Scientific Officer-Plant Breeding-Practice-2

Prepare for the SPSC Scientific Officer – Plant Breeding examination through this 20-question practice test. The test develops understanding of chromosome linkage, mutation breeding, selection methods, combining ability, genetic inheritance, experimental designs, seed quality and plant biotechnology. Each question includes a correct answer and an explanatory note to help candidates understand important concepts, assess their preparation and identify areas requiring further study.

Practice questions

What is the expected effect of close physical linkage between two genes on their recombination frequency?
- It generally decreases recombination frequency
- It always increases recombination frequency
- It makes independent assortment more frequent
- It prevents chromosome replication
What is the maximum observable recombination frequency between two genes in a conventional linkage analysis?
- 10%
- 25%
- 50%
- 100%
Which of the following is commonly used as a chemical mutagen in plant mutation breeding?
- Ethyl methanesulfonate (EMS)
- Sodium chloride
- Calcium carbonate
- Potassium nitrate
Why are M2 generation plants particularly important in many mutation-breeding programmes?
- Recessive mutations may become detectable in this generation
- All plants become genetically identical
- Chromosome numbers always double
- Environmental variation disappears
What is the defining feature of mass selection in plant breeding?
- Selecting several superior plants based mainly on their phenotype and bulking their seeds
- Crossing every selected plant with a single tester
- Evaluating only molecular markers without field observation
- Producing chromosome-doubled plants through tissue culture
What is the principal purpose of diallel crossing in plant breeding?
- To evaluate crosses among a selected set of parents
- To measure soil fertility in different locations
- To determine seed moisture content
- To estimate crop water requirements
In a line × tester mating design, what is the basic procedure?
- Crossing selected lines with selected testers
- Crossing each plant only with itself
- Growing varieties without any planned crosses
- Crossing unrelated species without evaluating progeny
In combining ability analysis, general combining ability is mainly associated with which type of genetic effects?
- Additive genetic effects
- Temporary environmental effects
- Soil fertility differences
- Random measurement errors
What is a characteristic feature of cytoplasmic inheritance in plants?
- Traits may be transmitted through the maternal parent
- Traits are always controlled by genes on the Y chromosome
- Traits are inherited only through pollen
- Traits are independent of cellular organelles
In a genetic male-sterility system controlled by a recessive nuclear gene, which genotype is normally male sterile?
- MsMs
- Msms
- msms
- MsM
In a simple randomized complete block design (RCBD), what is the main purpose of forming blocks?
- To control variation among groups of experimental units
- To eliminate the need for randomization
- To ensure that every treatment has a different sample size
- To prevent all experimental error
Which experimental design is generally suitable when experimental units are relatively homogeneous and treatments are assigned entirely at random?
- Completely randomized design
- Randomized complete block design
- Latin square design
- Split-plot design
What is the principal function of analysis of variance (ANOVA) in agricultural experiments?
- To compare treatment means by analysing sources of variation
- To calculate only the median of observations
- To identify chromosome locations directly
- To determine seed purity without sampling
Which is the correct sequence of the three basic stages in a conventional PCR cycle?
- Denaturation, annealing and extension
- Extension, staining and centrifugation
- Annealing, filtration and denaturation
- Replication, translation and transcription
What is the biological principle underlying plant tissue culture?
- Cellular totipotency
- Natural selection only
- Independent assortment only
- Competitive exclusion
What is the principal purpose of embryo rescue in plant breeding?
- To recover embryos that may fail to develop normally in the seed
- To increase the water content of mature seeds
- To prevent meiosis in all reproductive cells
- To measure pollen viability in the field
What is a major advantage of doubled-haploid technology in crop improvement?
- Rapid development of completely homozygous lines
- Permanent maintenance of heterozygosity
- Elimination of all genetic variation from a species
- Prevention of chromosome segregation in every generation
What is meant by transgressive segregation in plant breeding?
- Progeny showing trait values beyond the range of both parents
- All progeny having exactly the same phenotype as one parent
- Complete absence of genetic variation in progeny
- Loss of all favourable alleles during crossing
Which seed class is normally produced from breeder seed under a formal seed multiplication system?
- Foundation seed
- Grain seed
- Commercial food seed
- Feed-grade seed
What is the primary purpose of a seed germination test in seed quality assessment?
- To determine the percentage of seeds capable of producing normal seedlings under specified conditions
- To measure the genetic distance between two varieties
- To determine the fertilizer requirement of a crop
- To identify the chromosome number of every seed