- RNA is a polymer of nucleotides.
- Nucleotides are made of phosphate, 5 carbon sugar i.e. ribose and an organic base i.e. AU CG.
- RNA is single stranded.
- DNA is a polymer of nucleotides
- Nucleotides are made of a 5 carbon sugar i.e. deoxyribose, an organic base i.e. AT CG and a phosphate
- The nucleotides are arranged in two chains which coil up and form a double helix
DNA polymerase - bonds nucleotides together.
Evidence that DNA is genetic material
Explanation of structure related to function
- The sugar phosphate backbone makes the molecule stable
- The molecule coils up so that it is compact, i.e. it can store a lot of information in a small space
- The sequence of bases allows it to carry coded information for making proteins
- It is a very long molecule so it can store a lot of information
- Complementary bases pairing allows the molecule to replicate itself accurately
- The double helix makes the whole molecule stable, as the base pairs are on the inside of the molecule where they are less likely to be damaged
- The bases are held together by weak hydrogen bonds, which allow the molecule to 'unzip' easily when it replicates
- Experimented on different strains of Diplococcus pneumoniae
- Some virulent i.e. cause disease and some were non-virulent i.e. do not cause disease
- Virulent strains had a slimy capsule but the non virulent did not
- When he injected a virulent S-strain of the bacteria into some mice they died
- When he injected a non-virulent R-strain into some mice they survived
- Then he killed some S-strain bacteria by heating them, injected them into some mice and they survived
- Finally, he mixed the dead S-strain with some living R-strain and injected it into the mice, they died, he found living S-strain bacteria from the dead mice
Somehow the dead S-strain bacteria had 'transformed' the R-strain into the virulent S-strain.
Genes and proteins
- The base sequence of amino acids determines the base sequence of the gene which codes for proteins.
- Gene - a section of DNa that carries coded information about a characteristic.
- Allele - an alternative form of a gene. For example, the gene coding for eye colour may have alleles coding for brown or blue eyes.
- Homologous chromosomes - paired chromosomes where genes occur at the same locus, but alleles are not the same.
- Phenotype - the observable traits or characteristics of an organism e.g. hair colour, eye colour or weight.
- Alkaptonuria - suffers have an allele that produces a faulty enzyme, which means they cannot break down homogentisic acid.
One strand of the molecule is kept the same and the other is newly made.
- DNA molecule 'unzips', hydrogen bonds between complementary bases break
- Free nucleotides align alongside their complementary bases
- DNA polymerase joins these new nucleotides together
- Each new strand is complementary to the old strand, and each of the new molecules formed are identical
- Same as above but one helix formed would be entirely made of new material and other other of old
- Both DNA molecules are made up of a mixture of old and new DNA