Multifactorial Birth Defects - Glossary

Allele - An allele is an alternative form of a gene loated on a given locus of a chromosome

Gene - Genes are located on the chromosomes and carry the information representing a protein

Chromosomes - Chromosomes are structures made up of DNA and proteins found in the cells of all organisms.The number of chromosomes is species- specific.In humans it is 46.

DNA - The DNA is the basic unit of heredity and is known as the blue print of life.It carries the genetic codes which stores the necessary information for all organisms.

Genotype - Genotype indicates the genetic constitution of an organism

Phenotype - Phenotype refers to the physical appearance of an organism which is controlled by the genotype and the enviornment

Haploid Cell - A cell having only one set of chromosomes,ie.23 numbers in humans

Diploid Cell - Having two sets of chromosomes,46 numbers in humans

Hybrid - An offspring of parents belonging to two different species,example mule which is the offspring of a horse and donkey

Mutation - An inheritable change in the gene or the chromosome

Wild Type - An organism having a normal phenotype

Mutant - An organism harboring a mutation

Trisomy - A condition ,which arises due to the presence of an extra chromosome.An example is Down syndrome, where the individual has an extra chromosome 21

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Mitosis - A division by which the cells reproduce, wherein the resultant cells are the replica of the parent cell.

Meiosis - A special kind of cell division,called reduction division, that takes place in the testes and the ovaries, which produces eggs and sperms that are haploid

Consanguinous marriage - A marriage between two closely related individuals

Euploidy - When an organism has the regular chromosome number,example 46 numbers in humans, it is euploid.

Aneuploidy - When an organism has an abnormal number of chromosomes as in Down Syndrome,it is known as aneuploidy.