Bio Exam 2

transcription process in prokaryotes

• polymerase binds non-specifically to dna

• sigma subunit binds to promoter sequences

• dna opens

• sigma subunit release

• rna elongates

transcription process in eukaryotes

• tfIId recognizes tataa box

• tfIIb binds to bre

• tfIIf brings rna polymerase II, and additional transcription factors assemble

• tfIIh helps open the dna and phosphorylates ctd

• transcription begins

• rna polymerase II is released and continues transcribing

• transcription is terminated when AAAAAAAA is reached

repressors

block the binding of activators to regulatory sequences

histone acetyltransferase

promotes transcription by adding an acetyl group to histone tail lysines, neutralizing the positive charge which loosens the chromatin

histone deacetyltransferase

represses transcription by removing the acetyl group from histone tail lysines, reinstating the positive charge and recondensing the chromatin

spliceosome

performs splicing and trimming of pre-mrna

process of splicing pre-mrna

• cleavage at 5’ splice site

• formation of lariat-like intermediate

• cleavage at 3’ splice site

• ligation of exons

incorrectly performed splicing can result in

muscular distrophy

nucleolus

site where ribosomes are assembled before being sent into the cytoplasm

what is done in the nucleolus

• transcription of ribosomal genes

• matures long, precursor rna into smaller rrnas

• assembles ribosomal subunits

granular component

area of nucleolus where later processing and ribosomal subunits are assembled

fibular component

area of nucleolus that contains rrna organization (storage) and transcription-related machinery

dense fibular component

area of nucleolus where early pre-rRNA processing and modification takes place

which cell cycle phases are hard to distinguish from each other?

late g1 from early s, and late s from early g2

cells in embryonic development don’t have

g1 or g2 phases

what is needed for cell cycle to begin

• nutrients

• cell must be large enough

• signal from growth factors

where are dna damage checks

• end of g2

• near end of g1

• middle of s

where are spindle damage checks

• almost end of m

what is g0

resting, non-dividing phase where cells perform normal metabolic and tissue specific functions

cyclins

regulatory switches that turn cdks off/on and direct them to regulatory targets

mitotic protein kinases

a specialized group of enzymes that catalyze the transfer of phosphate groups from ATP to target proteins

cohesins

glue sister chromatids together

condensins

condenses and compacts chromatin

leptotene

prophase begins, chromosomes start to condense

zygotene

synapses begins, synaptonemal complex forms

pachytene

crossing over, dna exchanged by non-sister chromatids

diplotene

synapses ends, chiasma visible within bivalent

diakinesis

prophase ends, nuclear envelope disintegrates

ribosomes in prokaryotes

60s, 30s

ribosomes in eukaryotes

60s, 40s

wooble theory

non-watson-crick base pairing between 3rd base of the mrna codon and 1st base of the trna anticodon

adaquete growth factor supply

stimulates intracellular signaling networks to start protein synthesis

stress/growth factor starvation

halts cell growth and protein synthesis by shutting down the cells main machinery

chaperone proteins

found along polypeptide chain to prevent premature folding

heat shock

helps proteins fold even when feverish

folding takes place in the

mitochondira

three areas of the golgi

cis, medial, trans

what do chondrotin and keratin do

added to the polypeptide chain to modify amino acids

ubiquitination

the targeting of bad proteins to be brought to the lysosome