Topic 7 Heredity-Genetics A. Heredity is the passing of traits - PDF document

4/12/2020 Topic 7 Heredity-Genetics A. Heredity – is the passing of traits from parent to offspring ( child ). • Eye color, nose shape, and many other physical features are some of the traits that are inherited from parents. 1 2 Heredity Heredity 3. During meiosis a pair of chromosomes 1. Genes on separates and alleles move into separate sex chromosomes cells. control the traits 4. Each sex cell now contains one allele for each that show up in an trait. (So you get one allele from each parent) organism. 2. The different forms of a trait that a gene may have are called alleles. 3 4 5. The study of how traits are inherited B. Gregor Mendel – The Father of Genetics is genetics. 1. Mendel was a monk who studied pea plants in the late 1800s. 2. He was the first to use the mathematics of probability to explain heredity and to trace one trait for several generations. 5 6 1

4/12/2020 C. GENETICS B. Gregor Mendel – The Father of Genetics 1. A hybrid receives different genetic information for a trait 3. Mendel had 3 main from each parent. principles of heredity. a. Dominant allele – covers up or dominates the other a. Traits are controlled trait. by alleles on chromosomes. b. Recessive allele – the trait seems to disappear. b. An allele’s effect is dominant or recessive. c. When a pair of chromosomes separates during meiosis, the different alleles for a trait move into separate cells. 7 8 C. Genetics C. Genetics 2. Probability helps you 4. Genotype – the genetic predict the chance that makeup of an organism something will happen. (what alleles it has for a 3. A Punnett square can gene) help you predict what an a. homozygous – an offspring will look like. organism with two alleles a. Upper case letters for one trait that are the stand for dominant same (TT or tt) alleles. b. Heterozygous – an b. Lower case letters organism with two alleles stand for recessive for one trait that are alleles. different . (Tt) 9 10 C. Genetics Topic 7 Genotype = Ee or EE Genotype = ee Phenotype = Phenotype = Unattached earlobe attached earlobe Genetics Since Mendel • 5. Phenotype – the way an organism looks and behaves as a result of its genotype. 11 12 2

4/12/2020 A. INCOMPLETE DOMINANCE Incomplete Dominance 1. Neither allele for a trait is dominant . Neither color is dominant, so heterozygous (hybrid) 2. The phenotype produced is offspring show a color that is a mixture of the intermediate between the two parents’ colors. homozygous parents. a. For traits that show incomplete Chestnut Cremello dominance, instead of using an uppercase letter and a lower case letter, the same uppercase letter is used, but one allele gets the ‘ or prime symbol. Palomino 13 14 B. MULTIPLE ALLELES How does blood type work? 1. More than two alleles that There are 3 alleles for blood type in humans control a trait are called A, B, and O multiple alleles. 2. Traits controlled by multiple alleles produce more than There are 6 genotypes possible AB, AA, three phenotypes AO, BB, BO, and OO 3. Human blood type is an example of having 3 different There are 4 phenotypes for blood type in alleles which combine to make 4 different phenotypes. humans AB, A, B, and O 15 16 Blood type cont. C. POLYGENIC INHERITANCE 1. A group of gene pairs act a. The A and B alleles are codominant which together to produce a trait, means they are both expressed. The O allele is which creates more variety in recessive. phenotypes. b. A person with type A blood could have the 2. Many human traits are genotype AA or AO controlled by polygenic inheritance, such as hair and c. A person with type B blood could have the eye color. genotype BB or BO 3. Many polygenic traits are d. A person with type O blood can only have the affected by the environment , genotype OO since O is recessive. for example many alleles are expressed only under certain e. A person with type AB blood can only have the temperature conditions. genotype AB since they are codominant. 17 18 3

4/12/2020 D. MUTATIONS – genes that are E. RECESSIVE GENETIC DISORDERS altered or copied incorrectly 1. A mutation can be 1. Both parents have a recessive allele harmful , helpful, or have responsible for the disorder and pass it to no effect . their child. 2. Chromosome disorders – caused by 2. Because the parents are heterozygous , more or fewer they don’t show any symptoms. They are chromosomes than called a carrier . normal. 3. Down’s syndrome – 3. Cystic fibrosis is a homozygous caused by an extra copy recessive disorder. of chromosome 21. 19 20 F. SEX DETERMINATION G. SEX-LINKED DISORDERS 1. An allele inherited 1. Chromosomes that X Y on an X or Y determine the sex of chromosome is a an organism are XX sex-linked gene. in females and XY in X males. XX XY 2. Females produce 2. Color blindness eggs with an X is a sex-linked chromosome only. disorder caused by a X Males produce sperm recessive allele on with either an X or a the X chromosome. XX XY Y chromosome. 21 22 G. Sex Linked TOPIC 7 3. A pedigree follows a Heredity – Advances in Genetics trait through generations of a family. a. females are represented as circles b. males are represented as squares 23 24 4

4/12/2020 A. Genetic Engineering A. Genetic Engineering 1. Recombinant DNA a. Insertion of a useful segment of DNA into a bacterium. b. Example: Insulin is made by genetically engineered organisms. Genetic Engineering – changing the arrangement of DNA that makes up a gene. 25 26 A. Genetic Engineering B. Genetic Engineered Plants B. Genetically engineered plants – created by inserting the genes that 2. Gene Therapy produce desired a. A normal allele is placed into a virus , traits in one plant into which delivers the normal allele when it a different plant. infects its target cell. b. May be used to control cystic fibrosis or other genetic disorders. 27 28 B. Genetic Engineering B. Genetic Engineering 2. Concerns a. the long-term effect 1. Examples of consuming a. tomatoes are genetically engineered given a gene that lets food is unknown them be picked green and then ripen slowly so they are firm when b. some stores label they reach stores. genetically engineered b. other crops have food now so you can been engineered to choose to eat it. be resistant to diseases and pests . 29 30 5