LOCATION OF GENES ON CHROMOSOMES

• Chromosomes


  Structures located in the nucleus of a cell that play a big role in cell division, as some of their parts divide to generate new cells that make up a species
• In humans, a fertilized egg cell called zygote contains a total of 46 chromosomes, 23 of which come from the mother and the other 23 from the father
• Karyotype


  The complete number and appearance of chromosomes in human beings
• Karyotype diagram


  • Shows the total number of chromosomes of a single person and the distinguishing factor between the chromosomal structure of males and females
• Autosomes


  The first 22 chromosome pairs in the nucleus that are identical for all humans
• Sex chromosomes


  The 23rd pair of chromosomes, also known as the X and Y chromosomes, that determine whether a person is biologically male or female
• Ploidy


  The number of chromosome sets that an organism or a species contains
• Haploid


  A single set of 23 chromosomes
• Diploid


  A chromosome set that doubles to 46 chromosomes when sex cells combine to form a zygote
• Polyploidy


  A ploidy that exceeds 2N, such as 3N, 4N, etc.
• Chromatid


  A single strand of a replicated chromosome, often divided into an upper (p arm) and lower (q arm) section
• Centromere


  The middle region of the chromosome where the two chromatids meet
• Kinetochore


  The part contained within the centromere, holding the spindle fibers that extend during a cell division
• Telomeres


  The caps at the two ends of the chromosomes, containing a repetitive DNA sequence that is believed to carry the telomerase, an enzyme that influences the aging process of an individual
• Locus (pl.: loci)


  A specific section along the chromatids in which a particular gene is located
• Gene


  The basic unit of heredity, made up of DNA sequences that often serve as "instructions" for the production of protein molecules
• Each of the 46 chromosomes in humans carry thousands of genetic information, and each human being is said to have about 20 000 to 25 000 genes in total
• Alleles


  Identical pairs of genes that account for the similarity or difference of characteristics that offsprings inherit from their parents