Cell division Flashcards
How many chromosomes in one gamete?
In human body cells the chromosomes are normally found in pairs. The karyotype diagram below shows the 23 chromosome pairs for a female human.
What does the nucleus contain?
The nucleus of a cell contains the instructions for making proteins and new cells. In the nucleus there are structures called chromosomes. The chromosomes are made of coiled strands of DNA molecules. A section of DNA that codes for a specific protein or characteristic is called a gene.
Human embryo stem cells info
Human embryo stem cells: can be cloned and made to differentiate into most different types of human cells.
Human adult stem cells: can form many (but not all) types of cells including blood cells.
Human stem cells can be used to help treat diseases like diabetes and paralysis.
How are embryo’s produced?
Embryos produced by therapeutic cloning have the same genes as the patient. This means stem cells from the embryo are not rejected by the patient’s body. This is why they can be used for medical treatments.
What are the risks of using stem cells?
The risks of using stem cells risks such as transfer of viral infections.
Objections to stem cell use
Some people have objections to stem cell use for ethical and religious reasons. During Fertility treatment doctors usually fertilise many more eggs than are going to be used. The embryos then formed are used to obtain stem cells. In the UK scientists can use these embryos for research but only under very strict guidelines.
Describe the stages of cells dividing
Stage 1 – Growth: Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria.
Stage 2 - DNA synthesis: The DNA replicates to form two copies of each chromosome.
Stage 3 – Mitosis: One set of chromosomes is pulled to each end of the cell and the nucleus divides. Then the cytoplasm and cell membranes divide to form two cells that are identical to the parent cell.
Why does mitosis occur?
Mitosis occurs during growth and to repair or replace damaged cells.
Asexual reproduction occurs by mitosis in both plants and simple animals.
What are undifferentiated cells?
Most types of PLANT cells can differentiate throughout their life cycle.
Undifferentiated stem cells in plants are grouped together in structures called meristems. The undifferentiated cells can then specialise e.g. root hair cell, xylem or phloem cells.
Stem cells in plants
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
* Rare species:
can be cloned to protect from extinction.
* Crop plants:
with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
e.g. potatoes, strawberries and dates
