1E. nucleus DNA RNA

Do all cells have nucleus?

Some ‘cells’ do not have a nucleus or some contain one or more cells (e.g. liver cells have 2 nuclei and red blood cells do not have any nucleus)

What is the nucleus for?

It holds the instructions for protein synthesis and also help the cell repair itself

Describe the membrane of the nucleus.

• The membrane of the nucleus is a double sided membrane with pores in it

• The pores are guarded by proteins — no passive transport

• Inside the membrane is the genome

What is a genome?

It refers to all the genetic information a cell contains; the DNA and proteins

How is the human genome organised in the cell?

• 46 thin chromatin fibres

• DNA material is in thin 46 chromatin fibres

• we usually do not contain chromosomes in our cells

What do the chromatin fibres do?

• form new genetic material

• form RNA molecules

• correct things that are wrong in the DNA

Where is the nucleoli and what is it?

• The nucleolus (plural: nucleoli) is located inside the nucleus surrounded by chromatin fibres

• Its function is the production of ribosome-RNA (rRNA) molecules

List the differences between DNA and RNA

DNA

• 2 strands; helix

• deoxyribose sugar

• Thymine

RNA

• 1 strand

• ribose sugar

• Uracil

• for protein synthesis

What is the basic structure of RNA and DNA?

• It has a ribose or deoxyribose sugar which is bound together by phosphoric acid

• DNA 4 bases: Adenine - Thymine and Cytosine - Guanine

• RNA 4 bases: Adenine - Uracil and Cytosine - Guanine

• the bases are bonded with a hydrogen bond

What codes for one amino acid?

three bases; triplets

How many DNA double helixes are in our cells?

• 46 packages paired

• 2×23 for females

• 2×22 for males and Yx