Lecture notes
DNA structure and chromosomes
- Institution
- University Of Exeter (UoEX)
A summary of the lecture on the structure and principles of DNA and chromosomes
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Content preview
History What DNA needs to be: A large base (purine – A, G) pairs1868 – Friedrich Miescher isolated - Stable over time (for storage) with a small base (pyrimidine –
nuclein – now called nucleic acid. He - Be able to be faithfully C, T) giving a DNA molecule of
noticed it had a high nuclear weight, replicated so progeny cells have 2nm diameter.
contained lots of phosphorous and the same genetic information Adenine pairs with thymine via 2
was acidic - Be able to control expression of hydrogen bonds, and guanine
1944 – Avery, MacLeod & McCarthy traits/encode proteins pairs with cytosine via 3
found that pathogenic bacteria can - Be able to change in a controlled hydrogen bonds. The bonds
turn non-pathogenic bacteria way to allow for variation and themselves are fairly weak
pathogenic, and though isolating adaptation allowing the strands to be
components of the cell found that it separated. However, due to the
was DNA that was transferred DNA is formed of two antiparallel large number of bonds it takes a
1953 – Hershey and Chase labelled strands held together by hydrogen lot of energy to break up the
DNA and protein with different bonds forming a double helix. Each molecule. This leads helps it in
isotopes and showed that it was the strand is a liner polymer made up of its function.
DNA that was transferred despite it repeating units called nucleotides and
originally being thought of as too has its own directionality (5’ -> 3’) DNA is also non-symmetrical,
simple with only 4 base types. Nucleotide= sugar group + base + having both a minor and major
Rosalind Franklin showed the DNA’s phosphate groove as the backbones are
helical structure and the use of Note that a nucleoside is just the closer on one side that the other.
phosphates as a ‘backbone’ through sugar group and a base. Each of its bases are planar and
x-ray crystallography
stacked on top of each other.
Genome – All the DNA in
(the nucleus of) a cell , or of
an organelle like
DNA and The bases house the genetic
information which is classed a
mitochondria or
chloroplasts. chromosome digital and quaternary code (4
bases) which allows for easy
Autosome – non-sex
storage and analysis by a
chromosome
structure computer.
The genetic material is distributed Nucleosides:
amongst discrete units – chromosomes, Deoxy-ribose + adenine = deoxy adenosine
and if stretched out would reach 2m + guanine = deoxy guanosine
long. Therefore, the DNA must be tightly + cytosine = deoxy cytidine
packed to fit into a cell. + thymine = deoxy thymidine
DNA wraps twice around 8 core histone
proteins ( 2 x 4 different types) to form The nucleoli are regions where
nucleosomes, set out like ‘beads-on-a- chromosomes carrying rRNA cluster
string’ to form chromatin. The together, rRNAs are synthesised and
chromatin is then further packaged by ribosomes are assembled.
histone H1 which brings the
nucleosomes together to form a
chromosome fibre. The chromatin is There are two types of chromatin:
then further condensed by scaffold - Euchromatin: a less compact DNA form
proteins making the DNA 10,000-fold containing genes that are readily
shorter than at its stretched length. So, expressed
chromosomes are composed of protein - Heterochromatin: a more compact form
and nucleic acids. containing DNA that is not transcribed
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Alysmay. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
70055 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now