General Genetic Bio 221 Lab 8 Most traits

General Genetic Bio 221 Lab 8

Most traits are non-mendelian , meaning they do not follow the rules of mendelian traits. Almost all traits in humans are non-mendelian , the trait is determined by : 1 - more than one gene. 2 - or the environment affects the trait. Allelic or gene interactions 1 - The gene in an organism can interact in many different ways. 2 - The effect of dominant allele is diluted or modified so that the phenotypic expression of the concerned trait in a hybrid (Heterozygous ) is distinguishable from both parental types ( Homozygous ).

Type of non-mendelian 1 - in complete ( partial , semi , intermediate ) dominance : * The dominant characteristics in an allele influences , but does not overwhelm the heterozygote. * Phenotype and genotype ratios in F 2 generation are 1: 2: 1. * EX : Red shaded chrysanthemum breed with white shaded chrysanthemum , the resulting is pink. The mixture of colors shows incomplete dominance between colors.

2 - Co - dominance ( Mosican dominance ) : * Both allelic genes of a genetic trait are equally expressive , there is complete lack of dominance. When the heterozygotic organism shows the characteristics of two dominant alleles. * Phenotype and genotype ratios in F 2 generation are 1: 2: 1. * EX: 1 - White cat and black cat generate offspring that the dominant alleles share dominance. 2 - Red and white coat colors in short-horn cattle expressions ( Phenotype) , and they are homozygous dominant and homozygous recessive genotypes. The hybrids exhibit a roan coat color is intermediate.

* EX: 3 - The AB blood group is due to co-dominance. AB group is controlled by the genes A and B. The A and B are equally dominant. A produces antigen A and B produces antigen B. 4 - Sickle cell anemia is recessive disease. In heterozygous which have abnormal red blood cells under some conditions.

Multiple alleles Which a population has more than two alleles in it. EX: ABO blood groups in humans , in which there are 3 possible alleles A, B or IA and IB ( codominant ) , and i. type O blood is recessive.

Poly-genic inheritance More than one gene affecting a trait. Most traits in humans are polygenic , such as weight , height. IQ , personality , ( skin color is environmental determined and determined by 5 genes , each with 2 alleles giving 9 phenotypes. ) Modifier genes Genes that influence a trait indirectly. Such as , a dominant gene affects whether people can get early cataracts , but modifier genes determine how cataracts are likely to be. Often these modifier genes are located on different chromosome.

A - Mendelian Ratios and Lethal genes B - Epistasis

A - Mendelian Ratios and Lethal genes In 1905 , Lucien Cuenot observed unusual patterns when studying inheritance of a coat color gene in mice. After mating 2 yellow mice , observed that the offspring never showed a normal 3: 1 phenotype but observed 2: 1 , with 2 yellow mice and one non-yellow mice. This is lethal genes cause the death of the organisms that carry them. Sometimes , death is not immediate it may take yeas depending on the gene. Kind of Lethal Genes : 1 - Recessive Lethal genes. The ratio 3: 0. EX : Cystic fibrosis and Sickle cell anemia 2 - Dominant lethal genes. The ratio 2: 1. EX: Huntington disease 3 - Semi or Sub Lethal genes. EX : Hemophilia 4 - Synthetic Lethal genes. 5 - Conditional lethal genes. EX: favism allele

Kind of Lethal Genes 1 - Recessive Lethal genes. That occur in dominant or recessive traits but they do not cause death an organism carries 2 copies of lethal allel. The ratio 3: 0. EX : Cystic fibrosis and Sickle cell anemia. 2 - Dominant lethal genes. Are expressed in both homozygotes and heterozygotes. The ratio 2: 1 EX: Huntington disease , a neurological disorder in humans. Dominant traits can also be maintained in the population through mutations or the gene is less than 100%. 3 - Semi or Sub Lethal genes. The allele responsible for hemophilia is carried on the X chromosome , affected mainly in males , and they inherit the allele from their mothers. Hemophilia = is affected in individual bleed as longer period of time until clotting occurs , this means that normally minor wounds can be fatal in a person. 4 - Synthetic Lethal genes. Some mutations are only lethal when paired with second mutaion

5 - Conditional lethal genes EX: 1 - In enzyme ( glucose 6 phosphate dehydrogenase ) and favism allele that common among people of Mediterranean , African and Southeast Asian. The disease was named because when affected individuals eat fava beans , they develop hemolytic anemia , a condition in which red blood cells break apart and block blood vessels. But that disease is resistant to malaria because it is difficult for malaria to multiply in cells with deficient a mount of glucose 6 phosphate dehydrogenase. 2 - Temperature.

B - Epistasis The effects of one gene are modified by one or several other genes. Hypostatic : the phenotype altered or suppressed. Epistatic : The gene whose phenotype is expressed. Epistasis can be contrasted with dominance which is an interaction between alleles at the same gene locus. The interaction between two or more genes to control a single phenotype and identify and recognize the 9: 3: 3: 1 that results of crossing 2 dihybrids produced a modified mendelian. Kind of Epistasis : 1 - Dominant Epistasis : (12: 3: 1 ) from ( 9: 3 : 1 ) EX: Fruit color in squash 2 - Dominant duplicate Epistasis : (15: 1 ) from ( 9: 3: 3 : 1 ) EX: Kernel Color in wheat 3 - Recessive Epistasis: (9: 4: 3 ) from ( 9: 3: 3 : 1 ) EX: mice coat color 4 - Recessive duplicate Epistasis : (9: 7) from ( 9: 3: 3 : 1 ) EX: Flower Color in sweet pea

Kind of Epistasis : 1 - Dominant Epistasis. * Definition : Complete dominance at both gene pairs ; when one gene is dominant , it hides the effects of other gene. And the ratio is 12: 3: 1 * EX: Fruit color in squash. Color is recessive to no color at one allelic pair. At the first gene white colored squash is dominant to colored squash , and that gene code are W=white , w=colored. At the second gene yellow is dominant to green , and that gene code are G=yellow , g=green. The result in dihybrid is 3 phenotypes and produced 12: 3: 1. The following table explanation for that ratio because the dominant W allele masks the effects of either the G or g allele. Genotype Phenotype Enzymatic Activites 9 W_G_ White Dominant white allele negates effect of G allele 3 W_gg White Dominant white allele negates effect of G allele 3 ww. G_ yellow Recessive color allel allows yellow allele expression 1 wwgg Green Recessive color allel allows green allele expression 12 3 1

2 - Dominant duplicate Epistasis. * Definition : Complete dominance at both gene pairs ; when either gene is dominant , it hides the effects of other gene. And the ratio is 15 : 1 * EX: Kernel Color in wheat. That effect by 2 enzyme A or B can produce a product from common precursor , only one dominant allele at either of 2 loci is required to generate the product. * If pure wheat plant with colored kernal ( genotype = AABB) is crossed to plant with white kernels ( genotype =aabb ) and resulting F 1 plants are selfed a modifiction of the dihybrid 9: 3: 3: 1 ratio will be produced. The following table explanation for the ratio 15: 1 because the genes can provide the wild type phenotype. Genotype Phenotype Enzymatic Activites 9 A_B_ Colored Kernels Functional enzymes from both genes 3 A_bb Colored Kernels Functional enzymes from A genes 3 aa. B_ Colored Kernels Functional enzymes from B genes 1 aabb Colored Kernels Non Functional enzymes from both genes 15 1

3 - Recessive Epistasis. *Definition: Complete dominance at both gene pairs ; when one gene is homozygous recessive , it hides the effects of other gene. And the ratio is 9: 4: 3 * EX: mice coat color. in some casses recessive allele (a) masks the effect of dominant allele (B). When black mouse crossed to albino mouse , only agouti progeny were produced , but in F 2 , 9 agouti , 3 black and 4 albino (9: 3: 4) were produced. Coat color in mouse is controlled by 2 dominant genes C and A. In agouti color both the genes are dominant. When only C is dominant , mouse color will be black. When both recessive genes c and a are homozygous recessive , albino mice are produced. Black mice ( CCaa) X Albino(cc. AA) mice F 1 Cc. Aa ( agouti)

4 - Recessive duplicate Epistasis. * Definition : Complete dominance at both gene pairs ; when either gene is homozygous recessive , it hides the effects of other gene. And the ratio is 9: 7 * EX: Flower Color in sweet pea. That effect by 2 genes are functional products from both for expression , then one recessive allelic pair would result in mutant phenotype. * If pure line pea plant with colored flowers ( genotype = CCPP) is crossed to pure line , homozygous recessive plant with white flowers , the F 1 plants will have colored flowers and Cc. Pp genotype. The normal ratio from dihybrid is 9: 3: 3: 1. But Recessive duplicate Epistasis interaction between C and P genes will give modified 9: 7 because both genes are required for correct phenotype , this epistatic interaction is called complementary gene action. The following table explanation for the ratio 15: 1 because either the genes can provide the wild type phenotype. Genotype Phenotype Enzymatic Activites 9 C_P_ Colored colored : anthocyanin produced Functional enzymes from both genes 9 3 C_pp Flowes white : no anthocyanin produced p enzyme non-functional 7 3 cc. P_ Flowes white : no anthocyanin produced c enzyme non-functional 1 ccpp Flowes white : no anthocyanin produced C and p enzymes non-functional

Experimental Separate the drosophelia (F 2 ) From second Low and record the changes for chi –square ++ e vg Vg e Male Obs. 1 - ++ 2 - e 3 - vg Female Total /D. S 4 - vg-e