Biotechnolgy

Basic Molecular Biology

• Core of biotechnology

Began in 1940’s• Scientists studying animal

and plant viruses

1953• James Watson and Francis

Crick identified the structure of DNA

1960’s• The genetic code was

worked out

1970’s• Restriction enzymes were

discovered.

Broad range of studies• DNA-RNA• genetic engineering• cloning• gene therapy• recombinant DNA• gene splicing

Nucleotides• composed of three parts

–a phosphate molecule

–a sugar molecule

–a nitrogen base molecule

Sugar molecules• ribose as in RNA

• deoxyribose as in DNA

Nitrogen bases• five bases in RNA and

DNA

DNA• Cytosine - C

• Thymine - T

• Adenine - A

• Guanine - G

RNA• A, C, G &

• Uracil - U

• found only in RNA

• Substitutes for Thymine

Structure of DNA • genetic material of the cell

- makes up the genes

• genes are organized in chromosomes

Chromosomes• make up the genetic info of

the cell or genome

The nucleotides…..• ACT&G form two long

strands

• The strands are complimentary

• Bases on one strand are paired with those on the other strand

Base Pairing• A with T

• C with G

• ALWAYS this way!

Double Helix• forms when the two

strands intertwine

• like a ribbon around a pole

Antiparallel• The two strands run

antiparallel

• They face each other and run in opposite directions

Strands run in different directions

• one strand runs from 5’ to 3’

• the other strand runs 3’to 5’

Prime ends• 3’ & 5’ are differentiated

by the arrangement of the sugar on each nucleotide

• 5’ ends in a Phosphate (P)

• 3’ ends in a Hydroxide (OH)

DNA Structure• unique for three reasons

• complimentarity of the two strands - base pairing

• variability of base sequence along the two linear strands

DNA Structure• independence of the two

strands–their ability to separate and

rejoin without destroying the molecule.

DNA in Humans• 6 billion base pairs in a

human cell

• 100 trillion cells in human body.

• DNA in a human would reach to the moon and back 250,000 times

Turns of the helix• There are ten base pairs per

complete turn of the helix

• Distance of one complete turn of the helix is 34 A ( Angstrums)

Functions of DNA• carry genetic information

• express genetic information

Express genetic info• directs the synthesis of

proteins

• proteins determine the traits of an organism

Eukaryotic Cells• having a true membrane

bound nucleus

• DNA of nucleus is stored by wrapping it around five proteins to form a nucleosome.

Nucleosome• forms the chromosome

• the genes are located along the DNA molecule

• chromosomes occur in pairs

Prokaryotic Cells• chromosome is not associated

with proteins• exists as a single, circular

chromosome of double stranded DNA.

• Also contain smaller circular DNA called a plasmid

Plasmids• can pass between bacteria

• are vehicles for introducing new genes into bacteria in nature and in the lab

Transcription • Replication

• goes from the 5’ to the 3’ end of DNA

Reading DNA• DNA is read from 3’ to 5”

Synthesis of DNA• synthesized only in the 5’

to 3’ direction

• Cannot initiate synthesis of a new strand - requires a 3’OH as a primer

Types of RNA• messenger - mRNA carries

the code for a protein

Codon• sequence of three bases

• each three bases represents an amino acid

Transfer RNA• tRNA

• carries appropriate Amino Acid with it

• anticodon - pairs with the codon

Ribosomal RNA• rRNA• required for bonding to

occur by Amino Acids• Ribosome has two parts

–big–small