Human Genome 2

Question 1

How much of the human genome is exonic?

Answer 1

2.9% is exonic

Question 2

What is a gene?

Answer 2

A gene is a union (Exons, introns and regulatory elements) of genomic sequence encoding a coherent set of potentially overlapping functional products (alternative splicing)

Question 3

Describe 3 ways in which genes are found in a sequenced genome

Answer 3

1. Correlating with expression by identifying sequence complementary to:
   - known proteins and mRNAs
2. Detecting putative functional sequence by identifying DNA sequences that are conserved between organisms
3. Ab initio gene prediction
   - this is easier in prokaryotes

Question 4

What does ab initio gene prediction software look for?

Answer 4

• sequences that appear to be exons i.e. consensus splice sites
• putative exons that can be combined to give a large open reading frame
• sequences that show evolutionary conservation
• sequences that show evidence of being transcribed

Question 5

What percentage of human genes show alternative splicing?

Answer 5

20-90% of genes show alternative splicing

Question 6

Each alternative spliced gene produces an average of how many RNAs?

Answer 6

4

Question 7

If we have 20,000 protein coding genes, how many proteins can be encoded if we assume that we have alternative splicing in each gene?

Answer 7

60,000 proteins

Question 8

If genes do not encode proteins what can they encode?

Answer 8

tRNA
rRNA
Small nuclear RNA 
Long non coding RNA 
Micro RNA

Question 9

Define a paralogue

Answer 9

A paralogue is a gene that has arisen as a result of a duplication and encodes a similar but not identical function to the original gene

Question 10

What is an ortholog?

Answer 10

Orthologs are genes that are related by vertical descent from a common ancestor and encode proteins with the same function in different species

Question 11

Genes that share a common ancestor are referred to as what?

Answer 11

Homologs