Similar organisms generally have similar genome sizes. Given
this, would two species of yeast have the same number of genes
and chromosomes? Edit: Fixed with thanks to @daniel-standage
This question appears to start from the premise that different
species of yeast are closely related, but they aren't.
Saccharomyces cerevisae and Schizosaccharomyces pombe, both
Ascomycetes, are thought to have diverged at least 300 million
years ago (c.f. the mammalian divergence from other vertebrates
was about 200 million years ago). S. cerevisiae has a genome
size of 12.1 Mb, with 5821 protein coding genes (plus another
786 dubious ORFs) spread over 16 chromosomes. S. pombe has a
genome size of 12.6 Mb with 5124 protein coding genes on just 3
chromosomes. Filamentous fungi have larger genomes and gene
numbers. From memory, Aspergillus nidulans has 8 chromosomes and
over 9,000 protein coding genes. So, the similarity in gene
numbers in the two yeasts probably reflects their broadly
similar lifestyles.