DNA and the Genetic code Flashcards
Components of a nucleotide
- Phosphate group
- Deoxyribose sugar
- Organic base
Where DNA and RNA is found inside cells
- In eukaryotic cells, DNA is found in the nucleus
- RNA is usually found in the cytoplasm
Sugars present in RNA and DNA
DNA- Deoxyribose
RNA – Ribose
How are nucleotide chains made?
- They are made by condensation reactions between the carbon 5 and the carbon 3 with the phosphate groups
- Also complementary base pairs will form hydrogen bonds with each other
- Water molecules are formed when nucleotide chains are formed
How are nucleic acids made?
When nucleotide chains bond together
The five organic bases
Purines – Adenine, Guanine
Pyrimidines – Thymine, Cytosine, Uracil
Problems with too much nucleic acid
- Uric acid is produced when excess purines are hydrolysed in the liver
- Uric acid is normally excreted through the urine system
- As uric acid is normally insoluble at lower temperatures, when in excess can form crystal deposits at areas of the body where bloodflow is weak
- This condition is painful and is reffered to as gout
Nitrogenous
Contains nitrogen
Nucleotide
The monomeric unit of all nucleic acids
DNA
The stable polynucleotide chain that acts as an information store as each organic base helps code for amino acids
Importance of DNA being a stable molecule
The hydrogen bonding between the bases makes the molecule stable. Without this stability, the genetic sequence could end up being changed easily and things could go very wrong
DNA structure
- Made from two polynucleotide chains that are anitparallel to each other
- Double helix shape
- Made up of a sugar phosphate backbone
- Sugar phosphate back bone is held together by phosphodiester bonds
- Complementary bases are held together by H-bonds
Process of making a new copy of DNA
-Double helix structure is untwisted
-H-bonds are broken by DNA helicase
-Complemetary bases are unzipped
-Nitrogenous bases are exposed
-DNA polymerase
uses free nucelotides to re bond exposed bases according to base pairing rules
Semi conservative replication
The replication of DNA where a DNA strand unzips and a new strand is assembled onto each conserved strand according to base pairing rules
Advantages of the DNA structure
- The sequence of bases are a good code for information
- Molecules are long so a lot of information can be stored
- Base pairing rule means that complementary strands of DNA can be replicated
- Double helix structure gives the molecule stability
- H-bonds break easily so allow for easy unzipping and copying of information
Gene
The sequence of amino acids that code for a specific protein
Difference between RNA and DNA
- In RNA, sugar molecule that makes up nucleotides is ribose
- The nitrogenous base thymine is replaced with urcail
- The poly nucleotide chain is usually single stranded
- Three forms of RNA exist
The three forms of RNA
- mRNA
- tRNA
- rRNA
Function of mRNA
mRNA or messenger RNA exists to send the information of how to assemble the amino acids found to form protein in the ribosomes. This happens during protein synthesis inside the cell.
What does degenerate mean?
Some amino acids in the genetic code have more than one codon
What is the advantage for the genetic code to be degenerate?
If a mutation occurs on the third base, it may not affect the coded amino acid
What does non-overlapping mean?
There is no sharing of bases between codons
What is a triplet sequence?
When amino acids are read in groups of three codons
What is the purpose of a stop codon?
To tell the ribosome where the protein should end
