biomg 2800 Exam review
histones ** Answer ** proteins that DNA wraps around to form chromatin and chromosomes
condensins ** Answer ** protein complexes that form rings around DNA, organizing chromosomes into loops
chromatin ** Answer ** any complex of DNA and protein found in a nucleus...
biomg 2800 Exam review
histones ** Answer ** proteins that DNA wraps around to form chromatin and
chromosomes
condensins ** Answer ** protein complexes that form rings around DNA, organizing
chromosomes into loops
chromatin ** Answer ** any complex of DNA and protein found in a nucleus of a cell
nucleosomes ** Answer ** structure that forms by winding of DNA around histones,
resemble beads on a string
heterochromatin ** Answer ** tightly condensed so no room for transcription factors so
no expression
euchromatin ** Answer ** relaxed so room for transcription factors so expression
transcription requires ** Answer ** changes in chromatin structure
why does transcription require change in chromatin structure ** Answer ** promoters of
inactive genes are hidden in nucleosomes
how are genes activated ** Answer ** transcription factors bind to enhancers and
recruit chromatin remodeling proteins
enhancers ** Answer ** DNA sequence where transcription factors can bind to
enhance or decrease expression
barrier elements ** Answer ** DNA segments that block the spread of heterochromatin
position effect variegation ** Answer ** variable expression of a gene in a population of
cells, caused by the gene's location near highly compacted heterochromatin
gene silencing can be caused by ** Answer ** spreading of heterochromatin
facultative heterochromatin ** Answer ** regions of chromosomes that are
heterochromatic in some cells and euchromatic in other cells
Barr bodies ** Answer ** inactivated x chromosomes (in some cells) because x
chromosomes become completely heterochromatic in some cells while other copies of
this same chromosome remain euchromatic
, - give greater access to transcription factors and other proteins.
new nucleosomes must be formed during DNA replication ** Answer ** replication fork
disassembles nucleosomes on the parental DNA but new nucleosomes assemble on
daughter DNA molecules
new nucleosomes are composed of ** Answer ** recycled and new histones
histone modifications can only happen on ** Answer ** recycled histones
telomeres are ** Answer ** "caps" that protect the ends of eukaryotic chromosomes
telomeres consist of ** Answer ** specific repetitive sequences and do NOT contain
genes so they do NOT encode proteins
telomeres prevent ** Answer ** chromosome fusions and maintain integrity of
chromosomal ends
DNA polymerase functions ** Answer ** 5' to 3' so it adds only to the 3' end of an
existing chain so it relies on RNA primers since it can't add to the 5' end
eukaryotic chromosomes are ** Answer ** linear so replication of the ends is
problematic
ribonucleases remove RNA primers so DNA polymerase cannot fill the gap ** Answer
** so an RNA primer's length of nucleotides will be missing on every newly copied stand
T-loop (3'single- stranded overhang) ** Answer ** It is a protective structure that
prevents the ends of chromosomes from exonuclease activity formed by complementary
base pairing of telomeres
telomerase fixes the limitation of DNA polymerase because it is ** Answer ** An
enzyme that catalyzes the lengthening of telomeres. The enzyme includes a molecule
of RNA that serves as a template for new telomere segments
not all cells take advantage of telomerase activity ** Answer ** germ-line cells, stem
cells, and tumor cells express telomerase and there fore maintain chromosome ends
somatic cells ** Answer ** have a low expression of telomerase
Promoter ** Answer ** specific region of a gene where RNA polymerase can bind and
begin transcription
Enhancers ** Answer ** A DNA sequence that recognizes certain transcription factors
that can stimulate transcription of nearby genes.
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