A partial DNA sequence for normal hemoglobin and a partial DNA sequence for sickle-cell anemia are shown below. G-G-A-C-T-T-C-T-T Normal hemoglobin G-G-A-C-A-T-C-T-T Sickle-cell anemia Based on the DNA sequences, sickle-cell anemia is caused by A. a sex-linked trait. B. a dominant nucleotide. C. a mutation in the genetic code. D. an incomplete separation of chromosomes.

C. a mutation in the genetic code.

Explanation:

A mutation refers to any change or alteration to the nucleotide sequence of a gene caused by mutagen or mistakes during replication. Depending on the manner of occurrence, mutation can be of different types. In this question, partial DNA sequence for normal hemoglobin is given as: G-G-A-C-T-T-C-T-T while the partial DNA sequence for sickle cell anaemia is given as: G-G-A-C-A-T-C-T-T.

From careful observation of the two two DNA sequences above, it can be realized that a SUBSTITUTION MUTATION from T to A has occurred in the sequence of sickle cell. Note that substitution mutation is the replacement of one base by another in a sequence.

they each offer a fresh glut of resources to the organisms that can arrive and exploit them. as individuals and new species continue to appear, they actively and passively alter the environment. competition for shared resources increases, local abiotic and biotic conditions shift, and the relative abundances of species change accordingly. the process is called ecological succession, and it is one of the earliest and most well-known concepts in ecology.