Summary
The two alleles for a trait separate during gamete formation so each gamete carries only one.
In depth
Each organism has two copies of each factor, which separate during gamete formation so each gamete gets one. Fertilisation brings the pair back together. This corresponds to separation of homologues in meiosis I.
The law explains a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio in a monohybrid F2.
The law applies because homologous chromosomes separate in anaphase I of meiosis, so each gamete receives one allele of each gene. Equal gamete production follows, and random fertilisation gives the classic 1:2:1 genotype and 3:1 phenotype ratio from a heterozygote cross.
Exceptions include meiotic drive, where some alleles are over-transmitted (the t allele in mice, segregation distorters in fruit flies), and nondisjunction. These do not cancel the rule but show it is a statistical pattern based on a physical process.
Example: a heterozygous Tt plant makes 50 percent T gametes and 50 percent t gametes.
Frequently asked questions
What is Law of Segregation?
The two alleles for a trait separate during gamete formation so each gamete carries only one.
Which area of biology covers Law of Segregation, and how advanced is it?
Law of Segregation is one of the 54 topics in Genetics. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Law of Independent Assortment, Test Cross, Incomplete Dominance.
Can you give an example of Law of Segregation?
Tt x Tt gives 1 TT : 2 Tt : 1 tt.
What should I learn before Law of Segregation?
Law of Segregation is a Beginner topic, so no earlier topic is required. Other Beginner topics in Genetics that pair well with it include Heredity, Gene, Allele.
What topics are related to Law of Segregation?
The closest topics to Law of Segregation are Law of Independent Assortment, Test Cross, Incomplete Dominance, Genotype and Phenotype. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Law of Segregation?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Law of Segregation. To practise the whole of Genetics, use the Genetics quiz.
How is Law of Segregation different from Law of Independent Assortment?
Law of Segregation: The two alleles for a trait separate during gamete formation so each gamete carries only one. Law of Independent Assortment: Alleles of different genes are distributed to gametes independently when the genes lie on separate chromosomes. Read both side by side and note what each one explains.
How should I study Law of Segregation step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Law of Independent Assortment and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.