Micro 2- microbial genetics Flashcards
the genetic code is
a set of rules that determines how a nucleotide sequence is converted to an amino acid sequence of a protein
central dogma
DNA -> RNA -> Protein
DNA expression
genetic information is used within a cell to produce the proteins needed for the cell to function
DNA recombination
genetic information can be transferred horizontally between cells of the same generation
DNA replication
genetic information can be transferred vertically to the next generation of cells
genotype
the genetic makeup on an organism
phenotype
expression of the genes
STRs- short tandem repeats
repeated sequences of noncoding DNA
DNA backbone makeup and formation
- forms a double helix
- “backbone” consists of deoxyribosephosphate
- two strands of nucleotides are held together by hydrogen bonds between A-T and C-G
- strands are antiparallel
in DNA replication, what is the significance of the order of nitrogen containing bases
it forms the genetic instructions of the organism
DNA replication:
topoisomerase and gyrase
relax the strands
DNA replication:
helicase
separates the strands
DNA replication:
DNA polymerase
adds nucleotides to the growing DNA strand
most bacterial DNA replication is
bidirectional
why is replication highly accurate
due to the proofreading capability of DNA polymerase
ribonucleic acid (differences)
- single stranded nucleotide
- 5 carbon ribose sugar
- contains uracil (U) and thymine (T)
ribosomal RNA (rRNA)
integral part of ribosomes
transfer RNA (tRNA)
transports amino acids during protein synthesis
messenger RNA (mRNA)
carries coded information from DNA to ribosomes
in prokaryotes, when does transcription begin
when RNA polymerase binds to the promoter sequence on DNA
what is a codon
they are groups of 3 mRNA nucleotides that code for a particular amino acid
how many codons and how many amino acids
61 sense codons, 3 stop, 1 start
20 amino acids
in translation what do the tRNA molecules do
they transport the required amino acids to the ribosome
tRNA molecules also have an
anticodon that base-pairs with the codon
why is translation different in prokaryotes than in eukaryotes
in prokaryotes
- translation can begin before transcription is complete
- mRNA is produced in cytoplasm
- no mRNA editing necessary (no introns)
why is translation different in eukaryotes than in prokaryotes
in eukaryotes
- transcription occurs in the nucleus, whereas translation occurs in the cytoplasm
- mRNA must be completely synthesized and moved through nuclear membrane
- mRNA undergoes processing in nucleus before transport to cytoplasm (eons, introns)
exons vs. introns
extrons- regions of DNA that code for proteins
introns- regions of DNA that do not code for proteins
small nuclear ribonucleoproteins (snRNPs)
remove introns and splice extrons together
3 types of genetic exchange in bacteria
- transformation
- conjugation
- transduction
transformation
genetic exchange in bacteria
genes transferred from one bacterium to another as “naked” DNA
what is the process for transformation
- recipient cell takes up donor DNA (dead)- but must be a competent cell that can take up this donor DNA
- donor DNA aligns with complementary bases
- recombination occurs between donor DNA and recipient DNA
conjugation
genetic exchange in bacteria
plasmids transferred from one bacterium to another
how does conjugation work?
- requires cell to cell contact via pili
- donors carrying plasmid (F+ cells) transfer a replicate to recipients (F- cells)
what is Hfr and how does it occur?
high frequency of recombination
-F factor (plasmid) integrates into F+ cell chromosome
why is conjugation important?
important mechanism for transfer of R-factors (plasmids with antibiotic resistance)
transduction
genetic exchange in bacteria
DNA is transferred from a donor cell to a recipient via a bacteriophage
both generalized and specialized
generalized vs. specialized transduction
generalized- random bacterial DNA is packaged inside a phage
specialized- specific bacterial genes are packaged inside a phage
