B1.7 - Variation Flashcards
What are gametes?
Gametes are sex cells (sperm and egg in humans, pollen and egg in plants)
Why do plants and animals share similar characteristics as their parents?
Plants and animals receive genes from their parents which is why they are similar to their parents.
How many chromosomes are present in human sex cells?
Each sex cell contains 23 chromosomes, the sperm and egg combine to make the full number of chromosomes.
How many chromosomes are present in normal cells?
46
What do we find in the nucleus of cells?
In the nucleus of cells, we find chromosomes which are made of DNA.
What is a gene?
A gene is a section of a chromosome that controls the development of a characteristic.
Why are organisms of the same species different?
Organisms can have different genetics or have been exposed to different environmental conditions or a mixture of both.
What is meant by sexual reproduction?
In sexual reproduction, the male and female gametes join. The offspring show variation because they receive genetic information from two different parents.
What is meant by asexual reproduction?
In asexual reproduction, there is only one parent and no joining of gametes. The offspring are genetically identical clones, there is no variation in the offspring.
How can new plants be produced quickly?
New plants can be produced quickly by taking cuttings and planting them to produce genetical copies of the original planet.
Describe how tissue culture works.
Tissue culture is where a few plant cells are put in a growth medium with hormones, and they grow into new plants. These plants are made quickly in very little space to be grown all year.
Describe how animals can be cloned by embryo transplants.
In an embryo transplant, a developing embryo is split into two before the cells become specialised.
The two balls of cells, embryos, are transplanted into the host mothers and develop into two clones.
Describe the stages of animal cell cloning.
First, the nucleus is removed from an unfertilised egg cell and the nucleus is discarded.
An adult body cell is taken from the adult to be cloned and the nucleus is removed.
This nucleus is inserted into the empty egg cell. An electric shock triggers the cell to divide into an embryo. This is transferred into the womb of a female and develops into a clone of the original adult who provided the cell.
Describe what happens during genetic engineering.
First, we identify a gene which is desirable. The gene is cut out of the chromosome of a cell. This is done using enzymes.
The gene is then transferred into the cell other organisms. For instance, the human insulin gene can be inserted into bacteria to produce human insulin.
What do scientists call crops which have had genes transferred into them from different organisms?
They are called genetically modified crops.
