter

A specific DNA sequence recognized by the sigma factor of RNA pol to allow RNA pol to start transcription

How may spaces away from the Initiation Site (TATA box) is the Promoter located?

-10 to -35

What is a rho-independent transcription Terminator?

A specific sequence in DNA that transcribes an RNA hairpin loop, stalling RNA pol and terminating transcription

What is a rho-dependent transcription Terminator?

A terminator where rho protein follows RNA pol and pops it off the DNA when it reaches a termination sequence