Discussion
The phenotypic ratio obtained in F2 is 2 : 1 in the progeny of cross due to presence of :
Answer: C
A 2 : 1 ratio is due to a lethal allele.
Crossing two heterozygotes normally gives 1 AA : 2 Aa : 1 aa. If the allele is lethal when homozygous, one class dies before it can be counted, and the survivors appear in a 2 : 1 ratio. The classic case is the yellow coat allele AY in mice (Cuenot): yellow x yellow gives 2 yellow : 1 non-yellow, because AYAY embryos die.
A plain dominant allele gives 3 : 1, a recessive one also 3 : 1, and a co-dominant (or incompletely dominant) one 1 : 2 : 1. Only lethality removes a class and leaves 2 : 1.
No comment is present. Be the first to comment.
Loading…
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development