Genetics ;genes, chromosomes and crossin over
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Genetics ;genes, chromosomes and crossin over

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Genetics ;genes, chromosomes and crossin over Genetics ;genes, chromosomes and crossin over Presentation Transcript

  • Genetics    Genetics is the branch of biology that deals with the study of heredity and variation. Heredity ; the transmission of characters from parents to offsprings. Variation ;the differences between closely related organisms. Azhar Zeb M.Sc Zoology izhaar99@yahoo.conm
  • CHROMOSOMES AND GENES         CHROMOSOMES are known as hereditary vehicles because they transfer characters from one generation to the next generation. chromosome is an organized structure of DNA and protein that is found in the nucleus of the cells. Chromosomes are in pairs, one from each parent. Genes are carried on the chromosomes. Genes control the characteristics of living Organisms. Before a cell starts dividing, the chromosomes are duplicated. This process produces sister chromatids. sister chromatids joined at the centromere. Azhar Zeb M.Sc Zoology izhaar99@yahoo.conm
  •      Eukaryotic chromosomes exist in four major types based on the position of the centromere with equal arms. Metacentric chromosome;centromere is present at the middle point. Acrocentric;centromere located closer to one endwith unequal arms. Telocentric;centromere located at the end of chromosome. Submetacentric;chromosome having arms of unequal length. Azhar Zeb M.Sc Zoology izhaar99@yahoo.conm
  • Azhar Zeb M.Sc Zoology izhaar99@yahoo.conm
  •     Each species have a constant number of chromosomes e.g humans have 46 chromosomes. Any deletion or addition in this number results in serious disorders like down,s syndrome etc. The process of meiosis is responsible for maintaining a constant number of chromosomes. Homologous chromosomes ;Identical Chromosome which forms pairs during meiosis in diploid organisms. One of maternal origin (inherited from mother) the other of paternal origin (inherited from father). Azhar Zeb M.Sc Zoology izhaar99@yahoo.conm
  •      Genes A gene is a segment of DNA on a chromosome thad codes for a specific protein thus determines a particular trait. Genes are the units of inheritance and are linearly arranged on chromosomes Each gene transfers a particular trait e.g. skin colour from parents to offsprings.. In 1903 walter sutton found that genes and chromosomes behave in a parallel fashion. Morgan work on drosophila confirmed that genes are linearly arranged on chromosomes. Azhar Zeb M.Sc Zoology izhaar99@yahoo.conm
  • Crossing over      Crossing over ;The exchange of segments between homologous chromosomes during the diplotene stage of meiosis. During the early stages of meiosis similar chromosomes forms pairs and exchange parts with one another. This exchange may occur in more than one place. Crossing over produces chromosomes which are different from parental chromosomes. Vast genetic diversity is produced in a population as a result of crossing over. Azhar Zeb M.Sc Zoology izhaar99@yahoo.conm
  • Crossing Over Azhar Zeb M.Sc Zoology izhaar99@yahoo.conm