unit 1: central code and genetic material paz etcheverry ns 315
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Unit 1: Central Code Unit 1: Central Code and Genetic Materialand Genetic Material
Paz EtcheverryPaz Etcheverry
NS 315NS 315
Topics to coverTopics to cover
Cell structureCell structure DNA structureDNA structure DNA replicationDNA replication RNA structureRNA structure The Central Dogma of BiochemistryThe Central Dogma of Biochemistry Transcription: DNA to mRNATranscription: DNA to mRNA Translation: mRNA to proteinTranslation: mRNA to protein Codons and anticodonsCodons and anticodons
The nucleus: contains23 pairs of chromosomes.DNA is arranged in thesechromosomes.Where replication and transcription occurs.
The ribosome: where protein is synthesized (i.e. translation occurs)
Cytosol or cytoplasm
The nucleus: contains23 pairs of chromosomes.DNA is arranged in thesechromosomes
23 pairs of chromosomes:
http://ghr.nlm.nih.gov/handbook/basics/howmanychromosomes
How many chromosomes How many chromosomes does each human cell does each human cell have?have?Each human cell contains 46Each human cell contains 46
chromosomes:chromosomes:– 22 pairs of somatic (non sex) 22 pairs of somatic (non sex)
chromosomeschromosomes– 2 sex chromosomes:2 sex chromosomes:
Female sex chromosomes: 2 XFemale sex chromosomes: 2 X Male sex chromosomes: 1 X and 1 YMale sex chromosomes: 1 X and 1 Y
Inside each of the Inside each of the 23 pairs of 23 pairs of chromosome, there chromosome, there is DNA.is DNA.
DNA is tightly DNA is tightly packed inside each packed inside each of the of the chromosomes.chromosomes.
Each chromosome is Each chromosome is composed of two composed of two chromatids joined chromatids joined by a centromere.by a centromere.
Centromere
DNA
A chromosome pair
DNA DNA (deoxyribonucleic (deoxyribonucleic acid)acid)
Double helixDouble helix Double= 2 Double= 2
polynucleotide chainspolynucleotide chains Helix= helical Helix= helical
structure (like a structure (like a spring)spring)
Each chain contains Each chain contains nucleotides (joined to nucleotides (joined to each other) and a each other) and a sugar/phosphate sugar/phosphate backbonebackbone
http://instruct.westvalley.edu/svensson/CellsandGenes/dna-structure%5b1%5d.gif
Nucleotides in DNANucleotides in DNA
The nucleotides areThe nucleotides are– Adenine (A)Adenine (A)– Thymine (T)Thymine (T)– Cytosine (C)Cytosine (C)– Guanine (G)Guanine (G)
A binds to TA binds to T C binds to GC binds to G A and G= purine A and G= purine
basesbases T and C= pyrimidine T and C= pyrimidine
basesbases
http://instruct.westvalley.edu/svensson/CellsandGenes/dna-structure%5b1%5d.gif
Sugar backboneSugar backbone
Notice how the two sugar chains run opposite each other:
The 5’ end (which hasa phosphate group), faces the 3’ end (which has a hydroxyl (OH) group)and vice versa.
Who discovered the Who discovered the structure of DNA?structure of DNA? James Watson, a young American scientist and Francis James Watson, a young American scientist and Francis
Crick, a young English researcher. Crick, a young English researcher. In 1953, Watson and Crick published a paper in which In 1953, Watson and Crick published a paper in which
they proposed and described the structure of DNA.they proposed and described the structure of DNA. Rosalind Franklin (an English researcher) was within a Rosalind Franklin (an English researcher) was within a
couple days of coming to the same conclusion when couple days of coming to the same conclusion when their paper was published. their paper was published.
Watson and Crick received the Nobel prize in 1962. Watson and Crick received the Nobel prize in 1962. Rosalind Franklin died in 1958 of ovarian cancer, Rosalind Franklin died in 1958 of ovarian cancer,
probably due in large part to her work with x-rays. probably due in large part to her work with x-rays. Since the Nobel prize is not awarded posthumously, Since the Nobel prize is not awarded posthumously,
people have often wondered if the Nobel committee people have often wondered if the Nobel committee would have included Franklin if she had still been would have included Franklin if she had still been alive. alive.
http://biology.clc.uc.edu/courses/bio104/dna.htm
What is DNA What is DNA replication?replication?
DNA replication is a DNA replication is a fundamental fundamental process occurring in process occurring in all living organisms all living organisms to copy their DNA. to copy their DNA.
The point of DNA The point of DNA replication is to replication is to ensure that each of ensure that each of our cells contain the our cells contain the same copy of DNA same copy of DNA when the cells when the cells divide. divide.
http://www.le.ac.uk/ge/genie/vgec/images/mitosis_meiosis.png
Replication-StepsReplication-Steps
1)1) The DNA unzips (helix opens up)The DNA unzips (helix opens up)2)2) DNA polymerase (enzyme) DNA polymerase (enzyme)
starts bringing new nucleotides starts bringing new nucleotides and building two DNA moleculesand building two DNA molecules
3)3) At the end of the replication At the end of the replication procedure, there will be 2 DNA procedure, there will be 2 DNA molecules each with a parent molecules each with a parent chain and a daughter (new) chain and a daughter (new) chainchain
http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-2/ch10_DNA-rep.jpg
DNA replication is DNA replication is very importantvery important
Replication Replication ensures that ensures that when our cells when our cells divide, so does divide, so does our genetic our genetic information information (DNA)(DNA)
RNA RNA (ribonucleic acid)(ribonucleic acid)
The structure is like the DNA except The structure is like the DNA except that it is single stranded (1 strand as that it is single stranded (1 strand as opposed to 2 strands/chains)opposed to 2 strands/chains)
It contains 1 polynucleotide chain and It contains 1 polynucleotide chain and the nucleotides are:the nucleotides are:– Adenine (A)Adenine (A)– Uracil (U) –no Thymine in RNAUracil (U) –no Thymine in RNA– GuanineGuanine– CytosineCytosine
Types of RNATypes of RNA
Messenger RNA (mRNA)Messenger RNA (mRNA) Transfer RNA (tRNA)Transfer RNA (tRNA) Ribosomal RNA (rRNA)Ribosomal RNA (rRNA)
• Life depends upon the ability to Life depends upon the ability to change genetic information into change genetic information into functional proteins. functional proteins.
• This is referred to as the This is referred to as the central central dogma of biochemistrydogma of biochemistry and and consists of two processes: consists of two processes: • transcriptiontranscription• translationtranslation
The Central Dogma of The Central Dogma of BiochemistryBiochemistry
DNA RNA Proteintranscription translation
in the nucleus in the cytosol
The Central Dogma of The Central Dogma of BiochemistryBiochemistry
DNA RNA Proteintranscription translation
in the nucleus in the cytosol
The Central Dogma of The Central Dogma of BiochemistryBiochemistry
TranscriptionTranscription
Occurs in the nucleus (in eukaryotes)Occurs in the nucleus (in eukaryotes) It is the process whereby a copy of DNA It is the process whereby a copy of DNA
(called mRNA) is made, via action of (called mRNA) is made, via action of RNA RNA polymerasepolymerase
RNA polymerase reads DNA from 5’ to 3’ endRNA polymerase reads DNA from 5’ to 3’ end The residues are pairedThe residues are paired
DNADNA RNARNAAA U U (remember no T in RNA)(remember no T in RNA)
TT AAGG CCCC GG
TranscriptionTranscription
Occurs in the nucleus (in eukaryotes)Occurs in the nucleus (in eukaryotes) It is the process whereby a copy of DNA It is the process whereby a copy of DNA
(called mRNA) is made, via action of (called mRNA) is made, via action of RNA RNA polymerasepolymerase
RNA polymerase reads DNA from 5’ to 3’ endRNA polymerase reads DNA from 5’ to 3’ end The residues are pairedThe residues are paired
DNADNA RNARNAAA U U (remember no T in RNA)(remember no T in RNA)
TT AAGG CCCC GG
Transcription (contd)Transcription (contd)
When RNA polymerase binds to When RNA polymerase binds to DNA to transcribe the DNA into DNA to transcribe the DNA into mRNA, it binds to a part of DNA mRNA, it binds to a part of DNA called the promoter region.called the promoter region.
Promoter region(where RNA polymerase binds)
Area that will be ‘read’ by RNApolymerase to create mRNA
Response element
DNA
5’ 3’
Promoter region
RNA polymerase
5’ 3’
DNA
5’ 3’
DNAmRNA
RNA polymerase
Notice how RNA polymerase reads DNA from the5’ end to the 3’ end strand.
5’ 3’
DNAmRNA
RNA polymerase
5’ 3’
mRNA
RNA polymerase
RNA polymerase dislodges from the DNA whenit reads an unusual sequence of DNA
DNA RNA Proteintranscription translation
in the nucleus in the cytosol
The Central Dogma of The Central Dogma of BiochemistryBiochemistry
TranslationTranslation
Once mRNA was synthesized (via Once mRNA was synthesized (via transcription), it leaves the nucleus of transcription), it leaves the nucleus of the cell and goes to the cytoplasm the cell and goes to the cytoplasm (aka cytosol)(aka cytosol)
In the cytoplasm, there is an In the cytoplasm, there is an organelle called the endoplasmic organelle called the endoplasmic reticulum (ER) which contains reticulum (ER) which contains ribosomesribosomes
Ribosomes facilitate protein synthesisRibosomes facilitate protein synthesis
Translation (contd)Translation (contd)
During translation, mRNA binds to rRNA During translation, mRNA binds to rRNA (ribosomal RNA).(ribosomal RNA).
tRNA (transfer RNA) holds one amino tRNA (transfer RNA) holds one amino acid in the form of amino acyl-tRNA acid in the form of amino acyl-tRNA complexcomplex
The mRNA guides the order (sequence) The mRNA guides the order (sequence) of amino acids forming the protein of amino acids forming the protein
rRNA serves as an anvil, aligning both rRNA serves as an anvil, aligning both mRNA and tRNA so that a peptide or mRNA and tRNA so that a peptide or protein is formedprotein is formed
AUG
mRNA
CCA ACG AUA UCCAGGGAG UAG
Step 1 of TranslationStep 1 of Translation
mRNA, produced in the nucleus throughthe process of transcription, is now in thecytoplasm of the cell.
rRNA(ribosomal RNA)
AUG
mRNA
CCA ACG AUA UCCAGGGAG UAG
Step 2 of TranslationStep 2 of Translation
rRNA binds to the mRNA strand. It servesto hold the mRNA in place.
rRNA(ribosomal RNA)
AUG
mRNA
CCA ACG AUA UCCAGGGAG UAG
Step 3 of TranslationStep 3 of Translationmet
UAC
tRNA
A tRNA (transfer RNA) that matches the sequence in mRNA (AUG) arrives, carrying anamino acid. AUG codes (codon) for methionine (met)
rRNA(ribosomal RNA)
AUG
mRNA
CCA ACG AUA UCCAGGGAG UAG
Step 4 of TranslationStep 4 of Translation
met
The first tRNA leaves the scene.Another tRNA that matches the sequence CCA in mRNA arrives, carrying the amino acid proline (pro).
pro
GGU
rRNA(ribosomal RNA)
AUG
mRNA
CCA ACG AUA UCCAGGGAG UAG
Step 5 of TranslationStep 5 of Translation
met
The second tRNA leaves the scene.Met and pro form a bond (peptide bond)Another tRNA that matches the sequence ACG arrives, carrying the aminoacid threonine (thr).
pro
thr
UGC
rRNA(ribosomal RNA)
AUG
mRNA
CCA ACG AUA UCCAGGGAG UAG
Step 6 of TranslationStep 6 of Translation
met
The last tRNA leaves the scene.Pro and thr form a bond (peptide bond)Another tRNA that matches the sequence AUA arrives, carrying the aminoacid tyrosine (tyr).
pro thr
tyr
UAU
rRNA(ribosomal RNA)
AUG
mRNA
CCA ACG AUA UCCAGGGAG UAG
Final Step of Final Step of TranslationTranslation
met
UAG is a stop codon, which tells the tRNA thatno more amino acids should be incorporated.When a stop codon is reached, rRNA dissociates from mRNA and a protein is formed.
pro thr tyr ser arg glu
Stop codon
The protein that is The protein that is synthesized via synthesized via translationtranslation Can become enzymes (compounds Can become enzymes (compounds
that speed up a reaction):that speed up a reaction):– Enzymes involved in digestionEnzymes involved in digestion– Enzymes involved in metabolismEnzymes involved in metabolism
Can become muscle proteinsCan become muscle proteins Can become transport proteins that Can become transport proteins that
allow entry of certain molecules inside allow entry of certain molecules inside the cellthe cell
Can become hormones (insulin, Can become hormones (insulin, cortisol, adrenaline, etc)cortisol, adrenaline, etc)
Etc…Etc…
Amino acids and Amino acids and proteinprotein Amino acids (there are 20 of them Amino acids (there are 20 of them
in nature) are the building units of in nature) are the building units of protein.protein.
Amino acids include: Amino acids include: Alanine, Alanine, Arginine, Asparagine, Aspartic acid, Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Cysteine, Glutamic acid, Glutamine, Glycine, Histidine, Isoleucine, Leucine, Glycine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Lysine, Methionine, Phenylalanine, Proline, Serine, Threonine, Tryptophan, Proline, Serine, Threonine, Tryptophan, Tyrosine, ValineTyrosine, Valine
More about More about translation…translation… Three nucleotides (in a specific Three nucleotides (in a specific
order) code for a specific amino order) code for a specific amino acidacid
The nucleotide sequence in the The nucleotide sequence in the mRNA is called mRNA is called codoncodon
The corresponding nucleotide The corresponding nucleotide sequence in the tRNA is called the sequence in the tRNA is called the anticodonanticodon
rRNA(ribosomal RNA)
AUG
mRNA
CCA ACG AUA UCCAGGGAG UAG
TranslationTranslation
met pro thr
tyr
UAU
codon
anticodon
rRNA
tRNA
amino acid
mRNA
protein
http://www.biologycorner.com/resources/translation_lettered.jpg
anticodon
codon
Amino Acid DNA Base Triplets mRNA Codons tRNA Anticodons
alanine CGA, CGG, CGT, CGC GCU, GCC, GCA, GCG CGA, CGG, CGU, CGC
arginine GCA, GCG, GCT, GCCTCT, TCC
CGU, CGC, CGA, CGGAGA, AGG
GCA, GCG, GCU, GCCUCU, UCC
asparagine TTA, TTG AAU, AAC UUA, UUG
aspartate CTA, CTG GAU, GAC CUA, CUG
cysteine ACA, ACG UGA, UGC ACA, ACG
glutamate CTT, CTC GAA, GAG CUU, CUC
glutamine GTT, GTC CAA, CAG GUU, GUC
isoleucine TAA, TAG, TAT AUU, AUC, AUA UAA, UAG, UAU
leucine AAT, AAC, GAA, GAGGAT, GAC
UUA, UUG, CUU, CUCCUA, CUG
AAU, AAC, GAA, GAGGAU, GAC
lysine TTT, TTC AAA, AAG UUU, UUC
methionine TAC AUG UAC
phenylalanine AAA, AAG UUU, UUC AAA, AAG
proline GGA, GGG, GGT, GGC CCU, CCC, CCA, CCG GGA, GGG, GGU, GGC
serine AGA, AGG, AGT, AGCTCA, TCG
UCU, UCC, UCA, UCGAGU, AGC
AGA, AGG, AGU, AGCUCA, UCG
stop ATG, ATT, ACT UAA, UAG, UGA AUG, AUU, ACU
http://waynesword.palomar.edu/codons.htm
The start and end The start and end codoncodon The start codon is the one that makes The start codon is the one that makes
the tRNA insert its first amino acidthe tRNA insert its first amino acid The start codon is usually AUG and The start codon is usually AUG and
codes for methioninecodes for methionine So almost all proteins begin with So almost all proteins begin with
methionine as its first amino acidmethionine as its first amino acid The stop codon is the one that makes The stop codon is the one that makes
the tRNA stop inserting amino acidsthe tRNA stop inserting amino acids UAA, UAG, UGA are all stop codonsUAA, UAG, UGA are all stop codons
The nucleus: contains23 pairs of chromosomes.DNA is arranged in thesechromosomes.Where DNA replication and transcription occurs.
DNA replication: DNA copiesitself, every time the cell divides.Transcription: A copy ofDNA is made. This copy is called mRNA.
The ribosome: where protein is synthesized (ie translation occurs).In translation, mRNA isconverted into protein.
Cytosol or cytoplasm
DNA RNA Proteintranscription translation
in the nucleus in the cytosol
replication
Replication of DNAReplication of DNA is important, since it ensures that every cell will have a is important, since it ensures that every cell will have a Copy of DNA each time the cell undergoes division.Copy of DNA each time the cell undergoes division.
Central Dogma of BiochemistryCentral Dogma of Biochemistry::Life depends upon the ability to change genetic information into functional Life depends upon the ability to change genetic information into functional proteins, via the processes known as transcription and translation.proteins, via the processes known as transcription and translation.