Lecture 7 - Genomes Flashcards
What is the first level of packaging of DNA?
Beads on a string
What is Chromatin?
DNA extracted from the nucleus
DNA-protein complex
Proteins spaced at regular intervals
How was the composition of chromatin discovered?
Digestion with an endonuclease
What are histones?
The proteins in chromatins
What is Histone H1?
The linker histone
Attaches to the outside of the nucleosome
What is a chromatosome?
Made up of a nucleosome, DNA and a linker histone
What is a nucleosome?
DNA and histones together
Each one is made of 8 proteins
What is the second level of packaging of DNA?
The 30nm chromatin fibre
What is the 30nm chromatin fibre?
Decreases length of DNA to another 1/7th
Nucleosomes are stacked with non-neighbours and zig zag back and fourth
Nucleosomes connected by a straight DNA linekr
How is the 30nm chromatin stabilised?
The off axis asymmetric binding of histone H1 stabilises it
What is the importance of histones and nucleosomes?
Histones let DNA be packed into nucleosomes
The chemical modification of histones can change the structure of chromatin
Nucleosomes detach or shift to allow transcription of DNA
Nucleosomes detach for replication of DNA
What is euchromatin?
Contains active genes
DNA is in the form of the 30nm
Attached to the nuclear matrix and nuclear lamina so the DNA doesn’t get tangled up
Maintains shape of the nucleus
What is heterochromatin?
Contains inactive genes
What are the two types of heterochromatin?
Constitutive heterochromatin = tightly packed in all cells
Facultative heterochromatin = tightly packed in some cells
What is the highest level of DNA packaging?
The metaphase chromosome