how genes impact plant propagation.ppt...
TRANSCRIPT
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How Genes Impact Plant Propagation
David G. ClarkUF Environmental Horticulture
Genes
• Provide the physical mechanism for reproduction of traits
• Provide information for controlling expression of traits
Pre-Mendel
• Accounting for species diversity
• Carolus Linnaeus –(17th C.) systematic hierarchy for classifying living things (taxonomy)
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Pre-Mendel
• Species Diversity• Charles Darwin –
Origin of Species(1859)
• Theory of evolution, survival of the fittest, adaptive change
• Visual inspection and Mass Selection
Then came Mendel…
Mendelian Geneticsmarked the start of an era in which selection became based on hereditary principles
Predictability
Mendelian Genetics
• How are traits passed from one generation to the next?
• Mendel (1866) -Experiments in Plant Hybridization - was the first to relate the outward appearance of an organism (phenotype) to its inner genetic constitution (genotype)
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Mendelian Genetics
Mendel’s Garden - 2001
Brno, Czech Republic
Mendelian Genetics & Beyond
• Where are genes located?
• Thomas Hunt Morgan (1910) – Drosophila(fruit flies), linkage and chromosomes
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Mendelian Genetics & Beyond
• What is the job of the gene?
• George Beadle (1940)One gene one enzyme hypothesis
• Neurosporamutations
Mendelian Genetics & Beyond
• What molecule is the genetic material?
• Oswald Avery (1941) –work on bacteria proved that genes were made of DNA
Mendelian Genetics & Beyond
• What molecule is the genetic material?
• Alfred Hershey (1952) – The Blender Experiment proved that DNA is the molecule of heredity
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DNA-based Genetics
• What is the structure of a DNA molecule?
• Watson and Crick
• DNA structure = function
DNA-based Genetics
• Lots of people helped Watson and Crick
Pauling
Chargaff
Wilkins & Franklin
DNA-based Genetics
• April 2, 1953 -Watson and Crick –Published a paper in Nature solving the structure of DNA
• This structure was the key to unlocking the technology of life
• It is perhaps the most important biological discovery of the 20th
century – this was the start of the biotechnology era
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Watson and Crick’s Double Helix
Implications of Watson & Crick
• DNA embodied the organizing thesis of molecular biology
• Understanding the structure of a molecule gives clues to its biological function
After Watson & Crick
• Francis Crick (1957) – laid the intellectual framework to guide the cracking of the genetic code
• Sequence hypothesis– DNA sequence and protein sequence are co-linear
• Central Dogma – Information stored in DNA flows through RNA to proteins
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After Watson & Crick
After Watson & Crick
After Watson & Crick
• Cracking the Genetic Code
Holley Khorana Nirenberg
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The Genetic Code
What is a gene?
What is a gene?
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Regulation of Genes
• Cell differentiation is a function of regulated gene expression
• Plant cells are totipotent–every cell has the genetic potential
to regenerate into a fully differentiated plant
How do different cell types occur?
• Not all genes are active in all cells at all times
• Gene expression – regulated by development and environment– Controlled at many levels
Regulation of genes
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Regulation of genes
After Watson & Crick
Coordinating Gene Expression
• Gene Promoters – regulatory elements that function in recruiting proteins that facilitate transcription
• Cis-acting DNA elements–Act on the same DNA strand as the
gene being regulated
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Coordinating Gene Expression
• Transcription factors – DNA binding proteins that interact with promoters and RNA polymerase
• Trans-acting factors–Bind DNA and other proteins
Coordinating Transcription
DNA Transcription
• Occurs mainly in the nucleus• Synthesis of RNA on the DNA
template– A primary control step in regulation of
gene expression• All RNAs are transcribed by RNA
polymerase– Copies DNA sequence into RNA
sequence
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DNA Transcription• Occurs mainly in the nucleus
DNA & RNA
RNA Polymerase
• Copies DNA sequence into RNA sequence
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RNA
• Primary product of gene expression – single stranded
• Decodes DNA info into proteins• 3 types of RNA:
– rRNA - platform– tRNA - adapter– mRNA - messenger
Ribosomal RNA (rRNA)
• The bulk of cellular RNA
• Ribosome - A platform for reading mRNAs
Transfer RNA (tRNA)• Adapters – bind mRNA & amino acids
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Messenger RNA (mRNA)
• Encode amino acid sequences of proteins
Protein synthesis - Translation• Occurs mainly in the cytoplasm
Protein synthesis - Translation
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Why is this important?
• Enzymes are proteins• Enzymes catalyze biochemical
reactions• Biochemical reactions determine
how plants respond to external and internal stimuli
Biotechnology
• How we actually use all of this knowledge to make a difference
• Cell and Tissue Culture• DNA Marker technology• Recombinant DNA technology
Cell and Tissue Culture
• Micropropagation - aseptic
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DNA Marker Technology
• DNA Fingerprinting
Recombinant DNA Technology• Cloning
Recombinant DNA Technology• Transgenic Plants
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Genomics – The Future
Functional Genomics
We can now look at expression of thousands of genes at a time
Bright Futures
• We are just now seeing the tip of the iceberg in plant biotechnology
• The next decade will prove to be a time of biotechnology applications to new crops
• We need to know how to efficiently propagate new biotech plants:sexually and asexually
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Propagators will make a difference!