GENETIC VARIATION ESSAY. Describe how point mutations, frame-shift mutations and meiosis contribute to genetic variation. Synthesis : 3 Content : 17 NOTE: NO marks will be awarded for answers in the form of flow charts or diagrams. GENE MUTATIONS - Errors /mistakes/changes may occur during transcription / DNA replication - POINT MUTATIONS: replacing/substituting one base of a codon with another - Small change that may possibly result in one amino acid changing in a protein - FRAME-SHIFT MUTATIONS: addition/deletion of one or more bases of a codon - Resulting in changing the order/sequence of all the bases of the codons - Resulting in forming a different protein with different functions - Lead to different phenotypes MEIOSIS CROSSING OVER - Homologous chromosomes /bivalents pair up - Each chromosome has 2 chromatids - Non-sister chromatids overlap/cross over - Points at which crossing-over takes place are referred to as chiasmata - Genetic material is exchanged between non-sister chromatids - After the process of crossing -over chromosomes have alleles from its homologous partner -This means that each gamete formed will have a mix of alleles from both parents - Brings about variation in the gametes formed and also the offspring RANDOM ARRANGEMENT OF CHROMOSOMES AT THE EQUATOR - Each pair of homologous chromosomes may line up either way up on the equator of the spindle - Independently of what the other pairs are doing -This means that gametes will have differing number/mix of both parental chromosomes ESSAY ASSESSMENT (SYNTHESIS) 1 mark = RELEVANCE - All information provided is relevant to the topic 1 mark = LOGICAL SEQUENCE - Ideas are arranged in a logical/cause-effect sequence 1 mark = COMPREHENSION - All aspects required by the essay have been sufficiently addressed LIFE SCIENCE ACADEMICS – 2014
Posted on: Thu, 16 Oct 2014 14:56:05 +0000
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