2. This question requires you to think about the numbers of crossovers during homologous recombination required to achieve the stated outcomes. (a) How many recombination events are required for plasmid F to become an F' carrying a single segment of the bacterial chromosome? (1 mark) Three genes are arranged in the order abcD, mnoP and xyzA. In a transformation experiment, the DNA is made from a donor prototrophic strain and used to transform a triple mutant recipient strain. (b) How many crossovers would be required to generate a stable strain from this transformation experiment that is phenotypically Abc+ Mno- Xyz+ (1 mark) (c) Illustrate your answer to 2b) using a simple diagram to show the crossovers involved (2 marks) In a second transformation experiment, the DNA is made from a triple mutant donor strain and used to transform a prototrophic recipient strain. (d) How many crossovers would be required from this transformation experiment to generate a stable strain that is phenotypically Abc+ Mno- Xyz+ (1 mark) (e) Illustrate your answer to 2d) using a simple diagram to show the crossovers involved (2 marks)
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Step 1: (a) One recombination event is required for a plasmid F to become an F' carrying a single chromosomal segment. Show more…
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Three genes are arranged in the order abc, mno, and xyz. In a transformation experiment, the DNA is made from a prototrophic strain and used to transform a triple mutant. How many crossovers would be required to generate a stable strain that is phenotypically abc+ mno- xyz+? Also, illustrate the answer using a simple diagram to show the crossovers involved.
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3) (10.5 point Question) There are four main types of chromosomal mutations: deletions, duplications, inversions, and translocations. A) (2 point) Which two types of mutation are the least detrimental to an individual and why are they less detrimental? B) (1 point) Which two mutations result in a reduction in fertility? C) (1.5 points) Considering your answer to part B): There are different reasons for the reduction in fertility for the two types of mutation. Briefly, explain the differences in 3 sentences or less. D) (4 points) Dicentric chromosomes are the products of recombination. Draw a cartoon to indicate how the recombination event can result in this structure. Your drawing should illustrate the crossing over due to recombination, sister chromatids, centromeres and genetic loci A, B, C, D, E, F, G, H on one chromosome, and a, b, c, d, e, f, g, h on the homologous chromosome. The centromere is known to be between C and D. You need to decide how the two homologous chromosomes will differ, with respect to gene order, to allow the dicentric chromosome to form. E) (2 points) Based on your drawing in part D. Consider how this tetrad with a single chiasma will go through meiosis I and meiosis II to form gametes. Draw the four possible chromosomes (centromeres and alleles) that could be in the gametes.
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