Genotype – what is and definition

Genotype Definition Genotype – the contents of an individual’s GENETIC CODE. The genotype directs the structures and functions of the human body. A person’s genotype is to the human body what an architect’s blueprint is to a house: It provides the directions for the construction and operation of the human organism. See also GENOME; KARYOTYPE; PHENOTYPE. Genotype – what […]

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Inheritance Patterns – types, traits and mutations

Inheritance Patterns Definition Inheritance Patterns – the ways in which genotypes pass among individuals and generations. Many inherited traits are either autosomal or Xlinked and either dominant or recessive. Such inheritance patterns reflect statistical calculations assessing the mathematical likelihood of certain traits or mutations passing from one generation to the next. Inheritance patterns consider the genotypes […]

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Nucleotide – definition

Nucleotide Definition Nucleotide – a structural component of DNA and RNA. A DNA nucleotide contains deoxyribose and a nitrogen base of adenine, guanine, thymine, or cytosine, which form pairs called base pairs. An RNA nucleotide contains ribose and a nitrogen base of paired adenine, guanine, uracil, or cytosine. Each DNA or RNA molecule contains thousands of nucleotides. The order […]

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Allele – what is, definition and blood type

Allele Definition Allele – any of the variations of a GENE that may occupy the same position (locus) on a CHROMOSOME. The gene controlling a particular trait or function always occupies the same locus on the same chromosome. Genes occur as pairs, with one gene coming from each parent. The pairing determines how the gene’s traits are expressed in […]

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Replication Error

Replication Error Definition Replication Error – a mistake that occurs when DNA sequences duplicate before cell division. Replication errors are accountable for CHROMOSOMAL DISORDERS such as AUTOSOMAL TRISOMY, in which a GAMETE (also called a sex cell or germ cell) receives two copies of a CHROMOSOME instead of the normal single copy. Gametes, which are haploid cells, each carry one-half the complement of chromosomes […]

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Apoptosis – definition and cell death

Definition of Apoptosis The natural mechanism through which a cell engages in actions that lead to its death, often called programmed cell death or cell suicide. Apoptosis appears linked to SENESCENCE, an inherent limitation on the number of times a cell can divide. Both apoptosis and senescence play significant roles in the aging process. Once the cell […]

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RNA – ribonucleic acid – what is, definition and function

Ribonucleic Acid Definition RNA – the abbreviation for ribonucleic acid. RNA is a single-strand molecule consisting of ribose; a sugar; and nucleotides made up of the nitrogen bases adenine, uracil, guanine, and cytosine. RNA exists in a number of forms, all of which serve as biochemical messengers that carry the instructions of DNA to the ribosomes, […]

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Autosome – definition

Autosome definition Autosome is a CHROMOSOME that appears as a pair in which both chromosomes are the same in either sex, also called a nonsex chromosome. In contrast, the sex chromosomes appear as a pair that is different in males and females. The human GENOME contains 22 autosomes and one pair of sex chromosomes for a total complement of 46 […]

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Senescence – definition

Senescence Definition Senescence is the gradual and progressive slowing of cellular activity, including cell division, that occurs with aging. Cells lose the ability to divide over time, a phenomenon researchers call Hayflick’s limit. The limit relates to the number of times the cell divides. During cell division, fibers of DNA called telomeres attach to the chromatids, facilitating their […]

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Cell Structure and Function

Cell Definition The cell is the basic structural and functional unit of all living organisms. About 100 trillion cells make up one of the most complex of such organisms, the human. Types of Cells in the Human Body There are three basic types of cells in the body: stem cells, germ cells, and somatic cells. […]

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