Contents
• 11-1 DNA: The Molecule of Heredity• 11-2 From DNA to Protein• Protein Synthesis video• 11-3 Genetic Changes
11-1 DNA: The Molecule of Heredity
• Genetic info in DNA controls organism’s traits• Determines structure of proteins built
11-1 DNA: The Molecule of Heredity
• Genetic info in DNA controls organism’s traits• Determines structure of proteins built• Hershey & Chase (1952) used radioactively tagged
viruses to infect bacteria and proved DNA is genetic material
11-1 DNA: The Molecule of Heredity
• Genetic info in DNA controls organism’s traits• Determines structure of proteins built• Hershey & Chase (1952) used radioactively tagged viruses
to infect bacteria and proved DNA is genetic material
Nucleotide Structure
• DNA polymer of repeating units called nucleotides.
• 3 parts– Simple sugar– Phosphate
• Phosphorus w/ 4 O – Nitrogenous base
Nucleotide Structure
• DNA polymer of repeating units called nucleotides.
• 3 parts– Simple sugar– Phosphate
• Phosphorus w/ 4 O – Nitrogenous base
• C ring w/ 1 or more N & a base
– Adenine (A)– Cytosine (C)– Guanine (G)– Thymine (T)
Nucleotides
• Join in long chains • with phosphates
connecting • to sugar of next unit • to form a backbone
Nucleotides
• Join in long chains • with phosphates
connecting • to sugar of next unit • to form a backbone • with the bases sticking
out like the teeth of a zipper.
• Adenine = Thymine• Guanine = Cytosine
Structure of DNA
• James Watson & Francis Crick (1953) unraveled the structure of DNA.
• Double Helix structure
Nucleotide Sequence
• Forms unique genetic information of organism
• Can be used to determine evolutionary relationships between organisms
Nucleotide Sequence
• Forms unique genetic information of organism
• Can be used to determine evolutionary relationships between organisms
• Or familial relationships• DNA can identify
victims or criminals
Replication of DNA
• Copies DNA in chromosome during interphase• Enzyme breaks the hydrogen bond between bases
Replication of DNA
• Copies DNA in chromosome during interphase• Enzyme breaks the hydrogen bond between bases• Complimentary base pairing allows duplication
Replication of DNA
• Copies DNA in chromosome during interphase• Enzyme breaks the hydrogen bond between bases• Complimentary base pairing allows duplication• Each strand is a template
11-2 From DNA to Protein
• DNA controls the production of proteins.
• Proteins are key cell structures & regulators of cell functions.
11-2 From DNA to Protein
• DNA controls the production of proteins.
• Proteins are key cell structures & regulators of cell functions.
• RNA, another nucleic acid carries out DNA’s instructions
11-2 From DNA to Protein
• DNA controls the production of proteins.
• Proteins are key cell structures & regulators of cell functions.
• RNA, another nucleic acid carries out DNA’s instructions
• Structure differs 3 ways– Single-stranded– Sugar is ribose– Uracil replaces thymine
Three Types of RNA
• Protein assembly line:• Messenger RNA (m-RNA) • Ribosomal RNA (r-RNA)• Transfer-RNA (t-RNA)
Three Types of RNA
• Protein assembly line:• Messenger RNA (m-RNA)
– Brings instructions from DNA to ribosomein the cytoplasm
• Ribosomal RNA (r-RNA)• Transfer-RNA (t-RNA)
Three Types of RNA
• Protein assembly line:• Messenger RNA (m-RNA)
– Brings instructions from DNA to ribosomein the cytoplasm
• Ribosomal RNA (r-RNA)– Reads instructions to
assemble protein by binding to m-RNA
• Transfer-RNA (t-RNA)
Three Types of RNA
• Protein assembly line:• Messenger RNA (m-RNA)
– Brings instructions from DNA to ribosomein the cytoplasm
• Ribosomal RNA (r-RNA)– Reads instructions to
assemble protein by binding to m-RNA
• Transfer-RNA (t-RNA)– Delivers amino acids for
assembly to ribosome
Transcription
• Occurs in the nucleus by enzymes copying part of the DNA– Enzyme unzips DNA– Assembles single-
strand copy
Transcription
• Occurs in the nucleus by enzymes copying part of the DNA– Enzyme unzips DNA– Assembles single-
strand copy– DNA rezips after m-
RNA detaches
Transcription
• Occurs in the nucleus by enzymes copying part of the DNA– Enzyme unzips DNA– Assembles single-
strand copy– DNA rezips after m-
RNA detaches– m-RNA leaves nucleus
by nuclear pore to enter cytoplasm
Transcription
• Occurs in the nucleus by enzymes copying part of the DNA– Enzyme unzips DNA– Assembles single-
strand copy– DNA rezips after m-
RNA detaches– m-RNA leaves nucleus
by nuclear pore to enter cytoplasm
– Carries instructions to ribosome
Translation
• Occurs in the ribosome• Process of converting
series of bases into chain of amino acids forming a protein
Translation
• Occurs in the ribosome• Process of converting
series of bases into chain of amino acids forming a protein– r-RNA reads sequence
of 3 bases (codon)
Translation
• Occurs in the ribosome• Process of converting
series of bases into chain of amino acids forming a protein– r-RNA reads sequence
of 3 bases (codon) – t-RNA anticodon
matches up with the codon from m-RNA and supplies the amino acid needed
Translation
• Occurs in the ribosome• Process of converting
series of bases into chain of amino acids forming a protein– r-RNA reads sequence
of 3 bases (codon) – t-RNA anticodon
matches up with the codon from m-RNA and supplies the amino acid needed
– Ribosome translates the next codon until finished assembling the protein
RNA & Protein Synthesis
RNA Processing
• Introns- noncoding nucleotide sequences• Exons- expressed sections of nucleotides• Enzymes cut out the introns & paste the exons
together
Genetic Code
• Amino acids are the building blocks of proteins.
• A sequence of 3 nucleotide bases code for each of the 20 amino acids.
• 64 different codons in m-RNA
• AUG start codon• UAA stop codon• All organisms use the
same genetic code.
Translating the m-RNA Code
• T-RNA leaves amino acid in position to form peptide bond with previous amino acid
Translating the m-RNA Code
• T-RNA leaves amino acid in position to form peptide bond with previous amino acid
• The ribosome continues to assemble amino acids until stop codon is reached.
Translating the m-RNA Code
• T-RNA leaves amino acid in position to form peptide bond with previous amino acid
• The ribosome continues to assemble amino acids until stop codon is reached.
• Translation is complete
Translating the m-RNA Code
• T-RNA leaves amino acid in position to form peptide bond with previous amino acid
• The ribosome continues to assemble amino acids until stop codon is reached.
• Translation is complete• Amino acid chain is
released & twists into complex folded shape of protein
Translating the m-RNA Code
• T-RNA leaves amino acid in position to form peptide bond with previous amino acid
• The ribosome continues to assemble amino acids until stop codon is reached.
• Translation is complete• Amino acid chain is
released & twists into complex folded shape of protein
• Become enzymes & structures
11-3 Genetic Changes
• Mutation- any change in DNA sequence
• Caused by errors in– Replication– Translation– Cell division– Or by external agents
such as UV or chemical exposure
Mutations in Reproductive Cells
• Changes in the sequence of nucleotides can cause:– Altered gene in offspring– New traits– Nonfunctional protein
with structural or functional problems in cells
– Embryo may not survive– Positive effect
Mutations in Body Cells
• Does not pass on to offspring
• May cause problems for the individual
• Impair function of the cell• Contributes to aging• Can cause cancer by
making cells reproduce rapidly
Effects of Point Mutations
• Point mutation - Change in a single base pair in DNA
• Can change entire structure of the protein
• Error may or may not affect protein function
• Ex. Sickle cell anemia
Frameshift Mutations
• A single base is added to or deleted from DNA
• Shifts the reading of the codons by one base
• Nearly every amino acid after the insertion or deletion will be changed
Chromosomal Alterations
• Chromosomal mutations• Deletions -Parts break &
are lost during mitosis or meiosis
• Insertions- Parts rejoin incorrectly
• Inversions- Rejoin backwards
• Translocations- Join other chromosomes
• Common in plants
Causes of Mutations
• Mutagens- agents that cause change in DNA– Radiation
• X-rays• Gamma rays• Ultraviolet light• Nuclear radiation
– Chemicals• Dioxins• Asbestos• Benzene• Formaldehyde
– High temperaturesaflatoxinaflatoxin
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