MCBG Lec 1 Flashcards
Active Recall Tests
How many pairs of chromosomes do humans have?
23 pairs (46 total) 1-22 and then x and y chromosomes
Heterochromatin is what colour on an electron microscope, and why, what are the consequences of this?
Same question for euchromatin.
- Black, this is as it is more densely packed DNA Strands (in solenoid form), this means it is less accessible, and will not be expressed by the cell
- White, Less densely packed DNA (Beads on a string form), means it is accessible and will be transcribed
Explain the process of making chromatin expressible or non- expressible?
active chromatin has acetyl groups on it
to deactivate - deacetylation and DNA methylation
this gives it methyl groups which males it inactive
to activate - acetylation and DNA demethlyation
DNA is a double helix with two grooves
What are they?
Which of these is accessible and why?
Major groove - accessible to be read
Minor groove- largely inaccessible, this is due to steric hindrance between base and the sugar phosphate backbone
Describe the orders of packing for DNA.
Start with a DNA strand
This strand is wrapped round histone proteins, to form neuclosome groups, joined by linker DNA. This is called bead on a string.
These beads then group together to form larger, more dense solenoids.
Solenoid groups then ziz zag around scaffolding proteins to from solenoid loops.
These solenoid loops form the chromosomes.
Describe the structure of a chromosome
A chromosome is made of two chromatids joined by a centromere
They have a shorter P branch and a longer Q branch
Define Genome
The entire DNA sequence of a Species
What is the difference between a nucleoside and a nucleotide ?
A nucleotide has a sugar, a base and a phosphate
a nucleoside is lacking the phosphate group
What differentiates DNA and RNA?
DNA is made with a 2’ deoxyribose sugar
RNA is made with a ribose sugar
RNA uses Uracil instead of Adenine to join to Thymine
What is the clinical use of a nucleoside?
- it lacks a phosphate group, and can have a different group to OH on 3’
- DNA polymerase can recognise it, and will use as a DNA building block
- It will add it to DNA chain
- It can lack the 3’ hydroxy group, which means nothing can add to it
- this terminates the reaction
- Effective treatment for cancers/viruses
AAGCCGA
What are the two ends of this sequence known as?
What do these two ends have attached to them?
what is the complementary sequence?
5’ and 3’
5’ has a phosphate group attached
3’ has a hydroxy group attached
TTCGGCT
Which direction is the polarity in a sequence?
5’ to 3’ as the 5’ has an e- dense phosphate group attached
What are the two types of base groups?
Place the 4 base groups into these types
Which groups bond to each other and why?
the two types are purines and pyrimidines
Adenine (A) and Guanine (G) are purines
Cytosine (C) and Thymine(T) are pyrimidines
A-T and G-C
This is A-T have a 2 H bond interaction
G-C a 3 H bond interaction
DNA is ?
Complimentary and anti-parallel
Describe the cell cycle in detail
M phase is meiosis and mitosis (division section)
next the G1 phase replicates cell contents ie organelles and cytoplasm
next the S phase is DNA replication
then the G2 phase is to double check and repair mistakes
There are cell cycle checking points
