Main Ideas

• Eukaryote genomes vary greatly in size and base sequences.
• This variation is greater between species than within a species.
• Large genomes aren't necessarily "better" or more functional.

Examples

• The human genome is like a vast library, but almost half of it is filled with "junk DNA" called transposons. Imagine a bookshelf with loads of books, but half of them are filled with gibberish. That's what our DNA can be like!

Main Ideas

• Genome size is measured in base pairs.
• There's a huge range in genome sizes, even among closely related species.
• Large genomes can contain a lot of "junk DNA."

Examples

• The Paris japonica, a flowering plant, has the largest known genome, which is 50 times larger than that of humans! Imagine having 50 human-sized closets filled with clothes, but only half of them are wearable. That's what this plant's DNA is like!

Main Ideas

• Two populations of a species will have some differences in base sequences.
• Differences increase if the populations diverge into separate species.
• Some genes change infrequently because they have essential functions, like cytochrome c.

Examples

• The gene for cytochrome c, vital in respiration, is like a classic family recipe. It doesn't change much over generations, because it's essential and works perfectly.