VIDEO: Backcrossing in Biology

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This makes heredity one of the areas of science of biologythat fascinate many people. Because the genetic characteristics of an individual not only determine the appearance, the size and the The tint of the skin, but also whether someone reacts fearfully in life or dares to undertake unfamiliar tasks concerns.

The process of backcrossing in biology

  • Who is with genetics as a branch of biology, so learns a little about the laws that have led to him becoming the person he is.
  • Backcrossing is one of the scientific procedures that were developed from Mendel's laws. Backcrossing is carried out in genetics in order to track down the laws under which genes are passed on through practical evidence.
  • Even if the name backcrossing suggests that, it's not about z. B. to turn a dog into a real wolf again, but the backcrossing process is used to check the purity of the genetic make-up of an individual.
  • A backcross is, so to speak, a test cross, which allows the genotype of an individual to be tested to see whether certain genetic traits were passed on in a pure or mixed manner.
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Backcrossing in practical use

  • Each individual inherits certain characteristics determined by genes, where a gene through which a characteristic is passed on can be dominant or recessive. A dominant gene prevails over a recessive gene and passes on its genetic information.
  • Every gene that transmits a trait does so through two alleles. Two dominant alleles can come together in one gene, two recessive ones or one dominant and one recessive one.
  • The dominant gene "wins", the corresponding genetic makeup is passed on if two dominant alleles are present, but also if a dominant and a recessive gene are paired. Then you can z. B. recognize from the phenotype that the dominant trait was inherited. However, it is not possible to identify which of the above-mentioned gene combinations is behind this result.
  • The inheritance through two dominant alleles is referred to as homozygous or pure-breeding, the trait became through a pairing of Passed on a dominant allele and a recessive allele, this inheritance is called mixed-inheritance or in biology heterozygous.
  • If you want to find out whether the inheritance was pure or mixed, you can definitely determine this by backcrossing.
  • One only needs to cross the individual to be examined with another individual who is known to do so the trait in question is inherited recessive, i.e. the corresponding gene is occupied by two recessive alleles is.
  • So if in a plant allele A is dominant and produces red flowers and allele b is recessive and white If flowers are inherited, a red flower may have been produced by a gene that carries the alleles AA or Ab is.
  • If this plant is now crossed with a plant in which this gene is occupied by the bb alleles, only very specific descendants can be identified Combinations result: If the plant is homozygous, its AA alleles mix with the bb alleles to form Ab alleles, so the descendants all turn red bloom. If it is mixed, its Ab alleles can mix with the bb alleles to form Ab alleles or bb alleles, so around half of the next generation will bloom red, the other half white.
  • If the red flowering plant was pure breeding, 100% red flowering offspring will be found in the next generation. In the event that the red-flowering plant was mixed, you will get 50% red-flowering and 50% white-flowering pea plants in the next generation.


It is different only with an intermediate inheritance, here not always an allele prevails, but all alleles influence the expression of the inherited trait. So here there is a mixed characteristic expression, the internal design of which unfortunately cannot be explored by such a clearly transparent process as backcrossing.

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