Exam 1: Lecture 15 & 16 Flashcards
telomere organization:
region of repetitive nucleotide sequences at each end of a chromosome (TTAGGG)n
telomere fcn:
protects the end of the chromosome from deterioration or form fusion with neighboring chromosomes (sticky ends can cause breakage)
centromere structure/organization:
constricted region of a chromosome where spindle fibers attach, surrounded by heterochromatin
centromere fcn:
essential for chromosome separation
dna at the ends of euk chromosomes consists of telomeric short repeated sequences. the G-rich strand at the telomere is longer than the C-rich strand. this is relevant for:
T-loop; G-rich strand folds over and pairs with a short stretch of dna to form t-loop
shortened telomeres are associated with
shorter life span and increased incidence of disease
when telomeres are never shortened, ie able to extend their life span indefinitely, this is associated with
cancer; cells never dying
telomere length is inversely associated w/
aging
region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division
centromere
a complex of proteins associated with the centromere of a chromosome, to which the microtubules of the spindle attach during cell division
kinetochore
a small, cylindrical cell organelle, located near the nucleus in the cytoplasm of most euk cells, that divides in perpendicular fashion during mitosis
centriole
the centromere is the chromosomal locus essential for
chromosome inheritance and genome stability
the physical role of the centromere is to
act as the site of assembly of the kinetochore
the kinetochore is a highly complex multiprotein structure that is responsible for
the actual events of chromosome segregation
- binding microtubules
- signalling to the cell cycle machinery when all chromosomes have adopted correct attachments to the spindle
positive supercoiling is for
packaging dna ( no access to dna)
negative supercoiling is for
unwinding dna (for the process of transcription)
topoisomerase is for
enzyme responsible for adding and removing turns in the coil (supercoiled dna is overwound or underwound, causing it to twist on itself)
bacterial have _ dna which is advantageous how?
circular; no tips exposed to nucleases like proks and their need for telomeres
define histones
proteins that condense/wrap/package and order dna
histones have a _ charge and dna has a _ charge
histones have positive and dna negative charge
nucleosome
segment of dna wound in sequence around 8 core histone proteins (histone unit)
chromatosome
histone octamer plus linker histone (H1) and 166 bp of dna
linker dna
double stranded dna inbtwn two nucleosome cores (holds cores together)
what are the 2 main biochemical modifications histones/dna are subjected to?
histone acetylation = de-condense (gene activation)
dna methylation = compact/condensing
