The Nucleus

What is a nucleus?

The organelle that defines the eukaryotes: a membrane bound compartment containing the genetic material

What are the functions of the nucleus?

• Store genetic information

• Scrutiny and repair of the code

• Replicate genetic code prior to cell division

• Transcribe the genetic code into messenger RNA

• Edit the messages

• Regulate message production

• Assemble ribosomal RNA (rRNA) and ribosomes that read messenger RNA and translate the messages into appropriate proteins

Why does the nucleus have to edit the messages it receives?

So that different proteins can be produced from the same code.

Why does the nucleus have the regulate message production?

So that protein production is controlled and co-ordenated

Explain the nucleus' role in controlling gene expression in Eukaryotes.

In any cell, the DNA has to be transcribed to messenger RNA (mRNA) and then translate on the ribosomal machinery into the amino acid sequences that make up the cell's proteins.

Genome

The collection of genetic information

Chromosomes

Storage units of genes

Gene

Basic unit of genetic information

What do genes determine?

The inherited characters

DNA

A nucleic acid that contain the genetic instructions specifying the biological development of all cellular forms of life.

Locus

A gene's specific position along a chromosome.

What are the different types of genomes eukaryotes can have?

• Nuclear genome

• Mitochondrial genome

• Plastid genome

What are chromosomes made up from?

DNA and proteins

What do proteins in DNA aid?

They aid in condensing and folding the very long DNA molecules into chromosomes as well as in the unwinding and access to relevant genes when required.

The name for loosely packed chromatin

Euchromatin

What does the nucleolus act as?

A site for ribosome assembly

Function of the nucleolus

Where the genes for ribosomes are transcribed

Nuclear envelope

A double membrane which surrounds the nucleus, and separated the nucleoplasm from the cytoplasm.

What happens to the nuclear envelope during cell division in many organisms? Why?

The nuclear envelope dissipates so that the chromosomes can be bound by the cytoskeleton

What is the role of nuclear pores?

Control the traffic of the cell contents between the cytoplasm and the nucleus

What is present in the nucleolus?

The parts of DNA strands which code for ribosomal RNA