B1- Genetic variation and its control

Question 1

Where are chromosomes found and what do they contain?

Answer 1

Chromosomes, found in the cell nucleus, contain many genes.

Question 2

What is a gene?

Answer 2

A gene is a section of DNA, which carries coding for a particular protein. Different genes control the development of different characteristics of an organism. Many genes are needed to carry all the genetic information for a whole organism.

Question 3

What is inherited variation and what are some examples?

Answer 3

Variation due to genetic causes is inherited variation.
eye colour
hair colour
skin colour

Question 4

What is environmental variation and what are some examples?

Answer 4

Variation caused by the conditions is called environmental variation
    climate
    diet
    accidents
    culture
    lifestyle.

Question 5

What is variation caused by?

Answer 5

Some variation within a species is inherited, and some variation is due to the environment; some variation is due to a combination of both.

Question 6

What are gametes?

Answer 6

sex cells

Question 7

What happens during sexual reproduction?

Answer 7

Male and female gametes fuse in a process called fertilisation. exual reproduction allows some of the genetic information from each parent to mix, producing offspring that resemble their parents but are not identical to them. In this way, sexual reproduction leads to variety in the offspring.

Question 8

How do chromosomes in a gamete work to produce an embryo?

Answer 8

In human beings, each gamete contains 23 chromosomes, half the number found in the other cells of the body. When the male and female gamete fuse, the new embryo contains the full 46 chromosomes – half from the father and half from the mother.

Question 9

What is asexual reproduction?

Answer 9

Asexual reproduction only needs one parent, unlike sexual reproduction, which needs two parents. Since there is only one parent, there is no fusion of gametes and no mixing of genetic information. As a result, the offspring are genetically identical to the parent and to each other: in other words, they are clones.

Question 10

How does asexual reproduction in plants work?

Answer 10

Many plants develop underground food storage organs that later develop into the following year’s plants: potato plants and daffodil plants are examples of this.Some plants produce side branches with plantlets on them. Busy Lizzy does this. Other plants, such as strawberries, produce runners with plantlets on them.

Question 11

Can asexual reproduction happen in animals?

Answer 11

Asexual reproduction in animals is less common than sexual reproduction but does happens in sea anemones and starfish, for example.

Question 12

What are the advantages of cloning plants?

Answer 12

it allows a successful variety of a plant to be produced commercially and cheaply in a short space of time and on a massive scale.

Question 13

How does taking a cutting work?

Answer 13

A branch from the parent plant is cut off, its lower leaves removed and the stem planted in damp compost. Plant hormones are often used to encourage new roots to develop. The cutting is usually covered in a clear plastic bag at this stage to keep it moist and warm. After a few weeks, new roots develop and a new plant is produced. The method is easy enough for most gardeners to do successfully.

Question 14

How does a tissue culture work?

Answer 14

A tissue sample is scraped from the parent plant, and then placed in agar growth medium containing nutrients and auxins. Samples grow into plantlets which are then transferred to compost.

Question 15

What is the disadvantages of tissue cultures?

Answer 15

Sterile agar jelly with plant hormones and lots of nutrients is needed. This makes tissue culture more expensive and difficult to do than taking cuttings.

Question 16

What are the advantages of cloning an animal?

Answer 16

Just like the cloning of plants, the cloning of animals has many important commercial implications. It allows an individual animal with desirable features, such as a cow that produces a lot of milk, to be duplicated several times.

Question 17

How does embryo cloning work?

Answer 17

A developing embryo is removed from a pregnant animal at an early stage, before the embryo’s cells have had time to become specialised. The cells are separated from one another. They are then grown for a while in a laboratory and transplanted into host mothers.
When the offspring are born, they are identical to each other and genetically related to the original pregnant animal. They are not related to their host mothers because they contain different genetic information.

Question 18

How does adult cell cloning work?

Answer 18

the nucleus is removed from an unfertilised egg cell and discarded
the nucleus is removed from an adult body cell and injected into the egg cell
an electric shock is applied to fuse them together and make the egg cell begin to divide to form an embryo
while it is still a ball of cells, the embryo is inserted into the womb of an adult female
the embryo continues to grow and develop
The new individual is genetically identical to the animal that donated the nucleus from one of its body cells.

Question 19

What is the difference between cloning and genetic engineering (genetic modification or GM for short)?

Answer 19

Cloning produces exact copies, whilst GM produces a unique set of genes. Cloning only allows genes to be copied within the same species, but GM allows genes to be swapped across species.

Question 20

How does GM work?

Answer 20

Certain enzymes can cut pieces of DNA from one organism, and join them into a gap in the DNA of another organism. This means that the new organism with the inserted genes has the genetic information for one or more new characteristics. For example, the organism might produce a useful substance, or be able to carry out a new function. We say that the organism has been genetically modified.

Question 21

What are the advantages of GM?

Answer 21

Can make insulin produces bacterium- medical properties. Can make crops resistant to herbicides and pests. GM crops generally have increased yields, useful for feeding a growing population. Tobacco plants that glow in the dark when they need watering have even been produced.

Question 22

What are the disadvantages of GM?

Answer 22

Some believe the process is unethical and should be banned. There are concerns about the effect of GM crops on wild flowers and insects, and whether eating GM food may harm human health.