Prokaryote And Extrachromosomal Genetics 1

Question 1

Describe the mitochondrial genome

Answer 1

Mitochondria has its own genome which is required for energy production
It is circular DNA

Question 2

Describe the chloroplast genome

Answer 2

It is circular and encodes genes required for photosynthesis and pigment production
It is inherited maternally

Question 3

Why are traits encoded by mitochondrial genomes only inherited maternally ?

Answer 3

Both sperm and eggs contain mitochondria, but only the sperm nucleus and NOT sperm mitochondria are transferred into the egg cells

Question 4

What is homoplasmy ?

Answer 4

All copies of DNA within an organelle are identical
So can result in normal function or no function

Question 5

What is heteroplasmy ?

Answer 5

A mixture of normal and mutant organelle genomes
Can cause impaired function

Question 6

Describe homo and heteroplasmy in chloroplast mutations

Answer 6

Can cause variation in colour
White tissue= homoplasmic non-functional chloroplasts
Green tissue= homoplasmic functional chloroplasts
Yellow tissue= heteroplasmic mix of chloroplasts

Question 7

How is 3 parents IVF used to treat mitochondria diseases ?

Answer 7

1. Nuclear DNA taken from mums egg that has defective mitochondria
2. It is inserted into egg donor that has healthy mitochondria but its own nuclear DNA removed
3. Dads sperm nucleus is added into egg donor and fertilised and implanted into mum

Question 8

Why do mitochondria and chloroplasts have genomes ?

Answer 8

They were originally bacteria - Cyanobacteria and aerobic bacterium

Question 9

Describe bacterial infections that may be considered extra chromosomal

Answer 9

Wolbachia
It alters reproduction and is inherited maternally
They are not part of the hosts nuclear DNA, but are inherited through the cytoplasm, acting similarly to organelles

Question 10

Why may prions be seen as extra chromosomal ?

Answer 10

They are protein based elements of inheritance that are not directly encoded by chromosomal changes