What makes up the protein component of a nucleosome core?
a. histone h1 protein
b. two tetramers of histone proteins
c. one tetramer of histone proteins
d. eight different histone proteins

The correct answer is b. Two tetramers of histone proteins.

Explanation:

Nucleosomes are made of eight histones, that can be divided into two tetramers. The first one is made of H3 and H4 histones, forming a dimer and the second one is made of H2A and H2B histones forming another dimer. Two dimers of each one are then linked, forming tetramers and finally, when these two are formed, they bind so that way they form the octamer.

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:

biology is the study of life. it is the study of living organism.