3.1) DNA - the code of life Flashcards
What are the 2 nucleic acids found in cells?
1) Deoxyribonucleic acid (DNA)
2) Ribonucleic acid (RNA)
Who discovered DNA and who did not receive the Nobel Peace Prize?
Maurice Wilkins
Francis Crick
James Watson
Rosalind Franklin (didn’t get Nobel Peace Prize)
Where is DNA found?
Mainly in the nucleus of a cell
Forms part of the chromosomes that make up the chromatin network
Define chromatin
Chromosomal material made up of DNA, RNA and histone proteins as found in a non-dividing cell
What is extranuclear DNA?
Small amounts of DNA are found outside the nucleus in mitochondria in plants/animals and chloroplasts in plants
What is the shape of the DNA
Long, twisted ladder
3D double helix
How is a nucleotide made up
sugar (deoxyribose)
phosphate molecule
nitrogenous base
What are the 4 nitrogenous bases
adenine
thymine
guanine
cytosine
How is the double helix made up
- Outer two strands formed by chain of alternating sugar/phosphate links - strong
- rungs of ladder - pairs of bases linked by weak hydrogen bonds
- base pairs attached to sugar molecules
Which base pairs link together
A - T (or U)
G - C
How are base pairs classified ?
Purines & Pyrimidines
Define purines and examples
Purines - 2 fused rings of nitrogen, carbon and hydrogen atoms
Eg. Guanine and adenine
Define pyrimidines and examples
Pyrimidines - 1 ring of similar atoms - SMALLER than purines
Eg. Thymine, cytosine and uracil
What determines the genetic code?
Sequence of nucleotides
What is the role of DNA?
1) carry hereditary info in the form genes
2) coding for protein synthesis
3) can replicate
What is non-coding ?
1) less than 2% codes, rest is non-coding
2) protein-coding of DNA called exons and are interrupted by non-coding regions called introns
3) complex organisms have more non-coding
4) non-coding regions form functional RNA molecules
Define replication
Process defined as the process of making a new molecule DNA from an existing DNA molecule that is identical to the original molecule.
Why is replication necessary?
Genetic code is passed on to each new daughter cell formed during cell division
Explain replication process
1) process is catalysed by the enzyme polymerase
2) double helix unwinds
3) weak hydrogen bonds holding the base pairs together break, allowing the two strands to part
4) each of the single bases are exposed
5) free nucleotides in the nucleoplasm become attached to their matching, exposed base partners
1 double helix becomes 2 double helices; 2 daughter DNA molecules each to form a double helix & winds itself around the histones which forms a chromosome.
