Genetic Factors and the Interaction Crop Science Colloquium PDF

Colloquium CROP SCIENCE Genetic Factors and the Interaction between Genetics and Environment BARBOSA, MARISSA B. MSc. DEPARTMENT OF PLANT BREEDING AND GENETICS College of Agriculture and Food Science Visayas State University Question: Orga...

Colloquium CROP SCIENCE Genetic Factors and the Interaction between Genetics and Environment BARBOSA, MARISSA B. MSc. DEPARTMENT OF PLANT BREEDING AND GENETICS College of Agriculture and Food Science Visayas State University Question: Organisms that have two the different alleles for a particular trait are said to be: A. purebred B. Homozygous C. Heterozygous D. Dominant  ▪ Genotype - gene combination for a trait (e.g. RR, Rr, rr) ▪ Phenotype - the physical feature/observable traits copyright cmassengale 3 resulting from a genotype (e.g. red, white)  ▪Alleles – alternative version of a gene (like Alleles ‘flavors’ of a trait). ▪ Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. BB or bb); also called pure ▪ Heterozygous genotype - gene combination of one dominant & one recessive allele. (e.g. Bbr); also called hybrid Question 2 Which of the following statements below is true about recessive alleles? a. Recessive alleles are randomly expressed b. Recessive alleles can never be expressed. c. Recessive alleles are displayed when there is one recessive allele is present d. Recessive alleles shows up when no dominant allele is present  Question In mango plants, tall is dominant to short. If a homozygous tall mango plant is crossed with a heterozygous plant, what is the probability that the offspring will be short? T t a.100% b.0% c.25% T Tt Tt d.15% e.50% T TT Tt  Question In eggplants, the allele for Purple fruit (P) is dominant to the allele for green fruit (p). A plant with genotype PP is crossed with a plant with genotype Pp. What are the expected genotype percentages in the offspring of this cross? a. 25% homozygous dominant, 50% heterozygous, and 25% homozygous recessive b. 50% homozygous dominant and 50% heterozygous c. 50% homozygous dominant and 50% homozygous recessive d. 100% heterozygous and 0% homozygous  Question 5 In eggplants, the allele for Purple fruit (P) is dominant to the allele for green fruit (p). A plant with genotype PP is crossed with a plant with genotype Pp. What are the expected genotype percentages in the offspring of this cross? b.50% homozygous dominant and 50% heterozygous P p P PP Pp P PP Pp  Question 7 If the phenotypic ratio of a dihybrid cross population with 16,000 individuals is 9:3:3:1, how many individuals have at least one dominant allele? a.3,000 b.9,000 c.15,000 d.1,000 e.6,000 Questions: A red flowered plant (RR) breeds with a White flowered plant (WW). The gene for petal color in these plants expresses incomplete dominance. What percentage of the offspring will have pink (RW) flowers? W W A. 100% B. 0% R RW RW C. 50% D. 25% R RW RW Question 9 In some Gumamela flowers a cross is made between Red (R) and white (W) flowers. The offspring shows speckled flowers (RW) that show both colors. What type of inheritance is this? a. overdominance b. incomplete dominance c. codominance d. complete dominance  INHERITANCE OF PLANT TRAITS Extensions of the law of inheritance alternative to dominance and recessiveness codominance Both traits are dominant, and show up in the offspring's phenotype together. https://biologywise.com/codominance-explained-with-examples Question 9 What is the phenotypic frequency of the offspring when two speckled red/white flower are crossed? a. 25 % red, 50% speckled, 25% white b. 50% red and 50% white c. 25% red, 75% speckled R W d. 25% red, 25% speckled, 50% white R RR RW W RW WW  Question: In which inheritance pattern are heterozygous individuals expresses the dominant allele and completely masks the effect of the recessive allele? a. complete dominance b. incomplete dominance c. over-dominance d. codominance e. multiple alleles  Question: Which of the following statements could be considered as incomplete dominance inheritance? a. When the phenotype of homozygous dominant offspring is the same as the homozygous dominant parent b. When the phenotype of the heterozygous offspring is the same as the homozygous dominant parent c. When the phenotype of the heterozygous offspring is the same as the homozygous recessive parent d. When the phenotype of the heterozygous offspring shows an in between or intermediate appearance to both parents INHERITANCE OF PLANT TRAITS codominance  Question: How are Incomplete Dominance and Co-dominance different than a normal Mendelian cross? a. There is no difference b. The heterozygous genotype has a unique phenotype d. There is no heterozygous genotype e. There is only one phenotype regardless of genotype.  Question: A type of gene interaction when a dominant allele at one locus can mask the expression of both alleles (dominant and recessive) at another locus. a. additive gene action b. recessive epistasis c. dominant epistasis d. epistasis e. complementary gene action  INHERITANCE OF PLANT TRAITS Extensions of the law of inheritance epistasis The interaction of different gene loci, so that one gene locus masks or suppresses the https://www.groupe-esa.com/ expression of another gene locus. The controlling allele is the epistatic allele Recessive epistasis :9:3:4 The masked allele is the Dominant Epistasis : 12:3:1 hypostatic allele  Dominant Epistasis Example: Fruit color in summer squash (Cucurbita pepo) Genotypes and Phenotypes: x WWyy wwYY W-/YY = white White Fruit Yellow Fruit W-/Yy = white F1 AaBb W-/Yy = white White Fruit ww/G- =yellow WY Wy wY wy WY WWYY WWYy WwYY WwYy ww/gg = green Wy WWYy Wwyy WwYy Wwyy F2 wY WwYY WwYy wwYY wwYy Phenotypic ratio = wy WwYy Wwyy wwYy wwyy 12:3:1 If a dominant W allele is present, there will be no expression of any color regardless of whether there is a dominant Y allele present. Dominant allele at the W locus suppresses the expression of any allele at the Y locus W is epistatic to Y or y and give a 12:3:1 ratio Question: Which of the following represent the phenotypic ratio of dominant epistasis? a.12:4:1 b.12:3:1 c.9:3:3:1 d.1:2:1 e.9:3:4  Question: Which of the following statements describes the "Law of independent assortment, except? a. Independent assortment leads to creation of genetic variation b. Independent assortment leads to formation of new combinations of characters c. When an individual inherits two or more characters, the inheritance of one character is dependent on the inheritance of the other. d. genes assort independent of each other when more than 1 pair of characters are present  Law of Independent Assortment Alleles for different La traits are distributed to sex cells (& offspring) independently of one another. YyRr x YyRr YR yR Yy yr YR yR Yy yr Question: In AaBb, the fact that the four gamete possibilities AB, Ab, aB, and ab are produced shows what? A. Law of Segregation B. Law of Independent Assortment C. Law of Inheritance D. Law of Multiple Alleles  Question In which of the following cases heterosis is present? I. F1 yields higher over its inbred parental lines II. F1 flowers and matures early as compared to its parents III. F1 is more sterile than parents IV. F1 has increased homozygosity than parents a. I and IV b. I, III and IV c. I and II d. I, II, and IV e. I, II, III and IV  The Concept of Heterosis also known as hybrid vigor Superiority over parents leads to superiority in adaptation, yield, quality, disease resistance, maturity, and general vigor over its parents Heterosis describes the superior performance of heterozygous hybrid plants over their homozygous parental inbred lines.  Question: For which of the following character negative heterosis is useful? a. Yield per plant b. No. of tillers c. Disease resistance d. Days to maturity Manifestation of Heterosis Increased yield Increased reproductive ability Increased size and general vigour Better quality Earlier flowering and maturity - negative heterosis Greater resistance to diseases and pests Greater adaptability Faster growth rate Question: The reduction of vigor and fertility due to self- pollination a. Isolines b. heterosis c. inbreeding depression d. hybrid vigor Inbreeding Depression The decrease in fitness and vigour due to inbreeding. Inbreeding The mating between individuals related by descent or having common ancestry. (Brother - Sister mating or sib mating). The highest degree of inbreeding is obtained by selfing. fixation of unfavorable recessive genes in F2 However in heterosis the unfavorable recessive genes of one line (parent) are covered by favorable dominant genes of other parent.  Effects of inbreeding 1. Appearance of lethal and sub lethal alleles: - Chlorophyll deficiency, rootless seedlings and other malformations. 2. Reduction in vigour 3. Reduction in reproductive ability - Less seed set, sterility 4. Segregation of population in distinct lines. 5. Increase in homozygosity 6. Reduction in yield.  Question: The following statements are effects/consequences of inbreeding depression except; a. Reduction in heterozygosity b. Reduction in yield c. Increased homozygosity d. Reduction in reproductive ability e. Increased in vigor  Question: Which of the following statements is incorrect about phenotype? a. The degree to which an allele or gene is expressed may depend on environmental factors b. Genotype is the function of phenotype and environmental influence and their interaction c. P=G+E + (GXE) d. The phenotype of an organism is independent on the genetic information it carries & the environment factors were they lived  Question: It is when two different genotypes respond to an environmental variation in different ways. a. Phenotypic expression b. Pleiotropy c. GE interaction d. Environmental variance P=G+E+(GxE) Phenotype = Genotype + Environment + GxE the physical the genetic makeup Factors that appearance of of an organism the factor sustain the responsible for an organism Factors that dictates the growth and the different direction of development responses of organism’s of the various phenotypic growth organism genotypes to and behavior Nurture factor environmental Nature factor variations P=G+E+(GxE) Phenotype = Genotype + Environment + GxE Indica tropical and Stronger slender subtropical tolerance grains (GG) environments under salinity and drought Non- stress (Hossen glutinous (G-) Temperate et.al, 2022) Japonica environments Lesser roundish at higher tolerance grain (gg) latitudes or under drought Glutinous altitudes. and salinity (G+) stress  NATURE VS NUTURE P = G + E + (G x E) Genotype x Environment Interaction when different genotypes respond to environmental variation in different ways some plants are exposed in a more favorable environment Overcoming the difficulty of breeding drought tolerant wheat (Koreis, 2019) Year 1 Year 2 genotype x location genotype x season Is what you see, what you get? genotype x year  GENOTYPE-ENVIRONMENT INTERACTION A norm of reaction is a graph The differential performance of genotypes that shows the relationship in different environments (locations, years, between genes and or seasons) environmental factors when phenotypic differences are continuous. When the norm of reaction is not parallel, there is a gene - environment interaction, indicating that each genotype responds to environmental variation in a different way. Demonstration of GXE Interaction Question: The ability of one genotype to produce more than one phenotype when exposed to different environments a. Plasticity b. Adaptation c. GE Interaction d. Genotypic variance e. Phenotypic variance Plant Plasticity The ability of one genotype to produce more than one phenotype when exposed to different environments Question: In phenotypic plasticity, a phenotype changes in response to: A. The environment B. Other genes C. Preference D. Evolution Question: The observable variation present in a particular character in a population. a. Phenotypic variation b. Dominance variation c. Genotypic variation d. Environmental variation Mechanics The innate tendency of offspring to resemble their parents is called A. Variation B. Heredity Inheritance D. Resemblance Mechanics In rambutan, the stem length may result in a tall (T) or dwarf (t) plant. What proportion of the offspring in the TT x tt cross would be expected to be tall? a.10% b.25% c.50% d.100% Mechanics The use of Punnett square is important in a breeding experiment. The results from a Punnett square can be used to find the ______________ that a certain allele combination will occur in offspring. a. traits b. pedigree c. genes d. probability  Mechanics The following are the reasons why there are two or more different genes acting together to modify a particular trait EXCEPT a. The expression of a trait may rely on the interaction of two or more genes, on the interaction of genes with non-genetic factors, or both. b. There’s only one gene that influence a trait c. The dominance of one allele over another allele may not be complete. d. There could be several alleles for a given locus within the population  Mechanics A form of allelic interaction in which the heterozygote is equal to the homozygote in effects, thus, when the recessive gene in Aa is replaced by a dominant gene there is no effect either positive or negative. a. epistasis b. pleiotropy c. additive gene action d. dominance gene action Mechanics A dominance relationship wherein the heterozygous offspring is phenotypically better to either of the homozygous parents a. incomplete dominance b. complete dominance c. co-dominance d. over dominance Mechanics If a plant with genotype AaBb is self-fertilized, the probability of getting AABB genotype will be (A and B are not linked) A.½ B.¼ C.⅛ D. 1/16 Mechanics The genotypic ratio of a monohybrid cross is A.1:2:1 B. 3:1 C. 2:1:1 D. 9:3:3:1 Mechanics In the Monohybrid cross, when Tall (TT) is crossed with Dwarf (tt) then the F1 generation shows.. a) Tall (TT) b) Dwarf (tt) c) Tall (Tt) d) Dwarf (tT) Mechanics In pea plants, the trait for tall stems is dominant over the trait for short stems. If two heterozygous tall plants are crossed, what percentage of the offspring would be expected to have the same phenotype as the parents? A. 100% B. 75% C. 50% D. 25% Mechanics In snapdragons, Tallness (T) is dominant to dwarfness (t). In a cross between two plants that are heterozygous for this trait, the percent of offspring expected to exhibit dwarfness is A. 100% B. 0% C. 50% D. 25% Mechanics In a genotype for plant height, such as Tt, what does each letter represent? A. One genotype B. One gene C. One allele D. One gamete Question 3 An allele whose trait only shows up when no dominant allele is present. A. homozygous allele B. dominant allele C. recessive allele D. heterozygous allele Question: The following is true about inbreeding depression, except? a. Increased fertility b. It shows a lethal effect c. Increased homozygosity d. decrease in fitness due to inbreeding Question: The physical appearance of a plant with respect to a particular character. a. ideotype b. phenotype c. genotype d. prototype  Question: This genetic bases of heterosis is due to superiority of dominant alleles over recessive alleles and that heterosis is directly proportional to the number of dominant genes contributed by each parent a. Over-dominance hypothesis b. epistasis hypothesis c. Additive gene action d. Dominant hypothesis  Genetic Basis of Heterosis Heterosis due to superiority 1. Dominant hypothesis of dominant alleles over recessive alleles. Heterosis is directly proportional to the number of dominant genes contributed by each parent  2. Overdominance hypothesis The overdominance hypothesis attributes heterosis to the superior fitness of heterozygous genotypes over homozygous genotypes of the parents. the heterozygote (Aa) at one or more loci is superior to either homozygote (AA or aa) Aa > aa or AA