Nucleus genes DNA Flashcards
Structure of the nucleus
surrounded by nuclear envelope
contains DNA and protein assembled into chromatin
role of nucleolus
site of ribosome assembly
nuclear envelope
continuous with ER has pores forms a protective barrier forms ring structures to anchor proteins has fibres to guide things out of pores
how is DNA packaged into the nucleus
wrap around histones to form nucleosomes
wrap around each other to form solenoids
screw together to form chromatin
chromatin can condense further to form chromosomes
structure of DNA
double helix
contains bases which allow proof reading
run from 5’ to 3’
nucleotides form linear strings with phosphate backbone
why does DNA wrap around histones
contain correct charge and spacers
when is chromosome visible
metaphase of dividing cells
what are alleles
alternate copies of a gene
what does a gene encode
gene product and regualtory regions
when does replication of DNA occur
S phase
explain replication of DNA on leading strand
replication bubble made by loosening of chromatin
DNA polymerase moves along the strand adding bases 5’ to 3’
continuoeus
replication of DNA on lagging strand
RNA primer brought in by enzyme primase DNA polymerase adds and proof reads creates Okazaki fragments when fragments are close primers are removed fragments joined by DNA ligase
types of RNA
rRNA
tRNA
mRNA
transcription of RNA
DNA opens up to create transcription bubble
RNA polymerise adds correct bases to create single strand
(directed by promoter sequences in DNA)
- enzyme and transcription machinery binds to promoter sequences and elongates sequence
DNA bubble closes and RNA separates from the DNA
after transcription of RNA
addition of S methyl guanine gap to stabilise and guide
spliced to remove introns
add adenines to form pol A tail
goes out of cell and associated with riosomes
