The gene density for each organism is shown in the last column of this data tabl

Question

The gene density for each organism is shown in the last column of this data table Organism H. influenzae (bacterium) S. Gene density (genes per Mb) Size of genome (base pairs) Size of Genome (Mb)Number of Genes 1.8 million 12 million 4.6 million 100 million 165 million 120 milliorn 430 million 3.0 billion 2.8 billion 3.1 billion 2.9 billion 12 4.6 100 165 120 430 3000 2800 3100 2900 1800 227 1700 6300 4400 20100 14000 25500 42000 21000 20000 20000 22000 18500 27900 944 525 957 201 85 213 98 7 7 cerevisiae (yeast) E. coli (bacterium) C. elegans (roundworm) D. melanogaster (fruit fly) A. thaliana (mustard plant) O. sativa (rice) sapiens (human) norvegicus (lab rat) P. troglodytes (chimanzee) M. mulatta (macaque) O.anatinus (duck-billed platypus) 1.8 billion P persica (peach) 10 227 million 123 Use the table to identify three statements that are true regarding the genomes of organisms O A genome size of 2 billion base pairs is the same as a genome size of 200 Mb More complex organisms (e.g., vertebrates) generally have larger genome sizes O An organism's number of genes is not a good predictor of its gene density. O Humans have a smaller genome size than yeast. More complex organisms (e.g., vertebrates) generally have lower gene densities than less complex organisms (e.g., bacteria)

Explanation / Answer

1. The first statement is wrong, a genome size of 2 billion base pairs makes 2000 Mb. Simple maths: 1 billion = 1000Mb

2. According to this table, it might hold good, except for one exception which is genome size of chimanzee is slightly larger than humans, but this is not always true. it is the complexity and modernity of genes and complexity of processes and proteins produced that make organism move above in taxa rather than genome size.

3. Organisms number og genes and size of genome both are indicator of gene density. The smaller the size of genome with higher number of genes, more is the gene density. While larger the genome size with fewer genes lesser is the gene density. Moreover, the exact calculation of gene desity can only be done ones we know how much introns or non coding regions exist inside organism's genome.

4. No. this is wrong, humans have a bigger genome than yeast in respect of genome size and number of genes (humans have a genome size of 3 billion and 21000 genes, while yeast have genome size of 12 million with 6300 genes). But yes, the gene denisty for yeast is higher as compared to humans. (for yeast its 535 genes/Mb while for humans its 7 genes/Mb).

5. This is very true, because there is more non coding regions, also called as introns in complex organisms, the exact function of these introns is still to be established. But what is speculated is that they serve as enhancers or inhibitors for various proteins. Which helps in increasing or decreasing there function effectively. Moreover it is also proposed that introns might serve as binding sites for various miRNAs which can quickly and recisely regulate various protein machinaries.

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