2.1 & 2.2 DNA and RNA (Nucleic Acids) (DNA structure (BASE PAIRING ,…
2.1 & 2.2 DNA and RNA (Nucleic Acids)
Each nucleotide is made up of 3 components:
a pentose sugar (pentose because it has 5 carbon atoms in each molecule)
a phosphate group
a nitrogen-containing organic base. Cytosine, Thymine, Uracil, Adenine, Guanine.
All the elements join up by
to form a single nucleotide (mononucleotide). Then Mononucleotides can join together in a chain as a result of condensation reactions between the deoxyribose sugar in one molecule, and the phosphate group of another.
This bond is called a
and the structure is now a
. Continuous linking in a chain forms a
Ribonucleic acid is a short chain polymer made up of nucleotides.
The pentose sugar is always
the organic bases are adenine, guanine, cytosine and
One type of RNA transfers genetic information from DNA to ribosomes. Ribosomes are made of another type of RNA and protein. Another type of RNA is involved in protein synthesis.
The pentose sugar is deoxyribose and the organic bases are adenin, thymine, guanine and cytosine.
DNA is made up of two extremely long strands of polynucleotides joined together by hydrogen bonds formed between the bases. It takes a ladder form where phosphate and deoxyribose molecules form the uprights and base pairings make up the rungs.
Bases in DNA pair together by hydrogen bonds.
adenine always pairs with thymine
guanine always pairs with cytosine.
These are the
and therefore the quantities of each are always equal.
The "ladder" structure of DNA is twisted and wind around to form a double helix. This allows the phosphate and deoxyribose backbone to protect the more chemically reactive bases on the inside.
The hydrogen bonds also make the DNA molecule very stable.
DNA is hereditary material that is responsible for passing genetic information from cell to cell and generation to generation. There is an incredibly vast number of DNA base pairs in each mammal (around 3.2 billion). There is an infinite variety of bases along each molecule providing great diversity within living organisms.
DNA has a very stable structure which very rarely mutates between generations.
The two strands are joined by hydrogen bonds which allows them to "unzip" during DNA replication and protein synthesis
The large molecule and carries an immense amount of genetic information.
The helix structure prevents the bases from being corrupted by an outside chemical or physical force.
Base pairing allows DNA to replicate and transfer information as mRNA
Cell division occurs in 2 main stages
when the nucleus divides (mitosis and meiosis)
is ater nuclear division and is the process by which the whole cell divides.
Before a nucleus divides it must replicate the DNA. DNA replication is precise because all cells DNA is identical to the original.
SEMI CONSERVATIVE REPLICATION
Requirements for semi conservative replication:
Each of the four types of nucleotide with each of their bases (adenin, guanine, cytosine, thymine) must be present
Both strands of the DNA molecule act as a template for the attatchment of these nucleotides
the enzyme DNA polymerase
A source of chemical energy
1) the enzyme
breaks the hydrogen bonds linking the base pairs of DNA.
2) the double helix separates and unwinds
3) the exposed polynucleotide strand now acts as a template for the complementary free nucleotides to bond to.
4) The nucleotides are joined together by condensation reaction with the ezyme
5) each of the new DNA molecules contains one of the original DNA strands and one newly formed complementary DNA strand built into it.