DNA/ RNA

DNA• DeoxyriboNucleic Acid• Made up of Nucleotides• Contains deoxyribose sugar• Contains the genetic

(hereditary) code for all living organisms.

• Provides a “blueprint” or directions for all cellular processes

Nucleotide

DNA• DNA is found in the nucleus in Eukaryotic cells• DNA is found in Chromosomes• In order of decreasing size– Nucleus Chromosome Gene DNA

DNA

• Discovered by Watson and Crick

• They determined that DNA was in the form of a double helix (twisted ladder)

• Sides of the ladder are made of sugar and phosphorous

• Steps (rungs) made of nitrogenous base pairs

DNA base pairs

• Adenine• Thymine• Guanine• Cytosine

• What are the base pair rules?

DNA base pair rules

• Adenine always attaches to Thymine• Guanine always attaches to Cytosine

Example:• A-T and T-A• G-C and C-G

DNA base pair practice

A-G-G-C-T-A-

Fill in the correct base pair sequence for the following:

A-TG-CG-CC-GT-AA-T

More Practice

TTACGTCAG

T-AT-AA-TC-GG-CT-AC-GA-TG-C

What would happen if the code was altered?

Mutation: any change or alteration in the sequence of DNA (genetic material)

Types:Deletion: one or more bases are removed(deleted)Example: AATCG AACG The T was deleted

More Mutations

• Addition (aka Insertion): One or more bases are added

• Example:AATTCGC AATTCCGC A “C” was added

Substitution: A base is replaced with a new baseAATTGCG AATGGCG The “T” was replaced with a “G”

RNA

• RiboNucleic Acid• Made of nucleotides• Contains Ribose sugar• Contains Uracil instead of

Thymine• Is vital in making proteins• Is single stranded

RNA base pair rules• There is only one difference in pairing the

bases• Adenine always pairs with Uracil• Thymine still pairs with Adenine• Guanine still pairs with Cytosine• Example:

A-U T-AG-C or C-G

Protein Synthesis

RNA

• Two types– mRNA- • messenger RNA• translates the DNA code into codons

– tRNA- • Transfer RNA• lines up amino acids in order of codons

• Both used in protein synthesis at the ribosome

Protein Synthesis• Protein Synthesis: The process of making proteins• Remember proteins are made from long chains of amino

acids• The sequence(order) of the amino determines what type

of protein is being made• This process will need:

– DNA– RNA

• mRNA• tRNA• Ribosome

Protein Synthesis Steps• DNA Replication:

DNA will “unzip” and copy itself

• It will then “unzip” again to make a single strand that can make a strand of RNA

• Transcription: The process of making an RNA sequence based on the DNA sequence.

Transcription practice

DNA Unzipped DNA mRNA (transcription)A-T A UT-A T AG-C G CG-C G CT-A T AA-T A U

More Practice

DNA mRNAAAGTTC

A-UA-UG-CT-AT-AC-G

Protein Synthesis

• Translation: The process by which mRNA “translates” the genetic code into triple letter combinations that represent the key to figuring out the correct order of amino acids

Protein Synthesis• Codon: The triple letter combination of nitrogenous

bases

(DNA Template) AATTTAAAGCCGGAT(mRNA) UUAAAUUUCGGCCUA

Codons UUA AAU UUC GGC CUA

Hint: to make codons, just break up the mRNA code into three letters

Protein Synthesis• The codons will then

be used to code for a particular Amino Acid

• A chart will be used to determine the Amino acid

• The first 3 letters are used to represent the Amino Acid

• Always use mRNA for chart

More Practice

DNA mRNA Codon Amino AcidA UA U UUCG CT AT A AAGC G

Phe

Lys

• Use this chart with your mRNA codons to determine amino acids

• Start from the center and work your way out

• AAG Asp

• This chart can also be used to code for amino acids

Protein Synthesis• Once codons are

determined mRNA brings the information to the Ribosome.

• It is there that the tRNA will transfer or bring the correct amino acid into place.

Protein Synthesis• Transfer RNA (tRNA) will bring

the correct amino acid into place

• tRNA will match its code (anti-codon) to the mRNA codon

• This will provide the correct sequence needed to make a protein

• Remember: the sequence of Amino Acids determines what protein is being made

The anti codon AAG matches up to the codon UUCThis combination will always bring Phe into place

STEP 1DNA Replicates and mRNA created in the Nucleus

STEP 2 mRNA leaves the nucleus bringing codon information to the ribosome

tRNA

Random single amino acids

STEP 3tRNA brings the correct amino acid in to place based on the mRNA code

Protein synthesis

• STEPS• DNA copies itself (replicates)• mRNA matches up to DNA code following the

rules of the base pairing (transcription) • mRNA translates DNA code into codons (triple

letters) brings it to the ribosome• tRNA then “transfers” the amino acids into the

correct order.

Protein Synthesis

• (DNA) AATTTAAAGCCGGAT• (mRNA) UUAAAUUUCGGCCUA

Codons UUA AAU UUC GGC CUA

tRNA AAU UUA AAG CCG GAUAmino Acids Leu Asp Phe Pro Asp A

Mutations re-visited

DNA code:AATGGCCCTAAT

mRNA (codons): UUA CCG GGA UUA

Amino Acids:Leu Pro Gly Leu

Mutations re-visited• What happens if the DNA code on the previous

slide has a substitution of a “G” at the first “T”DNA (with mutations):

AAGCCGCCTAATRNA:

UUC GGC GGA UUAAmino Acids:

Phe Gly Gly LeuOne simple change makes a completely different protein!!!!!!