Lecture 26 - Genome Structures and DNA Replication Flashcards
how many base pairs does the human genome have?
~3x10^9
how long is the entire DNA double helix if unpackaged?
1m
genome ____ and _____ vary widely across ______
- size and gene
- species
what are 5 levels of chromosome packaging?
- Linker DNA
- 10 nm fibers
- 30 nm fibers
- chromosomes
how are eukaryotic DNAs packaged?
into nucleosomes by histone proteins
what are histone proteins?
they package eukaryotic DNAs into nucleosomes
_____ structure influences expression
chromatin
______ modifications also influence expression
histone
where are histone tails modified?
-on N-terminal regions that protrude from the nucleosome core region
how are histone tails modified?
-methylated, acetylated, phosphorylated, or ubiquintinated at specific amino acids
modification of one site on histone influence the modification of _______
a second site
what do nucleosome-remodeling complexes do?
rearrange DNA packaging around nucleosomes
what does chromatin remodeling do?
ATP-dependent chromatin remodeling exposes DNA binding sites
DNA methylation also exerts _______
epigenetic control
where does DNA replication initiate?
-at specific chromosomal sites (origins of replication, ori)
organisms that have circular DNA (eg bacteria) also have ______
replication terminus regions (ter)
organisms that have linear DNA (eg humans) often have _______ and
multiple ori
entire DNA is replicated without specific ter sequences
human chromosomes have ______ and _______
centromeres and telomeres
can replication of linear DNA copy the template to the very end?
no
what happens because replication of linear DNA cannot copy the template to the very end?
-telomeric DNA sequences must be added to the ends of the chromosome to protect them from being omitted from the copy
what do telomeric sequences usually consist of?
T and G
where does DNA replication initiate?
at replication origins
