SBP 2008 Trial SPM
An ex-champion runner in 800m has two sons. The first son has a body with well develop muscles built very much like his father. He is also a good athlete, who practices every day. The second son is small in build, choosy in his diet, reluctant to exercise and prefers to spend his time indoors sleeping and reading.
Discuss the factors affecting the variation in the two sons. [10 marks]
Answer:
Able to discuss genetic and environment factor affecting variation
Sample answer
Genetic factors
F1: crossing over during prophase 1/meiosis 1
P1:occur between chromatid from a pair of homologous chromosomes
P2:the exchange of parts between chromatid results in new genetic combination.
P3:produced a large number of gametes with different genetic composition.
F2:independent assortment
P4:homologous part of chromosome are arranged randomly on metaphase plate/during metaphase 1
P5:during anaphase 1,each homologous pair of chromosomes separate.
P6:resulting in an independent assortment of maternal and paternal chromosomes into daughter cells
F: Random fertilization
P7; sperms and ovum with a variety of combinations of chromosomes/genetically different are randomly fertilized.
P8:Thus,variation exists between individuals from the same species//zygote produces wll have a variety of diploid combination.
F:Mutation
P10:mutation causes permanent change in the genetic composition/genotype of an organism
Environmental factor
F1: (can cause variation among individuals at same species)by interacting with genetic factor.
P: examples of factor at least 2 type of food/exercise/skill/experience/education/sunlight/climatic
Any 9 from genetic factor And any 1 from environment factors.
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