Chapter 7 Learn Smart

Quorum sensing can best be described as the ability of microorganisms to ____________.

"sense" the density of cells within their own population

RNA polymerase can only add nucleotides to the ______ end of a growing strand

3'

The eukaryotic ribosome is 80S, and its subunits are __________.

40S; 60S

The subunits of the 70S ribosome are ____________.

50S; 30S

What happens during the elongation phase of translation?

A peptide bond is formed between amino acids on adjacent tRNAs. Empty tRNAs leave the ribosome via the E-site. tRNAs carrying amino acids occupy the A-site and the P-site of the ribosomes.

Describe antigenic variation and phase variation.

Antigenic = changes in the characteristics of surface proteins Phase variation = the routine switching on and off of certain genes

Describe the following post-transcriptional modifications: cap and polyadenylation.

Cap: methylated guanine derivative at the 5' end Polyadenylation: adenine derivatives at the 3' end

Explain what the following enzymes regulate: constitutive, inducible, repressible

Constitutive: constantly synthesized Inducible: synthesized only when needed Repressible: synthesis is turned off when not needed

________ is an essential macromolecule that contains all of the information needed by a cell to synthesize its components.

DNA

Bacteria use two-component regulatory systems to detect and react to changes in the ________________.

External environment

What proteins are involved in the initiation of DNA replication?

Helicase and DNA gyrase

Name the events of transcription in order.

Initiation, elongation, termination

Why is the genetic code said to be redundant?

It is degenerate: more than one codon can code for a specific amino acid.

What enzymes function in DNA replication?

Ligase, Primase, DNA polymerases, and Helicases

In replication of DNA, the lagging strand is replicated in a discontinous manner, forming ________ fragments that must be joined together by the enzyme DNA ligase.

Okazaki

Describe the anti-parallel orientation of strands in DNA

One strand in 5' to 3' and the other is 3' to 5'

To initiate replication of a DNA molecule, specific proteins must bind to a specific DNA sequence called the _______.

Origin of replication

The ________ strand of DNA contains the same order of nucleotides as the corresponding RNA transcript.

Plus (+)

Transcription is initiated when the RNA polymerase binds to a ____________ on the DNA.

Promoter

How does RNA differ from DNA?

RNA is usually single-stranded and in RNA, uracil replaces thymine.

During transcription, RNA polymerase synthesize ________ from a(n) ________ template.

RNA; DNA

What are the two general mechanisms by which different repressors can function?

Repressor is synthesized in a form that binds to the operator, blocking transcription; A molecule called an inducer attaches to the repressor, changing its shape so it can no longer attach to the operator Repressor is synthesized in a form that cannot bind to the operator, so transcription can proceed; A molecule termed a corepressor attaches to the repressor; the corepressor-repressor complex can bind to the operator, blocking transcription.

Two-component regulatory systems that microorganisms use to monitor their environment consist of which two proteins?

Response regulator; Sensor protein

What are the roles of ribosomes in translation

Ribosomes detect sequences that indicate where translation should start and finish. Aligning amino acids and catalyzing formation of peptide bonds between them.

Describe transcription, translation, and replication.

Transcription: copying DNA into RNA Translation: decoding RNA to synthesize protein Replication: duplication of the genome

Information is passed from the environment into the cell by a process known as signal _____________.

Transduction

A(n) ______________ is a regulatory protein that facilitates transcription by enhancing the ability of RNA polymerase to initiate transcription.

activator

The circle is marking which component of RNA

codon

Translation occurs in the ___________ of eukaryotic protozoa and the __________ of bacterial cells.

cytoplasm; cytoplasm

The functional unit of genome that codes for a product is a __________

gene

The complete set of chromosomes and genes in an organism is referred to as the ___________.

genome

The base pairs in double stranded DNA are held together by __________ bonds.

hyrdogen

Carbon catabolite repression is a regulatory mechanism that ensures that a cell _________.

imports and uses the sugar that allows fastest cell growth

A(n) _________ is a molecule that can bind to a repressor protein, changing its shape and preventing it from binding to the operator.

inducer

Consider the lac operon: When ________ is not available, a repressor prevents transcritption. When lactose is available, some of it is converted into ______, which is an inducer.

lactose; allolactose

The lac operon only functions when ________ is present in the medium but ________ is absent from the medium.

lactose; glucose

Cells can regulate the level of protein production by controlling the level of __________________.

mRNA

__________ is transcribed from a DNA template and translated during protein synthesis.

mRNA

Identify the three different types of RNA use in gene expression.

mRNA, tRNA, and rRNA

Proteins are synthesized by translating _______ RNA.

messenger

The ____________ DNA strand is used as the template for RNA synthesis.

minus (-)

A prokaryote transcript that carries one gene is called _________ RNA while a transcript that carries multiple genes is called ______ RNA.

monocistronic; polycistronic

All DNA nucleotides contain the same deoxyribose and phosphate group, but different __________.

nucleobases

All DNA nucleotides contain the same deoxyribose and phosphate group, but different _____________.

nucleobases

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

operon

To initiate replication of a DNA molecule, specific proteins must bind to a specific DNA sequence called the _____________.

origin of replication

During DNA replication, why are primers necessary?

primers provide DNA polymerase with the 3' end needed for synthesis.

RNA polymerase binds to a ________ to begin transcription

promoter

During protein synthesis, many copies of a specific __________ can be synthesized from a single transcript.

protein

What is a post-translational modification event?

proteins are folded into functional shapes by chaperones

Which type of RNA molecule is included in the composition of ribosomal subunits?

rRNA

Duplication of a chromosome before cell division is called DNA ______________.

replication

Enzymes that are usually synthesized but are not made when they are not needed are ________ enzymes.

repressible

DNA-binding proteins control transcription. A binding protein that blocks transcription is called a(n) _______, while one that facilitates transcription is called a(n) _________.

repressor; activator

In prokaryotes, translation begins when the ribosome binds to the ______________ of the mRNA

ribosome-binding site

DNA replication is said to be ___________, because the newly made double helices are composed of one strand from the original molecule and one newly synthesized strand.

semi-conservative

Bacterial cells can control which genes are transcribed by producing various types of _______.

sigma factors

In prokaryotes, the first AUG after a ribosome-binding site typically functions as a ____________ codon.

start

Elongation of the polypeptide terminates when the ribosomes reaches a ___________ codon, which is a codon not recognized by a tRNA.

stop

Microorganisms must adapt rapidly to changes in their environment in order to ________________.

survive

The region of DNA that signals the end of an RNA transcript is the

terminator

The translation "machinery" reads the mRNA in groups of three nucleotides; as a consequence, any given sequence has _____________ possible reading frames.

three

Which nucleobases are found in DNA?

thymine, adenine, guanine, cytosine

mRNA is produced when a region of DNA known as a template is copied. The newly synthesized strand of mRNA is called the ____________.

transcript

mRNA is produced when a region of DNA known as the template is copied. The newly synthesized strand of mRNA is called the __________.

transcript

Alternative sigma factors allow cells to directly control __________.

transcription

Information is passed from the environment into the cell by a process known as signal ___________.

transduction

High temperatures melt double-stranded DNA, meaning the _____________.

two strands separate into single strands