B2 - Cell Division Flashcards
Why do organisms need new cells?
- To grow
- To replace worn out cells
- To repair damaged tissue
(The replacement needs to have the same genetic information)
How many chromosomes do human cells have, and how many pairs are there?
There are 46 chromosomes in the nucleus of human cells, which is split into 23 pairs.
Summarise the 3 stages of the cell cycle.
Stage 1: Replication of DNA to form two copies of each chromosome and synthesis of new sub-cellular structures
Stage 2: One set of chromosomes is pulled to each end of the dividing cell and the nucleus divides
Stage 3: The cytoplasm and the cell membranes also divide to form two identical daughter cells
What is an ‘embryonic stem cell’? What can they do?
An embryonic stem cell is a type of stem cell found in the embryo, capable of dividing into almost any cell type.
What is an ‘adult stem cell’?
An adult stem cell is a type of stem cell found in specific locations in adults e.g. bone marrow. They can only differentiate into a limited number of cell types.
What is Differentiation?
As cells begin to become ‘specialised’ for specific jobs, they start to develop different features.
What are some potential risk of stem cell research?
- Many stem cells come from aborted embryos
- Developing therapies are slow, hard and expensive
- Infected with virus’
- Diabetes
- Eyesight
- Damaged bone and cartilage
- Heart damage
- Spinal cord
What are the ethical objections to stem cell research?
- Destruction of human embryos
- Embryos cannot give permission (violation of human rights - playing God)
What are specialized cells with long extensions called?
Root hair cells
What do the xylem and phloem vessels transport?
Xylem - transporting water (transpiration stream)
Phloem - transporting sugary sap up and down (translocation)
What is a gene?
A gene is a section of DNA that controls characteristics.
What is mitosis?
Mitosis is part of the cell cycle where one set of new chromosomes is pulled to each end of the cell forming two identical nuclei during cell division
What happens in asexual reproduction?
The cells of the offspring are produced by mitsosis from the cells of their parent. This is why they contain exactly the same genes as their parent with little or no genetic variation.
How long would the cell cycle take?
Usually less than 24 hours or could take several years, depending on the cells involved and the stage of life of the organism.
