The human genome consists of approximately 21000 genes which...

The human genome consists of approximately 21,000 genes, which is only slightly more than the genome of the nematode Caenorhabditis elegans, which has 20,100 genes. How can two organisms with similar numbers of genes be so different in overall complexity? All of the listed responses are correct. RNAs that play regulatory roles in humans are not typically present in nematodes. Human genes typically contain multiple exons, which can be spliced together in different ways, leading to the production of many more proteins than the number of proteins in the nematode. Post-translational modifications of proteins are more common in humans than in nematodes. Extensive RNA splicing, which generates more than one polypeptide from a single gene, occurs in humans but is not typically seen in nematodes.

Transcript

00:01 First question, complete genome sequence indicates that a human genome has approximately 20 ,000 coded genes and a small nematode worm c.

00:10 Elegans also has about the same amount of genes.

00:12 How do you think the human genome with about the same number of genes as worms encodes an organism that is enormously more complicated? so this is because the human has more regulatory mechanism.

00:50 So those mechanisms include the let's say gene regulation or an alternative splicing.

01:08 So the idea is that when you have a single gene and a lot of time it can make more than one type of mrna with different length.

01:24 Depends on the region.

01:26 For example, you have axon, intron, and axon.

01:37 Certain cases you can see that what the intron is being cut out, the two axon are being put together.

01:48 Sometimes you only have one axon or in some other cases the entire sequence are retained.

01:57 No intron is being removed.

02:00 So you can see that although you only have one gene, you may have three different mrna and each of them will give you different protein product.

02:15 So you can see although we have the same amount of gene, each gene will give you different protein product which can actually carry out more complicated functions.

02:24 So this is one of the important mechanism.

02:29 And sometimes you also have let's say non -coding rnas that which will have also regulatory functions.

02:46 What is non -coding rnas? so some of the rna will give proteins.

02:53 So this is called the coding rna.

02:56 The non -coding rna doesn't give you any protein product.

03:01 But a lot of time non -coding rnas such as microrna, they actually have important function when they regulate gene expression.

03:12 The microrna let's say, it doesn't produce protein but it regulates gene expression.

03:26 It is able to control the gene expression at different, according to different stimulus.

03:34 So again, the non -coding rna provides extra regulatory mechanism for human.

03:42 So this also makes it a little more complicated.

03:45 So these two are main factor will affect the regulation of gene expression in human and c.

03:53 Elegans.

03:53 So you can see due to the more complicated or advanced regulatory mechanism, although they have the same amount of gene, humans have more advanced regulatory mechanism so that they're able to carry on more, carry out more cellular activity.

04:12 The next question, what sequence information of a gene is lacking in cdna library? the cdna library come from the mature mrna.

04:21 So mature mrna go through the reverse transcription...

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