Extensions of Mendelian Genetics PowerPoint Presentation

BASED ON MENDELIAN GENETICS, WHAT ARE MENDEL’S FOUR (4) POSTULATE/HYPOTHESIS WITH REGARDS TO HEREDITY? Extensions Mendelia of n Genetics  Incomplete Dominance Codominance Multiple Alleles Extension isncludes Multiple Genes Sex-limited tra...

BASED ON MENDELIAN GENETICS, WHAT ARE MENDEL’S FOUR (4) POSTULATE/HYPOTHESIS WITH REGARDS TO HEREDITY? Extensions Mendelia of n Genetics  Incomplete Dominance Codominance Multiple Alleles Extension isncludes Multiple Genes Sex-limited traits Sex-infl uenced traits Sex-linked traits  Assumptions of Mendelian Inheritance Traits  genes  2 alternative alleles  Complete Dominance  Alleles are found on autosomes  No Gene Interaction  A situation in which a single phenotype is aff ected by more than one set of genes  Complete Penetrance  Percentage that individual express the trait given their genotype ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Incomplete Dominance ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  R W R RR RW W RW WW  How are we to interpret lack of dominance?  Consider gene expressions in quantitative way and careful observations of gene product rather than phenotype  In the case of snapdragon, the gene product of:  Wild-type allele (R1) is an enzyme that participates in a reaction leading to the synthesis of red pigment  Muta nt allele (R2 ) produces an enzyme that cannot catalyze the reaction leading to pigment (loss of function)  Thus, heterozygote produces only about half the pigment of red-fl ©Ma. Arra B. Santos,2020. ower Do not and modify, reproduce, the phenotype isthe or exhibit without pink written consent from the author.  Codominance  Infl uence of both alleles in a heterozygote is clearly evident  MN blood group (Karl Landsteiner and Philip Levin)  A glycoprotein molecule found on the surface of RBC that act as native antigen for biochemical and immunological identity to individuals  M and N is under the control of locus on chromosome 4  ABO blood group ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Codominant Blood Group Alleles ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  A and B  These are Antigens glycolipids which are carbohydrate bound to groups lipid molecules protruding from RBC membrane. Its specifi city is based n the terminal sugar of carbohydrate group. H substance is where one or two terminal sugars are added ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Sickle-Cell  Gene Anemia the concern affects molecule hemoglobin, transports oxygen which There is incomplete dominance in ter ms of blood cell shape. But there is also codominance in A and S form of hemoglobin. These shows that the types of dominance inferred depend on the phenotypic level – organismal, cellular or molecular. ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Multiple Alleles  When three or more alleles of the same gene are present in a population, the resulting mode of inheritance may be unique.  This can only be studied only in populations.  Number of possible genotypes =  ½ n (n+1)  ABO blood groups (K. Landsteiner)  A and B antigens are present on the surface of RBC under the control of chromosome 9  The I designation stands isoagglutinogen, another term for antigen. for ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  ABO Blood Groups ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Skin Colour of rabbits  Agouti – full color, wild-type, dominant over all the remaining color  Chinchilla – lighter than agouti; dominant over Himalayan and albino Himalayan – white body while tips of ear, feet, tail and snout are colored; dominant over albino  Albino – pure white fur; recessive to all other types ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Skin Colour of rabbits C c C CC Cc c Cc cc ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  BLOOD TYPE 1. BLOOD TYPE A X BLOOD TYPE B Hetero A x hetero B – 4pts Homo A x homo B – 1pt Homo B x hetero A – type B – 50% type AB – 50% - 2pts Hetero B x homo A – Type A – 50% Type AB -50% - 2pts Total: 9pts 2. BLOOD TYPE AB X BLOOD TYPE A Type AB x Homo A - type AB – 50%; Type A – 50% -2pts Type AB x Hetero A – 3pts 3. BLOOD TYPE 0 X BLOOD TYPE AB Type O x Type AB – Type A – 50%; Type B – 50% 4. BLOOD TYPE A X BLOOD TYPE A Homo A x homo A – Type A 100% homo A x Hetero A – type A 100% hetero A x Hetero A – type A 75%; type O – 25% 5. BLOOD TYPE AB X BLOOD TYPE AB Type AB x Type AB answer: type A – 25; type B – 25%; type AB – 50%  Combinations of Two Gene Pairs with Two modes of Inheritance Modify the 9:3:3:3 Ratio  Mendel’s principle of independent assortment applies provided that the genes controlling each character are not located on the same chromosome. Thus, there in no genetic linkage. For example, two humans who are heterozygous for autosomal recessive gene that causes albinism and are both of blood type AB. What is the probability of a particular phenotypic combination occurring in each of their children? ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Combinations of Two Gene Pairs with Two modes of Inheritance Modify the 9:3:3:3 Ratio ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Gene  several genes Interaction infl uence a particular characteristic. Wherein, the cellular function of numerous gene products contributes to the development of a common phenotype.  Epigenesis – each step of development increases the complexity of organ or feature of interest and is under the control and infl uence of many genes  Ex. Inner ear formation to detect and interpret sounds  Epistasis – expression of one gene pair mask or modifi es the eff ect of another gene pair  Ex. Grain color of corn, coat color in dogs ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Gene Interaction ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Gene Interaction ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Multiple Genes of Two or Polygenes more pairs of genes account for the phenotype Alleles do not exhibit dominance but has quantitative eff ect Contributory/eff ective allele (C) vs. non-contributory/non-eff ective alleles (c) Eff ects of contributory alleles are equal but cumulative (additive) ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Examples of Ana tomicalPolygenes – height, weight, ear length in corn, degree of pigmentation in fl ower and skin Physiological – metabolic traits, speed of running, milk production Behavioral – mating calls, courtship rituals, ability to move to light  Complex disease – diabetes, hypertension, arthritis, obesity ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  X-linkage in Drosophila  By Thomas H. Morgan in 1910 He observed the diff erence found in the sex-chromosome composition of male and female Drosophila. He hypothesized that recessive alleles for white eye is found on the X chromosome and absent in Y chromosome. Males cannot be either homozygous or heterozygous for X-linked genes. The individual is called hemizygous. ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  X-linkage Describes Genes on the Chromosome X X chromosomes exhibit patter ns of inheritance that are very diff erent from those seen with autosomal genes Hemizygous: in males as Y chromosomes lacks homology with X chromosomes  SRY genes (sex-determining region Y) is what makes men ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  X-linkage ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Chromosomal Basis of Sex ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Chromosomal Basis of Sex ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author. ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Sex-Linked Traits controlled by genes on sex chromosome – the X and Y. It shows a patter n of inheritance related to sex X-linked recessive traits are when rare recessive allele is located on X chromosome. This type of rare phenotype is more common on males than females. X-linked dominant traits can occur if the male is aff ected, then he can pass the condition to all his daughters but none to his son. Y-linked or Holandric traits happen to every son of an aff ected male who has the trait. Females are not aff ected since they do not have Y chromosome. ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  X-linked Recessive Traits Transmission ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Human X-linked Traits CONDITION CHARACTERISTICS Color blindness Insensitivity to green light and red light G­6­PD deficiency Deficiency of glucose­6­phosphate dehydrogenase; severe anemic reaction following intake of primaquines in drugs and certain foods, including fava beans Hemophilia A Classic form of clotting deficiency; deficiency of clotting factor VIII Hunter syndrome Mucopolysaccharide storage disease resulting from iduronate sulfatase enzyme deficiency; short stature, claw­- like fingers, coarse facial features, slow mental deterioration, and deafness Lesch– Deficiency of hypoxanthine­guanine phosphoribosyltransferase enzyme (HPRT) leading to motor Nyhan and mental retardation, self­mutilation, and early death Syndrome Duchenne Progressive, life­shortening disorder characterized by muscle degeneration and weakness; sometimes associated with muscular ©Ma. Arra B. Santos,2020. Do not reproduce, modify, mental or exhibit without retardation; the written deficiency of theconsent fromdystrophin protein the author. dystrophy  Sex-Limited Traits autosomal traits that are expressed exclusively in one sex. It means that genes are found both in male and female. But it is only shown in one sex which has the suitable sex hormone for its expression. ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Sex-Influenced Traits autosomal traits that are expressed in both sexes but more frequent in one than in other sex ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Sample 1. Problem Carlo is colorblind but his wife, Valerie, has no history of the disorder in her family. What is the chance that their son will become colorblind? 2. Deafness is an example of X-linked recessive trait. A female who suff ered deafness married a normal man. What is the probability of their sons and daughters to become normal or deaf? 3. If two parent who are both type A and have a normal vision produce a son who is colorblind and is type O, what is the probability that their next child will be female who has normal vision and is type O? ©Ma. Arra B. Santos,2020. Do not reproduce, modify, or exhibit without the written consent from the author.  Reference s Klug, W.S., Cummings, M.R., Spencer, C.A., and Palladino, M.A. 2012. Concepts of Genetics, 10th ed. Pearson Education, Inc. Putz, C. (2008). Preparing for the unthinkable. Retrieved from https: //www.publicaffairs.af.mil/News/Features/Display/Article/143302/prepar ing­for­the­unthinkable/ T h a yo u Thank you for your active participation. See you again next meeting. nk !