What is a DNA? • A nucleic acid that carries the genetic information in the cell and is capable of self-replication and synthesis of RNA. DNA consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or cytosine and guanine. The sequence of nucleotides determines individual hereditary characteristics.
What is a Nucleotide? • A single molecule of DNA comprised of 2 basic parts made from 3 distinct molecules. • Sugar/Phosphate Backbone • Nitrogenous Base
Sugar/Phosphate Backbone • Comprised of deoxyribose sugar and a simple phosphate molecule • Forms a strong bond that creates the backbone of a DNA strand • EXACTLY THE SAME IN ALL DNA
Nitrogenous Base • Bond with complimentary bases in other nucleotides to form the rungs of the DNA ladder (zip DNA together) • Only 4 types in all DNA-Adenine, Cytosine, Guanine, and Thymine • Adenine and Thymine bond only with each other • Cytosine and Guanine bond only with each other
DNA form • DNA nucleotides combine in cells to form long strands in the shape of a double helix (looks like a twisted ladder)
DNA Form • Nucleotides bond at two spots • Sugar/Phosphate molecules form the backbone (outside rails) • Nitrogenous bases bond in the middle by hydrogen bonds (steps or rungs) • Hydrogen bonds between nitrogenous bases are MOST EASILY BROKEN
DNA Form • The order of the nucleotides is the determining factor in the expression of genes in organisms.
DNA • Accounts for all genetic variation between different individuals and organisms by the use of different: • Sequences of nitrogenous bases • Lengths of DNA segments • Numbers of Chromosomes and amounts of DNA in an organism • The amount of DNA in an organism DOES NOT relate to the size or complexity of an organism.
DNA Replication • The process through which cells copy DNA for transmission to daughter cells during cell division. • The double helix structure allows DNA to easily unzip down the center between nitrogenous bases. • Free floating nucleotides attach to each of the separated DNA strands forming 2 new strands of DNA, each an exact copy of the original.
Mutations • A mutation is an unexpected change in a DNA sequence, usually occurring during the replication/cell division. • Mutations are common in most organisms (especially simple organisms) though only a small percentage produce noticeable changes in organisms.
Genetic Hierarchy • A group of nucleotides=a gene/allele=45-150 base pairs • A group of genes=1 strand of DNA • Several condensed strands of DNA=1 chromosome • 2 chromosomes=1 chromatid pair • All possible gene forms in a population=Genome
Gene Mapping • 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. • Changes in the genome of a species occur slowly in response to environmental changes.
Transferring of DNA • DNA is passed to offspring during sexual reproduction through single chromosomes.
Human Genetics • Almost all humans have 46 chromosomes. • Individuals with Down Syndrome have one extra chromosome. • Humans generally differ from each other by approximately 3 million nitrogenous base pairs, or 0.1% of the total gene sequence.
Genetic Disorders • Diseases or other problems resulting from errors in the transmission of genetic information, or the expression of certain negative gene sequences.
Genetic Disorders • Most genetic disorders are recessive, and thus cannot be predicted without genetic analysis • Recessive disorders are transmitted by carriers-parents with one dominant gene (normal) and one recessive gene (disorder) • Example-Tt
Genetic Disorders • Certain disorders are more common in certain populations • Example: The occurrence of sickle cell in African Americans.
Common Genetic Disorders • Inherited Disorders • Examples: Tay-Sachs, Sickle Cell Anemia, Hemophilia • Mutations • Cancer-uncontrolled division of abnormal cells • Treatment must destroy mutated cells
Genetic Mutations • Sudden unexpected changes in the genetic code of an organism which appear most often during the process of replication
Genetic Mutations • Often result from increased levels of stress on cells just prior to or during cell division • Stresses include-radiation, UV rays, environmental, etc.
Genetic Mutations • Almost all mutated cells die immediately, or never impact living organisms • Most mutations in humans are harmful such as cancer • A small fraction of noticeable mutations are beneficial, such as Chimeras which are used to give us variegated plants.
Genetic Mutations • Most mutations occur in developed plants and animals, affecting isolated groups of cells. • Mutations are most devastating when the occur in the early development of organisms. (STEM CELL STAGE)
Types of Mutations • Point mutation • A mutation that changes DNA at a single point, substituting one nucleotide pair. • Frameshift • Nucleotides are inserted or deleted, altering the entire DNA sequence after the mutation
What is Mitosis? • The process of cell division in all diploid cells • Constantly occurs in cells throughout plants and animals at all times • Muscle cells • Skin cells • Stem cells • Cambium cells • Results in two diploid daughter cells
Stages of Mitosis • Interphase • Prophase • Metaphase • Anaphase • Telephase • Cytokinesis
Interphase • The period of cell growth and function prior to the beginning of true mitosis, in which the cells store energy for cellular division • The cell replicates DNA and produces chromatid pairs • This is the longest period in the life of a cell
Prophase • The first true stage of mitosis • The nuclear membrane dissolves, centromeres form, and centrioles move toward opposite ends of the cell
Metaphase • The second and shortest stage of mitosis • Chromatids align in the center of the cell and spindle fibers attach to centromeres from centrioles
Anaphase • The third stage of mitosis • Chromatids are separated and pulled towards opposite ends of the cell by spindle fibers • Errors in the transmission of genetic information are most likely to occur at this stage
Telephase • The final and longest stage of mitosis • Chromosomes reach opposite ends of the cell, and new nuclear membranes form for each new daughter cell
Cytokinesis • The actual division of daughter cells at the end of mitosis • A cleavage furrow forms pinching apart cells in animals • In plant cells, a cell plate forms between daughter cells, dividing cells and forming the new section of the cell wall.
What is Meiosis? • The specialized form of cell division that occurs only in haploid cells • Sperm • Egg • Pollen • Ovum • Very similar in process to mitosis, except with two cycles, producing 4 haploid daughter cells (23 chromosomes each)
Spermatogenesis • Production of male sex cells through meiosis • Produces 4 sperm
Oogenesis • Production of female sex cells through meiosis • Usually produces 1 viable egg-other 3 abort
Stages of Meiosis • Interphase • Meiosis I • Meiosis II • The stages of Meiosis I and Meiosis II are identical to the stages of Mitosis, but with different cells for a different purpose
Interphase • Same as mitosis • Period of growth and function
Meiosis I • Prophase I • Metaphase I • Anaphase I • Telephase I • Cytokinesis • Reduction process-changes cells from diploid to haploid
Meiosis II • Prophase II • Prophase II is responsible for aligning chromosomes for the final division • Metaphase II • Anaphase II • Telephase II • Cytokinesis
DNA Extraction • The process of isolating nucleic acids (DNA) from organic material. • DNA can be extracted from almost any intact cellular tissue (more cells make it easier) • Skin, blood, saliva, semen, mucus, muscle tissue, bone marrow, etc. • DNA cannot be extracted from hair, unless skin is attached at the bottom • Mitochondrial DNA can often be extracted long after nuclear DNA has degraded.
Simple DNA Extraction • For observation only, not feasible for analyzing DNA • Works well with fruit (Example: Strawberries)
Simple DNA Extraction • Step 1 • Physically break apart plant material, usually fruits • Step 2 • Use a detergent to break apart the cell membrane • Step 3 • Treat with ethyl alcohol to isolate DNA from remaining proteins and sugars • Step 4 • Spool using a glass rod to view a large clump of nucleic acids (DNA)
Advanced DNA Extraction • The organism to be tested is chosen, and a sample is taken from which DNA can be extracted. • Detergents are used in simple DNA extraction procedures to break down cell membranes, blending the contents of the cell.
Advanced DNA Extraction • The DNA sample is treated with enzymes to isolate nucleic acids, usually both DNA and RNA • Enzymes dissolve proteins, sugars, and other materials • Examples: protease, amylase, etc (enzymes end with the suffix –ase) • A second enzyme may be applied to cut DNA into gene segments for analysis