Chapter 8 Microbial genetics Flashcards
what are introns?
regions of DNA that do not encode protein
what are exons?
regions of DNA expressed
what are snRNPs?
small nuclear ribonucleoproteins
remove introns and slice exons together to help form mRNA
which cell type uses introns, exons, and snRNPs? where exactly?
eukaryotes ONLY
within the nucleus
what are genes?
segments of DNA that code for functional products
what are chromosomes?
structures containing DNA (carry hereditary information)
what are the two types of nucleic acids?
DNA
RNA
what are the three parts to a nucleotide?
sugar
nitrogenous base
phosphate group
what is the sugar in DNA?
deoxyribose
what is the sugar in RNA
ribose
what are the nitrogenous bases in DNA?
A T C G
what are the nitrogenous bases in RNA?
A U C G
what are the enzymes involved in DNA replication?
leading strand: DNA polymerase
lagging strand: DNA polymerase
RNA primase
DNA ligase
what is the meaning of semiconservative replication?
the process by which DNA makes copies of itself, each strand, as it separates, synthesizing a complementary (daughter) strand. (Uses 1 DNA to make 2)
how is bacterial DNA replication different than eukaryotic DNA replication?
eukaryotic DNA replication consists of vertical gene transfer
bacterial DNA replication consists of horizontal gene transfer
how is DNA nucleotide differ than RNA nucleotide?
DNA: deoxyribose sugar and is double helix
RNA: ribose sugar and is single strand
what are the three basic forms of RNA?
ribosomal RNA (rRNA)
transfer RNA (tRNA)
messenger RNA (mRNA)
what is the job of rRNA?
integral part of ribosomes
what is the job of tRNA?
transports amino acids during protein synthesis
what is the job of mRNA?
carries coded information from DNA to ribosomes
what is transcription?
the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA)
what is the end goal of transcription?
DNA -> mRNA
what key enzyme is responsible for transcription?
RNA polymerase
where does transcription occur in eukaryotes?
nucleus
where does transcription occur in prokaryotes?
cytoplasm
what is translation?
the process by which a cell makes proteins using the genetic information carried in messenger RNA (mRNA).
what is the end goal of translation?
a protein
where does translation take place in eukaryotes/ prokaryotes?
occur in cytoplasm and ribosomes of either eukaryotes/prokaryotes
what is expression broken down into?
transcription and translation
what is the end goal of expression?
using DNA to make a protein
what is a codon?
mRNA language includes groups of three nucleotides such as AUG, GGC, or AAA
what does degeneracy mean?
several codons can signal the same one amino acid
what is the starting amino acid? which codon signals this?
Methionine
AUG
what are three stop codons?
UAA
UAG
UGA
why do these codons cause translation to stop?
in order to signal end of protein synthesis
why is it that in bacteria, translation can begin before transcription is complete? but in eukaryotes, not?
because both steps occur in cytoplasm of bacteria cells
unlike eukaryotes where transcription occurs in nucleus first
what is a mutation?
change in the nitrogenous base of DNA sequence
what are three possible results of base substitution (point mutation)?
missense mutation
nonsense mutation
frameshift mutation
what is missense mutation?
nitrogenous base substitution results in change in amino acid
what is nonsense mutation?
nitrogenous base substitution results in a nonsense (stop) codon
what is frameshift mutation?
insertion or deletion of one or more nucleotide pairs (shifts the entire sequence out of reading order)
which type of mutation is the worst kind and is also most common?
frameshift mutation
what is a silent mutation?
change in DNA base sequence that causes no change
what are the three possibilities of silent mutations?
- degeneracy of genetic code (might still code for the same amino acid)
- function of protein may not change if amino acid is non-vital portion of protein
- changed amino acid is chemically similar
what are the two major ways DNA can become mutated?
base substitution
chemical mutations
how does ionizing radiation cause mutations?
causes formation of hydroxyl radicals and break the deoxyribose phosphate backbone
how does UV radiation cause mutations?
cause thymine dimers
what is the enzyme that repairs UV damage? how?
photolyase
separates thymine dimers
what is the process that repairs mutation damage not caused by UV radiation? how?
nucleotide excision repair: enzymes cut out incorrect bases and fill in correct ones
what is the baseline error rate for DNA polymerase?
1 in a million
what is the error rate for DNA polymerase when mutagens are added into the mix?
1 in a thousand
what is the difference between horizontal and vertical gene transfer?
horizontal gene transfer: genetic recombination
vertical gene transfer: DNA replication
explain transformation
genes transferred from one bacterium to another as a “naked” DNA
can occur from “naked/floating” DNA appearing after cell death/lysis has occurred.
name the two types of transduction that can occur
generalized transduction
specialized transduction
describe the difference between generalized and specialized transduction
both generalized and specialized transduction involve packaging bacterial DNA inside a phage and transferring it to a recipient cell
but in generalized, random bacterial DNA is packaged.
in specialized, specific bacterial DNA is packaged.
describe conjugation
plasmids transfer via sex pili
(only transfers plasmids that the other cell does not already contain)
what does the F factor indicate?
plasmid
what does F positive indicate?
donor cell
what does F negative indicate?
recipient cell
describe transposons
“jumping genes” segments of DNA that can move from one region of DNA to another
what does transduction require in order to happen?
bacteriophages
describe the long process of leading strand and lagging strand in DNA replication
Leading strand: enzymes unwind the double helix. DNA polymerase directly adds nucleotides to form new duplicated strand
Lagging strand: enzyme helicase “unzips” DNA helix at the hydrogen bonds, RNA primase indicates the beginnings of the multiple short sections of nucleotides which DNA polymerase then adds nucleotides in a reverse direction, these fragments are called Okazaki fragments, DNA polymerase then has to go back and change all the RNA primase nucleotides with its own, DNA ligase joins all these various attachments
what direction does the DNA polymerase add nucelotides?
5’ to 3’ direction
describe how antibiotic resistance occurs?
bacteria undergo random mutations. some mutations are more effective at making them resistant to some antibiotics. while antibiotics kill off the non-resistant mutated bacteria, the more resistant ones have time to transfer their resistant DNA via transformation/conjugation/transduction/transposons making for an abundance of these “super bugs”
name some physical examples of how super bugs resist anitibiotics
-have cell walls made to be impenetrable
-have enzymes that break down antibiotics before coming into contact
-physically boot antibiotics that are able to enter cell wall
where does DNA come from in transformation? do cells need to be in contact for transformation?
it is naked and floating around the cell
so no cells do not need to be in contact
do cells need to be in contact for conjugation?
yes, because they use their sex pili to transfer plasmids
what happens to recipient cell after conjugation is complete?
(Becomes a F+ cell) cell now has a plasmid that it can also transfer to other bacteria
what is a Hfr cell? What does it stand for?
high frequency cell
occurs when plasmid has fused with bacterial chromosome
what is transferred during conjugation with an Hfr cell?
part of the plasmid-containing chromosome of Hfr cell
what happens to the recipient cell after conjugation is complete with a Hfr cell?
a recombinant F- cell results
what do transposons contain that help do their job? What enzyme helps with that function?
insertion sequences (IS)
code for transposase that cuts and reseals DNA (can cause neg or pos mutations
