ADD The nucleus

Question 1

Why do we have a nucleus in cells?

Answer 1

-separated transcription + translation
-can modify mRNA before translation
-can translate mRNA immediately, later or not at all
-enables alternative splicing (remove introns)

Question 2

What is the first hypothesis as to where the nucleus comes from?

Answer 2

-ancient prokaryotic cell
-membrane moves in around DNA
-results in encapsulation of DNA - formation of primitive nucleus

Question 3

What is found within the nucleus?

Answer 3

-DNA in nucleus packaged into chromosomes
-DNA wrapped around histones for effective packaging

Question 4

In non-dividing cells, how is DNA packed?

Answer 4

Loosely packed forming a tangle of strands - chromatin

Question 5

What technique reveals additional chromatin organisation?

Answer 5

EM staining

Question 6

What is heterochromatin?

Answer 6

Dense staining of interphase DNA

Question 7

What is euchromatin?

Answer 7

Less dense staining of interphase DNA

Question 8

What is the nucleolus?

Answer 8

Highly dense staining of RNA