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B1.7 Genetic Variation And Its Control
- B1.7.1 Why Organisms Are Different
- There are not only differences between different species of plants and animals but also between
individuals of the same species. These differences are due partly to the information in the cells they
have inherited from their parents and partly to the different environments in which the individuals live and
grow. Asexual reproduction can be used to produce individuals that are genetically identical to their
parent. Scientists can now add, remove or change genes to produce the plants and animals they want.
- The information that results in plants and animals having similar characteristics to their parents is carried by
genes, which are passed on in the sex cells (gametes) from which the offspring develop.
- The nucleus of a cell contains chromosomes.
Chromosomes carry genes that control the
characteristics of the body.
- Different genes control the development of
different characteristics of an organism.
- Differences in the characteristics of different individuals of the same
kind may be due to differences in the genes they have inherited
(genetic causes), the conditions in which they have developed
(environmental causes) or a combination of both.
- Differences in the characteristics of different individuals of the same
kind may be due to differences in the genes they have inherited
(genetic causes), the conditions in which they have developed
(environmental causes) or a combination of both.
- Different genes control the development of
different characteristics of an organism.
- The nucleus of a cell contains chromosomes.
Chromosomes carry genes that control the
characteristics of the body.
- The information that results in plants and animals having similar characteristics to their parents is carried by
genes, which are passed on in the sex cells (gametes) from which the offspring develop.
- There are not only differences between different species of plants and animals but also between
individuals of the same species. These differences are due partly to the information in the cells they
have inherited from their parents and partly to the different environments in which the individuals live and
grow. Asexual reproduction can be used to produce individuals that are genetically identical to their
parent. Scientists can now add, remove or change genes to produce the plants and animals they want.
- B1.7.2 Reproduction
- There are two forms of reproduction. Sexual
reproduction is the joining (fusion) of male and
female gametes. The mixture of the genetic
information from two parents leads to variety
in the offspring. Asexual reproduction has no
fusion of gametes and only one individual is
needed as the parent. There is no mixing of
genetic information and so no genetic variation
in the offspring. These genetically identical
individuals are known as clones.
- New plants can be produced quickly and
cheaply by taking cuttings from older
plants. These new plants are genetically
identical to the parent plant.
- Modern cloning techniques include tissue culture, embryo transplants and adult cell cloning. A tissue culture is a small group of cells from a part of a plant.
Embryo transplants involves splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos
into host mothers. In adult cell cloning, the nucleus is removed from an unfertilised egg cell. The nucleus from an adult body cell is then inserted into the egg
cell. An electric shock then causes the egg cell to begin to divide to form embryo cells. These embryo cells contain the same genetic information as the adult
skin cell. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
- In genetic engineering, genes from the chromosomes
of humans and other organisms can be 'cut out' using
enzymes and transferred to cells of other organisms.
- Genes can also be transferred to the cells of animals, plants or microorganisms at an early
stage in their development so that they develop with desired characteristics. New genes can
be transferred to crop plants. Crops that have had their genes modified in this way are called
genetically modified crops (GM crops). Examples of GM crops include ones that are resistant
to insect attack or to herbicides. Genetically modified crops generally show increased yields.
- Concerns about GM crops include the
effect on populations of wild flowers and
insects, and uncertainty about the
effects of eating GM crops on human
health.
- Concerns about GM crops include the
effect on populations of wild flowers and
insects, and uncertainty about the
effects of eating GM crops on human
health.
- Genes can also be transferred to the cells of animals, plants or microorganisms at an early
stage in their development so that they develop with desired characteristics. New genes can
be transferred to crop plants. Crops that have had their genes modified in this way are called
genetically modified crops (GM crops). Examples of GM crops include ones that are resistant
to insect attack or to herbicides. Genetically modified crops generally show increased yields.
- In genetic engineering, genes from the chromosomes
of humans and other organisms can be 'cut out' using
enzymes and transferred to cells of other organisms.
- Modern cloning techniques include tissue culture, embryo transplants and adult cell cloning. A tissue culture is a small group of cells from a part of a plant.
Embryo transplants involves splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos
into host mothers. In adult cell cloning, the nucleus is removed from an unfertilised egg cell. The nucleus from an adult body cell is then inserted into the egg
cell. An electric shock then causes the egg cell to begin to divide to form embryo cells. These embryo cells contain the same genetic information as the adult
skin cell. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
- New plants can be produced quickly and
cheaply by taking cuttings from older
plants. These new plants are genetically
identical to the parent plant.
- There are two forms of reproduction. Sexual
reproduction is the joining (fusion) of male and
female gametes. The mixture of the genetic
information from two parents leads to variety
in the offspring. Asexual reproduction has no
fusion of gametes and only one individual is
needed as the parent. There is no mixing of
genetic information and so no genetic variation
in the offspring. These genetically identical
individuals are known as clones.
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