Molecular bio of the gene 1+2

Question 1

What is this graph and what does it show? (Replication)DNA–> RNA–>Proteins

Answer 1

Central dogma of molecular biology shows conversion of heritable info into molecules that carry out functions. All of which are also catalysed by proteins

Question 2

What is a codon

Answer 2

3 nucleotides that code for an amino acid, A series of which build up a protein and its structure also deciding its 3D shape.

Question 3

Explain the aevery macdonald mccarty exp. and what it proves

Answer 3

Two cultures of bacteria were made
Live encapsulated virulent bac will kill mouse but nonencapsulated one wouldn’t
Live encapsulated but heat killed will not kill mouse
However, mixture of heat killed virulent and non-encapsulated DOES kill
Due to DNA isolated from heat killed (Burst) bacteria transforms the nonvirulent into pathogenic harmful VIRULENT ones
This is called a transforming factor
This proves that DNA stores genetic info as this info (burst from heat killed) is what caused harmless bacteria to become virulent

Question 4

Explain the Hershey-Chase exp.

Answer 4

o Showed that proteins weren’t the only way to carry info from cell to cell
o Two cultures one with radioactive and one with non-radioactive DNA in bacteriophage cells that inject into bacteria
o Blended to shear bacteriophage heads off
o After centrifuge mix shows the radioactive DNA injection shows proteins were rad but in the non rad culture, the supernatant liquid outside was rad

Question 5

Name and explain the two types of nucleotides

Answer 5

Purines are A and G and contain multiple rings
Pyrimidines are C and T and U and only contain one ring

Question 6

DNA is deoxygenated due to what structural difference

Answer 6

The OH is now a H at the second carbon on the pentose ring

Question 7

what structural difference separates nucleotide from nucleoside

Answer 7

Absence of phosphate from the pentose-base structure

Question 8

Explain the difference in stability of RNA and DNA

Answer 8

They both have 3’ and 5’ ends at which H bonds occur but because RNA is oxygenated, it is more susceptible to chemical attack at those bonds causing subsequent bond breakages making it more unstable

Question 9

what are the properties of purines and pyrimidines

Answer 9

o Hydrogen bonding complementarity drives base pairing as they bond exactly to the one with highest affinity and takes up exactly the right space in the final structure
o Results in the perfect double helix with 2 sugar-phosphate backbones and the complementary bases down the middle
o Proteins usually dock/react with the major groove which is about 6 nucleotides large
However different shapes of Helixes can form too

Question 10

Describe structural variation of the Double Helix

Answer 10

o A form, compact DNA minimal groove spacing
o B form, Average with minor and major groove
o Z form, inverse twisting with minor and major grooves
o Some adopt unusual structures due to DNA sequences
 Palindromes
 Mirror repeats
 Hairpin loops
 Cruciform (double hairpins)

Question 11

Explain Chargaffs rules

Answer 11

 Base composition of DNA generally varies from one species to another
 The specimens isolated from different tissues of the same species have same base comp
 Base comp of DNA in a given species doesn’t change with age, nutrition, or environment
 However in ALL cellular DNAs indifferent to species the no. of A and T residues is equal along with C and G (ratio)
 Sum of purine = Sum of pyrimidine
o So a Double helix is ALWAYS formed however different shapes of double helix exist

Question 12

Explain the differences in structure from DNA to RNA

Answer 12

o The same as DNA but
o It’s a SINGLE polymer chain
o Sugar contains OH
o T–>U
o No simple, regular secondary structure they can be as unique as DNA complications
o Single strands, Bulges, Internal loops, Hairpins

Question 13

Briefly describe denaturing and renaturing properties

Answer 13

• BOTH can be denatured ‘melted’ through heat or pH changes however annealation can occur id returned to normal and mixed
• Renatured if they are mixed and cooled and doesn’t matter if there are different samples as strands wil be complimentary

Question 14

what do non-enzymatic changes do to nucleotides

Answer 14

Nucleotides undergo multiple spontaneous alterations in their covalent structure

Question 15

what are some cell-altering nonenzymatic factors?

Answer 15

o Radiation and UV
o Chemicals like nitrous acid, tobacco
o Oxidation damage by excited oxygen atoms, Hydrogen peroxide. Cells have multiple defence mechanisms to destroy free radicals but can still cause damage to DNA

Question 16

why are nonenzymatic alterations important?

Answer 16

usually slow but important as the permanent changes lead to mutations essential for evolution and gene diversity

Question 17

why do mutations happen due to non-enzymatic alterations

Answer 17

DNA has two strands which allows accurate repair possible unlike in RNA which can lead to easier mutations