Targeting a DNA sequence for editing by the CRISPR‑Cas9 system requires that a protospacer‑adjacent motif (PAM) sequence appear just downstream of the target sequence. For S. pyogenes Cas9 this PAM is the trinucleotide NGG, where N represents any nucleotide. Assuming a fragment of DNA includes equal amounts of A, C, G, and T bases, how many bases apart, on average, would one expect to find the NGG PAM?

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation:

i dont know this but ask your teacher for !

the answer is: reproductively

i think i spelled it wrong lol

anyways hope i

-lavira: )