How Many Genes Does It Take To Build A Cell

Question 1

How big is an Escherichia coli cell?

Answer 1

2micrometres

Question 2

How big is a Valonia ventricosa cell and what is it nicknamed?

Answer 2

• 10cm
• sailor’s eyeball

Question 3

How big is a blue whale’s dorsal root ganglion?

Answer 3

~25m

Question 4

How big is a human’s dorsal root ganglion?

Answer 4

~2m

Question 5

How long ago to cellular life arise?

Answer 5

~4bn years

Question 6

The more DNA you have, the more genes you have

Answer 6

• Shown on a log-log plot of the total number of annotated proteins submitted to GenBank as a function of genome size
• based on data from NCBI genome reports
• genome size (Mb) on x from 0 to 1000
  Number of genes in y from 0 to 100,000

Question 7

Due to triplet coding, all RNAs must be

Answer 7

3x longer than proteins

Question 8

What is driving the reduction of bacterial genomes?

Answer 8

Reproductive efficiency

Question 9

What causes the breakdown of the linear relationship between genome size and gene number?

Answer 9

Genomes explode

Question 10

What are the core functions of genes?

Answer 10

1. DNA replication
2. RNA synthesis
3. Protein synthesis (mRNA stability)
4. Food hydrolysis

Question 11

How many genes do you need for DNA synthesis?

Answer 11

~30

Question 12

How many genes do you need for RNA synthesis?

Answer 12

~30

Question 13

How many genes do you need for protein synthesis?

Answer 13

~70

Question 14

How many genes do you need for food hydrolysis?

Answer 14

~100

Question 15

So how many genes do you roughly need to make a cell?

Answer 15

~230

Question 16

What is the relationship between core genome size and genome size?

Answer 16

Even the smallest cells have much larger number of genes in their genome, above their core genome

Question 17

Describe the whole genome of Mycoplasma mycoides

Answer 17

• 1,000,000bp of DNA
• 1077 genes

Hutchinson et al, 2016

Question 18

Describe the core genome of Mycoplasma mycoides

Answer 18

• 531,000 bp
• 473 genes
• 230 core
• 100 look similar
• 149 no known function

Hutchinson et al, 2016

Question 19

Answer!

Answer 19

We don’t know yet.