BIOL 2P02 Lecture Notes - Lecture 4: Dna-Binding Domain, Dna Supercoil, Alpha Helix
16 Jun 2018
School
Department
Course
Professor
Spring BIOL 2P02 Section 1 Lecture 4 May 31, 2018
Will add more to the note after my botany midterm!
• Bacteria
o How much the total amount of DNA is in the organisms
▪ E coli -> 4.6million bp & one chromosome
• Supercoiling
o Dot eed to fit i a uleus -> they are w/n a cell
• Nicked -> lightest type -> fully circular
• Linear -> completely cut
• Supercoiled -> migrates far
• Circular single stranded -> taels futhe / its lighte
• Eukaryotic DNA Organization (Chapter 10~first half)
o Cells must deal with a lot of DNA!
▪ Each human chromosome is a single long DNA double helix containing ~140
million base pairs that is ~4.8 cm long
▪ In total, every human cell contains ~2 metres of DNA in a nucleus with a
diameter of ~6 µM
• Taking a single that is 3.3m long and put it in a marble
▪ Nuclear DNA associates with proteins to form chromatin, which is coiled and
compacted to form chromosomes
• Helps fit the DNA into the nucleus
• Helps keep long DNA molecules organized
• Epigenetic gene regulation!
▪
▪ Majority of cells life the DNA is not as condensed as we think
• Condenses during replication
▪ Epigenetic-> allows expression of genes to occur
•
find more resources at oneclass.com
find more resources at oneclass.com
Spring BIOL 2P02 Section 1 Lecture 4 May 31, 2018
•
o 1st level of compaction -> histone octamers can be slid along the helix
▪ Interphase chromatin -> transcription is happening
o Chromosomes do not allows have the X shape
•
• Q1: A supercoiled plasmid will travel further on a gel than a relaxed plasmid. True or False?
o True
find more resources at oneclass.com
find more resources at oneclass.com
Spring BIOL 2P02 Section 1 Lecture 4 May 31, 2018
•
o Isolate chromosome treats it w/ restriction enzymes -> cuts between protein
• One nucleosome has 200bp
•
o Octamer -> DNA wraps around it
▪ 5 histones involved in DNA compaction
▪ H1
▪ 2H2A
▪ H2B
▪ H3
▪ H4
o 10-80bp present
o Octamer of the eight proteins doest fo atually
▪ H3 & H4 like one another -> highly conserved
• Will form a tetramer
o H2A and H2B dimerize w/ one another
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
May 31, 2018: 1st level of compaction -> histone octamers can be slid along the helix. Interphase chromatin -> transcription is happening: chromosomes do not allows have the x shape, q1: a supercoiled plasmid will travel further on a gel than a relaxed plasmid. In bacteria -> plectonemic: right hand coiling, have branches, will see it in a plasmid. May 31, 2018: q2: you mix two of each h2a, h2b, h3 and h5 in a solution that mimics the inside of the cell. If you remove h1 the 30nm filament can still form: h1 is always on the inside. May 31, 2018: salt causes dna to dissociate from proteins -> neutralizes charge. May 31, 2018: heterochromatin: regions of chromatin that remain highly condensed and transcriptionally inactive during interphase, q3: a 30nm chromatin fiber cannot form w/o the h1 histone. Ife cycle of human chromosomes: humans are n=23.
