Two species of a flowering plant, $P(2 n=20$ chromosomes) and $Q$ ( $2 n=30$ chromosomes) are reciprocally crossed with each other as male or female as shown below to produce F1 seeds. Which of the following seed tissues from both the F1 seeds ( $R$ and $S$ ) will have the same chromosome numbers?

Which of the following plasmid vectors can be used for cloning of a gene, with restriction enzymes BamHI and EcoRI, and ampicillin-containing nutrient agar for selection? [Ori - origin of replication; $\mathrm{Amp}^R$ - gene for ampicillin resistance]
Polymerase chain reaction (PCR) is used to amplify a gene of interest (GOI). If, after 30 cycles of PCR, 1 billion copies of GOI are produced, approximately how many copies of GOI were present at the end of the $20^{\text {th }}$ cycle?