DNA It’s not just for college anymore!
DNAIt’s not just for college anymore!
Web Sites
• DNA structure and replication animation
• Overview of gene expression
• DNA Models & Translation model
http://207.207.4.198/pub/flash/24/menu.swf
http://www.genomicseducation.ca/animations/gene_expression.asp
http://www.indigo.com/models/dna-models.html
Learning Goals for DNA & Genetics
• Know structure/function of DNA• Know DNA is genetic material• Illustrate how DNA specifies traits• Understand mutations are change in DNA
sequence• Understand relationship between
mutations in DNA and expressed phenotype
What Is DNA
• Deoxyribonucleic acid– Everyone knows this?
• Molecule of heredity– Constitutes our genes– Genes are stretches of DNA sequence– DNA is present in each cell – Passed on to gametes and into progeny
What is DNA, Really
• Polymer of nucleotides
• Polymer? Nucleotides?
• Polymer– A large molecule that is a series of joined smaller
molecules• Nucleotides
– The small molecules that make up the large DNA polymer
DNA Concepts
• Genes• Chromosomes • Complementary base-paired double helix• Polymer of nucleotides• The sequence of nucleotides is the
information of DNA
DNA Concepts
• DNA controls traits of organism• Traits pass from parent to offspring • DNA is copied during cell division• DNA is present in sex cells • DNA is passed from parent to offspring
Why are DNA Concepts Difficult?
• Chemical names?– Deoxyadenosine, purine, pyrimidine
• Chemical processes?– base pairing, hydrogen bonds
• Genetic principles? – DNA replication– Mutations– Chromosome segregation & assortment
Why is DNA So Difficult?
• Chemical Names– Deoxyadenosine monophosphate– Pyrimidine
• Persons Names– Martina Navratilova– Hakeem Olajuwon
How About Pictures + Names
__ Hakeem Olajuwon __ Purine__ Kareem Abdul-Jabbar__ Deoxyadenosine monophosphate__ Pyrimidine__ Martina Navratilova__ Deoxycytidine monophosphate
__ Nadia Comaneci
A B C
E
F G HA
B
C
D
D
F
E
G
H
NucleotidesThe building blocks of DNA
Base always attached here
Phosphates are attached there
Nucleotide Structure
Adenosine monophosphateCytidine monophosphateGuanosine monophosphateUridine monophosphate
Deoxyadenosine monophosphateDeoxycytidine monophosphateDeoxyguanosine monophosphateDeoxythymidine monophosphate
Nucleotides
Nucleotide Polymerization Reaction: Phosphodiester Bond Formation
Order of Nucleotides
• As nucleotides join the strand they generate a sequence
• Inherent fidelity of DNA replication
AGTCCGATCGTAACTGGGTCACATCGTAAGTGTACACGTATCAGGCTAGCATTGACCCAGTGTAGCATTCACATGTGCAT||||||||||||||||||||||||||||||||||||||||AGTCCGATCGTAACTGGGTCAGGCTAGCATTGACCC|||||||||||||||||| TAAGTGTACACGTA
AGTGTAGC
TCACATCG
ATTCACATGTGCATTCACATCGTCAC
ATCGTCACAT
CGTAAGTGTACACGTATAAGTGTACACGTATAAGTGTACACGTA
AGTGTAGCAGTGTAGC
ATTCACATGTGCATATTCACATGTGCAT
||||||||||||||||||||||
ATTCACATGTGCAT
TAAGTGTACACGTA
DNA Sequence
• Human Genome Project– sequencing the human genome
• What does “sequencing” mean? – To determine the order of the nucleotides in the human DNA
molecules– Human DNA molecules are our chromosomes– Each chromosome is a DNA double helix– Each DNA double helix is two single DNA molecules intertwined– Each single DNA molecule is a chain of nucleotide units – Sequencing is the method to determine what the exact order of
units is in this chain
DNA
Gene
Transcription
Translation
RNA (messenger RNA)
Protein(sequence ofamino acids)
Functioning of proteins within livingcells influences an organism’s traits.
Gene Expression
A Gene is a Transcription Unit
DNA
mRNA 5
Promoter & Regulatorysequences
Terminator
Ribosome binding site
Transcription
Startcodon
Stopcodon
Open reading frame
3
Coding sequences
CodingTranscription
Overview of gene expression
A C
Translation
Translation Elongationaa-tRNA entry
Peptidyl transferase
Translocation Termination
Translation
The code is 3 letter words, but what about punctuation?
GROWANDNOWTHECATSAWTHEDOGBUTDIDNOTRUNENDSEW
• Code written in three letter words - codons • Ribosomes must start at the right place to read
the message• There are three frames, but only one is read to
give an intelligible message • Need a start codon (NOW) and a stop codon
(END) to define the frame to use• frame b
– NOW THE CAT SAW THE DOG BUT DID NOT RUN
acbb
Reading Frames & Mutation Types• Frame shift mutations
– Original reading frame is frame a– Insertions or deletions shift the reading frameROWANDNOWTHECATSAWTHEDOGBUTDIDNOTRUNENDSEW
abc
ROWNDNOWTHECATSAWTHEDOGBUTDIDNOTRUNENDSEWabc
^
Reading Frames & Mutations
• Once a ribosome begins translation in a particular frame (a) it does not shift frames
• Therefore, if a mutation shifts the reading frame in the mRNA, the ribosome will read the wrong frame.
ROWANDNOWTHECATSAWTHEDOGBUTDIDNOTRUNENDSEWabc
ROWANDNOWTHECATSAWTHEADOGBUTDIDNOTRUNENDSEWabc
^
NOW THE CAT SAW THE ADO GBU TDI DNO TRU NEN DSE W..
Reading Frames & Mutations
• A change that creates a stop codon is a non-sense mutation
• Generates a truncated protein
ROWANDNOWTHECATSAWTHEDOGBUTDIDNOTRUNENDSEWa
ROWANDNOWTHECATSAWTHEDOGBUTENDNOTRUNENDSEWa
^
NOW THE CAT SAW THE DOG BUT END
^
Reading Frames & Mutations
• A change that creates a different codon is a mis-sense mutation
• Generates a protein with an altered sequence
ROWANDNOWTHECATSAWTHEDOGBUTDIDNOTRUNENDSEWa
ROWANDNOWTHECATSAWTHEHOGBUTDIDNOTRUNENDSEWa
^
NOW THE CAT SAW THE HOG BUT DID NOT RUN END
Molecular Basis of Phenotype
Effect of Mutations
• Sickle cell disease– single nucleotide change AT