general structure of nucleotides
- phosphate group
-pentose sugar
-nitrogen-containing base
differences between the DNA and RNA nucleotides
- DNA has deoxyribose, RNA has ribose
- RNA has uracil instead of thymine
how does nucleotides join together to form DNA/RNA polymers
by condensation reaction
phosphodiester bond - between pentose sugar and phosphate group
mRNA function
carry a copy of genetic code of one gene to a ribosome in the cytoplasm
tRNA function
carriers specific amino acids to the mRNA on the ribosome
rRNA
combines with proteins to form a ribosome
DNA structure
Polymer of nucleotides;
Each nucleotide formed from deoxyribose, a phosphate (group) and an organic/nitrogenous base;
Phosphodiester bonds (between nucleotides);
Double helix held by hydrogen bonds;
(Hydrogen bonds/pairing) between adenine, thymine and
cytosine, guanine;
Name the two scientists who proposed models of the chemical structure of DNA and of DNA replication.
Watson and Crick
Give two features of DNA and explain how each one is important in the semi-conservative replication of DNA.
- easily broken hydrogen bonds between bases allow two
strands to separate
-Two strands, so both can act as templates;
-may appear in the same feature
Complementary base pairing allows accurate replication
Describe the role of two named enzymes in the process of semi conservative replication of DNA.
DNA helicase causes breaking of hydrogen between DNA
strands
DNA polymerase joins the DNA nucleotides
Forming phosphodiester bonds;
Contrast the structures of ATP and a nucleotide found in DNA
ATP has ribose and DNA nucleotide has
deoxyribose;
ATP has 3 phosphate (groups) and DNA
nucleotide has 1 phosphate (group);
ATP – base always adenine and in DNA
nucleotide base varies
explain why the arrows point in opposite directions in DNA replication
DNA has antiparallel strands
nucleotides aligned differently
Enzymes have active sites with specific shape;
Only substrates with complementary shape can bind with active site of DNA polymerase
Semi conservative replication
ensures genetic continuity between generation of cells
- The DNA unwinds, then DNA helices breaks the hydrogen bonds between the complimentary base pairs
- the double helix unwinds and separates the two strands of DNA
- new DNA nucleotides bind to exposed bases on the DNA template strand
- DNA polymerase catalyses the condensation reaction that joins adjacent nucleotides
properties of water
1- is metabolite- can take part in condensation reaction, hydrolysis and photosynthesis
2- its the solvent where metabolic reaction take place
3- has a relative high heat capacity- buffers temperature changes
4- relative large latent heat of vaporisation- losing small amounts of water through evaporation has a cooling effect
5- strong cohesion between water molecules- support of water columns of water in xylem for the transpiration stream and produce
