Transcript Standard 7
Mendel’s Laws of Probabilities in Offspring Standard 7 Ashley and Irum Mendel’s Laws: A History Gregor Mendel was born in Heinzendorf bei Odrau, Czech Republic. He worked as a gardener studying beekeeping and as a physics teacher in an abbey. He was known as the father of modern genetics. He studied about dominant and recessive alleles in pea plants. He wrote a paper called, “Experiments on Plant Hybridization”. It was published in 1866. After peas, he studied honeybees again. He became an abbot in 1868, after which he discontinued his scientific work on account of his increased administrative responsibilities. Mendel’s Laws The Law of Segregation of Characteristics: States that from a pair of characteristics, only one can be represented in a reproductive cell. The Law of Independent Assortment: States that the genes for two different characteristics are inherited independently. Punnett Squares This table represents three possible genotypes. It indicates how likely a particular offspring of this mating is to have a certain genotype. The capital letters represents the dominant gene, while the lower case letters represents the recessive gene. Incomplete Dominance In incomplete dominance, neither allele is dominant so there is a blending of __________ traits when two different alleles for the ______ same trait occur together. Colors blend together heterozygous (______________ individuals = 3rd phenotype) red pink white Codominance is seen in these pictures. All of the colors are dominant and you get spots of each one. Codominance Andalusian chickens show this pattern of inheritance. If you cross a black (BB) chicken With a white (WW) chicken You get black+white speckled (BW) chicken Vocabulary Phenotype-the appearance of an organism, like hair color or eye color Genotype- the genetic make-up of an organism and is shown with letters ( Bb would be a heterozygous genotype) Heterozygous-they got a DIFFERENT trait from their mom than they did from their dad. (Bb) Homozygous-They got the SAME trait from their mom that they did from their dad ( BB or BB) What’s the Difference? Homozygous genes are represented as either both capital letters (BB) or both lower case letters (bb). Heterozygous genes are represented as one capital letter and one lower case letter (Bb). Monohybrid Crosses A monohybrid cross crosses only one trait. A 4 square Punnett Square is a monohybrid cross A A A a Dihybrid Cross A Dihybrid cross, crosses two different traits at the same time A Dihybrid cross is shown using a 16 square Punnett square This one crosses fur color & tail length. . QUIZ TIME!!! Take out your pens and paper!!!!!!!! #1: Egyptian Mau cats are genetically crossed for certain lengths of fur. A breeder knows that short hair is dominant over long hair. If 75% of the kittens are born with short hair, what are the parents’ most likely genotypes? A: the male is a heterozygous, short-haired cat, and the female a homozygous short-haired cat. B: the male is a homozygous, long-haired cat, and the female is a heterozygous, short-haired cat. C: the male is a homozygous, short-haired cat, and the female is a heterozygous, short-haired cat. D: the male is a heterozygous, short-haired cat, and the female is a heterozygous, short-haired cat. D. The Answer is To answer this question you need to put the information form each answer choice into a Punnett square & work it out. Short hair is dominant so we show it with a capital letter Answer choice D would be as follows: B b bb would be long haired (25%) Bb & BB each have the dominant B BB Bb short haired trait ( 75%) b Bb bb #2: Brown eye color is dominant over blue eye color. A heterozygous brown eyed father and a blue eyed mother have four children. Which statement best describes the children’s predicted phenotypes? A: 50% of children will have brown eyes, and 50% will have blue. B: 75% of the children will have brown eyes and 25% will have blue. C: 75% of the children will have blue eyes and 25% will have brown. D: 100% of the children will have brown eyes. A The correct answer is The father is Brown eyed & Heterozygous ( different trait from each parent) Bb Mother is blue eyed. It is recessive bb B b b Bb bb b Bb bb #3: Which genetic cross will produce all heterozygous offspring? A: RR x rr B: rr x rr C: RR x RR D: Rr x Rr Hint: Try them out & see!!!! A is the correct answer R r Rr Rr r Rr Rr All R are heterozygous Rr ( different trait from each parent) #4:Which of the following is Homozygous? A: RR B: Rr RR got the Same trait ( both dominant) from each parent. Homo means the same #5:Which of the following is Heterozygous? A: RR B: Rr They got a different trait from each parent ( one Dominant gene R & one recessive gene r so they are Hetero zygous # 6 Read this dihybrid cross What is the ratio of yellow to green peas in this cross? 4 to 12 3 to 1 12 to 4 You can’t tell The correct answer is C __ yellow 12 4 green __ #7: What was one of Mendel’s Laws? A: The Law of Conservation of Mass. B: The Law of Segregation of Characteristics. C: The Law of Recessiveness. D: The Law of Intensity of Alleles. The 2 Laws are the Law of Segregation of Characteristics and the Law of Independent Assortment #8: What things did he study? A: Pea plants and human babies B: Pea plants and honeybees C: Chickens and lima beans D: Garbanzo beans and lima beans Mendel studied the genes of Pea plants and honeybees. #9: What is a Phenotype? A: The appearance of an organism like brown hair or light skin B: The genetic makeup of an organism C:Blending D:Spots Your phenotype is your physical appearance