Module 2: Molecular Basis of Inheritance and DNA Mutations Flashcards
What are the 3 functions of Genetic material?
Genotypic (replication)
Phenotypic (gene expression)
Evolutionary (mutation)
What are chromosomes made of?
DNA and proteins (sometimes RNA)
What is the difference between DNA and RNA
2nd C in DNA has H, 2nd C in RNA has OH - making RNA more reactive and degrades faster
What Nucleotides are Pyramidines?
Uracil, Thymine and Cytosine
What Nucleotides are Puriens?
Adenine and Guanine
What is the difference between A-T and C-G pairings
A-T have 2 H bonds, G-C have 3, making them stronger
What bonds are there in the DNA double helix?
- Covalent bonds in backbone
- H bonds between bases
- Hydrophobic bonds of bases in interior
What are the 2 flows of genetic information?
DNA –> DNA
DNA –> RNA –> Proteins
What did the Sia and Dawson experiment discover about genetic information?
Discovered that DNA carries genetic information by a series of experiments where they destroyed DNA, RNA and Proteins, and only when the DNA was destroyed was the genetic information not passed on.
What are the purposes of the 4 regions in a gene?
- regulation of transcription
- Regulation of translation
- Coding region - Usually starts with ATG
- Signal for termination of transcription - Usually TAA
How to the major and minor grooves of DNA double helix differ?
Major groove is wider and is also where proteins bind easier.
What are the 3 alternative forms of DNA?
A, B and Z
A and B are RIGHT HANDED
- B is more compact than A, fewer bases per turn and smaller diameter
Z is LEFT HANDED (Only seen in labs)
How does super-coiling of DNA occur?
Enzymes cleave one half of the DNA backbone - twist DNA then reseal to form a turn.
Most commonly forms L) handed turns - opposite to DNA helix.
What amino acids are most common in Histones and why?
Lysine and Arginine are most common because they have (+) charge, and therefore interact more with negatively charged DNA.
Define nucleosome
Bead structure of chromatin subunit - DNA wrapped twice (166 nucleotides long) around protein octamer (8 protein complex)
When do nucleosomes form?
During Interpahse
How does modifying proteins in the nucleosome octet affect then nucleosome?
More positively charged side chains –> more condensed DNA
What are the 3 levels of DNA condensation and when do they occur?
DNA (2nm) –> Interphase (11nm) –> Metaphase (30nm)
What are the 2 main models of 30nm fibre?
Solenoid (nucleosomes on same side of DNA linker - all pointing up) and Zig Zag (nucleosomes on alternating sides of DNA linkers - one up, one down etc.)
How does the structure of chomosomes form?
30nm fibre is packed in solenoid or zig zag formation then non-histone proteins act as scaffold to hold in x structure of chromosome
What are the 3 levels of DNA packaging in Eukaryotic cells
Interphase: 11nm fibre
Interphase and Metaphase: 11nm fibre folded and supercoiled into 30nm fibre
Metaphase: Scaffold proteins and 30nm fibre form Metaphase chromosomes
What is a centromere?
Constricted region of chromosome where spindle fibres attach. Primary consists of a satelite sequence alpha (171 base-pair-long sequence repeated over and over)
What is a telomere?
Sequence at the end of 3’ DNA that surpasses 5’ end of paired single strand DNA. Forms T LOOP to protect end of DNA and to prevent fusion of DNA.
Also facilitates the complete replication of the 5’ end of linear DNA molecules
What is the telomere sequence in vertebrates?
TTAGGG