Cell Continuity Flashcards
How many steps does it take to form a new cell?
3
What are chromosomes?
- Structure in the nucleus
- Made of DNA & Protein
What is the chromatin like when it is not dividing?
Long thin threads
What is the chromatin like when it is dividing?
Chromatin forms a number of clearly distinguishable chromosomes
How many chromosomes does humans have?
46
What are genes?
A section of DNA that contains the instructions for the formation of protein
What is a haploid cell?
A haploid cell has one set of chromosomes.
What letter symbolises a haploid cell?
The letter ‘n’
What two human cells are examples of haploid cells?
Eggs and sperm
Haploid n=23
What is a diploid cell?
A diploid cell has two sets of chromosomes
Chromosomes are in pairs in diploid cells, what are these pairs called?
Homologous pairs.
How is diploid symbolised?
‘2n’
In diploid cells, where does each pair come from?
One comes from the mother and one comes from the father
What is cell cycle?
Describes the life of a cell
What is the period in the cycle were the cell is not dividing called?
Interphase
What is the period when a cell divides called?
Mitosis
What % of a cell’s life is in interphase?
90%
What is happening at the start of interphase?
- Cell is very active
- Produces new organelles eg. mitochondria, chloroplasts
- Chemicals needed for growth eg. enzymes and proteins
What is happening at the end of interphase?
- Chromosomes make identical copies of themselves
- Double stranded chromosome
What is the next phase after interphase?
Prophase
Describe what happens in prophase.
- The chromatin contracts
- Chromosomes become visible as a double stranded structure
- Spindle fibres appear in cytoplasm
- Nucleolus disappears
- Nuclear membrane starts to break down
What phase comes after prophase?
Metaphase
Describe Metaphase.
- Nuclear membrane is broken down
- Chromosomes line up across the centre of the cell.
- Spindles fibres from each pole attach to each chromosome at the centromere.
What phase follows the metaphase?
Anaphase
Describe anaphase.
- Spindle fibres contract
- One chromosome from each double-stranded chromosome is pulled to opposite poles of the cell
- The four chromosomes pulled to each pole have identical sets of genes
What follows anaphase?
Telophase
Describe telophase.
- The four chromosomes at each pole elongate to form chromatin
- The spindle fibres break down
- The nucleolus re-form
- A nuclear membrane forms around the chromatin at each pole.
