natsel_neutral – a test for selective neutrality

We employ codon models to test hypotheses regarding the mode of natural selection that has operated on a gene.

Noting that ω (omega) is the ratio of nonsynonymous substitutions to synonymous substitutions, ω=1 is indicative a gene is evolving neutrally.

Warning

I’m setting optimise_motif_probs=False to speed up execution of the examples, not because it’s a good idea!

from cogent3 import get_app

loader = get_app("load_aligned", format_name="fasta", moltype="dna")
aln = loader("data/primate_brca1.fasta")

omega_eq_1 = get_app("natsel_neutral",
    "GNC", tree="data/primate_brca1.tree", optimise_motif_probs=False
)
result = omega_eq_1(aln)
type(result)

cogent3.app.result.hypothesis_result

result

Statistics

LR	df	pvalue
4.5034	1	0.0338

hypothesis	key	lnL	nfp	DLC	unique_Q
null	'GNC-null'	-6715.5260	22	True	True
alt	'GNC-alt'	-6713.2743	23	True	True

result.alt.lf

GNC-alt

log-likelihood = -6713.2743

number of free parameters = 23

Global params

A>C	A>G	A>T	C>A	C>G	C>T	G>A	G>C	G>T	T>A	T>C	omega
0.86	3.54	0.98	1.67	2.20	6.26	7.92	1.23	0.80	1.29	3.07	0.82

Edge params

edge	parent	length
Galago	root	0.52
HowlerMon	root	0.13
Rhesus	edge.3	0.06
Orangutan	edge.2	0.02
Gorilla	edge.1	0.01
Human	edge.0	0.02
Chimpanzee	edge.0	0.01
edge.0	edge.1	0.00
edge.1	edge.2	0.01
edge.2	edge.3	0.04
edge.3	root	0.02

Motif params

AAA	AAC	AAG	AAT	ACA	ACC	ACG	ACT	AGA	AGC	AGG	AGT	ATA
0.06	0.02	0.03	0.06	0.02	0.00	0.00	0.03	0.02	0.03	0.01	0.04	0.02

continuation

ATC	ATG	ATT	CAA	CAC	CAG	CAT	CCA	CCC	CCG	CCT	CGA	CGC
0.01	0.01	0.02	0.02	0.01	0.02	0.02	0.02	0.01	0.00	0.03	0.00	0.00

continuation

CGG	CGT	CTA	CTC	CTG	CTT	GAA	GAC	GAG	GAT	GCA	GCC	GCG
0.00	0.00	0.01	0.01	0.01	0.01	0.08	0.01	0.03	0.03	0.02	0.01	0.00

continuation

GCT	GGA	GGC	GGG	GGT	GTA	GTC	GTG	GTT	TAC	TAT	TCA	TCC
0.01	0.02	0.01	0.01	0.01	0.01	0.01	0.01	0.02	0.00	0.01	0.02	0.01

continuation

TCG	TCT	TGC	TGG	TGT	TTA	TTC	TTG	TTT
0.00	0.03	0.00	0.00	0.02	0.02	0.01	0.01	0.02