Practice Questions

TLS Online TPP Program

#Question id: 35513

Which of the following statements about the pollen tube during double fertilization are correct?

#XL - R Botany

Pollen tube enters through the micropyle in most angiosperms
It bursts upon entering the embryo sac
It delivers two generative nuclei to the central cell
One of the synergids degenerates to facilitate pollen tube entry

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TLS Online TPP Program

#Question id: 5755

#XL - S Microbiology

A researcher studying bacterial toxin predicts that a lysine within the toxin is important for binding it’s target cell. She used site-directed mutagenesis to change a codon for lysine (AAA) to one for asparagine (AAU). However, the mutant toxin still binds to its target cell just as well as the wild-type toxin bound and appears to have no other changes. This type of mutation is probably

TLS Online TPP Program

#Question id: 5756

#XL - S Microbiology

Type of mutation caused by an addition or deletion of a base in a polypeptide-encoding part of a gene

TLS Online TPP Program

#Question id: 5757

#XL - S Microbiology

A new E. coli mutant was tested for auxotrophy. The mutant grows on:

minimal medium (M) + arginine (A) + proline (P)

M + P + histidine (H)

M + A + H + P

but not on M or on M + A + H. The mutant requires