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Concept 3 Genetics Science 9 Concept 3 – Genetics Learning Concept Describe, in general terms, the role and relationship of chromosomes, genes and DNA Concept 3 – Genetics There is a blueprint for each multicellular organism found within all the cells of the body Known as deoxyribonucleic acid, or DNA Inherited material responsible for variation Concept 3 – Genetics First identified in 1869 In 1953 a scientific paper by James Watson and Francis Crick presented the structure of DNA Rosalind Franklin had groundbreaking work in discovering the shape of DNA http://sciencecomm.wikispaces.com http://pippastephens.files.wordpress.com Concept 3 – Genetics Structure is a double helix Resembles a ladder that has been twisted into a spiral Rungs of the ladder are different in their composition Found in pairs Adenine (A) and Thiamine (T) Guanine (G) and Cytosine (C) Concept 3 – Genetics The arrangements of these four chemicals create a language that cells can read Read in triples Refer to this as the genetic code – a language the cell understands These chemicals are the same for all species on Earth http://upload.wikimedia.org Concept 3 – Genetics Chromosomes are packages within the cell which contain the DNA One chromosome only contains some of the instructions for making an organism These are paired within a cell In plants and animals, chromosomes are contained within the nucleus of the cell www.stanford.edu Concept 3 – Genetics Chromosome numbers vary from species to species The composition of the chromosomes also varies www.mun.ca www.research.uky.edu Concept 3 – Genetics Currently accepted in the scientific world Genes are responsible for inheritance of an organism’s characteristic features A single gene is an uninterrupted segment of DNA, with coded instructions http://fergusonbiology.homestead.com Concept 3 – Genetics Genes are located on chromosomes Chromosomes have numerous gene locations Genes come in pairs Both genes carry instructions for the same thing The same genes occupy matching locations on the chromosomes The DNA code may differ in each location http://ftdtheotherdementia.com Concept 3 – Genetics There are different forms of the genes coming from the parents These different gene forms are called alleles Concept 3 – Genetics Learning Concept Distinguish between: Cell division that leads to identical daughter cells Cell division that leads to formation of sex cells Describe, in general terms, the synthesis of genetic material that takes place during fertilization Concept 3 – Genetics Asexual reproduction produces offspring genetically identical to the parents Sexual reproduction produces offspring genetically different from the parents www.islamicmedicine.org Concept 3 – Genetics Binary fission occurs in unicellular organisms Examples: amoeba, paramecium Cell contents divided equally between the two new cells What happens if the DNA is split between the two cells? How is this corrected? www.biologycorner.com Concept 3 – Genetics Parent cell first makes an exact copy of its DNA For a short time, the parent cell has two copies of its DNA When the cell divides, each new cell gets one complete copy of the DNA http://biodidac.bio.uottawa.ca Concept 3 – Genetics A similar process occurs in multicellular organisms – called MITOSIS Two new cells are produced with the same number of chromosomes Occurs on the body cells Responsible for growth and cell repair in multicellular organisms www.bio.miami.edu http://royaleb.files.wordpress.com http://kvhs.nbed.nb.ca Concept 3 – Genetics Sexual reproduction requires the fusion of two gametes The sperm cell The egg cell Using humans as an example, What happens if each gamete contained 23 pairs of chromosomes? The zygote will not survive if it receives two times the amount of DNA needed http://2.bp.blogspot.com Concept 3 – Genetics MEIOSIS is a type of cell division that produces cells with only half the DNA of a normal cell A sperm cell will have half the DNA An egg cell will have half the DNA When the two unite to form the zygote, it will have a complete set of DNA http://laurent.penet.free.fr http://faculty.irsc.edu Concept 3 – Genetics Meiosis involves two cell divisions to produce four gametes A gamete will contain one copy of each different chromosome www.northcoastjournal.com Concept 3 – Genetics Textbook Activity – Who Has What Number? pg 48 Fill in the table in your notes using the information provided in your textbook Organism Cabbage # chromosomes in cell after mitosis # chromosomes in a body cell # chromosomes in a gamete # of pairs of chromosomes 18 Black Bear 38 Human Peanut # chromosomes in a zygote 23 40 Concept 3 – Genetics Plant and animal breeders have been conducting experiments in selective/controlled breeding for a long period of time Only organisms with desired traits were allowed to reproduce Certain patterns of inheritance were eventually detected Concept 3 – Genetics Learning Concept Identify examples of dominant and recessive characteristics Recognize dominance and recessiveness provides only a partial explanation for the variation of characteristics in offspring Concept 3 – Genetics Genetics looks at how heritable characteristics are passed from one generation to the next Work was began by Gregor Mendel, an Austrian monk Traced patterns of inheritance in pea plants Discovered fundamental principles that led to modern genetics www.tip.duke.edu Concept 3 – Genetics A purebred organism (plant or animal) is one whose ancestors ALL had the same form of a trait http://images.flowers.vg http://upload.wikimedia.org Concept 3 – Genetics A hybrid organism (plant or animal) is one who was produced from two purebreds with a different form of the trait http://image03.webshots.com Concept 3 – Genetics Dominant traits are those which are typically always expressed/observed if ONE is present Two dominant alleles are inherited Example Female provided allele for Yellow seed (dominant) Male provided allele for Yellow seed (dominant) Offspring will inherit both alleles Two dominant alleles are inherited and yellow seeds will be observed Concept 3 – Genetics Two opposite-acting alleles are inherited Example Female provided allele for Tall plants (dominant) Male provided allele for Dwarf plants (recessive) Offspring will inherit both alleles Tall is a dominant alleles, so while both alleles are inherited, a TALL plant will be observed Concept 3 – Genetics http://image.wistatutor.com Concept 3 – Genetics Recessive traits are those which are ONLY expressed/observed when TWO are present Two recessive alleles are inherited Example: Female provided allele for white flowers Male provided allele for white flowers Offspring will inherit both alleles Two recessive alleles are inherited and a white flower will be observed Concept 3 – Genetics Which of the examples listed in these notes (seed color, tall/dwarf plants, flower color) represents A hybrid? A purebred? Concept 3 – Genetics Learning Concept Investigate the transmission of characteristics from parents to offspring, and identify examples of characteristics in offspring that are: The same as the characteristics of both parents The same as the characteristics of one parent Intermediate between parent characteristics Different from both parents Concept 3 – Genetics Recall that each adult has a pair of chromosomes, and alleles are gene variations carried on those chromosomes There is written “code” for genetics to show dominant versus recessive traits We call the written “code” the organism’s genotype Concept 3 – Genetics Dominant traits are always written as the capital letter Recessive traits are always written as the lower case of the same letter For yellow seeds Dominant trait for yellow could be Y Recessive trait for green will then be y Concept 3 – Genetics A pea plant with the yellow seed color will have two alleles Dominant traits are expressed when: Two dominant alleles are inherited Two opposite-acting alleles are inherited What are the two possible genotypes for this pea plant? Concept 3 – Genetics A pea plant with the green seed color will also have two alleles Recessive traits are expressed when: Two recessive alleles are inherited What are the one possible genotypes for this pea plant? Concept 3 – Genetics Science Log Why is it possible for two plants that express the dominant yellow seed color to have one green seed offspring? Concept 3 – Genetics www.scq.ubc.ca Concept 3 – Genetics Give it a try ... Page 52 – Exploring Genetic Possibilities Concept 3 – Genetics Other patterns of inheritance also exist, due to Incomplete dominance Complex patterns of inheritance Environmental factors Concept 3 – Genetics Incomplete dominance arises when traits are not truly dominant or recessive A purebred red snapdragon, when crossed with a purebred white snapdragon, will produce all pink offspring What is the genotype of the red snapdragon? What is the genotype of the white snapdragon? What is the genotype of the pink snapdragon? Concept 3 – Genetics Environmental factors can cause variations in things such as height, weight, etc. Presence of environmental factors can influence the genes Consumption of alcohol during a pregnancy will interfere with normal development of brain structures and facial features Medication can cause structural deformities Example: thalidomide in the late 1950s Concept 3 – Genetics www.chm.bris.ac.uk http://i66.photobucket.com www.dw-world.de www.newsciencejournalism.net