Nucleotides and nucleic acids Flashcards
what 3 components structure a nucleotide
a phosphate group, a pentose sugar and an organic base
what are 2 polymers of nucleotides
DNA and RNA
what is the structure of ATP (adenosine triphosphate)
one molecule of adenine, one ribose sugar and 3 phosphate groups
what are the components of a DNA nucleotide
a deoxyribose sugar, a phosphate group and one of the 4 organic bases (adenine, guanine, cytosine or thymine)
what is the structure of a DNA molecule
double stranded that twists into a double helix, the 2 strands are anti-parallel and therefore run in opposite directions, that 2 sugar - phosphate backbones are held in place by pairs of complimentary bases joined by hydrogen bonds
what are the components of a RNA nucleotide
a ribose sugar, a phosphate group and one of the organic bases (adenine,guanine,cytosine or uracil)
what is the structure of a RNA nucleotide
a relatively short molecule and single-stranded
what bond is formed between 2 nucleotides due to a condensation reaction
phosphodiester bond/ester bond
what is a phosphodiester bond
a phosphate group and 2 ester bonds
what reaction breaks the phosphodiester bond
hydrolysis
what 2 organic bases are purines
adenine and guanine
what 2 organic bases are pyrimidines
cytosine and thymine
how many hydrogen bonds from between the complimentary base pairs
cytosine+guanine=3 hydrogen bonds
adenine+thymine=2 hydrogen bonds
what is the first stage of DNA replication
DNA helicase breaks the hydrogen bonds between the 2 polynucleotide DNA strands, the helix unzips to form 2 single strands
what is the second stage of DNA replication
each original strand acts as a template for a new strand , free-floating DNA nucleotides join to the exposed bases on each original template strand by complimentary base pairing
what is the third stage of DNA replication
the nucleotides of the new strand are joined together by DNA polymerase, forming the sugar-phospahte backbone, hydrogen bonds form between the bases on the original and new strand, this twists to form a double-helix
what is the fourth stage of DNA replication
each new DNA molecule contains one strand from the original DNA molecule and one new strand
what is semi-conservative replication
half of the strands from each molecule are from the original piece of DNA
what is the first stage of transcription
DNA helicase breaks the hydrogen bonds which unzips and unwinds the section of DNA that contains the gene
what are the 2 strands called and used for after being seperated by DNA helicase
one of the strands is a sense strand which contains the code for the protein to be synthesised it runes from 5’ to 3’, the anti-sense strand is a complimentary copy that doesn’t code for a protein and acts as a template strand
what is the second stage of transcription
RNA polymerase moves along the DNA template strand and attaches free nucleotides to their complimentary bases on the DNA, phosphodiester bonds are formed
what is the third stage of transcription
RNA polymerase continues making a strand of mRNA until a stop codon is reached
what happens to the mRNA after it is produced through transcription
the mRNA detaches from the DNA template and leaves the nucleus via a nuclear pore, the DNA double helix reforms, mRNA then travels to a ribosome for translation
what is splicing
when mature mRNA is formed by the introns (non-coding regions of genes) being removed from the pre - RNA molecule, and the exons (coding regions) joining together.
what is the first stage of translation
rRNA (ribosomal RNA) makes up the ribosome that moves along the mRNA strand, and one end of the mRNA attaches to the ribosome
what is the second stage of translation
a tRNA (transfer RNA) with a complimentary anticodon, carrying a specific amino acid moves to the ribosome and pairs with the first mRNA codon
what is the third stage of translation
the ribosome moves along the mRNA to the next codon and again pairs up with a complementary tRNA, to bring the two amino acid-carrying tRNAs together
what is the fourth stage of translation
energy released from ATP is used to form a peptide bond between the amino acids bought to the ribosome by tRNA
what is the fifth stage of translation
the ribosome moves to the third mRNA codon, releasing the first tRNA and pairing up a third (only space for 2 tRNA at a time)
what is the sixth stage of translation
this continues until the ribosome reaches a stop codon, then the polypeptide is complete and the mRNA and tRNAs are released from the ribosome
the tRNA molecules released from the ribosome can’t be reused
true or false?
false
they can be reused
what does it mean that the genetic code is non-overlapping
each base triplet is read in sequence,seperate from the triplet before it and after it and the base triplets don’t share their bases
what does it mean that the genetic code is universal
the same base triplets code for the same amino acid in all living organisms/things
what does it mean that the genetic code is degenerate
more combinations of base triplets than amino acids (20 amino acids but 64 possible base triplets), some amino acids are coded for by more than one base triplets
what is the method for DNA purification
1- use a fruit or vegetable e.g. strawberries and break up the cells e.g. through use of a blender
2- make up a solution of detergent (dilute washing-up liquid), salt (sodium chloride) and distilled water
3- add broken cells to a beaker containing detergent solution, incubate the beaker in a water bath at 60 degrees for 15 minutes
4- once incubated put beaker in an ice bath to cool the mixture down, when its cooled filter the mixture e.g. pass through a mesh
5- add protease enzymes to the filtered mixture
6- slowly dribble some ice cold ethanol at a 45 degree angle to the solution, so it forms a layer on top of the DNA-detergent mixture
7- once left for a few minutes, the DNA will form a white precipitate (solid) which can be removed using a glass rod
how is the detergent solution suited to make the method work
detergent- breaks down the cell membranes
salt- binds to the DNA and causes it to clump together
temperature- the temperature of the water bath should stop enzymes in the cells from working properly and breaking down the DNA
how does the protease enzymes work
these will break down (hydrolyse) some proteins in the mixture
what does adding the ethanol do to the DNA
causes it to precipitate
