156. Maize transgenic for bacterial CspA (a RNA chaperone) imparts tolerance to: Answers : 1. Water stress 2.
High temperature stress 3. Salt stress 4. Nutrient stress Question 157 : Assume gene “A” is dominant over
“a” and “B1 ” is codominant over “B2 ” in petunia. A cross is made between two individuals – AAB1B 2 x
aaB1B 2 . Assuming that there is no gene interaction, the progeny will segregate in a phenotypic ratio of:
1. 9:3:3:1
2. 1:1:1:1
3. 1:2:1
4. 3:1
Introduction
Genetic engineering has enabled the development of transgenic crops, such as maize, which can withstand environmental stresses more effectively. One such modification involves the incorporation of CspA (Cold shock protein A) from bacteria, which has been shown to impart tolerance to high-temperature stress. This article explores the role of bacterial CspA in maize stress tolerance and how to calculate phenotypic ratios in genetic crosses, focusing on a scenario involving dominant and codominant traits in petunia.
The Role of Bacterial CspA in Maize Stress Tolerance
CspA is a bacterial RNA chaperone protein known for its role in stabilizing RNA structures under stress conditions. When introduced into maize, transgenic plants expressing CspA exhibit enhanced tolerance to high-temperature stress, allowing them to survive in environments that would normally impair plant growth. CspA helps plants maintain proper RNA function even at elevated temperatures, providing a crucial survival advantage in hot climates.
Key Benefits of CspA in Maize:
-
Increased Heat Tolerance: CspA protects maize from heat-induced damage by stabilizing RNA structures that might otherwise denature under extreme temperatures.
-
Enhanced Protein Stability: The RNA chaperone activity ensures proper folding and function of proteins crucial for cellular processes.
-
Adaptation to Climate Change: With rising global temperatures, transgenic maize with CspA can help ensure food security in areas prone to heat stress.
Answer to Question 156: The maize transgenic for bacterial CspA imparts tolerance to high-temperature stress (Option 2).
Genetic Cross Analysis in Petunia: Understanding Codominance and Dominance
In genetics, analyzing the inheritance patterns of traits involves understanding dominant and codominant alleles. In petunia, a cross between two individuals with different genotypes can be used to predict the offspring’s phenotypic ratio. Let’s consider a cross between AAB1B2 and aaB1B2.
Key Terms:
-
Dominant trait: A dominant allele masks the expression of a recessive allele. In this case, A is dominant over a.
-
Codominant trait: Both alleles are expressed equally in the phenotype. In this case, B1 and B2 are codominant, meaning both alleles are equally expressed in the petunia.
The Cross:
-
Parent 1 (AAB1B2) has a homozygous dominant genotype for gene A and homozygous codominant for gene B.
-
Parent 2 (aaB1B2) has a homozygous recessive genotype for gene A and homozygous codominant for gene B.
Offspring Genotypes:
-
For gene A, the offspring will inherit one A from Parent 1 and one a from Parent 2, resulting in A_ genotype (dominant).
-
For gene B, the offspring will inherit B1 and B2 from both parents, so all offspring will have B1B2 codominant genotype.
Phenotypic Ratio:
-
Gene A: All offspring will show the dominant phenotype (since A is dominant).
-
Gene B: All offspring will display the codominant phenotype, expressing both B1 and B2 alleles.
Thus, the progeny will segregate into a 1:1:1:1 phenotypic ratio, where each phenotype combination is equally likely.
Answer to Question 157: The progeny from the cross will segregate in a 1:1:1:1 phenotypic ratio (Option 2).
Conclusion
Understanding how CspA enhances stress tolerance in maize and learning how to calculate phenotypic ratios in genetic crosses of petunia provides valuable insights into both plant biotechnology and classical genetics. Transgenic maize expressing CspA demonstrates enhanced resilience to high-temperature stress, and the principles of codominance and dominance in petunia genetics help predict offspring phenotypes in a cross. These concepts play a crucial role in both plant breeding and genetic research.
