Bio Unit 6 Gene Expression and Regulation
Pyrimidines
Cytosine and Thymine - nitrogen bases w/ one ring
telomeres
DNA at the tips of chromosomes
DNA replication (first step)
DNA helicase unwinds strands, topoisomerase prevents supercoiling
single stranded binding proteins (SSBP)
holds open replication bubble
inducible operon
off -> on in catabolic pathways (breaking) makes enzymes only when nutrients are available ex: lac operon -> if lactose is present, enzymes need to be turned ON to digest it
repressible operon
on -> off in anabolic pathways (building) when product is made, transcription is turned OFF ex: if tryptophan is present, no need to make it
operator (on operon)
on/off switch
leading strand
once RNA primer is added, DNA polymerase can add nucleotides
Conservative model of DNA replication
parental double helix remains intact, both strands of daughter helices are newly synthesized
episome
plasmid that can integrate into bacterial chromosome
repressor
prevents RNA polymerase from binding to DNA, prevents transcription
topoisomerase (Enzyme in DNA replication)
corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands
restriction enzymes
cut DNA into segments at specific spots
Lytic Infection
"quick" viral infection that causes a cell to burst fast to spread more viruses 1: virus attaches to host cell 2: injects DNA 3: host cell uses the viral genetic material to make new virus parts 4: new parts are assembled-makes new viruses 5: host cell bursts, releases new viruses
Structure of DNA
1. Strands are antiparallel - 3' has no phospate end, 5' has phosphate end 2. held together by hydrogen bonds 3. phosphodiester bonds hold phosphates and sugars together
Lysogenic Infection
1. virus attaches and injects genetic material 2. genetic material combines with host cell - forms a prophage 3.every time host cell dives, prophage replicates, passes on virus to new cells 4. signal triggers virus to separate from prophage and enter lytic cycle
Purines
Adenine and Guanine - nitrogenous bases w/ 2 rings
Helicase (Enzyme in DNA replication)
An enzyme that untwists the DNA at the replication forks.
Dispersive model of DNA replication
Each strand of both daughter molecules contain a mixture of old and newly synthesized DNA
semiconservative replication
Method of DNA replication in which parental strands separate, act as templates, and produce molecules of DNA with one parental DNA strand and one new DNA strand
capsid
Outer protein coat of a virus
lagging strand
The strand that is made in fragments using individual sections called Okazaki fragments
histone acetylation
acetyl groups are added to histones, prevents from DNA being wound so tightly, makes room for proteins to bind for transcription
rRNA
building blocks of ribosomes
genes (on operon)
code for proteins
missense point mutation
codes for a different amino acid
nonsense point mutation
codes for stop codon
silent mutation
codes for the same amino acid
DNA replication (second step)
complementary nucleotides match w each other
ligase (Enzyme in DNA replication)
connects DNA fragments together
DNA polymerase (Enzyme in DNA replication)
connects nucleotides together to make a strand reads in 3 -> 5, builds in 5 -> 3
translation (termination) 3
elongation continues until ribosome reaches stop codon in mRNA release factor (protein) causes polypeptide chain to separate from ribosome
operon
group of genes operating together transcription of these genes is caused by a single promoter
activator
helps RNA polymerase bind to DNA, prevents transcription
frameshift mutation
insertion or deletion of a base - changes all codons after the mutation
Transcription
making of an RNA molecule from a DNA template (template strand) RNA polymerase uses a single strand of DNA to make mRNA: 5 ->3
mRNA
messenger RNA - carries info from DNA to ribosome
DNA methylation
methyl groups attach to DNA - prevents transcription
translation (general)
occurs at ribosomes nucleic acid (mRNA) translated to amino acids (proteins)
virus
not made of cells - not alive must infect a host cell to reproduce - host specific
polymerase chain reaction (PCR)
process that makes many copies of DNA for analysis 1: denaturation by heat - DNA strands are separated 2: Annealing - cooling so primers can form hydrogen bonds w/ ends of target sequence 3: DNA polymerase adds nucleotides to 3' end of each primer
histone
protein that DNA is wrapped around
translation (elongation) 2
ribosome moves down mRNA 5 - 3 for each codon (3 bases), a tRNA w/ corresponding anticodon brings an amino acid to the ribosome amino acid is added to the preceding one by a peptide bond
DNA ligase (enzyme)
seals DNA into an opening on DNA created by the restriction enzyme
transformation
slurping up of loose DNA from a cell
microRNA
small RNA molecules that bind to RNA molecules to degrade them
translation (initiation) 1
small ribosomal subunit binds to mRNA and initiator tRNA, the large ribosomal subunit attaches
transforming factor
substance passed from dead bacteria to live bacteria
point mutation
substitution: base is changed but # of bases stays the same
tRNA
taxicab RNA - carries amino acids to the ribosome
conjugation
transfer of genetic material between two cells that are touching
retroviruses
use reverse transcriptase (an enzyme) to copy their RNA genome into DNA
transduction
when a virus transfers genetic material between bacteria
promoter (on operon)
where RNA polymerase attaches
RNA
working copy of DNA ribose sugar U, not T
