STRUCTURE OF DNA Flashcards
structure of strands in DNA
-DNA = double helix
- consists of 2 long chains (a polymer) of subunits
- called nucleotides (monomers
nucleotides
A nucleotide consists of three main components:
- Deoxyribose sugar
- Phosphate
- Nitrogenous base
The four nitrogenous bases are Adenine, Thymine, Guanine and Cytosine
deoxyribose sugar
- contains 5 carbons, this is why it is represented as a pentagon.
- The carbons are numbered 1’-5’ The phosphate group bonds to the 5’ (5 prime) carbon of the sugar.
- The 3’ carbon is exposed on the bottom of the pentagon
backbone of DNA
The components of a nucleotide that make up the backbone of DNA are the sugar-phosphate groups = sugar-phosphate backbone
complementary base paring rule
Adenine will only bond with thymine and guanine will only bond with cytosine or vice versa
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 anti-parallel structure
- strands have P.G expose on 5’ and D.S expose on 3’
- one strand runs 5’to3’ = opposite strand run 3’to5’
-anti-parallel structure = form double helix
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
- 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
name the proteins associated with chromosomes
- 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.
