Question 1

Why type at the locus rather than by phenotype?

Accepted Answer

Because mating behaviour on plates shifts with medium, temperature and strain background, so a phenotypic call can be wrong without looking wrong. Sequence or marker based typing at the locus gives an identity that does not move. Stating the primers or markers used lets another laboratory confirm the same assignment.

Question 2

How should a tester panel be maintained?

Accepted Answer

By re verifying identity at intervals rather than trusting the freezer label, since contamination and mix ups accumulate over years of subculture. Keeping a sealed reference stock separate from the working stock, and typing the working stock periodically, catches drift before it propagates through a crossing programme.

Question 3

Why run crosses in both directions?

Accepted Answer

Because a pairing can fail for reasons unconnected to type, including nuclear background effects and cytoplasmic factors that act asymmetrically. Setting up each pairing with either partner as the receiving strain distinguishes a genuine incompatibility from a one sided failure, and the reciprocal result belongs in the reported data.

Question 4

What must a pheromone response assay report?

Accepted Answer

The peptide source and purity, the concentration range tested, the responding strain background and the readout scored, since responses saturate and background genotype shifts sensitivity considerably. A single concentration produces a number nobody can compare; a dose series with a stated endpoint produces one they can.

Question 5

How many progeny does segregation analysis need?

Accepted Answer

Enough that the expected departure is distinguishable from sampling noise, which usually means calculating the number before the cross rather than genotyping whatever grew. Small progeny sets frequently show apparent distortion that disappears at larger numbers, so reporting the count and the statistical test matters as much as the ratio.

Question 6

How do one locus and two locus systems differ in practice?

Accepted Answer

In a one locus system two individuals either match or they do not, while a two locus arrangement multiplies the number of distinguishable types and greatly raises the chance that two strangers are able to mate. Which system a species uses shapes the tester panel size and the crossing design accordingly.

Microbiology

Microbiology

Research Frontiers in Fungal Mating Type Determination and Sexual Reproduction