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