How to solve a genetic problem
All tasks in genetics, as a rule, are reduced to a few basic types: design, to clarify genotype and figuring out how inherited trait. Similar problems can be schematic or illustrated. However, for the successful solution of any problem, including the genetic, it is necessary to read her condition closely. The very same solution is based on a series of specific actions.
You will need:
- notebook; - Textbook on genetics; - a pen.
Instruction how to solve a genetic problem
First, you must determine the type of the proposed task. It will have to figure out how many gene pairs responsible for the development of the proposed signs, what signs are considered. Learn homo- or heterozygous organisms, in this case, are crossed with each other, and whether the inheritance of a particular trait is associated with sex chromosomes.
Find out which of the proposed indication in the study is recessive (weak), and some - the dominant (strong). At the same time in solving genetic problems need to start from the premise that the dominant trait in the offspring will always be manifested phenotypically.
Determine the number and type of gametes (sex cells). It should be borne in mind that gametes can only be haploid. Accordingly, distribution of chromosomes during their division is uniform: each of the gametes will contain only one chromosome of a homologous pair taken. As a result, the offspring receives a "half" of a set of chromosomes from each of their parents.
Make a schematic entry in the notebook conditions genetic problem. At the same dominant characteristics for the homozygous test organism are indicated by a combination of AA, for heterozygous - Aa. Uncertain genotype is designated as A-. Recessive trait recorded as aa combination.
Record phenotypes and genotypes in crosses on the condition of specific tasks. Then, guided by paragraph 3 (definition of types of gametes), record phenotypes and genotypes obtained by crossbreeding offspring.
Analyze the results and assign this numerical ratio. This will be a response to a genetic problem.