Questions

Footsteps. 

Yes, as you walk forward, you will leave the footstep behind you.

Parvovirus B19 causes severe anemia because it preferentially infects erythrocyte precursors.

a. Parvovirus B19 binds preferentially to the erythrocyte blood group P antigen on erythroid precursor cells.

Answers B, C, D are incorrect:

b. after entry the single-stranded viral DNA genome is transported to the cell nucleus where the host DNA polymerase synthesizes the complimentary DNA strand.

c. Parvovirus B19 infection can be diagnosed by direct detection of viral DNA not RNA.

d. the fetus of a seropositive mother is protected from infection by maternal circulating antibodies.

A RNA copy of a DNA gene is called as messenger RNA or mRNA. mRna is used in translation because information is translated from one language (nucleotides) into another (amino acids).

Hence, mRNA is used to transfer genetic information by a cell.

Cholesterol is referred as an amphipathic molecule, that it contains its hydrophilic and hydrophobic parts.

Distributed systems work in a network. They can share the network resources,communicate with each other.