3. A cell specialized for reproduction, containing a haploid set of chromosomes, such as sperm or egg . 4. Haploid reproductive cells that combine at fertilization to form the zygote, called sperm (or pollen) in males and eggs in females.

Gametic selection
The  forces acting to cause differential reproductive success of one allele over another in a heterozygote

Gastropod
Meaning "stomach foot," this name refers to the class of mollusks that contains the most species. Gastropods include snails and slugs that are marine, freshwater, and terrestrial.

Gene
The fundamental physics and functional unit of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product (i.e., a protein or RNA molecule).See also : gene expression 2. Units of heredity which control growth, development and function of organis,s. Located on chromosomes, genes carry information from one generation to the next. A gene is comprised of a continuous sequence of DNA necessary to encode a functional protein. Our body has about 50,00 to 100,00 genes, each of which contains the cod for a specific product, typically, a protein such as enzyme. 3. A portion of a chromosome, too small to be seen under a microscope, which encodes a particular function.

Humans are estimated to have approximately 50,000 different genes. Abnormalities of genes can cause various problems, depending on the gene involved and specific changes within that gene. 4. The fundamental unit of heredity; a segment of DNA found at a fixed location on a chromosome that codes for a single polypeptide. 5. A sequence of nucleotides coding for a protein (or, in some cases, part of a protein); a unit of heredity. 6. A hereditary unit that occupies a specific position within the genome; it has one or more specific effects upon the phenotype of the organism; it can mutate to various allelic forms.