1 / 15

Introduction

Introduction. Heredity: tendency of an individual to resemble his parents. Variation: the differences between individuals of the same species. Genetics: the study of how characters are transferred or inherited from one generation to the next. Mendel’s Breeding Experiment.

hamlet
Télécharger la présentation

Introduction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introduction Heredity: tendency of an individual to resemble his parents Variation: the differences between individuals of the same species Genetics: the study of how characters are transferred or inherited from one generation to the next

  2. Mendel’s Breeding Experiment Monohybrid Inheritance: The inheritance of just one pair of contrasting characters Cross 2 pure breeding parents with contrasting characters

  3. x purple white pure-breeding parents first filial (F1) generation all purple second filial (F2) generation 705 purple 224 white monohybrid ratio 3:1

  4. Terms • Genotype - the genetic composition • Phenotype - the external appearance • Homozygous (pure-breeding) • with the same alleles in the same character • Heterozygous (hybrid) • with different alleles

  5. Terms • Dominant gene (or character) • which expresses its effect even in heterozygous condition • Recessive gene (or character) • which expresses its effect only in homozygous condition • Pedigree • it shows the inheritance of one or more characters in different generations

  6. Terms • Test cross • cross the organism with dominant character to an organism with homozygous recessive character • to test whether the organism with the dominant character is homozygous or heterozygous • Back cross • cross an organism with one of its parent

  7. Sex Determination • in human : by sex chromosomes • male : XY • female : XX XY XX • chromosomes other than sex chromosomes  somatic chromosomes which control normal body characters

  8. 22 pairs are identical in both sexes (human) • autosomes • The 23rd pair is different in male and female • sex chromosomes

  9. Twins • identical twins • one embryo separates into two and each develops into a new individual • they should have same characters and same sex • non-identical twins • formed from two different zygotes from two separate fertilizations • they usually have different characters • they may have different sexes

  10. Types of Variations • continuous variation • with a continuous range of intermediate values • eg. height, weight, intelligence quotient, heart beat No. of individuals continuous variation human height

  11. Types of Variations • discontinuous variation • the character is clear-cut & not showing intermediates • eg. tongue rolling, ear lobes and colour of corn albinism

  12. Causes of Variations • Meiosis • homologous chromosomes separate independently from each other and pass into a different gamete ( INDEPENDENT ASSORTMENT). As a result, a great variety of gametes are produced • Random Fertilization • since fertilization is a random process, there are many possible different combinations of genes in a zygote

  13. Causes of Variations • Mutation • genetic make-up may suddenly change • sometimes occur naturally • rate may greatly increased if the organism is exposed to radiation, certain chemicals or neutron bombardment • most mutation are harmful • Environmental Factors • cause variation in characters with continuous variation

  14. ~END~

More Related