Human Genetic Disorders

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Genetic Disorder Noun

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[juh-net-ik dis-or-der]

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Genetic Disorder

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A disease or condition caused by an abnormality in an individual's DNA, such as a gene mutation or chromosomal error.

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Example: This image shows how a change (mutation) in a gene's DNA sequence can cause the body to produce an abnormal protein, leading to a genetic disorder.

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Gene Noun

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[jeen]

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Gene

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A specific segment of DNA that contains the instructions for building a protein or functional RNA molecule, influencing traits.

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Example: This diagram shows that a gene is a specific section of a long DNA molecule, which is tightly coiled into a chromosome found inside a cell's nucleus.

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Chromosome Noun

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[kroh-muh-sohm]

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Chromosome

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A thread-like structure of tightly coiled DNA and proteins found within the nucleus, carrying an organism's genetic information.

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Example: This diagram shows that a chromosome is a structure found inside a cell's nucleus and is made of tightly coiled DNA.

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Allele Noun

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[uh-leel]

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Allele

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One of two or more alternative forms of a gene that arise by mutation and occupy the same position on a chromosome.

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Example: This image shows that alleles are different versions of a gene (like 'A' and 'a') located on corresponding positions on homologous chromosomes.

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Genotype Noun

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[jee-noh-tipe]

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Genotype

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The specific genetic makeup of an organism, representing the combination of alleles it possesses for a particular gene or genes.

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Example: This image shows that a genotype is the specific combination of alleles (gene versions, like B and b) an individual has for a particular gene.

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Phenotype Noun

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[fee-noh-tipe]

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Phenotype

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The set of observable physical or biochemical characteristics of an individual, resulting from its genotype and environmental interactions.

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Example: This image shows that an organism's genetic code (genotype), represented by DNA, determines its observable traits (phenotype), represented by the person.

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Meiosis Noun

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[my-oh-sis]

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Meiosis

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A type of cell division that reduces chromosome numbers by half, creating four unique gamete cells for sexual reproduction.

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Example: This diagram shows meiosis, a two-part cell division process that creates four unique haploid cells, each with half the number of chromosomes.

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Nondisjunction Noun

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[non-dis-jungk-shun]

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Nondisjunction

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The failure of homologous chromosomes or sister chromatids to separate properly during meiosis, resulting in abnormal chromosome numbers.

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Example: This diagram shows nondisjunction, where a pair of homologous chromosomes fails to separate during Meiosis I, resulting in gametes with either an extra or a missing chromosome.

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Gamete Noun

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[gam-eet]

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Gamete

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A mature reproductive cell, such as a sperm or egg, that contains half the number of chromosomes as a somatic cell.

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Example: This diagram shows the two types of human gametes, the sperm and egg. It explains they are haploid (n) and combine to form a diploid (2n) fertilized egg.

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Trisomy Noun

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[try-soh-mee]

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Trisomy

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A chromosomal condition characterized by the presence of an extra, third copy of a chromosome instead of the usual pair.

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Example: This karyotype shows all human chromosomes, highlighting that in Trisomy 21 (Down syndrome), there is an extra copy of chromosome 21, making three instead of the usual pair.