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SI Worksheet #14 (Chapter 14) BY 123Meeting 10/29/2015Chapter 14: Mendel and the Gene IdeaWhat is the difference between a character and a trait? Give some examples of each.A character is a heritable feature that varies among individuals such as flower color. Each variant for a character, such as purple or white is a trait. What is a true breeding plant?A kind of breeding in which the parents with a particular phenotype produce offspring only with the same phenotype.What is hybridization? What genotype is produced?The mating or crossing of two true-breeding varieties. It produces hybrids in the F1 generation whose genotype is heterozygous for the trait. What is meant when saying an organism is heterozygous for a gene? What is meant when saying an organism is homozygous for gene? An organism that has two different alleles for a gene is heterozygous for that gene.An organism that has two of the same alleles for a gene is homozygous for that gene. What is the difference between a genotype and a phenotype? Genotype is the genetic makeup or set of alleles for an organism. Phenotype is the physical and physiological traits of an organism. Phenotype is determined by genotype. What was the genotypic ratio of the F1 generation in Mendel’s experiment with the pea plants? What was the phenotypic ratio of the F1 generation in Mendel’s experiment? All heterozygotes are produced. What was the genotypic ratio of the F2 generation in Mendel’s experiment with the pea plants? What was the phenotypic ratio of the F2 generation in Mendel’s experiment? Genotypic ratio: 1:2:1 Phenotypic ratio: 3:1 What do you call alternate versions of a gene?Alleles Discuss the four related concepts that make up Mendel’s Model. Alternative versions of genes account for variations in inherited characters For each character, an organism inherits two alleles, one from each parentIf the two alleles at a locus differ, then one, the dominant allele, determines the organism’s appearance; the other, the recessive allele, has no noticeable effect on the organism’s appearanceThe law of segregation: the two alleles for a heritable character segregate (separate) during gamete formation and end up in different gametes.A pea plant heterozygous for inflated pods (Ii) is crossed with a plant homozygous for constricted pods (ii). Draw a Punnett Square for this cross. Assume pollen comes from the ii plant. IiiiIiiiPea plants heterozygous for flower position and stem length (AaTt) are allowed to self-pollinate and 400 of the resulting seeds are planted. Draw a Punnett Square for this cross. How many offspring would be predicted to have terminal flowers and be dwarf? AaTt x AaTt AT At aT at on topAT At aT at on side AATTAATtAaTTAaTtAATtAAttAaTtAattAaTTAaTtaaTTaaTtAaTtAattaaTtaattFor any gene with a dominant allele C and recessive allele c, what proportions of the offspring from a CC x Cc cross are expected to be homozygous recessive, and heterozygous?? homozygous dominant (CC), 0 homozygous recessive (cc), and ? heterozygous (Cc)In Mendel’s classic pea crosses, the F1 offspring always looked like one of the two parental varieties. What is the explanation for this phenomenon? (Hint: think about the genotype)The F1 generation was all heterozygous. They all looked the same as the parental varieties because one allele in a pair showed complete dominance over the other. When red snapdragons are crossed with white ones, the F1 hybrids have pink flowers. What is this called? What is the genotypic ratio of the F2 generation? What is the phenotypic ratio? Incomplete dominance. Both the genotypic ratio and the phenotypic ratio are 1:2:1Individuals homozygous for the M allele (MM) have red blood cells with only M molecules; individuals homozygous for the N allele (NN) have red blood cells with only N molecules; individuals heterozygous for the M and N alleles (MN) have red blood cells with M and N molecules. What is the reason for this?CodominanceWhy does the heterozygote condition of Tay-Sachs disease not lead to disease symptoms? An allele is not termed dominant because it somehow subdues a recessive allele. When a dominant allele coexists with a recessive allele in a heterozygote, they do not actually interact at all. Half the normal enzyme activity is sufficient to prevent lipid accumulation in the brain. Heterozygous individuals produce equal numbers of normal and dysfunctional enzyme molecules. Thus, at a molecular level, the normal allele and the Tay-Sachs allele are codominant. True or false. Dominant allele for a particular character is more common than recessive allele for a particular character in a population? FalseThe ABO blood groups in humans are determined by 3 alleles of a single gene: IA, IB, and i. What is this called? Multiple AllelesWhat does the A, B, or O refer to?Type A blood has A carbohydrate associated with their blood cells, B has B carbohydrate associated with their blood cells, O has neither carbohydrate Which blood group is the universal donor? Type OHow many blood groups (phenotypes) are there? 4 A, B, AB, OWhat are these blood groups and what are the genotypes associated with each phenotype? Use the table provided below. GenotypeRed blood cell appearance Phenotype (blood group)IAIA or IA iCarbohydrate AAIBIB or IBi Carbohydrate BBIAIBCarbohydrate A and BAB *codominance*iiNo carbohydratesOWhat is pleiotropy? When genes have multiple phenotypic effects. Pleiotropic alleles are responsible for the multiple symptoms associated with certain hereditary diseases. Epistasis is when a gene at one locus alters the phenotypic expression of a gene at a second locus. Give an example. Skin color in humans varies along a continuum and is an additive effect controlled by at least three separately inherited genes. What is this called? Polygenic inheritanceWhat is the name given to characters that vary along a continuum (in gradations)Quantitative charactersWhat is meant by characters being multifactorial? Many factors, both genetic and environmental, collectively influence phenotype What is this figure? Why is it used? How many generations are shown? Who are the males and who are the females? Who is affected and who is not affected? Widow’s peak is a dominant allele (W). Fill in the genotype for each family member.This is a pedigree. It is used to collect information about a person’s family history for a particular trait and assemble this information into a family tree describing the traits of parents and children across the generations. 3 generations are shown here. The males are the squares the females are the circles. The shaded ones are the affected one. 1800225410845 ................
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