Telomeres and Centromeres
BSCI 420
Lecture 7
Sept 24, ‘02
“Being paranoid is a problem only if people aren’t out to get you”
-Jim Lynch
Chromosomes, cont.
2. Telomeres are the structures at the ends of linear
eukaryotic chromosomes.
• They consist of a series of unique Dna sequences and
specialized proteins that bind to them.
• Telomerase adds a unique sequence on the ends of euk.
Chromosomes.
• Discovered in Tetrahymena macronucleus
• T. cells have the sequence (TTGGG)n, humans (ATTGGG)n
• Structure:
5’ TTGGGGTTGGGGTTGGGG
3” AAC
GGGG
GG hairpin
proteins
T loop
T loop
Telomeres are needed at the ends of chromosomes for
several reasons:
A. Telomeres prevent the chromosome ends from being
ligated together. Consequence?
B. Telomeres prevent the ends of chromosomes from being
attacked by exonucleases.
(Loop structure explains both of these)
C. Telomeres attach chromosomes to the NE lamina.
D. Telomeres begin pairing or synapsis of homologous
chromosomes during meiosis
E. Telomeres can compensate for incomplete replication of
linear chromosome ends.
Telomerase action
Telomerase
3. Centromeres