John Barrow Flashcards
(32 cards)
Which two experiments prove that DNA stores genetic information?
Avery-MacLeod-McCarty
&
Hershey-Chase
The Avery-MacLeod-McCarty experiment had 5 different controls; in how many of these controls, did the mouse die?
What were the controls?
3/5 controls resulted in the mouse dying.
- Live, encapsulated, virulent bacteria
- Live, non-encapsulated, non-virulent // heat-killed virulent mix
- Live, non-virulent // DNA of heat-killed virulent bacteria that was TRANSFORMED and encapsulated
What are the structural components of a nucleoside?
base + pentose sugar
What are the structural components of a nucleotide?
base + pentose sugar + phosphate
Cytosine, Thymine & Uracil have what in common?
They are all pyrimidines; their nucleotide structures are all 1 ringed.
Adenine & Guanine have what in common?
They are both purines; their nucleotide structures are both 2 ringed.
How do nucleotides polymerise?
via a phosphodiester linkage
Why is RNA less stable than DNA?
The -OH group is more open to degradation
What is Chargaff’s 4th rule?
What assumptions can we make from this?
(i) Adenine = Thymine & Guanine = Cytosine
(ii) Sum of purine residues = sum of pyrimidine residues
& Adenine + Guanine = Thymine + Cytosine
Give examples of 4 different unusual DNA structures.
- Palindrome
- Mirror repeat
- Hairpin
- Cruciform
Name the three ways in which RNA is structurally different to DNA
- Single polymer chain
- The sugar contains and OH group
- Thymine is replaced with Uracil
Give 3 examples of DNA damaging agents that can cause non-enzymatic transformations.
- UV light (& other types of radiation)
- Chemicals in the environment
- Oxidative damage (Hydrogen peroxide// hydroxyl radicals)
What are the main components of a chromsome?
Genes + Intergenic DNA
What is meant by “genes”?
Genetic data; coding for RNA and proteins
What is meant by “intergenic DNA”?
Regulatory sequences:
- for transcription of genes;
- DNA replication;
- Packing of genes
What are the two types of DNA supercoiling?
- Plectonemic
- Solenoidal
What catalyses the changes in the supercoiling of DNA
Topoisomerases
What is a nucleosome?
The fundamental organisational units of chromatin
What are the fundamental rules of DNA replication?
- DNA replication is semi-conservative
- Replication begins at an origin and usually proceeds bidirectionally
- DNA synthesis proceeds in a 5’–> 3’ direction and is semi-discontinuous
What can mutations alter?
- Protein-coding sequences to generate mutant proteins
- Sequences that regulate DNA replication, transcription or translation
What is DNA damage repaired by?
- Base excision repair enzymes
- Nucleotide excision repair enzymes
Briefly describe base & nucleotide excision repair
- Recognising damage within the DNA double helix
- Cleaving the damaged DNA strand with endonucleases to remove the damaged section
- Using DNA polymerase and the undamaged complementary DNA strand, the gap is filled.
Briefly describe the 5 general procedures of DNA cloning
- Cutting DNA at precise locations
- Selecting cloning vectors
- Covalently linking DNA fragments to form recombinant DNA
- Moving recombinant DNA from the test tube to a host cell
- Selecting or identifying host cells that contain recombinant DNA
What kind of sequences do type II restriction enzymes usually recognise?
Briefly describe the different kinds of cuts.
(i) 4 or 6 base pair palindromic sequences
(ii) Usually symmetrical although;
- Cuts can generate blunt ends
- Cuts can be staggered
