Male stickleback fish develop red colour on their ventral side in the breeding season and maintain territories. 

When a conspecific male intruder enters their territory, resident males perform an aggressive display. 

The ethologist Niko Tinbergen presented models of different shapes to territorial male stickleback fish. He found that models of any shape elicited aggressive displays, provided the ventral part of the models was coloured red.

TLS Online TPP Program

#Id: 6108

#Unit 3. Fundamental Processes

In ames test reversal mutants are formed by same mutagen which caused forward mutation.

A more potent mutagen translates

into a greater number of revertant colonies

TLS Online TPP Program

#Id: 6109

#Unit 3. Fundamental Processes

Some chemicals that cause cancers are not mutagenic to begin with, but rather are converted into mutagens by the liver, which metabolizes foreign substances. 

TLS Online TPP Program

#Id: 6110

#Unit 3. Fundamental Processes

There are 3 cellular ways to treat mutations on DNA

Repair- Most common

Reversal- Most expensive and rare

Bypass – Last resort and carry mutation without correction

TLS Online TPP Program

#Id: 6111

#Unit 3. Fundamental Processes

Genes whose products are involved in controlling the fidelity of DNA synthesis during either replication or repair may be identified by mutations that have a mutator phenotype called as mut system of repair or MMR

TLS Online TPP Program

#Id: 6112

#Unit 3. Fundamental Processes

Mismatch Repair removes errors that escape Proofreading

TLS Online TPP Program

#Id: 6113

#Unit 3. Fundamental Processes

In Escherichia coli, MutS scans the DNA, recognizing mismatches from the distortion they cause in the DNA backbone. 

MutS has an ATPase activity that is required for mismatch repair and recruits MutL, a second protein component of the repair system. MutL, in turn, activates MutH, an enzyme that causes an incision or nick on one strand near the site of the mismatch. Nicking is followed by the action of a specific helicase (UvrD) helicase unwinds the DNA, starting from the incision and moving in the direction of the site of the mismatch, and the filled in by DNA polymerase III