10.11-10.20 Flashcards
where is the lampbrush chromosome found
amphibians
how are lampbrush chromosomes formed
extended meiosis over long period of time
where do lateral loops extrude from in lamp brush chromosomes
chromomere
what do the loops in lamp brush chromosomes contain
nascent RNA chains
an increase in RNP length (RNA chains) of lamp brush chromosomes indicates what?
transcription unit
where are polytene chromosomes found?
dipteran insect larvae, in interphase nuclei of salivary glands and imaginal discs
how are polytene chromosomes formed
multiple rounds of replication without mitosis (endomitosis, endoreplication)
what does polytene chromosome consist of
4 synapsed diploid pairs held together are chromocenter (where centromeres aggregate)
in situ hybridization
uses labeled probes for specific genes to illustrate position on cytological map
where are chromosome puffs found
polytene chromosomes
chromosome puff
transcriptionally active region in which chromosome fibers unwind from usual state of packaging
Balbiani ring
large puff (more than one gene tcr)
pattern of puffs is related to what?
gene expression
when does puffing pattern change
during larval development
composition of nucleosome
8 histone proteins (H2A, H2B, H3, H4) plus 2 wraps of DNA
what happens when you treat chromatin with micrococcal nuclease
releases individual nucleosomes and destroys linker DNA between them
true or false: m. nuclease is an endonuclease that is sequence blind
true
what does micrococcal nuclease digestion generate
a ladder of DNA fragments with about 200 bp increments
each step on ladder represents what?
DNA derived from discrete number of nucleosomes
how much of DNA is not packaged in nucleosomes?
very little
as time increases with micrococcal digestion, what happens to the number of long pieces of DNA
decreases
nucleosome core particle length of DNA
146 bp
mononucleosome
after initial m nuclease cut, about 200 bp of DNA
trimmed nucleosome
if m nuclease continues digesting, about 165 bp of DNA
