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 DNA The genetic material of ALL LIFE on this planet is made up of only six components Sugar molecule (deoxyribose) Phosphate group Four nitrogen containing bases Adenine Guanine Cytosine Thymine

Nucleotide 1. 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 Phosphate Deoxyribose Sugar Nitrogen Base

Nucleotide a. Sugar / Phosphate Backbone i) 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.

Nucleotide b. Nitrogenous Base Hydrogen Bonds b. Nitrogenous Base i) 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. Thymine Adenine Guanine Cytosine Hydrogen Bonds

DNA Form Sugar Phosphate Backbone Sugar Phosphate Backbone Nitrogenous Base Pairs 1. 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 Nucleotide

DNA Form Two sugar phosphate backbones lie side by side One arranged 5’-3’ The opposite must be arranged 3’-5’ Therefore the bases are perfectly reflected of each other

Characteristics of DNA When the structure was first proposed by Watson and Crick (1953) Thought to be single helix and unfixed We later learned it is double, bends and can unwind-unzip The standard for is called a B-form It has 10.5 bp (base pairs)

Characteristics of DNA 1. 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 DNA 2. 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 DNA 4. 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 Terms 1. Genetic hierarchy a. 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 Terms 2. 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 Terms 3. Polygenic traits are controlled by more genes and therefore it is more difficult to improve polygenic traits.

Human Genetics 1. 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 Disorders 1. 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- Tt 3. 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 plants

Mutations 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 mutations a. 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 Disorders 1. Inherited Disorders a. Ex: Tay- Sachs, Sickle Cell Anemia, Hemophilia, etc. 2. Mutations a. 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.

Mitosis 1. 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 Mitosis a. 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 Mitosis b. Prophase.- the first true stage of mitosis. i) Nuclear membrane dissolves, centromeres form, and centrioles move towards opposite ends of the cell.

Stages of Mitosis c. 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 Mitosis d. Anaphase.- the third stage of mitosis. i) Chromatids are separated and pulled towards opposite ends of the cell by spindle fibers ii) Errors in the transmission of genetic information are MOST LIKELY to occur at this stage.

Stages of Mitosis e. 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 Mitosis f. 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.

Meiosis 1. 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 sperm c. Production of female sex cells = oogenesis – usually produces 1 viable egg - other 3 abort.

Stages of Meiosis a. Interphase - same as mitosis- period of growth and function

Stages of Meiosis b. Meiosis I : prophase I, metaphase I, anaphase I, telephase Icytokinesis i) Reduction process- changes cell from diploid to haploid.

Stages of Meiosis c. 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 Meiosis 3. The stages of Meiosis I & Meiosis II are identical to the stages of Mitosis, but with different cells for a different purpose.