Microbial Genetics Flashcards
Genome
- all genes in an organism
- most are associated with the chromosome
- extra chromosomal genes
In prokaryote: plasmids
In eukaryotes: mitochondria, chloroplasts, and plasmids in some one called organisms
Gene
A section of DNA that codes for a protein
Telomeres
- ends of linear chromosomes
- when they are frayed and worn, linked with aging and chronic diseases
Nucleotide
Building blocks for nucleic acids
- attachment- prime 1- nitrogen base
- attachment- prime 3- hydroxyl group
- attachment- prime 5- phosphate group
Purine
2 ring structure
Ex: Adenine , Guanine
Pyrimidines
1 ring structure
Ex: thymine, cytosine
In RNA- Uracil, Adenine
Complimentary Base Pairs
Pyrimidine and Purine
DNA- double stranded helix
Thymine, Adenine
Cytosine, Guanine
DNA Replication
Precursor for cells dividing( mitosis= interphase)
Antiparallel concept
Applies to DNA molecules
DNA always grow 5’~3’
DNA Replication- Leading Strand
- Helicase- help break down hydrogen bonds between complimentary bases.( unzips)
- Leading strand- always starts with RNA primer
(piece of RNA)- Primase-RNA Polymerase - DNA nucleotides are going to attach to RNA primer and continue to grow 5’~3’-grows continuously DNA polymerase 3 does this
- RNA primer is removed by DNA polymerase 1
DNA Replication- Lagging Strand
- Grows in fragments called Okazaki Fragments
each fragment grow 5’~ 3’ - Each fragment start with RNA primer( enzyme RNA polymerase)
- DNA nucleotides are built onto RNA primer( DNA polymerase 3)
- RNA primer removed ( DNA polymerase 1)
- DNA ligase attaches DNA fragments ( Okazaki fragments)
Gyrase- super coils DNA
Genetic Code
- based on triplets of DNA nucleotides
- plenty to cover the 20 aa used to make proteins
- each triple codes for an aa and or punctuation- where it start and stop
Transcription
- mRNA makes a complementary copy of DNA
- in euk- nucleus
- in prok- cytosol
Translation
- protein synthesis
- mRNA attaches to the ribosome and t- RNA brings in raw aa
- Codon- triplets in nucleotide in mRNA only
- Anticodon- triplets in nucleotide in tRNA only
Types of RNA
- mRNA- important in both transcription and translation
- tRNA- important in translation only; brings in aa to ribosomes as needed
Differences in Eukaryotes and Prokaryote
- eukaryotes- transcription and translation are separate events. Why? Nucleus have nuclear membrane
- prokaryote- transcription and translation can happen on mRNA
Exon
Expressed; needed “code”
Intron
Are not expressed “ cut out “
5th RNA
Works as enzyme, cuts out intron, splices exons together
Operon
Control enzymes and different products
Prokaryote
Regulatory genes
- codes for repressor protein that can fit on the operator gene and block transcription of the structural genes
- can be anywhere on the chromosome
- code for a protein that blocks operator
Operon
- Have to be found together on a chromosome
- promotor gene, operator gene, structural gene
Promoter Gene
- Consists of a palindrome of nucleotide bases that signals the beginning of a codon
- palindrome- a santa at NASA/ DNA Land
- signals start
Operator Gene
- works as a red/ green light
- if blocked nothing happens
- if not blocked transcribed and then translated into protein
Structural Gene
- code for specific enzymes that help in catabolic or anabolic reactions
- if operator gene is not blocked, the structural genes are transcribed, translated, and cell can now metabolize something
Two Different Operons
- inducible operons- are normally off, but can be turned on
- they normally are involved in catabolism
Ex: lac operon
- Repressible Operons- are normally on, but can be turned off, normally by excess product
- normally are involved in anabolism
Ex: trp Operons
Lac Operon
- control lactose digestion
Trp operon
- aa
Point Mutations
- one nucleotide is changed
- SNPs “snips”- single nucleotide polymorphisms
- silent mutations- 1nucleotide changes and codes for the same aa
- missense mutations-1 nucleotide changes, codes for diff. aa
- Nonsense mutation- 1 nucleotide changes, code for stop codon
Frameshift mutations
- the whole reading frame shifts due to an addition or deletion
Factors that increase Mutations
- radiation
- heat
- high dose of electricity
- extremes in ph
- some caustic chemicals
Chemical Factors
- benzopyrenes- produced from burned products
Frameshift mutagens - Alfa toxins- from aspergillus mold
Frameshift mutagens - base analogs- imitate nitrogen bases
Genetic Transfer
Conjugation
- bacterial sex
- f+ plasmid poke f- plasmid to make it fit
Genetic transfer ( Transformation)
- bacteria pick up pieces of DNA or plasmids from the environment, and incorporate this into their genome
- griffiths experiment
- bacteria picks up DNA outside of cell
Genetic transfer ( Transduction)
- genes are transferred accidentally by a bacteriophage
- species specific transfer
