2.1.3 Nucleotides and nucleic acids Flashcards
What elements do nucleotides contain?
C,H,O,N,P
Structure of a nucleotide
phosphate group, pentose sugar, nitrogenous base
Structure of DNA nucleotide
Deoxyribose sugar, phosphate group, nitrogenous base (A,G,C,T)
Structure of an RNA nucleotide
Ribose sugar, phosphate group, nitrogenous base (A,G,C,U)
What are the two different structural forms of nitrogenous bases?
Pyramidines and purines
List the purines found in DNA
adenine and Guanine
List the pyrimidines found in DNA
Cytosine, Thymine, Uracil
Structure of purines.
double ring
structure of pyrimidines
single ring
Explain sugar phosphate backbone
DNA molecules are made up of two polynucleotide strands lying side by side running in opposite directions. The sugar links with the parallel phosphate by a phosphodiester bond.
What type of bond joins nucleotides together?
Phosphodiester bond
Why are fruits such as kiwi’s and strawberries good for DNA purification?
They have large amounts of DNA in their cells.
Explain the method for DNA purification.
-Cut up fruit into small pieces.
-Add washing up liquid to water in a beaker.
-Add some of the fruit into the beaker.
-Place the beaker in a water bath for 15 minutes.
-Move the beaker into an ice cold water bath and stir.
-Using filter paper, filter the mixture into another beaker.
-Pour the filtrate into a test tube and add 2-3 drops of protease enzyme.
-Carefully trickle ice cold ethanol down the side of the test tube and sit until the DNA precipitate forms.
Why do you have to place the beaker in a water bath in DNA purification?
Disrupts phospholipid bilayer of fruit cell membrane and nuclear membrane so DNA is released.
Why do you add detergent in DNA purification?
Disrupts phospholipid bilayer.
Why do you have to cool the mixture in an ice cold water bath during DNA purification?
Stops the DNA itself from breaking down.
Why do you have to filter the mixture during DNA purification?
Removes cell debris.
Why do you have to add protease enzyme during DNA purification?
Denatures and removes the proteins just leaving DNA.
What is semi-conservative DNA replication?
One parental DNA splits to make 2 brand new DNA, each with a parent strand & daughter strand
Positive of semi conservative DNA replication.
Ensures genetic continuity.
How does semi conservative replication occur?
- DNA helicase enzyme breaks hydrogen bonds by unwinding the double helix. This forms two strands.
-Each new strand acts as a template to form two new polynucleotide strands.
-The new strands are joined by DNA polymerase enzyme.
-Original DNA strand and new strand join together via hydrogen bonds.
Why is the genetic code described as being degenerate?
More than one codon codes for one amino acid which reduces the risk of mutations.
What are the two stages of protein synthesis?
Transcription and translation
What is transcription?
The process of DNA being transcribed and producing an mRNA molecule.
What is translation?
The translation of an mRNA molecule and the formation of an amino acid sequence.
Where does transcription occur?
Nucleus of cell .
Where does translation occur?
ribosome
Explain transcription.
-Part of a DNA molecule unwinds by the enzyme DNA helicase and the exposed gene can be translation into a single stranded mRNA molecule.
-Free RNA nucleotides pair up with their now exposed complementary bases on the template strand of the unzipped molecule.
-The sugar phosphate groups of these RNA nucleotides are bonded together by DNA polymerase to form the sugar phosphate backbone.
-When the gene has been transcribed, the hydrogen bonds break between the DNA and mRNA molecule and the mRNA leaves via a pore in the nuclear envelope.
Explain translation.
-After leaving the nucleus, mRNA attaches to a ribosome.
-In the cytoplasm there are free molecules of tRNA which have a triplet of unpaired based at one end and a region where an amino acid can join to at the other.
-the tRNA molecules bind with their specific amino acids and bring them to the mRNA molecule.
-The triplet of bases on each mRNA molecule pairs with a complementary triplet in the mRNA molecule.
-Peptide binds form between the amino acid chains until a stop codon is reached.
