DNA & RNA

DNA & RNA are the 2 types of nucleic acid.

They are made up of structures: the pentose sugar, phosphate group and the nitrogen

base.

Nitrogen Base

Phosphate Group

Pentose Sugar

Keywords:• DNA

• Deoxyribonucleic acid.

• RNA (mRNA, tRNA)• Ribonucleic acid (mRNA stands for messenger RNA,

tRNA stands for transfer RNA).

• Nucleotide• A compound containing a pentose sugar, phosphate

group and a nitrogen base.

• Polynucleotide• A polymer made up of many nucleotides.

• Pentose Sugar• A sugar that contains 5 carbon atoms.

• Phosphate Group• A group important in energy transfer.

Keywords:• Nitrogenous or Nitrogen-containing Base

• A base that contains nitrogen and is necessary for protein synthesis.

• Semi-conservative• When a or chromatid is kept from the mother and its

joining chromatid is made from the free nucleotides in the nucleus.

• Codon• A series of 3 adjacent bases that code for a certain amino

acid.

• Anticodon• A series of 3 adjacent bases that correspond through

complementary base pairing to the codon on a RNA strand.

• Triplet• A series of 3 adjacent bases on a DNA strand.

Nucleotides and Polynucleotides

Nucleotides are a small cluster of molecules that build up a strand of DNA and RNA. Nucleotides can have 5 different bases and 2 different sugars, however this changes whether if they are DNA or RNA.

There are 2 groups of bases and 2 groups of sugars.• Pyrimidine

• Thymine• Cytosine• Uracil (only in RNA, replaces Thymine)

• Purine• Adenine• Guanine

There are two sugars, deoxyribose and ribose, the previous is in DNA (deoxyribonucleic acid) and the latter in RNA (ribonucleic acid).

Complementary-base PairingDNA and RNA structure uses complementary-base pairing

to pair the bases perfectly, such as adenine on one end and thymine on the other, similar to guanine being on one

side and cytosine being on the other as such:

Adenine Thymine

Cytosine Guanine

Don’t forget that A to T only have

2 hydrogen bonds while C to

G have 3!

TranscriptionTranscription is the process in which DNA uses mRNA to make a code in which they will collect amino acids via the

ribosome and create a protein, this is succeeded by translation.

The process starts with the DNA breaking up to unveil a strand in which it houses a code for a certain amino acid. Then through RNA

polymerase, a mRNA strand is created, nucleotide by nucleotide with complimentary

base pairing, Uracil replaces Thymine as you can see in the image. And then the mRNA leaves the nucleus to proceed to

translation.

TranslationTranslation takes place in the cytoplasm, it is when the mRNA

strand that was transcribed then goes to a ribosome to enter the translation phase. The ribosome collects tRNA which are made up of 3 adjacent bases that compliment the bases on the mRNA strand. These 3 bases create an amino acid which is then held onto the other amino acids being created by a peptide bond.

Remember that mRNA always ends with a ‘stop’

codon!The codon is always one of

three:• UAG• UAA• UGA

DNA ReplicationThis diagram shows how nucleotides free in the nucleus bind with the DNA to create a second strand.

The two phosphates are left free to bind

with another nucleotide to bind with another DNA

strand.

DNA Replication ~ pt.2DNA replication is a simple process, it takes place during the interphase after a cell has divided, due to the small number of chromosomes and only chromatids, nucleotides bind with the DNA chromatid and start its evolution into a chromosome.

A certain enzyme, DNA polymerase, will act upon the nucleotides to cause this process. And as told, DNA is a polynucleotide, with the smaller subunits being the nucleotides.

And from this we know that DNA is semi-conservative, in that it keeps one strand from the original cell and the other being fully created from nucleotides in the nucleus.

DNA Replication ~ diagram

The strands were once the same,

identical in every way. While now

they are 2 different strands.We say they are

semi-conservative.

Questions?

Thank you!