Human Genome - Molecular Organization and Gene Content | Molecular Organization Gene Content

Molecular Organization and Gene Content

The human genome is organized into chromosomes (very large linear DNA molecules contained within the cell nucleus) and the small mitochondrial DNA (a comparatively tiny circular DNA molecule). Basic information about these molecules and their gene contents are provided in the following table. (Data source: Ensembl genome browser release 68, July 2012)

Chromosome	Length (cm)	Base pairs	Variations	Confirmed proteins	Putative proteins	Pseudogenes	miRNA	rRNA	snRNA	snoRNA	Misc ncRNA	Links
1	8.5	249,250,621	4,401,091	2,012	31	1,130	134	66	221	145	106	EBI
2	8.3	243,199,373	4,607,702	1,203	50	948	115	40	161	117	93	EBI
3	6.7	198,022,430	3,894,345	1,040	25	719	99	29	138	87	77	EBI
4	6.5	191,154,276	3,673,892	718	39	698	92	24	120	56	71	EBI
5	6.2	180,915,260	3,436,667	849	24	676	83	25	106	61	68	EBI
6	5.8	171,115,067	3,360,890	1,002	39	731	81	26	111	73	67	EBI
7	5.4	159,138,663	3,045,992	866	34	803	90	24	90	76	70	EBI
8	5.0	146,364,022	2,890,692	659	39	568	80	28	86	52	42	EBI
9	4.8	141,213,431	2,581,827	785	15	714	69	19	66	51	55	EBI
10	4.6	135,534,747	2,609,802	745	18	500	64	32	87	56	56	EBI
11	4.6	135,006,516	2,607,254	1,258	48	775	63	24	74	76	53	EBI
12	4.5	133,851,895	2,482,194	1,003	47	582	72	27	106	62	69	EBI
13	3.9	115,169,878	1,814,242	318	8	323	42	16	45	34	36	EBI
14	3.6	107,349,540	1,712,799	601	50	472	92	10	65	97	46	EBI
15	3.5	102,531,392	1,577,346	562	43	473	78	13	63	136	39	EBI
16	3.1	90,354,753	1,747,136	805	65	429	52	32	53	58	34	EBI
17	2.8	81,195,210	1,491,841	1,158	44	300	61	15	80	71	46	EBI
18	2.7	78,077,248	1,448,602	268	20	59	32	13	51	36	25	EBI
19	2.0	59,128,983	1,171,356	1,399	26	181	110	13	29	31	15	EBI
20	2.1	63,025,520	1,206,753	533	13	213	57	15	46	37	34	EBI
21	1.6	48,129,895	787,784	225	8	150	16	5	21	19	8	EBI
22	1.7	51,304,566	745,778	431	21	308	31	5	23	23	23	EBI
X	5.3	155,270,560	2,174,952	815	23	780	128	22	85	64	52	EBI
Y	2.0	59,373,566	286,812	45	8	327	15	7	17	3	2	EBI
mtDNA	0.00054	16,569	929	13	0	0	0	2	0	0	22	EBI

Table 1 (above) summarizes the physical organization and gene content of the human reference genome, with links to the original analysis, as published in the Ensembl database at the European Bioinformatics Institute (EBI) and Wellcome Trust Sanger Institute. Chromosome lengths were calculated by multiplying the number of base pairs by 0.34 nanometers, the distance between base pairs in the DNA double helix. The number of proteins is based on the number of initial precursor mRNA transcripts, and does not include products of alternative pre-mRNA splicing, or modifications to protein structure that occur after translation. The number of variations is a summary of unique DNA sequence changes that have been identified within the sequences analyzed by Ensembl as of July, 2012; that number is expected to increase as further personal genomes are sequenced and examined. In addition to the gene content shown in this table, a large number of non-expressed functional sequences have been identified throughout the human genome (see below). Links open windows to the reference chromosome sequence in the EBI (E), NCBI (N), or UCSC (U) genome browsers.

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