It happens when the two groups become sufficiently different and the two can no longer interbreed. A known example of speciation is the London underground mosquito where it formed a new species within the existing genus. There are examples in micro-evolution but not in macro-evolution.
Answer:
The sarcoplasmic reticulum contain calcium ions in skeletal muscles which is involved in muscle contraction.
Explanation:
Sarcoplasmic reticulum is an intracellular system of closed saclike membranes involved in the storage of calcium in skeletal muscle cells. The sarcoplasmic reticulum regulates the concentration of calcium and determine muscle contraction.
Answer: a. express different genes.
Explanation:
The nerve cells is functional for controlling the coordination of the body, respond to the external stimuli, voluntary actions in the body. The muscle cells contract and relax to facilitate the locomotion.
All the somatic cells of a living being have the same genomic make up. However, completely differentiated cells of particular tissue lineages express distinct genes, as required so as to perform specialized functions in the body.
Answer:
The correct answer is b. recognizes foreign DNA sequences that have previously entered the cell and directs the Cas proteins to destroy them.
Explanation:
Clustered regularly interspaced short palindromic repeats (CRISPER) is the sequences of DNA found in the genome of prokaryotes and archaea. These sequences are added at a crisper locus in DNA by bacteria through capturing bacteriophage DNA during infection.
Then this sequence is used to detect a similar sequence of bacteriophage during subsequent infection and destroy them by Cas9 enzyme. Cas 9 enzyme uses a crisper sequence as a template to destroy similar phage DNA.
So the CRISPER Cas system provides an adaptive defense mechanism to bacteria against foreign DNA coming from bacteriophage. Therefore the correct answer is b.
