STRUCTRE OF DNA U1 Flashcards
DNA is a double helix and consists of
2 long chains (a polymer) of subunits called nucleotides (monomers).
A nucleotide consists of three main components?
Deoxyribose sugar
Phosphate
Nitrogenous base
The four nitrogenous bases are?
Adenine, Thymine, Guanine and Cytosine.
State the components of the nucleotide that make up the backbone of DNA and describe the complementary base paring rule
The components of a nucleotide that make up the backbone of DNA are the sugar-phosphate groups. The backbone is known as the sugar-phosphate backbone.
The complementary base paring rule is: -
Adenine will only bond with thymine and guanine will only bond with cytosine or vice versa.
A-T or T-A
G-C or C-G
Name the type of bond between complementary base pairs
Hydrogen bonds form between complementary base pairs and these are weak bonds.
Describe DNA in terms of a double stranded antiparallel structure
The strands have the phosphate group exposed on the 5’ and the deoxyribose sugar exposed on the 3’.
One strand runs in a 5’ to 3’ direction, whilst the opposite strand runs in 3’ to 5’ direction. This is an antiparallel structure forming the double helix.
Explain what is meant by the term ‘genetic code’
The sequence of bases on DNA forms the genetic code.
Describe the organisation of DNA in a prokaryotic cell
Prokaryotes have a single, circular chromosome (usually within the centre known as the nucleoid region)
Prokaryotes also contain small circular pieces of DNA known as plasmids.
Describe the organisation of DNA in a eukaryotic cell, naming the proteins associated within chromosomes
Eukaryotic cells contain linear chromosomes within a nucleus tightly coiled and packaged with associated proteins.
They also contain small circular chromosomes in the mitochondria and chloroplasts.
Histone proteins are tightly coiled within linear chromosomes.
Describe why yeast is a special example of a eukaryotic cell
Yeast is described as a special example of a eukaryote as it also contains plasmids.
