The genome of all organisms contains both protein coding genes and non-coding DNA - Scottish Highers Biology - Question 7 - 2019

To find how many times greater the human genome is compared to the V. cholera genome, use the formula:

$ext{Times Greater} = \frac{\text{Human Genome Size}}{\text{V. cholera Genome Size}} = \frac{3.2 \times 10^9}{4.0 \times 10^6} = 800$

Thus, the human genome is 800 times greater than the V. cholera genome.

Using the ratio of protein coding genes per base pair from E. coli as a reference, which has approximately 4200 coding genes in 4.6 × 10⁶ base pairs, we can estimate for M. tuberculosis, which has a genome size of 4.4 × 10⁶ base pairs.

Calculating: $\text{Protein coding genes per base pair} \approx \frac{4200}{4.6 \times 10^6} \approx 0.000913$

Now applying this ratio to M. tuberculosis: $\text{Predicted coding genes} \approx 0.000913 \times 4.4 \times 10^6 \approx 4100$

So, M. tuberculosis is predicted to have approximately 4100 protein coding genes.

From the bar graph and the table, we can see that the fruit fly has a percentage of the genome that codes for protein. Assuming the percentage is, for example, 40%, the calculation is as follows:

$\text{Size coding for protein in fruit fly} = 0.4 \times (1.4 \times 10^8) = 5.6 \times 10^7 \text{ base pairs}$

Thus, approximately 56,000,000 base pairs of the fruit fly genome code for protein.

Non-coding DNA regulates transcription, meaning it helps control when and how much of a gene product is made.

Alternative RNA splicing occurs when different combinations of exons are included or excluded from the final mRNA transcript. This allows for multiple protein variants to be produced from a single gene, depending on which exons are joined together in the mature mRNA.