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The passing of traits from parents to their offspring is called heredity. The branch of science that deals with the study of heredity is called genetics. Non-heritable traits: would not be passed from one generation to another i.e.) playing a musical instrument, environmental effects. For the most part organisms look like their parent. These characteristics are passed from parent to offspring through sexual reproduction and are called inherited or heritable traits ◦ Example: eye color, hair color, PTC paper, hands crossed Traits are passed on through genetic material YDNHTWTD Make a list of the traits listed on p38. Get into partners and record for each person which of the two forms of each trait each person displays. Continuous variation: characteristics that have a large range or continuum of possibilities i.e.) height, hand span, eye color. Discrete variation: characteristics that have a limited number of possibilities(YES-NO answers) i.e.) rolling your tongue, boy or girl, blood type etc. Variation is passed on through chromosomes Chromosomes – strings of genes, usually found in pairs in body cells… (one from your mom and one from your dad) Chromosomes are made up of genes… Genes are sequences of DNA that code for particular traits DNA: deoxyribonucleic acid p47 ◦ a double helix structure of nucleic acids consisting of: phosphate Sugar nitrogenous bases called adenine, thymine, cytosine and guanine Make it with marshmallows, fruit loops, licorice… Sugar Phosphate group Adenine bonds with thymine Guanine bonds with cytosine Nitrogenous bases Body cells have a complete set of chromosomes Body cells are found in every cell in your body! They are reproduced through mitosis. When cells divide uncontrollably, this is called cancer or a tumour ◦ The daughter cell is an exact replica of the parent cell ◦ Same number of chromosomes (two pairs of each) Sex cells are your gametes ie. Sperm and eggs Gametes only have half of a complete set of chromosomes for fertilization to create a zygote. They are produced through meiosis. ◦ The chromosomes are divided in half ◦ The daughter cells are not the exact same as the parent cell Sequences of DNA code for specific traits Each trait expressed by a gene (a sequence of DNA) is represented by a single letter (ie. blue eyes = b) Since you get one gene from your mom and one gene from your dad, you will always have two copies of each gene. Alleles – are different expressions of a trait (ie. blue eyes vs. brown eyes) and are represented by upper and lower case of the same letter (B and b) Dominant Trait: the gene that is expressed, even if there is only one. i.e.) “Tt” or “TT” you will be able to roll your tongue Recessive Trait: only when two genes are inherited will the offspring show that trait. i.e.) “tt” you will not be able to roll your tongue Not always will it be a dominant trait that shows up in a population, sometimes it will be a recessive trait that shows up most often. Use traits from before… Homozygous is a genotype that has two of the same “case” of letter ie. TT or tt Heterozygous is a genotype that has two different cases ie. Tt ◦ Heterozyous is also called a carrier for the recessive gene because it isn’t expressed You can use Punnett squares to determine the: ◦ Probability of getting a particular trait or gene ◦ Possible combinations of genes from parents 1) Put the genes for the sperm on the horizontal row and the egg on the vertical row. 2) Combine the genes to make the offspring in each box using one from the sperm and one from the egg. 3) Be sure to always put the capital letter first. 4) Then determine the trait that is expressed 5) If necessary, determine the probability. Furry Family Fill in the tables on the worksheet provided. In humans, brown eyes (B) are dominant over blue (b). A brown-eyed man marries a blueeyed woman and they have three children, two of whom are brown-eyed and one of whom is blue-eyed. a) Draw the Punnett square that illustrates this marriage. b) What is the man’s genotype? c) What are the genotypes of the children? In dogs, there is an hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be passed on. This can be tested by breeding the dog to a deaf female (dd). a) Draw the Punnett squares to illustrate these two possible crosses. b) In each case, what percentage/how many of the offspring would be expected to be hearing? deaf? c) How could you tell the genotype of this male dog? d) Also, using Punnett square(s), show how two hearing dogs could produce deaf offspring. Changes to DNA is called a mutation. ◦ Mutations cause changes in the structure of organisms ◦ These changes can happen due to exposure to X rays, ultraviolet rays, cosmic rays or chemicals. ◦ Mutagens cause mutations. ◦ Mutations can be beneficial, harmful or have not affect on a person. Cancer is an example of a Mutation There are two ways that certain organisms are selected to survive to pass on their genes to the next generation 1) Natural Selection the idea is that the environment "selects" organisms when only those organisms adapted to survive the "best" can live long enough to reproduce "survival of the fittest" is based on competition Adaptations can happen in one generation or over millions of years Always in a population Bears of Banff Bean Selection Disperse or Disease 2) Artificial Selection : process of selecting and breeding individuals with desirable traits select parents to create hybrid combination e.g.) beefalo, brociflower select parents with desirable traits already Reproductive technology: Eg) artificial insemination: sperm from a male is inserted into a female Eg) in vitro fertilization: sperm and eggs are mixed in a test tube and only the embryos with desirable traits are selected Eg) selective breeding: only use animals with pedigrees Eg) Genetic modification: bacteria making insulin Eg) Genetic engineering Eg) cloning Do you think animals should be tested for possible genetic disorders? Inbreeding depression Species conservation? In the zoo, reserves? How many do we need to keep a gene pool alive? Captive breeding? Zoos fund research? Transgenic manipulation? Cloning of rare animals? Natural habitat of animals? (insanity)