Block 2 - Microbial Genetics Flashcards
The entire complement of genes of all chromosomes.
Genome
What is the transfer of DNA from donor bacterium to recipient bacterium by using a bacterial virus as the vehicle?
Transduction
Which genes direct the synthesis of proteins with related functions and which are regulated as a “unit”?
genes of the operon
True or False:
The new double-stranded DNA re-winds into a helix as the parental DNA unwinds exposing more nucleotides to be replicated.
True
Describe “semiconservative replication”.
When the entire chromosome is copied, each double helix consists of one newly synthesized strand of DNA bound to one original parent strand
One entire double-strand of DNA containing multiple genes
[is always DNA, except in RNA viruses.]
Chromosome
This enzyme binds to DNA and inserts complementary nucleotides thereby generating a new strand.
DNA polymerase
What is the result of a frameshift mutation?
A frameshift mutation usually results in missense mutation or in a significantly different, nonfunctional or incomplete protein.
True or False:
The replication of the lagging strand is continuous because of this process of producing short fragments and joining them to the existing strand.
A new fragment is generated each time the replication fork advances a short distance. This process continues throughout the entire replication process until the entire DNA has been replicated.
False
The replication of the lagging strand is discontinous; not continuous.
What is the term for the strand that has the 5’ end of the exposed nucleotide facing toward the replication fork?
In which direction does the newly developing strand grow with regards to the replication fork? Toward the fork or away from the fork?
The “lagging” strand
Grows away from the fork
What are the two types of operon?
inducible and repressible
What assists protein synthesis by serving as a “facilitator” for the mRNA and tRNA functions?
rRNA, “ribosomal RNA”
In DNA, what are the “long chains” of nucleotides?
What does the term “antiparallel” refer to?
strand
The two strands run in opposite directions; i.e. the nucleotide of the 3’ end of one strand pairs up with the nucleotide of the 5’ end of the adjacent strand. Strands are not identical, but are complementary.
What are the genes that are expressed only when certain environmental conditions are present?
(e.g. genes for enzymes of a biosynthetic pathway are expressed only when the appropriate substrate is present, i.e. presence of substrate causes Operator site to be unblocked.)
inducible genes
The mRNA “docks” into what portion of the ribosome?
“into the groove”
When does transcription end?
Transcription ends when the RNA polymerase reaches the termination region of the gene, and the new single-stranded mRNA is released (the DNA re-winds).
Within the operon,
What is the site of the chromosome which controls, by either permitting or blocking, the access of RNA polymerase to the structural genes of the operon site to which the repressor protein binds (or fails to bind)?
operator site
What is the term for the direct uptake of DNA segment from one bacterium to another as “naked” DNA in solution?
transformation
What is the integration of the DNA of a temperate bacteriophage (virus) into the bacterial chromosome where it replicates along with the bacterial chromosome?
What is produced upon separation from the bacterial DNA?
Lysogeny
produces a new bacteriophage
What carries the genetic code from the DNA to the ribosome?
In mRNA, 3 nucleotides = 1 _________.
1 _________ = 1 amino acid
mRNA (messenger RNA)
codon
In regulation of gene expression,
The genes that are constantly expressed (transcribed and translated into functional products) (60-80% of genes are in this category) are considered to be what type of gene?
These genes can be “turned on”
These genes – can be “turned off”
constituitive genes
inducible
repressible
What molecules make up a nucleotide (3 parts)?
- ) 5-carbon sugar: ribose / deoxyribose
- ) nitrogenous base: bound to the first or 1’ (one prime) carbon position of the 5 carbon sugar
Purines:
Adenine
Guanine
Pyrimidine:
Thymine
Cytosine
Uracil (only in RNA)
3.) Phosphate Group - bound to the fifth or 5’ carbon of the sugar molecule
What is the transfer of the genetic code on DNA gene into a messenger RNA (mRNA) strand by means of DNA-dependent RNA polymerase?
transcription
What are related genes that are regulated as a group/series?
Within the above system:
What is the type of gene that codes for a “repressor” protein which can bind to the “operator” region of the operon?
What is the region of the chromosome to which the RNA polymerase binds during transcription?
Operon
“repressor gene”
promoter site
What is the result of “recombination” in gene segments?
It can result in major changes or a non-functional cell.
Where does the RNA polymerase bind to DNA during transcription?
at the promoter site (beginning of the gene)
What is the small, circular, self-replicating piece of the DNA that is separate from the normal chromosomal DNA in bacteria?
the plasmid
What is the synthesis of a polypeptide at the ribosome through linkage of amino acids in a sequence specified by a mRNA molecule?
translation
What is the transfer of the genetic code on DNA gene into a messenger RNA (mRNA) strand by means of DNA-dependent RNA polymerase?
What is the synthesis of a polypeptide at the ribosome through linkage of amino acids in a sequence specified by a mRNA molecule?
transcription
translation
True or False:
The anticodon is a part of the tRNA; the codon is a part of the mRNA.
True
What three types of base substitution mutations can occur?
- silent: no change in the protein
- missense: different amino acid in the protein; usually not highly significant
- nonsense: RNA polymerase is stopped from reading the code resulting in an incomplete, nonfunctional protein
Genetic mutations, at the cellular/molecular level, are typically caused by what three things?
spontaneous mutation
chemical mutagens
radiation
A segment of DNA that contains the genetic code (blueprint) for a functional product.
Gene
In DNA replication:
Replication forks form where short lengths of double-stranded DNA helix unwind, thus exposing the separated strands.
Unwinding (and rewinding) is due to action of what enzymes?
These enzyme break the hydrogen bonds between bases and/or hold part of the strand stable.
helicase
DNA gyrase
topoisomerase
What is the transfer of genetic material between donor and recipient cells involving direct
cell-to-cell contact?
What structure is used to transfer DNA from one cell to another in this form of genetic material transfer?
Conjugation
Sex pilus
Nucleotides are always added to which exposed end of the helix?
What is the term for the strand that is the newly growing strand?
3’; thus growing from 5’ to 3’-extending at the 3’ end
“leading” strand
“Leading” strand is the newly growing strand having the 3’ end of the exposed nucleotide “facing toward” (“leading into”) the replication fork
(a) The newly developing strand grows toward the replication fork, i.e. “leads into” the fork
(b) The strand is continuously replicated because of enzymatic simplicity and ease of access to the molecule
What is the definition of the changes (substitutions or deletions) in the sequence of DNA bases, thus changing the genetic code?
What are the two types?
genetic mutation
base substitution
frameshift mutation
This enzyme facilitates linkage of a nucleotide to both 3’ and 5’ binding sites simultaneously and inserts a nucleotide to join the newly replicated fragment with the existing strand.
DNA ligase
In/on the ribosome, the “50S” portion and the “30S” portion are located on what part of the ribosome, respectively?
50S = top (above the groove)
30S = bottom (below the groove)
What is needed to initiate strand growth in the absence of a nucleotide having a 3’ binding site?
The RNA primer provides what site?
RNA primer and RNA polymerase
a 3’ site
What molecule transports and then transfers the amino acid to the developing peptide chain?
What is the site on the tRNA that bonds with the codon on the mRNA (carries the three bases which complement the codon)?
This specifies which amino acid will be carried by the tRNA.
tRNA (transfer)
anticodon
What are the terms for each definitions regarding types of mutations:
A single base is replaced with another, thus changing the codon. May result in an improper amino acid in the protein.
Insertion or deletion of bases may shift the codon reading frame of the mRNA in the ribosome.
base substitution
frameshift mutation
The total genetic makeup of an organism.
The expressed properties of an organism.
Genotype
phenotype
What are the genes that are expressed except when certain environmental conditions are present?
(e.g. presence of certain metabolic products causes genes for metabolic enzymes to be repressed, thus slowing down metabolism, i.e. presence of metabolic products causes Operator site to be blocked.)
repressible genes
