GENETICSGENETICSRegents ReviewRegents Review
Wednesday, May 25Wednesday, May 25thth and Thursday, May and Thursday, May 26th26th
Ms. MendelsonMs. Mendelson
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Mr. MullerMr. Muller
DNA StructureDNA Structure
Double helix Double helix Watson and CrickWatson and Crick
Subunits (building blocks) : nucleotidesSubunits (building blocks) : nucleotides
Nucleotides are composed of a sugar, Nucleotides are composed of a sugar, phosphate and a nitrogenous base phosphate and a nitrogenous base Sugar and phosphate backboneSugar and phosphate backbone Bases: rungs of a ladderBases: rungs of a ladder
Organization of Genetic Organization of Genetic Information Within a Cell Information Within a Cell
NucleusNucleus
Chromosomes are structures which Chromosomes are structures which contain DNA.contain DNA.
DNA is composed DNA is composed
of genes.of genes.
KaryotypingKaryotyping
46 chromosomes in 46 chromosomes in
human body cellshuman body cells
(23 pairs)(23 pairs)
23 chromosomes in23 chromosomes in
human gametes human gametes
(sex cells)(sex cells)
Base PairingBase Pairing
Adenine (A) pairs with Thymine (T) Adenine (A) pairs with Thymine (T)
Cytosine (C) pairs with Guanine (G)Cytosine (C) pairs with Guanine (G)
( Complementary base pairs).( Complementary base pairs).
Held together by relatively weak hydrogen Held together by relatively weak hydrogen bondsbonds
DNA ReplicationDNA Replication
DNA molecule untwists and unzipsDNA molecule untwists and unzips
Enzymes match up free floating Enzymes match up free floating nucleotides to one of the original nucleotides to one of the original
DNA strandsDNA strands
One DNA strand acts as a template One DNA strand acts as a template (pattern or guide) for a new strand.(pattern or guide) for a new strand.
In order to ensure genetic continuity, DNA In order to ensure genetic continuity, DNA replication must occur before cell division.replication must occur before cell division.
TranscriptionTranscription
DNA is used as a template to make mRNADNA is used as a template to make mRNAOccurs in the nucleusOccurs in the nucleus4 bases of RNA: Adenine (A), Uracil (U), Guanine 4 bases of RNA: Adenine (A), Uracil (U), Guanine (G) and Cytosine (C)(G) and Cytosine (C) DNA RNADNA RNA
A UA U T AT A C GC G G CG C
mRNA leaves the nucleus and travels to the mRNA leaves the nucleus and travels to the ribosome of the cell.ribosome of the cell.
TranslationTranslation(Protein Synthesis)(Protein Synthesis)
At the ribosome, mRNA is used to At the ribosome, mRNA is used to synthesize a protein (polypeptide).synthesize a protein (polypeptide).Proteins are made up of a chain of amino Proteins are made up of a chain of amino acids.acids.Transfer RNA molecules (tRNA) bring the Transfer RNA molecules (tRNA) bring the amino acids to the ribosome.amino acids to the ribosome.The anticodon of the tRNA pairs up with The anticodon of the tRNA pairs up with the codon (3 bases) of mRNA.the codon (3 bases) of mRNA.
Let’s PracticeLet’s Practice
DNA- A-T-G-T-A-A-G-C-T-A-T-A-G-C-CDNA- A-T-G-T-A-A-G-C-T-A-T-A-G-C-C
mRNA- U-A-C-A-U-U-C-G-A-U-A-U-C-G-GmRNA- U-A-C-A-U-U-C-G-A-U-A-U-C-G-G
tRNA- A-U-G-U-A-A-G-C-U-A-U-A-G-C-CtRNA- A-U-G-U-A-A-G-C-U-A-U-A-G-C-C
Amino acidsAmino acids Tyr- Ile- Arg- Tyr- ArgTyr- Ile- Arg- Tyr- Arg
Gene ExpressionGene Expression
Each cell uses only some of the genetic Each cell uses only some of the genetic information it contains.information it contains.
Proteins are synthesized only from genes Proteins are synthesized only from genes that are expressed or “turned on;” all other that are expressed or “turned on;” all other genes are not expressed or “turned off.”genes are not expressed or “turned off.”
Ex: genes that code for liver enzymes are Ex: genes that code for liver enzymes are not expressed in nerve cellsnot expressed in nerve cells
Gene ExpressionGene ExpressionInfluenced by the environmentInfluenced by the environment
Example: Himalayan RabbitExample: Himalayan Rabbit
- cold temperature turns on gene for black - cold temperature turns on gene for black pigmentpigment
Example: identical twins raised separatelyExample: identical twins raised separately
- twin living in city may develop cancer - twin living in city may develop cancer
while twin living in the country may notwhile twin living in the country may not
MutationsMutations
A change/error in the linear sequence of a A change/error in the linear sequence of a DNA moleculeDNA molecule
A random alteration of DNAA random alteration of DNA
Source of variationSource of variation
Mutagens (agents that can cause damage Mutagens (agents that can cause damage to DNA): UV light, X-rays, pollutants, to DNA): UV light, X-rays, pollutants, tobacco smoke, asbestostobacco smoke, asbestos
MutationsMutations
If mutation occurs in the sex If mutation occurs in the sex
cells, it may be passed on to offspring.cells, it may be passed on to offspring.
If mutation occurs in the body cells, it may If mutation occurs in the body cells, it may only be passed on to other body cells; only only be passed on to other body cells; only affects the individual.affects the individual.
Types of Mutations: substitution, deletion, Types of Mutations: substitution, deletion, addition, inversion.addition, inversion.
Types of MutationsTypes of Mutations
(Different colors represent different genes)(Different colors represent different genes)
How do DNA mutations affect How do DNA mutations affect proteins?proteins?
Change in the nucleotide sequence of Change in the nucleotide sequence of DNA may lead to a change in the amino DNA may lead to a change in the amino acid sequence of a proteinacid sequence of a protein
The shape of the protein may be affected The shape of the protein may be affected (incorrect folding)and the protein doesn’t (incorrect folding)and the protein doesn’t do its job (malfunctions).do its job (malfunctions).
Example: Sickle Cell AnemiaExample: Sickle Cell Anemia
Genetic EngineeringGenetic Engineering
Transferring DNA from one organism to Transferring DNA from one organism to anotheranotherEx: transferring the human insulin gene Ex: transferring the human insulin gene into a plasmid (circular ring of bacterial into a plasmid (circular ring of bacterial DNA) and then inserting this plasmid into DNA) and then inserting this plasmid into a host cell (bacterial cell) a host cell (bacterial cell) As bacterial cell divides, so does human As bacterial cell divides, so does human insulin gene. Human insulin can be used insulin gene. Human insulin can be used to treat people with diabetes. to treat people with diabetes. Reduction in cost and side effects.Reduction in cost and side effects.
Using Bacteria PlasmidsUsing Bacteria Plasmids(Think of insulin production!)(Think of insulin production!)