Question

QUESTION 45

1. Which of the following statement regarding operons is FALSE?

   		A negative regulator of transcription is called a repressor.
   		The cistron region of an operon in the region of DNA that codes for a polypeptide chain.
   		The promoter is a region in the DNA upstream of an operon and the site of transcription initiation.
   		In the lac operon, LacY is a membrane protein that transports lactose into the cell. Once inside the cell, LacZ breaks down the lactose into allolactose.
   		Allolactose serves as an inducer of the lac operon by binding to the LacI repressor and preventing it from associating with the operator region of the lac operon.
   		An operon is a unit of transcription.
   		All of the statements are true.
   		All of the genes in an operon are transcribed simultaneously into a single mRNA molecule.

3 points   

QUESTION 46

1. Which of the following statements is FALSE?

   		Methanogens generate methane as a biproduct of their metabolism.
   		Bubbles that rise from a pond come from methane production by methanogens in the organically rich anaerobic mud at the of the pond.
   		Extreme halophiles avoid the loss of intracellular water (plasmolysis) by concentrating KCl inside of the cell.
   		Cyanobacteria contain precursors to the modern chloroplast giving them photosynthetic capabilities.
   		Since oxygen has a low solubility in high salt concentrations, halophiles synthesize special regions in their cytoplasmic membrane that house bacteriorhodopsin, a light-driven proton pump (works through ATP synthase) that generates sufficient ATP when oxygen is limiting.
   		Halophiles are said to have purple membranes due to the presence of  chloroplasts.
   		Firmicutes bacteria are the first colonizers of the intestines of human newborns.
   		All of the statements are true.

3 points   

QUESTION 47

1. True or False: Environmental factors (such as sunlight, chemicals, nutrient level, etc.) can trigger a lysogenic virus to enter a lytic cycle.

   True

   False

3 points   

QUESTION 48

1. Which of the following are ways that viruses are classified?

   		All are ways in which viruses can be classified.
   		host (plants, animals, bacteria, etc.)
   		presence of absence of an envelope
   		type of nucleic acid (DNA vs RNA)
   		amount of nucleic acid present (single stranded, double stranded, etc)

3 points   

QUESTION 49

1. Which of the following describes the innate immune system?

   		-part of the immune system we develop over time as we are exposed to our environment -includes mechanical components (like the skin), inflammation, compliment system and phagocytosis -involves cells like B cells and T cells
   		-part of the immune system we are born with -includes mechanical components (like the skin), inflammation, compliment system and phagocytosis -involves cells like neutrophils and monocytes
   		-part of the immune system we are born with -includes antibodies and cell-mediated immunity -involves cells like neutrophils and monocytes
   		-part of the immune system we develop over time as we are exposed to our environment -includes mechanical components (like the skin), inflammation, compliment system and phagocytosis -involves cells like neutrophils and monocytes

3 points   

QUESTION 50

1. True or False: During endospore formation, the forespore layers up and gets tough in STAGES IV, V, and VI). A thick murein layer (called the cortex) is laid down between the two membranes, spore coat forms on the very outside +/- a membranous layer called the exosporium.

   True

   False

Answer 1

Ans 45. Last statement is false i e. An operon is a unit of transcription.

Let me explain you a little bit about operon. Operon is complete contiguous unit which includes the structural genes, the operator and the promtor. Operon is coordinately regulated unit of gene expression. Lac operon is negative inducible system which works in the presence of lactose or allolactose ( Lac inducer). Three structural genes ( Z, Y and A) encode three enzymes involved in lactose metabolism. Lactose is broken down into glucose and galactose by beta- galactosidase; and beta-galactosidase permease pumps lactose into cell. Regulator gene encodes a repressor which binds to operator and does not let RNA polymerase bind to promoter and thus stops transcription.

Ans 48. All ways are used for classification.

Ans 49. Innate immune is sytem includes something we are born with. This includes physical and inflammatory barriers to pathogens. This is not adaptive or specialised. It is general for all kinds of pathogens and subsequent infections.