Chromosome – Definition and Function

Chromosome Definition A coiled dna molecule within the cell’s nucleus that carries an individual’s genetic code. Most of the time the chromosome’s structure is loose and indistinguishable. Only in the stage of cell division immediately before the cell divides (the metaphase) does the chromosome draw itself into a compact, rodlike structure the geneticist can see under a microscope after […]

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Telomere – definition

Telomere Definition A structure of noncoding DNA (DNA that does not convey genetic instruction) at each end of a chromosome. Telomeres are essential for chromosome duplication during cell division. They function as handles to pull the chromatids (dividing chromosomes) apart as the mother cell divides into the two new daughter cells. The process of cell division permanently destroys a […]

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DNA – Deoxyribonucleic Acid – Definition and Function

Deoxyribonucleic Acid Definition DNA – the abbreviation for deoxyribonucleic acid. DNA is the molecule of heredity; its sequences form the body’s genetic code. Each cell in the body contains DNA within the chromosomes in its nucleus (except erythrocytes, which do not have nuclei). DNA has a characteristic double-helix structure that resembles a gently twisting ladder. The supporting […]

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Variation (genetic) – Definition

Variation Definition The genetic differences among individuals. There are trillions of possible gene combinations within the human genome. Except for identical twins, no two people share exactly the same genotype (genetic constitution). Though any two individuals may have 99.9 percent of the same DNA sequences and gene pairings, the 0.1 percent of pairings that differ accounts for the endless details that make each […]

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Gamete – Definition

Gamete Definition Gamete is a spermatozoon (sperm cell) or an ovum (egg cell). A gamete, also called a germ cell or sex cell, is a haploid cell; it contains half the complement of chromosomes and genetic material necessary to encode (result in creating) an individual. When two gametes merge they produce a single diploid cell, the zygote, […]

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Zygote – (genetic) Definition

Zygote Definition The fertilized ovum (egg) before it begins to divide. The spermatozoon (sperm cell) and the ovum are each haploid cells (gametes); they contain half the complement of chromosomes necessary to create an organism. When two gametes join they form a single diploid cell that contains the full complement of chromosomes. The zygote then divides as […]

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Gene – Definition and Function

Gene Definition A segment of coding DNA (DNA that instructs the structure and function of cells throughout the body) composed of a specific sequence of nucleotides. The gene is the basic unit of inheritance that directs every facet of the body’s appearance and functions. Genes align along chromosomes in pairs. Each chromosome (autosome) contains thousands of genes, except the sex […]

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Genetic Carrier – Definition

Genetic Carrier Definition Genetic Carrier – an individual whose genotype contains a recessive gene mutation capable of causing a genetic disorder though the individual does not have or show symptoms of the disorder the mutation causes. Typically a genetic carrier has one “good” gene and one mutated gene. A genetic carrier may pass on the mutated gene to his or her […]

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Genetic Code – Definition

Genetic Code Definition Genetic Code – the organizations of nucleotides (DNA sequences) within messenger RNA into triplet structures called trinucleotides or codons. The codons convey the order of amino acids for the structure of the protein for which a particular gene encodes. The process of protein synthesis takes place in the ribosomes in the cell cytoplasm; the messenger RNA carries the […]

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Genome – Definition

Genome Definition Genome – the total genetic material, including coding and noncoding sequences, a cell contains in its chromosomes. Each organism has a unique genome. Scientists define the size of a genome by the number of its base pairs. The human genome contains 3.2 billion base pairs, which make up that comprise about 23,000 genes. See […]

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