Question

 

Fill in the blanks using words from the following list:

Recombination can only occur between two (or more) ______(answer)______ , ______(answer)______ of which is/are ______(answer)______  .

• locuses
• locusts
• loci
• locata
• non-homologues
• sister chromatids
• one
• both
• none
• homozygous
• heterozygous
• heterosis
• monozygous
• polygenic
• pleiotropic
• epistatic
• overdominant

Answer 1

Recombination can occur only between two (or more) LOCI, BOTH of which are HETEROZYGOUS.

Explanation :

Recombination is the process that leads to formation of non parental types in the offsprings with respect to genotype. This change in genotype is attained by exchange of chromosome segments. The exchanged segment and unexchanged segments should have atleast one gene each. The space occupied by a gene in a chromosome is called locus. Locus is also used synonymously to gene in many contexts. Loci is the plural form of Locus. For recombination to be expressed in the genotype, atleast two loci should be heterozygous in nature. (An example is attached along with this answer). If all the loci are homozygous, although exchange of segments takes place, it will not produce changes in genotype and hence no recombination. In cases where all the loci are heterozygous, here also, recombination takes place. If only one of the loci is heterozygous, non parental types are not formed and hence, no recombination.

Heterozygous means the loci has two different alleles of the same gene.