Variation

Question 1

Define the term variation and give an example

Answer 1

Variation is the differences which exist within a species or between different species
Eg eye colour in humans or type of fur in dogs

Question 2

Identify the causes of variation

Answer 2

1. Genetic factors - inherited characteristics from the parents such as blood group, inherited disorders
2. Environmental factors such as scars, tattoos, suntan etc
3. Combination of genetic and environmental, this is how your environment interacts with your genome. You may not achieve your potential height for example if you did not receive sufficient calcium as a child.

Question 3

Describe the types of variation

Answer 3

There are two types of variation, continuous and discontinuous.
Continuous comes in a range of values such as height, there will be additional values between them.  In a class of 30 there could be 30 different heights or there could be some people whose height is exactly the same.  Variations of even 1mm could be measured.  Data would be shown on a line graph or histogram.
Discontinuous data occurs when there are only a few groups and everyone falls into one or other of them.  A good example is blood group.  There are 4 blood groups A, B, AB and O everyone has one of them and you cannot be between groups or in 2 of them.  This data is usually shown in bar or pie charts.

Question 4

If data is displayed on a line graph what sort of data is it?

Answer 4

Continuous

Question 5

If data is displayed on a bar graph what sort of data is it?

Answer 5

Discontinuous

Question 6

Explain how normally distributed variation would appear on a graph

Answer 6

If sufficient data is collected then normal distribution appears as a bell shape on a graph. The more extremes show lower frequency with the most common results being in the middle at the top of the bell.
When you take your exam the results will appear as a bell shape. The most common mark will be at the top of the bell.
If you are spending lots of time learning these cards your mark will likely be to the right of the bell - lets hope so!

Question 7

Explain mutation and how it affects variation

Answer 7

Mutation is a change which occurs in the DNA of a species.
Mutations occur regularly in living organisms
Occasionally they can affect the phenotype.
Often however they do not affect it.
If the mutation is suited to the environment it can lead to changes in the evolution of that species.

Question 8

Explain how farmers used selective breeding to improve the traits of their livestock.

Answer 8

Selective breeding is when the parents are chosen for specific characteristics which are desired in the offspring. farmers may choose to breed two large animals so that the offspring is larger.
An example of this comes from two types of cows bred for their milk. Jersey cows produce lower yields of creamier milk and Friesian cows more milk but it is less creamy.
Flowers are selectively bred for their scent or size of flower.
Crops are selectively bred for their yield or disease resistance.

Question 9

Explain the difference between artificial selection and natural selection

Answer 9

Artificial selection involves choices being made by people to bring together parents which have desired characteristic with the aim of producing offspring with those characteristics.
Natural selection occurs as it’s name suggests naturally with no interference.
Selective breeding reduces the variation in a population and is called interbreeding. The gene pool is rduced and this can cause genetic weaknesses. Good examples of this are hip dysplasia in dogs such as German Shepherds and breathing difficulties in pugs.

Question 10

Explain how genetic engineering produces transgenic organisms?

Answer 10

Genetic engineering is a technique whereby genes are removed from one species and inserted into the genetic material of another.
A gene is removed from the DNA of a species using an enzyme. The same enzyme is then used to open the DNA of an embryo of a different species. The gene is then inserted into the DNA of the embryo and closed up again using a different enzyme. The embryo is transplanted into a female and when it is born the offspring with be transgenic.
Example glow in the dark gene from a jellyfish engineered into a rabbit which then glowed in the dark.

Question 11

Identify evaluative points you could make on an ethics question on genetic engineering

Answer 11

Positive
Can increase yield of crops- more food- less starvation
Can produce disease resistance crops - more food again
Can produce drought resistance crops - more food in poor countries with lack of rain
Can produce herbicide resistant crops which can be sprayed to kill weeds without killing the crop
Negative
Religious beliefs that humans should not interfere with God’s creation
Chance of genes spreading into the general gene pool creating for example herbicide resistance weeds
There could be an effect on human health, we do not fully understand the effects of GM yet.

Question 12

Explain how transgenic sheep have been modified to help haemophilliacs

Answer 12

Eggs (ova) are removed from the sheep and fertilized in vitro
The gene for blood clotting from a human is injected into the nucleus of a female embryo.
The embryo is implanted into the female sheep.
The lamb when it is born has the human gene for blood clotting which is produced in its milk and extracted to treat the disease.

Question 13

Explain how insulin in produced by genetic engineering.

Answer 13

1. Bacteria are genetically modified to produce insulin.
2. The circle of DNA called a plasmid is cut from the bacteria using an enzyme.
3. The same enzyme is used to cut open the human DNA and extract the gene for producing insulin.
4. The human gene is inserted into the plasmid and sealed with a 2nd enzyme
5. The plasmid is inserted into the bacterial cell and produces human insulin.
   The plasmid is called a vector because it delivers the human gene to the bacteria

Question 14

Describe how a vector can be used in genetic engineering and give examples

Answer 14

A vector is something which delivers the new gene into an organism.

Examples are plasmids of bacteria and viruses.

Question 15

Identify some advantages of using genetically engineered insulin over the insulin which was used from sheep or cattle.

Answer 15

1. It is human insulin rather than insulin from a different species which was not as effective because it was slightly different.
2. The production process is more efficient
3. Vegans and vegetarians do not have to compromise their principles to use it.