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DNA and Genetics in Agricultural Biotechnology Objective 13.01: Discuss the structure and function of DNA in relation to sexual reproduction in organisms. Structure of DNAThe genetic material of ALL LIFE on this planet is made up of only six componentsSugar molecule (deoxyribose)Phosphate groupFour nitrogen containing basesAdenineGuanineCytosineThymine Nucleotide1. Definition- a single molecule of DNA comprised of 2 basic parts made from 3 distinct molecules.The building block of the DNA molecule, also called a deoxynucleotide

PhosphateDeoxyribose SugarNitrogen BaseNucleotidea. Sugar / Phosphate Backbonei) Composed of deoxyribose sugar and a simple phosphate molecule.ii) Forms a strong bond that creates the backbone of a DNA strand.iii) EXACLTY THE SAME IN ALL DNA.Nucleotideb. Nitrogenous Basei) Bond with complimentary bases in other nucleotides to form the rungs of the DNA ladder. (zip DNA together)ii) ONLY 4 TYPES IN ALL DNA- Adenine, Cytosine, Guanine, & Thymine.iii) Adenine & Thymine bond only with each other.iv) Cytosine & Guanine bond only with each other.ThymineAdenineGuanineCytosineHydrogen BondsHydrogen BondsDNA Form1. DNA nucleotides combine in cells to form long strands in the shape of a double helix. (looks like a twisted ladder)a. Nucleotides bond at two spots:i) Sugar / Phosphate molecules form the backbone. (outside rails)ii) Nitrogenous bases bond in the middle. (steps or rungs)iii) Hydrogen bonds between nitrogenous bases are MOST EASILY broken.b. The order of the nucleotides is the determining factor in the expression of genes in organisms.Single NucleotideSugar Phosphate BackboneSugar Phosphate BackboneNitrogenous Base Pairs6DNA FormTwo sugar phosphate backbones lie side by sideOne arranged 5-3The opposite must be arranged 3-5Therefore the bases are perfectly reflected of each other

Characteristics of DNAWhen the structure was first proposed by Watson and Crick (1953)Thought to be single helix and unfixedWe later learned it is double, bends and can unwind-unzipThe standard for is called a B-formIt has 10.5 bp (base pairs)

Characteristics of DNA1. Accounts for all genetic variation between different individuals and organisms by the use of different:a. Sequences of nitrogenous bases.b. Lengths of DNA segments.c. Numbers of chromosomes

Characteristics of DNA2. The amount of DNA in an organism DOES NOT relate to the size or complexity of the organism.3. DNA replication is the process through which cells copy DNA for transmission to daughter cells during cell division.a. The double helix structure allows DNA to easily unzip down the center between nitrogenous bases.b. Free floating nucleotides attach to each of the separated DNA strands forming 2 new strands of DNA, each an exact copy of the original.Characteristics of DNA4. A mutation is an unexpected change in a DNA sequence, usually occurring during the replication / cell division.a. Mutations are common in most organisms (especially simple organisms) though only a small percentage produce noticeable changes in organisms.5. DNA is passed to offspring during sexual reproduction through single chromosomes.DNA and Genetics in Agricultural Biotechnology Objective 13.02: Explain the relationship between DNA, gene sequences, traits, and the genome. Relationship between Genetic Terms1. Genetic hierarchya. A group of nucleotides = a gene / allele = 45-150 base pairs.b. A group of genes = 1 strand of DNA.c. Several condensed strands of DNA = 1 chromosome.d. 2 chromosomes = 1 chromatid pair.e. All possible gene forms in a population = Genome.Relationship between Genetic Terms2. Mapping the genome of a species allows scientists to identify beneficial and harmful genes in a population, and is the first step in determining the location of specific genes on chromosomes.a. Changes in the genome of a species occur slowly in response to environmental changes.Relationship between Genetic Terms3. Polygenic traits are controlled by more genes and therefore it is more difficult to improve polygenic traits.Human Genetics1. Almost all humans have 46 chromosomes.a. Individuals with Down Syndrome have one extra chromosome.2. Humans generally differ from each other by approximately 3 million nitrogenous base pairs, or 0.1% of the total gene sequence.DNA and Genetics in Agricultural Biotechnology Objective 13.03: Summarize the role of DNA in genetic disorders and mutations. Basics of Genetic Disorders1. Definition- diseases or other problems resulting from errors in the transmission of genetic information, or the expression of certain negative gene sequences.2. Most genetic disorders are recessive, and thus cannot be predicted without genetic analysis.a. Recessive disorders are transmitted by carriers- parents with one dominant gene (normal) and one recessive gene (disorder). Ex- Tt3. Certain disorders are more common in certain populations. (The occurrence of sickle cell in African Americans.)Mutations 1. Definition- sudden unexpected changes in the genetic code of organism. Appear most often during the process of replication.2. Often result from increased levels of stress on cells just prior to or during cell division.a. Stresses include - radiation, uv rays, environmental, etc.Mutations 3. Almost all mutated cells die immediately, or never impact living organisms.a. Most mutations in organisms are harmful- ex: cancer.b. A small fraction of noticeable mutations are beneficial, such as Chimeras which are used to give us variegated plantsMutations 4. Most mutations occur in developed plants and animals, affecting isolated groups of cells. Mutations are most devastating when they occur in the early development of organisms. (STEM CELL STAGE)Types of mutationsa. Point mutation- a mutation that changes DNA at a single point, substituting one nucleotide pair.b. Frameshift- nucleotides are inserted or deleted, altering the entire DNA sequence after the mutation.Common Genetic Disorders1. Inherited Disordersa. Ex: Tay- Sachs, Sickle Cell Anemia, Hemophilia, etc.2. Mutationsa. CANCER uncontrolled division of abnormal cells.b. Treatment must destroy mutated cells.DNA and Genetics in Agricultural Biotechnology Objective 13.04: Outline the processes of mitosis and meiosis in plant and animal cells.Mitosis1. Definition the process of cell division in all diploid cells.a. Is constantly occurring in cells throughout plants and animals at all times (muscle cells, skin cells, stem cells, cambium cells).Stages of Mitosisa. Interphase - the period of cell growth and function prior to the beginning of true mitosis, in which the cells store energy for cellular division.i) The cell replicates DNA and produces chromatid pairs.ii) This is the longest period in the LIFE of a cell.Stages of Mitosisb. Prophase.- the first true stage of mitosis.i) Nuclear membrane dissolves, centromeres form, and centrioles move towards opposite ends of the cell.Stages of Mitosisc. Metaphase.- the second and shortest stage of mitosis.i) Chromatids align in the center of the cell and spindle fibers attach to centromeres from centrioles.Stages of Mitosisd. Anaphase.- the third stage of mitosis.i) Chromatids are separated and pulled towards opposite ends of the cell by spindle fibersii) Errors in the transmission of genetic information are MOST LIKELY to occur at this stage.Stages of Mitosise. Telephase.- the final and longest stage of mitosis.i) Chromosomes reach opposite ends of the cell, and new nuclear membranes form for each new daughter cell.Stages of Mitosisf. Cytokinesis.- the actual division of daughter cells at the end of mitosis.i) A cleavage furrow forms pinching apart cells in animals.ii) In plant cells, a cell plate forms between daughter cells, dividing cells and forming the new section of the cell wall.Meiosis1. Definition- the specialized form of cell division that occurs ONLY IN HAPLOID CELLS. (sperm, pollen, eggs, ovums)a. Very similar in process to mitosis, except with two cycles, producing 4 haploid daughter cells (23 chromosomes each)b. Production of male sex cells = spermatogenesis producing 4 spermc. Production of female sex cells = oogenesis usually produces 1 viable egg - other 3 abort.Stages of Meiosisa. Interphase - same as mitosis- period of growth and functionStages of Meiosisb. Meiosis I : prophase I, metaphase I, anaphase I, telephase Icytokinesisi) Reduction process- changes cell from diploid to haploid.Stages of Meiosisc. Meiosis II: prophase II, metaphase II, anaphase II, telephase II, cytokinesis/Prophase II is responsible for aligning chromosomes for the final division.i) Division process- creates 2 distinct haploid cells.Stages of Meiosis3. The stages of Meiosis I & Meiosis II are identical to the stages of Mitosis, but with different cells for a different purpose.