2.3 Nucleotides Flashcards
What is semiconservative replication
Two new molecules of DNA are formed, each with one old strand of DNA
What is nucleotides made from
Phosphate group, Pentose sugar, nitrogenous base,
What is one strand of DNA made from
Many nucleotides bonded together via phosphodiester bonds
What reaction creates DNA
Condensation
What reaction breaks down DNA
Hydrolysis
What is A double Helix of DNA made from
two strands of DNA running anti parallel to one another,
A T C G
Adenine, Thymine, Cytosine, Guanine
What are pyrimidines
Smaller bases - one ring - Thymine and cytosine
What are purines
Larger bases - two rings - Adenine, Guanine
What bases complimentory bond together
Adenine - Thymine
Cytosine - Guanine
Explain DNA replication
DNA helicase unzips two strands of DNA, free nucleotides in the nucleoplasm attach to their complementary base, DNA polymerase creates phosphodiester bonds between bases, Products are identical and contain one original strand
How are Okazaki fragments formed
DNA polymerase can only bind to the 3’ side, so moves from 3’ 5’ direction. The 5’ to 3’ (lagging strand) strand DNA polymerase has to wait until another section has been unwound. (discontinuous replication)
What happens to Okazaki Fragments
Ligase join Okazaki fragments on the lagging strands
What is DNA mutation?
Errors (change in the sequence of bases) created randomly
What is the Genetic code? What are 3 features about it?
DNA coding for an amino acid.
Triplet code - read in threes (codon)
Degenerate - Codons are not overlapping. amino acids can be coded for by many codons
Universal - genetic code is the same for most organisms
What is a start codon?
Met - Codon that starts of DNA translation/transcription, signalling the start of a gene
Put the order of Protein synthesis
Replication, Transcription, Translation
What is the difference between coding and template strands
The strand we want to copy is called the coding strand, The template strand is the one we transcribe
What are the 4 bases of RNA
Adenosine, Uracil, cytosine, Guanine
Pair complementory bases in RNA
Adenine - Uracil
Cytosine - Guanine
Explain DNA transcription
RNA helicase unzips DNA. Free RNA nucleotides pair with complementary bases on the template strand. Phosphodiester bonds form on the RNA nucleotides by the enzyme RNA polymerase. mRNA is formed, which is an exact copy of the Coding strand and complementary to the template strand, but with Uracil, instead of Thymine. MRNA detaches from the DNA, and leaves the nucleus through nuclear pores. Double Helix reforms
What is ribosomes split into, what does it contain
Small and large subunit, contains ribosomal RNA
What is the anticodon on tRNA. What does tRNA do?
Anticodon is complementary to mRNA strand. tRNA brings over amino acid, corresponding to that codon
Explain DNA translation
mRNA bonds to small subunit of ribosome, at the start codon. tRNA with complimentary anticodon then binds to the mRNA, only two tRNA can be bound at the same time. Peptide bonds are created between amino acids, catalysed by an enzyme. Ribosome moved down mRNA chain, until it reaches a stop codon, where the primary structure is released. The protein then folds into secondary and tertiary structures
What happens to proteins after translation
Protein moves to Golgi apparatus, to be modified
Explain the Mendel and Starr experiment
Two colonies of bacteria grown, one in 14N (normal) and 15N (Heavy)
After many generations of growing in N15, they were transferred into N14.
Samples were taken from the first generation, second generation… and analysed to the control
What does the Mendel and Starr experiment prove. How?
Semi-conservative replication.
in the first generation, there is one band in the middle of N15 and N14, showing that it is a mix of DNA. in the second generation, there are two bands, one at N14, and one at a mix of N15 and N14, as one is from pure N14 and another is mixed with N15
2.1.3
Extraction of DNA from a strawberry
Crush strawberry with 20cm3 of DNA extraction buffer (detergent (disrupts phospholipid bilayer) and salt (Neutralises charge))
Strain into beaker using tea strainer and muslin
Add 1cm3 of protease enzyme
Pour filtrate into a boiling tube
Add 5cm3 of ice cold ethanol, by tilting boiling tube at 45 degrees, rolling ethanol down the sides
Let stand for 5 minutes
Remove with inoculating loop
