Question

bisc161 lab 7 - molecular genetics and mitosis

1. what does a restriction enzyme, like apol, do? (1 pt)
2. gel electrophoresis is used to separate dna fragments based on their (1 pt)

a. size. b. function. c. color. d. chromosomes.

1. before dna is put into the wells of a gel, it undergoes a process called polymerase chain reaction (pcr). what is pcr and why is it necessary to perform before gel electrophoresis? (1 pt)
2. dna samples from a child, mother and two potential fathers were digested with a restriction enzyme. after pcr, the following gel electrophoresis resulted.

which father, if either, should be paying child support? how can you be sure? (0.5 pt)
why would crime scene dna have to match exactly, but not in a paternity case? (0.5 pt)

Explanation:

• Question 2: Restriction enzymes like Apol cut DNA at specific recognition sequences. This is a fundamental concept in molecular biology related to DNA manipulation.
• Question 3: Gel electrophoresis separates DNA fragments based on size. Smaller fragments move faster through the gel matrix.
• Question 4: PCR (Polymerase Chain Reaction) is a technique to amplify (make many copies of) specific DNA sequences. It is necessary before gel electrophoresis when the amount of starting DNA is very small (e.g., in forensic or ancient DNA analysis) so that there is enough DNA to be visualized after separation.
• Question 5:
• Which father?
• In paternity testing, a child inherits half of their DNA from the mother and half from the father. Looking at the gel, we compare the child's DNA bands (after restriction enzyme digestion and PCR) with the mother's and potential fathers'. Male 2 has DNA bands that are complementary to the child's (after accounting for the mother's contribution). For example, if the mother has certain bands, the remaining bands in the child should match the father.
• Crime - scene vs paternity DNA match
• In a crime - scene, DNA is from a single individual (the perpetrator in an ideal case), so it must match exactly. In a paternity case, the child's DNA is a combination (half from mother, half from father), so we are looking for a complementary match (not an exact clone - like match as in a crime - scene where we expect the DNA to be from one individual only).

Answer:

• Question 2: A restriction enzyme like Apol cuts DNA at specific recognition sequences.
• Question 3: a. Size
• Question 4: PCR is a technique to amplify specific DNA sequences. It is necessary before gel electrophoresis when the starting amount of DNA is very low, as it increases the quantity of DNA to a level detectable after gel separation.
• Question 5:
• Which father? Male 2 should be paying child support. By comparing the DNA bands, the child inherits half of its DNA from the mother and the other half (the non - maternal bands) should match the father. Male 2’s bands complement the child’s non - maternal bands.
• Crime - scene vs paternity: In a crime - scene, DNA is from one individual (the suspect), so it must match exactly. In paternity, the child’s DNA is a combination (half from mother, half from father), so we look for a complementary (not exact) match.