Dna structure and function notes
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  • 1. Name:_____________________ Date:______/___/__ Living Environment Rabbi Goldberg Genetic Material I. Introduction a. The characteristics of all living things depends ________________ _____________________________________________________ i. They have been inherited ___________________________ 1. this was done through _________________ a. All the traits of come from __________________________________ ii. Or inherited by __________________________ 1. Which is done through________________ a. All the traits come from _____________________________________ _____________________________________ 2. *** We are going top learn later a. though organisms get their traits from their parent(s) their traits can be changed _____________________________________ _____________________________________ II. What are the purposes for DNA? a. Structure and Function i. DNA provides the set of coded ______________________ ________________________________________________ ii. The DNA molecule also provides for a reliable way for ________________________________________________ ________________________________________________ iii. Heredity refers to this ________________________________________________ ________________________________________________ III. What is DNA? a. DNA is a double ________________________________________ _____________________________________________________ i. This shape is called a double helix. ii. The sides of this twisted ladder are ________________________________________________ ________________________________________________ iii. The rungs of the ladder are made up of pairs of nitrogenous bases.
  • 2. iv. These bases are called 1. adenine (A), Structure of the 2. thymine (T), DNA molecule 3. guanine (G), 4. and cytosine (C). b. How are these bases paired? i. Remember the acronym 1. All Teachers Go Crazy a. Adenine _____________ b. Guanine ____________ ii. This principle is sometimes called ____________________ IV. Where do we find thee DNA Molecules? a. DNA is contained in the ____________________________ Location of DNA V. Gene-Chromosome Model a. Hereditary information ______________________, b. which are ________________________________, c. located in the ______________________________ d. Chromosomes are found in the nucleus of each cell.
  • 3. The Gene Chromosome Model e. Each gene ________________________________________. f. An inherited trait of an ___________________________________ _____________________________________________________ _____________________________________________________ g. A single gene can influence more than one trait. VI. How do genes get messed up? a. Gene Mutations i. Changes in ________________________________ 1. therefore ____________________________. ii. A mutation may change the manner in which a trait is expressed by an organism.
  • 4. I. Asexual Heredity VS. Sexual Heredity a. Introduction i. For offspring to resemble their parents, there must be a reliable way to transfer information from one generation to the next. ii. Heredity is the passage of these instructions from one generation to another. iii. The DNA molecule provides the mechanism for transferring these instructions. b. Asexual Heredity i. In asexually reproducing organisms, all the genes come from a single parent. ii. As asexually produced offspring are produced by the cell division process of mitosis, all offspring are normally genetically identical to the parent. c. Sexual Heredity i. In sexually reproducing organisms, the new individual receives half of the genetic information from its mother through the egg ii. and half from its father from his sperm. iii. Sexually produced offspring resemble, but are not identical to, either of their parents. iv. Variations of sexual heredity 1. crossing over – Where a piece of a chromosome crosses over a piece of its counter part 2. genetic recombination, which is the combining of the genetic instructions of both parents into a new combination in the offspring when fertilization occurs. 3. The processes of crossing over and genetic recombination will result in offspring showing variation from the original parents. 4. The variations shown between different sexually produced offspring provide the driving force for the process of natural selection. II. Heredity and Environment a. The characteristics of an organism can be described in terms of combinations of traits. b. Traits are inherited, but their expression can be modified by interactions with the environment. c. The many body cells in an individual can be very different from one another, even though they are all descended from a single cell and thus have identical genetic instructions.
  • 5. d. This is because different parts of these instructions are used in different types of cells, influenced by the cell’s environment and past history. e. Poor health habits can have an adverse effect on the development and expression of many genes in human cells, resulting in sickness or even death. III. Mutation a. A mutation is a change in the genetic material of an organism. b. Mutations which occur in non sex cells of sexually reproducing organisms will not be passed on to the offspring, c. although they may result in disease or death for the organism involved. d. One possible consequence of a mutation in a non sex cell is uncontrolled mitotic cell division or cancer. e. Mutations which occur in sex cells or gametes may be passed to the offspring. f. Along with crossing over and genetic recombination, mutation provides for a source of variation in sexually reproducing individuals. DNA In all organisms, the coded instructions for specifying the characteristics of the organism are carried in DNA. The genetic code is contained in the four nitrogenous bases of DNA; adenine, guanine, cytosine, and thymine. These bases are often indicated only by using their beginning letters A, G, C, and T. Each individual DNA strand serves as a template or model for the formation of other DNA molecules by replication. RNA DNA codes for the formation of RNA in the nucleus of the cell. RNA is short for another kind of nucleic acid called ribonucleic acid. RNA is very similar in structure to DNA except for three small differences. These differences include the fact that RNA is a single stranded molecule, lacks the base thymine (T) as it is replaced by the base uracil (U), and its five carbon sugar ribose has one more oxygen atom than the sugar in DNA. Three different types of RNA exist, mRNA or messenger RNA, tRNA or transfer RNA, and rRNA or ribosomal RNA. Protein Synthesis Cells store and use coded information. The genetic information stored in DNA is used to direct the synthesis of the thousands of proteins that each cell requires. The chemical and structural properties of DNA are the basis for how the genetic information that underlies heredity. DNA is encoded in the sequence of nitrogenous bases which directs the
  • 6. formation of proteins in the cell. How does this process work? First, the DNA code is copied on to the mRNA (messenger RNA) codon. A codon is a sequence of three nitrogenous bases. This process is called transcription. This mRNA codon is then carried from the nucleus out to the ribosome. Messenger RNA attaches to another kind of RNA called tRNA (transfer RNA). Transfer RNA attaches to amino acids and carries them to the ribosome. This assembly of amino acids due to the code provided to RNA by the original DNA molecule is what produces proteins for the cell. Remember a protein is a long molecule formed from amino acid subunits. Protein Synthesis In summary, the code of DNA directs the synthesis of RNA, which in turn directs the making of proteins on the ribosomes. This is sometimes referred to as being the central dogma or idea of biology. There are 64 possible combinations of triplets (sequences of 3 nitrogenous bases) which code for the 20 different possible amino acids. As the DNA of different organisms and most individuals (except for identical twins) is different, this means the proteins produced by different humans and other organisms exhibit differences. It is these differences which make us unique individuals. The work of the cell is carried out by the many different types of molecules it assembles, mostly proteins. Protein molecules are long, usually folded chains made from 20 different
  • 7. kinds of amino acids in a specific sequence. This sequence influences the shape of the protein. The shape of the protein, in turn, determines its function. Offspring resemble their parents because they inherit similar genes (DNA sequences) that code for the production of proteins that form similar structures and perform similar functions. Cell Regulation Cell functions are regulated. Regulation occurs both through changes in the activity of proteins and through the selective expression of individual genes, as humans and other organisms have genes which direct the expression of other genes. This regulation allows cells to respond to their environment and to control and coordinate cell growth and division.
  • 8. I. Selective Breeding a. For many years many different varieties of plants and domestic animals have come about from selective breeding. i. Artificial Selection 1. this is where an individual with desirable traits are mated so that the offspring will have these traits ii. In breeding 1. is the same process of artificial breeding but is done with agriculture where the offspring from Artificial selection are mated together to reinforce these desirable traits. iii. Hybridization 1. is a special case of selective breeding. 2. This involves crossing two individuals with different desirable traits to produce offspring with a combination of both desirable traits. An Example of Selective Breeding Brahman cattle: English shorthorn Santa Gertrudis Good resistance to cattle: Good beef cattle: Formed by heat but poor beef. but poor heat crossing Brahman resistance. and English shorthorns; has good heat resistance and beef. II. Genetic Engineering a. In recent years new varieties of farm plants and animals have been engineered by changing their genetic instructions to produce new characteristics.
  • 9. b. This technology is known as genetic engineering or recombinant DNA technology. i. Different enzymes can be used to cut, copy (clone), and move parts of DNA. ii. An important category of enzyme used to cut a section of a gene and its DNA from an organism is known as a restriction enzyme. iii. When this piece of DNA, which has been cut out of one organism, is placed in another organism, that section of gene will show the characteristics that were expressed by this gene in the organism it was taken from. An Example of Genetic Engineering c. Health care and genetic engineering. i. Genetic engineering is being used make chemical needed for human health care. ii. It may be possible to use aspect of genetic engineering to correct some human health defects. 1. Some examples of chemicals being mass produced by human genes in bacteria include a. insulin, b. human growth hormone, c. and interferon. 2. While genetic engineering technology has many practical benefits, its use has also raised many legitimate ethical concerns. III. Other Genetic Technologies a. Cloning i. involves producing a group of genetically identical offspring from the cells of an organism. ii. This technique may greatly increase agricultural productivity. iii. Plants and animals with desirable qualities can be rapidly produced from the cells of a single organism. b. Genetic mapping, i. which is the location of specific genes inside the chromosomes of cells makes it possible to detect, and
  • 10. perhaps in the future correct defective genes that may lead to poor health. There are many ethical concerns to these advanced genetic technologies, including possible problems associated with the cloning of humans.