Chapter 9 Flashcards
What is a nucleotide?
Phosphate, sugar and N-containing base (Purine or pyramidine)
What is a nucleoside?
Sugar and N-containing base (Purine or pyramiding)
What is the function of the phosphate group?
forms covalent phosphodiester bond between adjacent nucleotides
How many ring(s) does a pyramidine have?
2
How many ring(s) does purine have?
1
What kind of ribose does RNA have?
it has a hydroxyl group
What kind of ribose does DNA have?
it has an H group
What is Chargaff’s rule?
A=C and G=C
What are the basic features of DNA?
Antiparallel Righted handed double helix 10 base pairs per turn A with T G with C
What is chromatin?
A complex of DNA, protein and RNA found in the chromosomes
How is DNA coiled? Why?
Supercoiled and the stored energy in supercoiled DNA is used in many DNA transactions that require opening of the DNA double helix including DNA replication, transcription and DNA repair.
What are histone proteins?
Basic proteins that act like spools for DNA to wound up on
List some aspects of histones
highly conserved proteins
Basic
Structural role in chromatin
Positively charged which interact with negatively charged phosphate groups in DNA
What is a nucleosome?
A nucleosome has a core of 8 histone proteins and DNA is wrapped around it but it is also anchored by a 9th histone
What are linker regions?
Linker regions are regions in between nucleosomes and they are susceptible to digestion by an endonuclease
What are the levels of DNA packaging?
3 levels
DNA double helix—> Nucleosomes—> chromatin fibre—> chromosome
What is the function of the eukaryotic centromeres?
Directs chromosome movement into daughter cells at cell division
What is the function of mammalian centromeres?
Contain satellite DNA sequences (AT-rich) repeated many thousands of times
What is a kinetochore?
Proteins assemble on the centromere to form the kinetochore
What is the function of a kinetochore?
Kinetochores are attachment site for the spindle fibres which pull chromatids apart
What is a “shelterin” complex?
A “shelterin” complex at the telomere protects chromosome ends from degradation
