Question

Please help me with these questions. Thank u very much.

Q1: A DNA sample from an individual is analyzed. The population frequency of one of the STR alleles is 1 in 50, a second STR allele is 1 in 100, and a third STR allele is 1 in 30. What is the combined frequency of these three STR alleles?
a.1 in 150,000
b.1 in 15,000
c.1 in 1,500
d.1 in 180
e.1 in 50

Q2: Which of the following hybridize with the ends of the gene to be amplified?
A)Taq-polymerase
B)deoxyribonucleotides
C)ribonucleotides
D)DNA molecules
E)DNA primers

Q3: Which of the following best describes the complete sequence of steps occurring during every cycle of PCR?
1. The primers hybridize to the target DNA.
2. The mixture is heated to a high temperature to denature the double-stranded target DNA.
3. Fresh DNA polymerase is added.
4.DNA polymerase extends the primers to make a copy of the target DNA.
a.2, 1, 4
b.1, 3, 2, 4
c.3, 4, 1, 2
d.3, 4, 2
e.2, 3, 4

Answer 1

1. Option A is correct.
Frequency of all STRs = 1/50 X 1/100 X 1/30
= 1/150000

2. Option E is correct.
Primers are short oligonucleotide sequences that bind to template strands due to sequence complementarity. They provide free 3'-ends for the strand extension and specificity to the PCR reaction.

3. Option A is correct.
Steps in PCR:
a. Denaturation
b. Annealing
c. Extension
d. Repeat