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What are the arguments for the endosymbiotic theory?

There are several facts that could prove that mitochondria and plastids - eukaryotic organella descend from prokaryotic organisms. One of the arguments is that the metioned organella posses their own DNA ...

Answered by Dorota D. • Biology tutor

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Describe how the human body can prevent the entry of organisms that cause disease. Include physical barriers and chemical defences in your answer.

Physical barriers:

skin to prevent entry of organisms into the bloodstream
cilia lining the nasal passages / bronchi to prevent entry to lungs / remove mucus

Answered by Khadija M. • Biology tutor

9745 Views

Which of these DNA mutations is likely to have the greatest effect on the structure of the encoded protein? Justify your answer. •Single base substitution •15 bases base deletion •Insertion of 2 bases

The most serious of these mutations will be the insertion of 2 bases. Becasue the genetic code is read in triplets, a 2 base insetion will alter the reading frame of the code causing a frameshift mutation...

Answered by Emma M. • Biology tutor

22090 Views

Describe the mechanism(s) as to which an enzyme binds to a substrate.

Two models have been proposed. The first being the 'Lock and Key Model' which simply describes the way in which the active site of an enzyme is complementary to the substrate shape, meaning that only the ...

Answered by Nicole B. • Biology tutor

3012 Views