What does human genome mean?

[scilearner]

Hello everyone,

 

Ok I read the definitions but I'm confused. What I'm thinking is genome, is the amount of DNA in one diploid cell. So when they say we have 20 000 genes in our body, are they referring amount of DNA in one diploid cell. Also what do they mean when they say human genome is extremely heterogenous. Thank you

Edited January 9, 2011 by scilearner

[cypress]

The genome sequence of sexually reproducing organisms is generally considered to be one set of autosome and one of each sex chromosome, however the genome of an individual human organism is one set of the diploid chromosomes, thus 23 chromosomes for a human.

 

When a genome is considered heterogeneous, it generally means that that there is a great deal of variation in percentage of guanine-cytosine content of the base pairs as one traverses the DNA sequence.

[scilearner]

The genome sequence of sexually reproducing organisms is generally considered to be one set of autosome and one of each sex chromosome, however the genome of an individual human organism is one set of the diploid chromosomes, thus 23 chromosomes for a human.

 

When a genome is considered heterogeneous, it generally means that that there is a great deal of variation in percentage of guanine-cytosine content of the base pairs as one traverses the DNA sequence.

 

Thanks Cypress However I have a little trouble understanding this. When you say human organism is one set of diploid chromomes, doesn't that mean 46 chromosomes. There are 46 chromosomes in a diploid cell right. Also isn't human a sexually reproducing organism? Also when there is a great deal of variation in G-C bonds, what does this mean, I can not picture it? Also if it is 23 chromosomes as you said, are there 2 different genoms for female and male?

Edited January 9, 2011 by scilearner

[cypress]

Thanks Cypress However I have a little trouble understanding this. When you say human organism is one set of diploid chromomes, doesn't that mean 46 chromosomes. There are 46 chromosomes in a diploid cell right. Also isn't human a sexually reproducing organism?

 

Yes, correct on all points. When the genome is sequenced the length, content and counts are based on only one of the diploid pairs.

 

Also when there is a great deal of variation in G-C bonds, what does this mean, I can not picture it?

 

The DNA sequence would be completely homogeneous if it contained only C-G base pairs. It would be nearly homogeneous if it alternated C-G and A-T, as the sequence becomes increasingly irregular and as the C-G density increasingly varies throughout the sequence that is said to be increasingly heterogeneous.

 

Also if it is 23 chromosomes as you said, are there 2 different genoms for female and male?

 

Strictly, yes there are.

[CharonY]

Simply put, the genome of an organism is the total of its genetic information. Thus, the genome sequence of humans consists of the sequences of the 46 chromosomes.

Heterogeneity can refer to a lot of things, including distribution of genes but also as mentioned the GC content. The latter is often indicative of horizontal gene transfer, or mutations and rearrangements of some sorts. Conserved genomic areas which share a long evolutionary history (i.e. derived from the same ancestor) tend to have similar GC contents.