TLS Online TPP Program

#Question id: 7303


The ‘quartet model’ explains how the protein products of the ABCE-function genes might interact to control floral organ identity. Following statements are based on this model. Which one of them is incorrect?

#SCPH28 | Zoology
  1. There are four combinations of floral MADS-box proteins. SEP proteins may form heterodimers with A (AP1) and B (AP3/ PI) proteins (for petals), B (AP3/PI) and C(AG) proteins (for stamens), and C (AG) protein (for carpels).
  2. All these genes, with the exception of AP2 (and its homologues), are MADS-box genes, a broad family of eukaryotic genes that encode transcription factors containing a highly conserved DNA-binding domain (MADS domain).
  3. The protein quartets are transcription factors and may function by binding to the promoter regions of target genes.
  4. According to the model, one dimer of each tetramer recognize two different sites on the same DNA strand, thus bringing these areas into proximity via DNA-bending.

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TLS Online TPP Program

#Question id: 15637

#SCPH28 | Zoology

You have isolated two mutations in the Lac operon that cause constitutive expression of Lac genes. You designate these mutants Lac1– and Lac2–. Making use of an F' that carries the Lac operon with the LacY gene mutated, you construct strains that you test for both ß-galactosidase activity and Lac permease activity with results shown below.
     
Classify each mutation as dominant or recessive and as cis- or trans-acting, giving the experimental result that allows you to arrive at each conclusion. Finally, deduce what type of Lac mutation best fits the properties of Lac 1– and of Lac 2–.

TLS Online TPP Program

#Question id: 15638

#SCPH01 Biochemistry

You have isolated two mutations that show decreased expression of the Lac operon. However, unlike like the promoter mutations, these mutations don’t respond to the inducer IPTG. These mutations, designated Lac3– and Lac4–, are evaluated for the quantity of ß-galactosidase and permease activity expressed with or without IPTG:
 
Mapping experiments reveal that Lac3– and Lac4– are different short deletions located in the region before the start of the LacZ gene. Given the data shown above suggest which genetic element(s) in addition to part of the promoter has been deleted in each mutant. 

TLS Online TPP Program

#Question id: 15638

#SCPH06 I Botany

You have isolated two mutations that show decreased expression of the Lac operon. However, unlike like the promoter mutations, these mutations don’t respond to the inducer IPTG. These mutations, designated Lac3– and Lac4–, are evaluated for the quantity of ß-galactosidase and permease activity expressed with or without IPTG:
 
Mapping experiments reveal that Lac3– and Lac4– are different short deletions located in the region before the start of the LacZ gene. Given the data shown above suggest which genetic element(s) in addition to part of the promoter has been deleted in each mutant. 

TLS Online TPP Program

#Question id: 15638

#SCPH28 | Zoology

You have isolated two mutations that show decreased expression of the Lac operon. However, unlike like the promoter mutations, these mutations don’t respond to the inducer IPTG. These mutations, designated Lac3– and Lac4–, are evaluated for the quantity of ß-galactosidase and permease activity expressed with or without IPTG:
 
Mapping experiments reveal that Lac3– and Lac4– are different short deletions located in the region before the start of the LacZ gene. Given the data shown above suggest which genetic element(s) in addition to part of the promoter has been deleted in each mutant. 

TLS Online TPP Program

#Question id: 15642

#SCPH05 I Biotechnology

The viscosity of a fluid decreases with increasing stirrer speed. This fluid would be best described as being:

TLS Online TPP Program

#Question id: 15643

#SCPH05 I Biotechnology

The decrease in apparent viscosity of a liquid with increasing shear rate, is known as