Micro Chapter 5 Study Guide

During DNA replication, which enzyme is involved in proofreading to prevent the incorrect matching of nucleotides?

DNA polymerase

RNA primers are removed from the leading and lagging strand by __________.

DNA polymerase I

In DNA replication, what is the main enzyme responsible for adding complementary nucleotides to the daughter strand while reading the parent strand?

DNA polymerase III

Which enzyme is the main contributor to the development of spontaneous mutations?

DNA polymerase III

Start codon

During the initiation phase of translation, this codon indicates where the ribosome is to add the first amino acid.

Helicase

Enzyme in the primosome that unwinds DNA during DNA replication.

Exons

In eukaryotic cells certain segments of mRNA that are decoded to build a protein.

Transduction

Introduction of new genetic material into a bacterial cell by a virus.

Of the following statements, which does NOT apply to a microorganism that has a fertility plasmid?

It can undergo vertical gene transfer.

Amino acids

Molecular building block of proteins; have a core structure consisting of an amine group (NH2) and a carboxyl group (COOH).

Messenger RNA (mRNA)

Mostly linear RNA molecules that carry the genetic messages stored in DNA; made by RNA polymerase during transcription; mRNA contains the triplet code that is translated to build proteins.

Carcinogens

Mutagens that cause a rate of mutation that promotes the development of cancers.

Substitution mutations

Mutations that occur when an incorrect nucleotide is added.

Horizontal gene transfer

Occurs when genetic information is passed between cells by a process independent of cell division, and therefore separate from reproduction.

Histones

Organizational proteins in eukaryotic chromosomes that help keep DNA from getting tangled.

Heritable

Passed from one generation to the next.

Plasmids

Pieces of DNA that exist outside of the chromosomal DNA in bacteria and a number of eukaryotic cells.

Which of the following statements is NOT a characteristic of plasmids?

Plasmids are part of the cell's chromosome.

Primase lays down a short piece of __________ as a primer to start DNA replication.

RNA

Ribosomal RNA (rRNA)

RNA molecules that fold up into elaborate three-dimensional structures and combine with proteins to form ribosomes.

What is the main enzyme required for transcription of a gene?

RNA polymerase

The role of transcription factors is to signal __________.

RNA polymerase to the promoter region of the intended gene to be transcribed

Small noncoding RNAs

RNAs that impact protein synthesis and regulate gene expression at a post transcriptional level.

Okazaki fragments

Segments of DNA that are built on the lagging strand during DNA replication; these segments are glued together by ligase to form a continuous DNA strand.

Lagging strand

The complementary strand of the parent DNA molecule that is copied/replicated in the opposite direction of helix unwinding; built in chunks called Okazaki fragments.

Transcription

The first stage of protein synthesis, in which genes in DNA are copied into a new format, RNA.

Genotype

The genetic makeup of an organism.

Deoxyribonucleic acid (DNA)

The genetic material in all cells; made of repeating subunits called nucleotides and exists as a double-stranded helical molecule.

Operator

The part of the operon that the repressor binds to in order to block transcription.

Promoter

The part of the operon with which RNA polymerase associates to start transcription.

Phenotype

The physiological and physical traits of an organism.

Peptidyl (P) site

The site on an active ribosome that, together with an exit site (E) and an acceptor site (A), coordinates the translation process.

Which of the following would be considered a FALSE statement about small noncoding RNAs?

They are found only in prokaryotic cells.

Of the following statements, which one is NOT related to transposable elements?

They create a stable, non-changing genome.

Bacteriophages (or phages)

Viruses that infect bacteria.

Which of the following is considered a pre-transcriptional regulation and NOT a post-transcriptional regulation?

a repressed operon

In an inducible operon, what protein is used to turn off transcription by binding to the operator sequence?

a repressor protein

A transposon that relies on an RNA intermediate is called __________.

a retrotransposon

After translation, protein modifications are necessary for a final functioning product. Which of the following is NOT part of protein modification?

addition of a methionine

Quorum sensing allows bacteria within communities to communicate with chemical messages, which may help regulate gene expression. The chemical messages are called __________.

autoinducers

If a cell is to be transformed in a lab, the cell must be __________ to uptake the available genetic information.

competent

The exchange of genetic information by use of a pilus and cell-to-cell interaction is called __________.

conjugation

During optimum conditions, E. coli will replicate every 20 minutes. Because the genes required for replication are needed as part of a routine function, these genes are considered __________.

constitutive genes

The term "redundancy" in molecular biology refers to __________.

different codons that code for the same amino acid

In DNA replication, protein factors are more heavily required for replication in __________.

eukaryotic cells

The process of removing incorrect nucleotides and replacing them with correct ones is referred to as __________.

excision repair

Which of the following mutations is the most detrimental to the cell?

frameshift mutation

The genetic makeup of an organism is its __________.

genotype

The Ames test is used to identify if a chemical will result in mutations. This test uses the microorganism S. typhimurium and the amino acid __________.

histidine

The process of transferring of genetic information between cells in the same generation is referred to as __________.

horizontal gene transfer

In eukaryotic mRNA, there are sequences of mRNA that do NOT encode for specific amino acids and do NOT contribute to the protein. These sequences are called __________.

introns

Where is the chromosomal DNA found in prokaryotic cells?

nucleoid

Riboswitches are best defined as __________.

parts of mRNA that are not translated and act as post-transcription regulators

Which functional group is found at the 5' end of DNA?

phosphate group

Which type of genetic material may be found in both prokaryotic and eukaryotic cells and may contain genes conferring antibiotic resistance?

plasmids

To start DNA replication, the origin of replication is recognized by a collection of factors called the __________.

primosome

One major difference between prokaryotic and eukaryotic translation is __________.

prokaryotic translation is polycistronic, and eukaryotic translation is almost always monocistronic.

cDNA is a product of the action of __________.

reverse transcriptase

RNA nucleotides are made of a sugar, a phosphate, and a nitrogen base. Which sugar is unique to RNA nucleotides and NOT found in DNA nucleotides?

ribose

There are two nonstandard encoding amino acids: __________.

selenocysteine and pyrrolysine

Transduction that involves a temperate phage integrating into the host cell genome is called __________.

specialized transduction

An anticodon is found on __________.

tRNA

A codon consists of __________ nucleotides.

three

UV radiation can result in __________ in a cell's DNA.

thymine dimers

Griffith's experiment proved that bacteria can take up naked DNA from the environment and use it as part of their genome. This process, which can occur in a laboratory or in a natural setting, is called __________.

transformation

Purines

A class of double-ring structured nitrogen bases; includes adenine (A) and guanine (G).

Stop codon

A codon that signals that translation should end.

Primosome

A collection of factors, including primase and helicase, that is recruited to a specific point in the chromosome to start DNA replication.

Spliceosome

A complex in the nucleus that performs mRNA editing.

Nitrogen base

A component of nucleotides; includes adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U).

Pilus

A hollow tube that serves as a bridge for transferring a copy of the fertility plasmid from one cell to a cell lacking it during conjugation.

Inducible operons

Mainly used by bacterial cells as a means to regulate gene expression at the pre-transcriptional level; inducible operons are by default "off" unless certain conditions arise under which they are activated (induced) to allow transcription; a key example of an inducible operon is the lactose (or lac) operon.

Post-translational modifications

Modifications made after the termination of translation that are often required for a protein to function and provide a way for cells to regulate gene product functionality.

Exit site (or E site)

Region of an active ribosome that, together with the ribosome's peptidyl site (P) and acceptor site (A), coordinates the translation process.

Acceptor or (A) site

Site in a ribosome that accepts incoming charged t-RNAs.

Topoisomerases

Specialized detangling enzymes that relieve the coiling tension that develops as the helix unwinds during DNA replication.

Ames test

Test used to identify potential mutagens.

Which type of RNA carries in amino acids and adds the amino acids to the "A" site in the ribosome?

tRNA

The term used by molecular biologists to describe the flow of genetic information from DNA, to RNA, to protein is __________.

the central dogma of biology

In DNA replication, Okazaki fragments are required in synthesizing __________.

the lagging strand, because the DNA polymerase can move only in the 5' to 3' direction

Which of the following nucleotides is found only in RNA and not in DNA?

uracil

Proteins provide cells with the necessary equipment to perform normal cellular activity. Without gene expression the cell __________.

would die

Missense mutation

A mutation in which the meaning of the codon is changed in a way that the wrong amino acid is added to the growing protein.

Frameshift mutation

A mutation in which the reading frame of an mRNA is altered due to nucleotides being inserted or deleted from the coding region of a genetic sequence.

Gyrase

A specialized detangling enzyme that relieves the coiling tension that develops as the helix unwinds during DNA replication.

Transformation

A type of horizontal gene transfer in which bacteria are genetically altered when they take up DNA from their environment.

Reverse transcriptase

A virally encoded enzyme that enables retroviruses to use their single-stranded RNA genome to direct formation of DNA. Special enzymes that carry out reverse transcription.

Gene expression

Also called protein synthesis; a cellular process in which genetic information within a cell is read and used to create proteins.

DNA polymerase I

An enzyme that replaces the RNA primer with DNA on the leading and lagging strand during DNA replication.

Ligase

An enzyme used in DNA replication; this enzyme joins DNA segments at the junction between where DNA polymerase I replaced the RNA primer with DNA and the rest of the DNA strand; covalently links Okazaki fragments.

Arginine (arg) operon

An example of a repressible operon that regulates the production of the amino acid arginine; a pre-transcription regulation for gene expression that allows bacterial cells to stop making the amino acid arginine if it is already abundant.

Lactose (lac) operon

An example of an inducible operon that is induced, or actively transcribed, only when lactose is present and the cell's preferred food, glucose, is absent.

Recombination

An exchange of genetic material that leads to new genetic combinations; a process important in nature and also used as a molecular biology tool that allows researchers to alter the genetic landscape of a cell.

Genes can be silenced by a process called DNA methylation. Which of the following compounds is a methyl group?

CH3

Chromosomes

Carefully packaged strands of DNA associated with organizational proteins; linear in eukaryotes and usually circular in prokaryotes.

Generalized transduction

Carried out by bacteriophages, this is one example of a horizontal gene transfer mechanism that can convey new genes to a bacterial cell; in this process a bacteriophage randomly takes up a bacterial gene and carries it from the prior host to the new host bacterium.

Semiconservative

Characteristic of the DNA replication process because it produces a hybrid molecule that is half new and half parent DNA.

Mutagens

Chemical, physical, or biological agents that increase the rate of mutation.

Transfer RNA (tRNA)

Cloverleaf-shaped RNA molecules that bring the correct amino acid to a ribosome to build proteins.

Operons

Collection of genes controlled by a shared regulatory element; mechanism used mainly by bacterial cells to regulate protein synthesis at the pre-transcriptional level.