Question

Gel Electrophoresis of Amplified PCR Samples 9. What is Alu? 10. Why is Alu useful for studying human ancestry? 11. Why do the two possible PCR products from our lab differ in size by 300 base pairs? 12. Explain how gel electrophoresis separates DNA fragments 13. Fill in the table below. For each genotype, write how many DNA bands (fragments) you would expect to see in a gel, along with the size of each (n base pairs) Table 1. Predicted number and size (In b.p.) of DNA bands, according to genotype. Number of DNA bands Size of DNA bands Homozygote (+/+) Heterozygote (+/- Homozygote (-)

Answer 1

9. Alu elements are transposable elements found ubiquitously in the human genome. Its is a juming gene which contains site of Alu restriction endonuclease from its origin in Arthrobactus luteus. These are reptitive elements of about 300bp length and many copies of it is present in the genome as they are self replicating

10. They are used to study population genetics in humans because the sequence is conserved and individuals have different number of these elements dispersed throughout the genome, hey also bring diversity to the human genome. Therefore, Alu insertion brings polymorphism in the humn genome and two individuals can be distinguished based on number and position of Alu elements. So they are called SINE - Short interspersed elements. They are useful for not only human evolution but also primate evolution.

11. 2 samples of DNA differ by 300bp or their mutliples depending on the difference in the number of Alu sequences in the genome. Alu is of length = 300bp. So DNA-PCR products will also show this difference while performing ALU- sequence based PCR. here Alu sequence is the primer used in the PCR.

12. Gel electrophoresis seperates DNA bsed on the Size of a DNA molecule. The shorter the length, the easier it is to move in the gel matrix and longer DNA face more hindrance so this leads to seperation of DNA based on size. DNA fragments are negatively charged, so they move towards the positive electrode and all DNA fragments have the same amount of negative charge per mass, so they seperate on the basis of size.

13. Not enough information provided in the question regarding the genotypes.