Major sources of new genetic change Considering classical genetics, in how many fundamental ways can new genetic variation arise within a lineage?

Introduction / Context:
New genetic variation within populations is classically attributed to two fundamental processes. Knowing these categories helps organize mechanisms from meiosis to horizontal gene transfer under broader headings used in genetics and breeding.

Given Data / Assumptions:

• We seek categories, not an exhaustive list of mechanisms.
• Mechanistic examples (crossing over, independent assortment, horizontal gene transfer) can be grouped.

Concept / Approach:
The two fundamental ways are: (1) mutation, which creates novel DNA sequences, and (2) recombination, which reshuffles existing genetic variants into new combinations. Many detailed processes are subtypes of these categories.

Step-by-Step Solution:

Verification / Alternative check:
Population genetics models (e.g., Hardy–Weinberg with mutation and recombination parameters) formalize these as distinct sources of variability.

Why Other Options Are Wrong:

• One way: ignores recombination or mutation respectively.
• Three/four ways: over-counts by splitting sub-mechanisms that still fall under mutation or recombination.
• Unlimited ways: not helpful for core classification.

Common Pitfalls:
Counting selection or migration as “genetic change” mechanisms; they alter frequencies, not the origin of novel sequences or combinations within individuals.

Final Answer:
Two ways