What is a gene? the different forms of a trait a segment of dna that is the basic unit of heredity the appearance or characteristics that are seen in an organism an organism's allele combination

A gene is a segment of DNA that is the basic unit of heredity.

A gene in molecular biology and in genetics indicates the fundamental hereditary unit of living organisms.

The genes correspond to portions of the genome located in precise positions within the DNA sequence and contain the information necessary to ultimately encode molecules that have a function, such as RNA or proteins. During the reproductive phase of the cell the genes are present in the chromosomes, which in human cells are present in 23 pairs of homologous chromosomes, with the sole exception of the gametes, which present a single copy of each chromosome.

A gene is an information unit in a locus of deoxyribonucleic acid (DNA) that encodes a functional product, proteins for example. It is the molecular unit of genetic inheritance, because it stores genetic information and allows transmitting to offspring. The genes are found in the chromosomes, and each occupies a correct position called a locus. The set of genes of a species is called a genome.

the earth’s crust is broken into separate pieces called tectonic plates (fig. 7.14). recall that the crust is the solid, rocky, outer shell of the planet. it is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. both types of crust rest atop solid, upper mantle material. the upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

each tectonic plate is free-floating and can move independently. earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. the term fault is used to describe the boundary between tectonic plates. most of the earthquakes and volcanoes around the pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. other observable results of short-term plate movement include the gradual widening of the great rift lakes in eastern africa and the rising of the himalayan mountain range. the motion of plates can be described in four general patterns:

collision: when two continental plates are shoved together

subduction: when one plate plunges beneath another (fig. 7.15)

spreading: when two plates are pushed apart (fig. 7.15)

transform faulting: when two plates slide past each other (fig. 7.15)

answer; evidence; reverseremand;