Eukaryotic Cells Flashcards
Describe the structure of a chromosome
- 2 chromatids attached centrally at the centromere
When is the structure of a chromosome visible in the cell cycle?
- During metaphase
Describe the structure of a chromatin
- has a beads on a string structure whereby the beads are Histone proteins and the string is DNA
Describe the properties of Histone Proteins.
- An octamer (8 units)
- Rich in Lysine and Arginine
- They are positively charged
In gene expression what is a Spliceosome?
- A multi-subunit complex that completes splicing
What is meant by protein diversity?
That several forms of a protein can be derived from the same gene due to splicing.
What is an intron?
- a non-coding portion of a gene
- What is transcription?
When RNA is written from DNA
What is the TATA box?
A section of bases that promotes transcription
- this occurs approximately 25 bases before the start of transcription
What is translation?
The writing of polypeptide chains from RNA
What is an Exon?
a Coding sequence in a gene
When does splicing occur?
- between Transcription and translation
What happens if splicing defects occur?
- disease occurs due to the mutations in the genes
In replication how may replication forks are there?
there a 2 replication forks working in both directions
What does telomerase do?
Extends the 3’ end under certain circumstances
When does telomerases function occur?
- in foetal development
- in cancer cells
Why does the lagging strand get shorter at each replication?
- in normal cells telomerase cannot extend the 3’ end meaning it will be shorter by approximately 50 bases at each replication
- This limits the cells life
What are the stages of the cell cycle?
- S (Synthesis)
- G2 (Gap 2)
- M (Mitosis)
- G1 (Gap 1)
What occurs during the S stage of the cell cycle?
The DNA is replicated and the Chromosome is duplicated
What occurs during the G2 stage of the cell cycle?
This is a period of cell growth as the cell prepares for mitosis
What occurs during the M stage of the cell cycle?
- Prophase - condensation of chromatin and the disappearance of the nucleus
- Metaphase - Chromosomes align in the centre of the cell
- Anaphase - The chromosomes split
- Telophase - Chromosomes move to the poles and the cell splits
What occurs during the G1 stage of the cell cycle?
This is a period of cell growth
- the organelles duplicate in preparation for synthesis
