DNA, Chromosomes and Genes

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Created by
Sakshi H

Cards (19)

  • Total length of DNA in a human cell is around 2 metres
  • DNA is packaged into chromosomes to fit into the nucleus of a cell
  • Chromosomes are long, thin, threadlike structures containing a very long DNA molecule tightly coiled around proteins called Histones
  • Humans have 46 chromosomes in the nucleus of most cells: 23 chromosomes from the father and 23 chromosomes from the mother
  • Gametes (eggs or sperm) have only 23 chromosomes
  • Chromosomes come in different sizes due to the different number of genes each contains
  • There are two sex chromosomes (X or Y) that determine whether an individual is male or female:
    • Females have XX chromosomes
    • Males have XY chromosomes
  • Autosomes are the other 44 chromosomes that are not sex chromosomes, grouped into 22 pairs
  • Homologous chromosomes in each pair of autosomes are the same length and have centromeres in the same position
  • Genes are sections of DNA arranged along chromosomes, with chromosomes having 200 to 2000 genes
  • Individuals have 2 copies of each gene, one from each parent
  • Genes for particular characteristics are at the same location on homologous chromosomes, but the versions of the genes may be different
  • Different organisms have different numbers of chromosomes:
    • Kangaroo has 16 chromosomes
    • Eucalyptus trees have 22 chromosomes
  • DNA is also found in mitochondria (organelles that produce energy) and in plants, DNA is found in chloroplasts (organelles for photosynthesis)
  • Proteins create structures and perform actions needed for cells to survive, grow, and function
  • Proteins may be structural (e.g. Collagen, Keratin), enzymes (e.g. Lactase), or regulatory (e.g. Growth hormone, Insulin)
  • Genes are responsible for an organism's characteristics and traits, coding for specific proteins
  • The order of bases (A-T or C-G) along the DNA strand is the genetic code, read in 3 bases at a time to code for one amino acid
  • Unique characteristics of organisms are determined by their genes, with different versions of genes found in different organisms