Mutations & Genetic Recombination

Mutation Permanent change in the genetic material of an organism All mutations in gametes are inheritable because they are copied during DNA replication

Somatic cell mutations occur in body cells Germ cell mutations occur in reproductive cells These are passed on from one generation to the next

Types of mutations Point mutations Chemical change that affects just one or a few nucleotides May involve substitution of one nucleotide for another Or the insertion or deletion of one or more nucleotides

Point mutations Minor effect on cell Change in coding sequence does not always result in a different polypeptide Ex. GGA  GGG both code for the amino acid, glycine

This is called a silent mutation Example: UAU and UAC Even if the aa is substituted for another, it may not have a significant function in the final structure This is called a silent mutation Example: UAU and UAC Mis-sense mutation Results in an altered protein Ex sickle cell disease is a point mutation that is very harmful

Nonsense mutation Deletes a start signal or results in a premature stop signal A nucleotide substitution that affects the regulatory sequence may result in a cell being unable to produce a functional protein

Frameshift When an insertion or a deletion the codon reading frame is shifted and each codon is read incorrectly. AAU GGU GCC AAU GGUG GCC

Chromosomal Mutations Crossing over Loss or duplication of portions of DNA during DNA replication Change to structural or regulatory DNA sequences

Causes of mutations Spontaneous mutations Induced Caused by naturally occurring molecular interactions Ex. Incorrect base pairing Induced Caused by agents outside the cell Mutagens increase the rate of mutation

Physical Mutagens Cause physical changes to the structure of DNA Ex. X-rays and gamma rays are the most damaging form of mutagen known Also UV rays cause chemical reactions to form between adjacent A and T bases, interfering with replication A single sunburn doubles the chance of getting skin cancer (melanoma)

Chemical Mutagens A molecule that can enter the nucleus of the cell and induce mutations by reacting chemically with DNA Can insert themselves and cause substitution or a frameshift mutation Ex. Nitrates (a food preservative), gasoline fumes, 50 different compounds of cigarette smoke.

Carcinogenic Chemical mutagens associated with one or more forms of cancer Cancer is uncontrolled cell division The result of somatic cells that disrupt the expression of genes involved in regulation of the cell cycle

Mutations and Genetic Variation Single mutation has little or no effect on an organism However, a series of mutations developed over time can be more serious. Mutations accumulate within a cell Different mutations over time help shed light on genetic variation

Tracing ancestry through mitochondrial DNA Mitochondria and chloroplasts have there own DNA (which replicates, transcribes, and translates separately from nucleic DNA. Evidence suggests that these organelles were once independent prokaryotic cells Endosymbiont theory proposes that eukaryotes arose when one prokaryote was engulfed by another

Mitochodrial DNA (mtDNA) Recall, the cytoplasm of the fertilized egg (zygote) is donated by the ovum. All of your mtDNA is identical to your mothers Mutations in mtDNA provide information about the evolutionary path of animals and plant species

The process of creating recombinant DNA involves 2 types of enzymes: Restriction Enzymes – (DNA scissors) cut the DNA strand at specific sites -palindromes- and often creates sticky ends

2. The now unpaired segments can be paired with complimentary nucleotides from a different strand of DNA 3. DNA ligase – is genetic glue that puts DNA strands back together. rDNA

Application Insulin used to be harvested from pigs, but some individuals did not tolerate it. we are now able to use bacteria to produce human insulin in large quantities. is tolerated much better by patients. This procedure was first marketed in Canada in 1983!

Other Aspects of Biotechnology Gene sequencing –determining the specific location and composition of specific genes. The Human Genome Project -1990 2000: mapped our 30 000 genes (3 billion nucleotides) NOVA Online | Cracking the Code of Life | Sequence for Yourself

RFLP – restriction fragment length polymorphism –cut DNA into pieces Gel Electrophoresis – separate the DNA pieces by size.

DNA fingerprinting identify an individual based on their unique genetic code. homologous segments of DNA are similar but contain unique patterns of nitrogen bases identify individuals involved in crimes, paternity

DNA Fingerprinting

Misc. Technology Polymerase chain reaction –making billions of copies of a piece of DNA- PCR Animation Paternity Testing - Paternity Testing Gene Gun - Genegun1

Recombinant DNA Genetic engineering Manipulating genetic material to alter genes and blend plant, animal, and bacteria DNA together. DNA that includes outside source is called recombinant DNA. Rapidly growing field Eg peppers

Restriction Endonucleases Restriction enzymes cut DNA at specific nucleotide sequences Restriction endonucleases cuts within the interior of a DNA molecule (rather than at ends) It recognizes a target sequence (short sequence of nucleotides) and cuts within it at the restriction site.

Specificity: cuts are specific and predictable Two characteristics Specificity: cuts are specific and predictable Meaning the same enzyme will cut the same target sequences producing the same set of DNA fragments called restriction fragments

Staggered cuts: leave a few unpaired nucleotides on a single strand at each restriction fragment called sticky ends. Sticky ends can pair with a complementary sticky end cut by he same restriction endonuclease from a different strand of DNA DNA ligase Spliced the paired sticky ends together resulting in a stable recombinant DNA molecule.

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