Question

Mitochondria and chloroplasts have small genomes because:

Question 9 options:

	they lack most protein-coding DNA
	over time, much of their DNA has migrated to the host cell nucleus
	their bacterial ancestors had small genomes
	the genes they need to function are shorter than eukaryotic genes

Answer 1

Chloroplasts and mitochondria derive their genes from endosymbiont genes, that code for products regulating their own gene transcription. The genes are transcribed and translated in these organelles. Chloroplast and mitochondria transfer their DNA to the nucleus by endosymbiotic gene transfer. Hence, their genome has decreased in reduced. Endosymbiotic gene transfer is a ubiquitous and continuous process. This influx of organelle DNA has increased nuclear complexity. The nucleus controls the synthesis of proteins from the chloroplast or mitochondria. Both the organelles are thought to originate from bacterial ancestors. However, their genomes are much smaller than the bacteria they originated form.

Right option is over time, much of their DNA has migrated to the host cell nucleus.