DNA Structure and Function

Watson and Crick

• An Englishman and an American discovered the structure of DNA in 1954.

• DNA is to small to see so they had to build a model using x-Rays and chemical information about Nitrogen bases

They Had Some Help• Roselyn Franklin took this x-ray picture of DNA

which lead Watson and Crick to the double helix structure of DNA but they failed to give her credit until much later.

Double Helix• DNA consists of two

strips, made of sugars and phosphates, twisted around each other and connected by nitrogen bases.

• Looks like a spiral staircase or a twisted ladder.

Sugar Backbone

• The backbone of DNA is made up of Deoxyribose (Sugar) molecules connected to each other using Phosphates

Nitrogen Bases• DNA contains 4

nitrogen bases that make up the “code” for all living things.

A = Adenine

T = Thymine

G = Guanine

C = Cytosine

A always bonds to T

G always bonds to C

Nucleotide

• The combination of a sugar, phosphate and nitrogen base is called a Nucleotide. These are the building blocks of DNA.

DNA Facts

• There is 6 feet of DNA in EVERY cell in your body

• Your DNA contains over 3 Billion base pairs

• Your DNA has over 23,000 genes which means you can produce 23 thousand different protiens.

RNA

• Two types

a. mRNA=messenger

b. tRNA = transfer• Single strand• Ribose backbone • Substitutes Uracil (U)

for Thymine (T)

Key Words for Protein Synthesis• Gene- section of DNA that codes for a

specific protein.

• Messenger RNA (mRNA)- nucleic acid that copies the DNA and takes it to the Ribosome.

• Ribosome- Organelle that builds proteins using mRNA and tRNA.

• Transfer RNA (tRNA)- nucleic acid that matches up codon to anticondon and drops off amino acids in the correct order.

Key Words ContinuedCodon- Group of three nitrogen bases

found on the mRNA that codes for a specific amino acid.

Anticodon- Group of three nitrogen bases found on the tRNA that matches up with the codon and drops off the correct amino acid.

Amino Acid- Building blocks of proteins that are placed in the correct order by matching codon to anticodon along the length of a gene.

Steps to Protein SynthesisTranscription• DNA Opens one Gene• One side of the DNA is copied by the mRNA• mRNA travels outside the Nucleus to the

Ribosome

Translation• Ribosome attaches to the mRNA.• tRNA matches up codon to anticodon and

drops off the correct amino acid• A chain of amino acids is created which is a

protein

Translantion

Protein Synthesis Models

• https://www.youtube.com/watch?v=NJxobgkPEAo&list=FLEezLUm-pa3vfMmQGp1aPTQ&feature=mh_lolz

• https://www.youtube.com/watch?v=Nmqhdozuf7Y&list=FLEezLUm-pa3vfMmQGp1aPTQ&index=1

Genetic Mutation

• Point mutation- substitution, addition or removal of a single nucleotide.

- substitution can cause a change in the amino acid sequence

- Deletion and addition mutation can cause a frameshift which means that the order of amino acids changes.

Sickle Cell Anemia