Your SlideShare is downloading. ×
Chapt 05
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Chapt 05

336
views

Published on

Published in: Technology

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
336
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
10
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. GENERAL BIOLOGY HDL 121 GENETICS MENDELS LAWPREPARED BY:MANEGASCHOOL OF MLTFACULTY OF HEALTH SCIENCE
  • 2. GENETICS MENDELS LAWLearning Outcomes After completing this lecture, students will be able to: (a) Know some terminologies used in genetics (b) Know the Mendel’s law (c) Recall the Mendel’s experiments (d) Describe the hybrid not in accordance to Mendel’s law (e) Explain genetic mapping Slide 2 of 10 Topics © 2010 Cosmopoint
  • 3. GENETICS MENDELS LAWTopic Outlines 1.1. Terminologies 1.2. Mendel’s experiment 1.2.1 Garden pea plant 1.2.2 Monohybrid cross 1.2.3 Dyhybrid Cross 1.2.4 Result & conclusion from the experiment 1.3. Hybrid not in accordance to Mendel’s law 1.3.1 Codominance 1.3.2 Imcomplete dominance 1.3.3 Multiple alleles 1.4. Genetic Mapping Slide 3 of 10 © 2010 Cosmopoint
  • 4. GENETICS MENDELS LAW1.1. TerminologiesIntroduction  Allele: is one member of pair or series of different forms of a gene found on the same locus on homologous chromosome  Gamete: Mature male or female reproductive cell (sperm or ovum) with a haploid set of chromosomes (23 for humans)  Gene: part of DNA molecule found in the chromosome that determines a polypeptide through which an inheritable trait is expressed  Genotype: The genetic constitution of an organism (only one or two genes are considered at one time). Genotype can be homozygous or heterozygous  Dominant allele: A gene is said to be dominant if it expresses its phenotype even in the presence of a recessive gene. 4 Slide 4 of 10
  • 5. GENETICS MENDELS LAW1.1. Terminologies  Phenotype: Observable trait / traits of an individual; arises from interactions between genes, & between genes & the environment. Phenotype determines individual structure, physiology & behaviour that include followings: (a) character that can be observed.eg. Colour (b) character that can be felt. eg. Texture of the hair (c) character that can be tested serologically. eg. Blood group (d) quantitative character that can be measured including intelligence using IQ test. 5 Slide 5 of 10
  • 6. GENETICS MENDELS LAW1.1. Terminologies  Heterozygote: a person possessing two different forms of a particular gene, one inherited from each parent. A heterozygote is also called a carrier (Eg. Pp, Tt)  Homozygous: genotype of an individual that has any of a pair or more of alleles considered are identical eg. AA, aa, AABB, Aabb, aaBB or aabb  Homozygote: diploid individual with two identical alleles at a given locus. 6 Slide 6 of 10
  • 7. GENETICS MENDELS LAW1.2. Mendel’s experimentMendel’s Experiment Crossed garden peas in his monastery garden & analysed the offsprings of these mating Reasons: (a) could be grown easily in large numbers (b) had a short life cycle (c) their pollination could be controlled (d) their reproduction could be manipulated (e) had easily observable characteristics. 7 Slide 7 of 10
  • 8. GENETICS MENDELS LAW1.2.1 Garden pea plant Pea plants Have both male & female reproductive organs Can either self pollinate / cross-pollinate with another plant 8 Slide 8 of 10
  • 9. GENETICS MENDELS LAW1.2.2 Monohybrid crossMonohydrid cross Established pure-breed stock for tall plants & a pure-breed stock for short plants Studied the inheritance of one trait, eg. Plant’s height 9 Slide 9 of 10
  • 10. GENETICS MENDELS LAW1.2.2 Monohybrid crossMonohydrid cross Gene – some DNA molecules that controls Trait – Height (short @ tall) Genotype Homozygote (TT) Heterozygote (Tt) Homozygote (tt) Phenotype – Tall Tall Short 10 Slide 10 of 10
  • 11. GENETICS MENDELS LAW1.2.2 Monohybrid cross Cross-pollinated tall pea plants (TT) with each other Parental generation (Genotype) TT X TT Gamete T T F1 TT Phenotype All tall 11 Slide 11 of 10
  • 12. GENETICS MENDELS LAW1.2.2 Monohybrid cross Cross-pollinated short pea plants (tt) with each other Parental generation (genotype) tt x tt Gamete t t F1 tt Phenotype All short 12 Slide 12 of 10
  • 13. GENETICS MENDELS LAW1.2.2 Monohybrid cross Crossed tall plants with short plants Parental generation (phenotype) tall plant short plant Parental generation (genotype) TT X tt Gamete T t F1 Tt Phenotype All tall plants 13 Slide 13 of 10
  • 14. GENETICS MENDELS LAW1.2.2 Monohybrid cross Allowed plants in the F1 generation to self-pollinate (Self- cross) F1 Tt X Tt Gamete T t T t F2 TT Tt Tt tt Phenotype Tall Tall Tall short Ratio 3 : 1 14 Slide 14 of 10
  • 15. GENETICS MENDELS LAW1.2.2 Monohybrid cross Monohydrid cross Height of plant must have been determined by certain factors Factors occur in pairs, because the offsprings of the F2 generation were both tall & short  F1 generation must contain both tall & shorts factors Two types of factor (a) dominant: tall hides the effect of short (b) recessive: short is recessive to being tall; hidden by the dominant factor 15 Slide 15 of 10
  • 16. GENETICS MENDELS LAW1.2.2 Monohybrid crossMendel’s Laws of Inheritance  Mendel first law of inheritance (The law of segregation) (a) states that from only one parent only one factor (allele) is passes from the parent to the offspring through the gamete. (b) This law can be explained by meiosis. In garden pea that is diploid, a heterozygous yellow seed (Yy) can only transmit one of the alleles to each of its offspring. (Y is a dominant allele for yellow seed coat whereas y is a recessive allele for green seed coat) Parent (P1): Yy (yellow) Gametes: Y y (c) Each gamete can only obtain one allele from the parent because meiosis reduces a diploid gamete mother cell to haploid gamete 16 Slide 16 of 10
  • 17. GENETICS MENDELS LAW1.2.2 Monohybrid cross 17 Slide 17 of 10
  • 18. GENETICS MENDELS LAW1.2.2 Monohybrid cross (d) Mendel used garden pea plants for his experiments. One of the characters was seed colour. He started by crossing two pure breeding strains; eg. One had yellow & the other had green seeds. He then allowed the offsprings (F1 generation of first filial generation) to self-fertilise (selfing) & the results are always the same as follows: P1: YY X yy Phenotype: yellow green Gametes: Y y F1: Yy Phenotypes: yellow 18 Slide 18 of 10
  • 19. GENETICS MENDELS LAW1.2.2 Monohybrid cross (e) The F2 generation (second filial generation obtained by random crossing or selfing of the F1 generation) has a ratio of ¾ of one character and ¼ of the contrasting character, the classical Mendelian ration is 3:1 P2 (selfing): Yy X Yy Phenotype: yellow yellow Gamete: Y y Y y F2: YY Yy Yy yy Phenotype: yellow yellow yellow green Genotypic ratio= ¼ YY : ½ Yy : ¼ yy Phenotypic ratio= ¾ yellow : ¼ green 19 Slide 19 of 10
  • 20. GENETICS MENDELS LAW1.2.2 Monohybrid cross 20 Slide 20 of 10
  • 21. GENETICS MENDELS LAW1.2.2 Monohybrid cross 21 Slide 21 of 10
  • 22. GENETICS MENDELS LAW1.2.2 Monohybrid cross 22 Slide 22 of 10
  • 23. GENETICS MENDELS LAW1.2.3.Dihybrid CrossDihybrid cross (f) He repeated his experiment using several contrasting characteristics, which include tall & dwarf plants, round & wrinkled seeds, inflated & constricted pods, red & white flower. Therefore, he concluded that each plant carried two factors through only one factor was exhibited in F1. When selfed, the F1 would segregate the factors & produced the characteristic ratio. 23 Slide 23 of 10
  • 24. GENETICS MENDELS LAW1.2.3.Dihybrid Cross Mendel second law of inheritance (a) Dihybrid cross (b) Mendel crossed pea plants that differed in 2 contrasting traits (pure breeding plants) (c) He crossed a yellow plant (Y) with round seed (R) with a green plant (y) with wrinkled seed (r) 24 Slide 24 of 10
  • 25. GENETICS MENDELS LAW1.2.3.Dihybrid CrossMendel’s Second Law Law of Independent Assortment During gamete formation, segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair. 25 Slide 25 of 10
  • 26. GENETICS MENDELS LAW1.2.3.Dihybrid Cross F2: 9 yellow, round: 3 yellow, wrinkled: 3 green, round: 1 green, wrinkled (9:3:3:1) 26 Slide 26 of 10
  • 27. GENETICS MENDELS LAW Dihybrid Punnet Square 27 Slide 27 of 10
  • 28. GENETICS MENDELS LAW1.2.3.Dihybrid Cross Mendel confirmed the results of his second law by performing a back cross where he crossed an F1 dihybrid with a recessive parent. 28 Slide 28 of 10
  • 29. GENETICS MENDELS LAW1.2.4 Result & conclusion from the experiment Conclusion on his 2nd experiment (a) During gamete formation, segregation of the alleles of 1 allelic pair is independent of the segregation of the alleles of another allelic pair (b) Genes that are on different chromosomes assort independently 29 Slide 29 of 10
  • 30. GENETICS MENDELS LAW1.2.4 Result & conclusion from the experiment 30 Slide 30 of 10
  • 31. GENETICS MENDELS LAW1.3. Hybrid not in accordance to Mendel’s lawHybrib not accordance to Mendel Law Codominance: when both alleles are fully expressed in the heterozygous form. Eg. Human MN blood typing 2 antigens, M & N, which are determined by a gene with 2 alleles, LM & LN Individual with genotype LM LM will have only M antigen in their RBC LN LN: N antigen only LM LN: M & N antigens 31 Slide 31 of 10
  • 32. GENETICS MENDELS LAW1.3. Hybrid not in accordance to Mendel’s law Cross between LM LM and LN LN P LM LM X LN LN Gametes LM LN F1 LM LN (individual produces both antigens) P LM LN X LM LN Gametes LM LN LM LN F2 LM LM LM LN LM LN LN LN 1 : 2 : 1 32 Slide 32 of 10
  • 33. GENETICS MENDELS LAW1.3.2 Imcomplete dominance Incomplete dominance: a blending of traits, condition when neither allele is dominant over the other Recognised by the heterozygote expressing an intermediate phenotype relative to the parental phenotypes Eg. Red flowered plant is crossed with a white flowered plant, all progeny will be pink. 33 Slide 33 of 10
  • 34. GENETICS MENDELS LAW1.3.2 Imcomplete dominance 34 Slide 34 of 10
  • 35. GENETICS MENDELS LAW1.3.3 Multiple alleles  Multiple allele: genes may exist in more than 2 allelic forms  Eg. ABO blood type  Three different alleles for blood type: (a) IA (Type A) (b) IB (Type B) (c) IO (Type O) 35 Slide 35 of 10
  • 36. GENETICS MENDELS LAW1.3.3 Multiple alleles  Only two of these alleles are presented in an individual  They combine to form genotypes that result from codominance. 36 Slide 36 of 10
  • 37. GENETICS MENDELS LAW1.3.3 Multiple alleles An individual with blood type O mates with an individual with blood type A. P: IO IO X IA IA Gametes: IO IA F1: IA IO (blood type A) Individual with IA IO genotype mate F2: IA IA IA IO IO IO 1 : 2 : 1 Phenotype3 blood group A : 1 blood group O 37 Slide 37 of 10
  • 38. GENETICS MENDELS LAW1.3.3 Multiple alleles 38 Slide 38 of 10
  • 39. GENETICS MENDELS LAW1.4. Genetic MappingGenetic Mapping  = chromosome mapping  Determination of the position of a gene on a chromosome by the means of recombination frequencies  The percentage of recombinant phenotypes can be used to map the chromosomes  Why? – Direct relationship btw frequency of crossing-over & the percentage of recombinant phenotypes 39 Slide 39 of 10
  • 40. GENETICS MENDELS LAW1.4. Genetic Mapping If we want to determine the order of any three genes on a chromosome, we can perform crosses that will provide us the map distance between the three pairs of alleles 40 Slide 40 of 10
  • 41. GENETICS MENDELS LAW1.4. Genetic Mapping 41 Slide 41 of 10
  • 42. GENETICS MENDELS LAW1.1. Hardy-Weinberg LawIntroduction Population genetics is the study of genes in a population i.e. the study of Mendelian inheritance mathematically in a population The population in this context is a Mendelian population, consisting of only one species of diploid organisms, which reproduce sexually within a certain geographical border The study of population is important for the understanding of evolution. Evolution is not the change of one individual but that of a population over a long period of time The study of population genetics reconciles the fact of Darwin theory of evolution with that of Mendelian genetics 42 of 10 42 Slide
  • 43. GENETICS MENDELS LAW1.1. Hardy-Weinberg Law Darwin theory of natural selection is based on variation created by mutation in the form of different genes / alleles. Individuals with certain combination of alleles survive over the years bringing about changes in a population The change in allelic frequency caused by environmental forces is evolution 43 Slide 43 of 10
  • 44. GENETICS MENDELS LAW1.2. Principle For easy calculation, a concept based on one gene locus is treated at one time. So, gene pool is diagrammatically represented as A A a A gene pool of A & a alleles  A a a a A a A a A a A 44 Slide 44 of 10
  • 45. GENETICS MENDELS LAW1.2. Principle1.1. Hardy-Weinberg Law Darwin theory of natural selection is based on variation created by mutation in the form of different genes / alleles. Individuals with certain combination of alleles survive over the years bringing about changes in a population The change in allelic frequency caused by environmental forces is evolution 45 Slide 45 of 10
  • 46. GENETICS MENDELS LAW1.2. Principle Only one gene or locus is considered. That locus consists of dominant & recessive alleles, i.e. A & a alleles The frequencies of alleles A & a depend on the genotypic frequencies of AA, Aa & aa. Hence, if the frequency of AA is very high, the frequency of A would be high too. From the frequencies of the alleles, the frequencies of the genotypes of the next generation can be calculated if we assumed that random fertilisation of the gametes occurs. 46 Slide 46 of 10
  • 47. GENETICS MENDELS LAW1.2. PrincipleConcept of a Gene Pool A gene pool is an aggregate of genes/gametes of a Mendelian population from which the next generation is produced It can be considered as the total genetic information possessed by reproductive members in a population of sexually reproducing organisms. Genes in the pool have dynamic relationships with one another & with the environment around where the organisms live Environmental factors such as selection can alter allelic frequencies & cause evolutionary changes in the population 47 Slide 47 of 10
  • 48. GENETICS MENDELS LAW1.2. PrincipleHardy-Weinberg Law  States that after one generation of random mating, a population will become in equilibrium  i.e. the allelic & genotypic frequencies will not change from one generation to the other  However, equilibrium is only achieved depending on conditions / assumptions as follows: (a) the population must be large (b) the mating must be random or panmitic (c) there must not be any selection (d) there must not be any migration (e) there must not be any mutation (f) meiosis must be normal 48 Slide 48 of 10
  • 49. GENETICS MENDELS LAW1.2. PrincipleUses of the law / its formula To study the changes of gene frequencies in a wild population so that the direction & rate of evolution can be determined. To study the changes of gene frequencies in an artificial population such as that of a herd of cattle / a plantation of crop. To plan for breeding programme so that a large population of animals or plants can be manipulated to produce more quantitatively and/or qualitatively 49 Slide 49 of 10
  • 50. GENETICS MENDELS LAW Slide 50 of 10 Topics

×