Reproduction and Cloning Flashcards
Why is adult cell cloning (Dolly the sheep) a form of asexual reproduction? (2 marks)
There was no mixing of genes / genetic material because the nucleus was removed from the egg cell before fusion
What is adult cell cloning? (Dolly the sheep) (4 marks)
This is where a nucleus is taken from the cell of an adult organism and put into an egg, where the original nucleus has been discarded, from another organism of the same species. An electric shock is given and the new embryo is put into the uterus of a surrogate mother. The cloned organism is genetically identical to the donor adult from which a cell was used to provide the nucleus/genetic material.
Why are the calves produced by embryo transplant not genetically identical to their true mother or their surrogate mother? (2 marks)
The calves are not genetically identical to their true mother because the embryos were produced by normal sexual reproduction – fusion of an egg and sperm. After fertilisation has taken place this embryo is divided and put into the uterus of different surrogates. Therefore the genetic material in the embryo is different from that of the mother. The surrogate mother is not related to the calves, so will have different genetic material.
Human cloning is illegal and is not carried out (except in nature in the form of identical twins). Discuss the social and ethical issues around animal cloning. (3 marks)
Sheep and cows can be genetically modified to make medicines for humans in their milk. Lots are needed to make enough medicine to treat all ill people, such as people with hereditary emphysema. Breeding from the transgenic sheep cannot guarantee that the offspring will have the gene to make the medicine. But if sheep were cloned from this transgenic sheep they would have that gene. The benefits to people who are ill are huge. However, some people wish to clone their pet. This may not harm the pets produced but is rather whimsical and not benefiting mankind/lots of people. It would cost a lot of money.
Evaluate the use of adult cell cloning to conserve endangered species. Remember to give a conclusion to your evaluation. (3 marks + 1 for conclusion)
Pros It is useful if species are difficult to breed. It also prevents extinction / continues genetic line. Cons It has a low success rate. There might also be development problem and cloning reduces the gene pool Any argued conclusion.
The use of cloned animals in food production is controversial. It is now possible to clone ‘champion’ cows. Champion cows produce large quantities of milk. Describe how adult cell cloning could be used to produce a clone of a ‘champion’ cow. (4 marks)
- nucleus / DNA / chromosomes / genetic material removed (from unfertilised egg) of a cow - nucleus from body cell of champion (cow) - inserted into the egg / ovum - electric shock to make cell divide or develop into embryo - (embryo) inserted into uterus / host / another cow
How many parents are involved in asexual reproduction?
One
How many parents are involved in sexual reproduction?
Two
Define sexual reproduction
Sexual reproduction involves the fusion of sex cells ( gametes ).
Why are offspring not identical to their parents after being produced by sexual reproduction?
Offspring produced by sexual reproduction are similar to both parents, but cannot be identical. That is because they have a combination of two sets of genes. Random mixing of genes leads to variation in the offspring. This is important in survival.
What is environmental variation? Explain with an example
Some differences between you and other people are due to the environment they live in. For example, if a have a scar from an accident or operation or you may change the colour of your hair. These are environmental variation not genetic.
What is Tissue culture? What are the pros and cons? (3 marks)
Taking small groups of cells from part of a plant and growing them under special conditions is called tissue culture. This is more expensive, but can be used to reproduce large numbers of a rare or top quality plant.
Is a cutting sexual or asexual reproduction?
Asexual
Is this picture and example of sexual or asexual reproduction?
Asexual
What does this diagram show?
Tissue culture
What does this diagram show?
Embryo transplantation
What is this an example of?
Adult cell cloning
