TLS Online TPP Program

#Question id: 3041


Which statement about gram-negative bacteria is correct?

#I Life Science/ Life Sciences Group – I-V
  1.  Penicillins are the best antibiotics to use against them.

  2. They often possess an outer membrane containing toxic lipopolysaccharides.

  3. Their chromosomes are composed of DNA tightly wrapped around large amounts of histone proteins.

  4. Their cell walls are primarily composed of peptidoglycan.

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TLS Online TPP Program

#Question id: 5556

#SCPH01 Biochemistry

Contact of a sea urchin egg with signal molecules on sperm causes the egg to undergo a brief ________.

TLS Online TPP Program

#Question id: 15152

#SCPH01 Biochemistry

In this problem we will explore some of the many ways that mutations in two different genes can interact to produce different Mendelian ratios. Consider a hypothetical insect species that has red eyes. Imagine mutations in two different unlinked genes that can, in certain combinations, block the formation of red eye pigment yielding mutants with white eyes. In principle, there are two different possible arrangements for two biochemical steps responsible for the formation of red eye pigment. The two genes might act in series such that a mutation in either gene would block the formation of red pigment. Alternatively, the two genes could act in parallel such that mutations in both genes would be required to block the formation of red pigment.
Further complexity arises from the possibility that mutations in either gene that lead to a block in enzymatic activity could be either dominant or recessive. If the crosses is made between a wild type insect with red eyes and a true breeding white eyed strain with mutations in both genes. Such considerations yield the Pathways in series with dominant mutations in both genes, determine the phenotype of the F1 progeny and the expected phenotypic ratio of red to white eyed insects in the F2.

TLS Online TPP Program

#Question id: 2119

#SCPH06 I Botany

A sodium-potassium pump:

TLS Online TPP Program

#Question id: 1399

#SCPH05 I Biotechnology

Loss-of-function mutations in which of the following genes typifies colorectal carcinomas?

a. myc              b. K-ras                       c. p53              d. APC

TLS Online TPP Program

#Question id: 846

#SCPH01 Biochemistry

The maintenance of the steady-state collection of active cellular proteins required under a particular set of conditions, called ______.