microbiology exam 2 review gene transfer and mutation

Sometimes the plasmids can also contain ______ ____ ___

antibiotic resistance genes

What happens last in conjugation?

A transformation complex form through which DNA passes from the donor to recipient cell.

What do plasmids contain?

All the genes necessary for pilus formation and DNA export.

In a methyl mismatch repair, the DNA polymerase makes a mistake during replication by adding what?

An undamaged but incorrect nucleotide

The site with out the base is then recognized and cleaved by another enzyme in what kind of mutation repair?

Base excision repair

In a silent mutation, why does it not change the amino acid sequence?

Because the genetic code is degenerate, a change in a codon might not lead to the change in the amino acid.

If a bacterial cell can destroy the phage DNA while protecting its own chromosome it will have a better what?

Better survival chance

Generalized transduction

Can transfer any gene from a donor to a recipient cell

Specialized transduction

Can transfer only a few closely linked genes between cells.

Mutations can be caused by mutagens, which are what?

Chemical agents or irradiation

In nucleotide excision repair, what seals the nicks?

DNA ligase

In base excision repair, the base is then replaced by the undamaged one by what?

DNA polymerase

In nucleotide excision repair, what fills in the gap with correct nucleotides?

DNA polymerase

Nucleotide excision repair

DNA polymerase fills in the gap with correct nucleotides and DNA ligase seals the nicks

Methyl mismatch repair

DNA polymerase makes a mistake during replication by adding an undamaged but incorrect nucleotide to the sequence of nucleotides.

Restriction and modification involve what?

Enzymatic cleavage (restriction) of alien DNA, by restriction endonucleases, and protective methylation (modification) of host DNA.

There are two types of transduction: which are:

Generalized transduction and specialized transduction

What is the most obvious risk of DNA transfer?

Is what occurs via bacteriophages.

Transition:

Purine -> purine or pyrimidine -> pyrimidine

Generalized recombination is ________

RecA dependent

Site-specific recombination is _______

RecA independent

In gene transfer by transformation what needs to be competent, or capable of importing new DNA into the cell and integrating it into the chromosome?

The recipient cell

What happens after contact between the donor cell and recipient cell in conjugation?

The sex pilus contracts bringing the 2 cells closer together and the two cell envelopes fuse

Why do cells need to import DNA through transformation?

They can use imported DNA as food and to fix damaged genomes

What is a bacteriophages goal?

To replicate at the expense of the host cell.

How does conjugation begin?

With contact between the donor cell and a recipient cell via sex pilus.

How do cells repair mutations?

base excision repair, nucleotide excision repair, methyl mismatch repair.

If it is a plasmid that can not self replicate, or if it is a linear piece of DNA, then it can be

degraded (RE) or integrated in the chromosome by a process known as recombination.

Silent mutation

does not change the amino acid sequence

Mutation

heritable change in DNA

Nucleotide excision repair

this system excise a path of 12-13 nucleotides including the damaged one.

Conjugation

transfer of DNA from one bacterium to another, following cell-to-cell contact

Gene transfer can occur by:

transformation, conjugation, and transduction

Mutations can be categorized in several information classes..

whether or not the mutation will affect the transfer of information in the cell from DNA to RNA to proteins.

The recipient cells needs to be competent, which means?

capable of importing new DNA into the cell and integrating it into the chromosomes

Point mutation

change in a single base

DNA sequences

change over generations through various mutations, rearrangements, and inter- and intraspecies gene transfer

Nonsense mutation

changes the amino acid to a stop codon

Missense mutation:

changes the amino acid to another (Change the codon and codes for another amino acid)

Frame-shift mutation

changes the open-reading frame of the gene, usually caused by an insertion or deletion that will shift the codons.

What are plasmids?

circular extra-chromosomal genetic material

Methly-directed mismatch repair enzymes recognize the mismatch and do what?

cleave the nucleotide from the not-yet methylated strand and uses the information in the methylated strand to correct the error.

If it is a plasmid that can self-replicate apart from the chromosomal replication... then

it will

horizontal gene transfer

lead to improved competitiveness of the recipient cell

Protective methylation of host DNA is what?

modification

Some cells are _____ competent

naturally

Cells needs to import DNA through transformation to adjust to ______

new environments

In a base excision repair, what is removed from the nucleotide without breaking the phosphodiester bond? Enzymes specific to the damaged base carry out this step

nitrogenous base

Others can be made competent in the lab by _____ the membrane by chemical or electrical (electroporation) methods

perturbing

Conjugation requires the presence of special transferable ______

plasmids

Mutations can come in several forms: which are?

point mutation and insertation (addition) or deletion (subtraction) of one or more bases.

Transduction

process in which bacteriophages (viruses) carry host DNA from one cell to another.

Gene transfer by transformation

process of importing free DNA into bacterial cells

transversion

purine <-> pyrimidine

Methyl mismatch repair depends on what?

recognizing the methylation pattern in DNA to repair the mismatch

Base excision repair

remove damaged bases

Enzymatic cleavage of alien DNA by restriction endonucleases is what?

restriction

This protection system is called what?

restriction and modification

Incoming phage DNA is cleaved by what?

restriction endonuclease

Bacteria have a developed kind of " " approach to gene exchange

safe sex

In conjugation, it is typically initiated by a _____ ____ known as a sex pili, protruding from the donor cell

special pilus

Newly recognized DNA are not methylated right away which means?

the newly synthesized strand of DNA will be unmethylated for a while, while the mother (old) strand is methylated.