B13 Variation

B13 Variation

By Samantha Argent

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Variation

Children generally look a little like their mother and their father, but are not identical to either. They inherit their features from each parent's DNA.

Examples of genetic variation in humans include blood group, skin colour and natural eye colour.

Whether you have lobed or lobeless ears is due to genetic causes.

Multiple Choice

The genetic difference between individuals in the same species is

• Interesting

• Harmful

• Variation

• Genetics

Environmental Variation

Characteristics of animal and plant species can be affected by factors such as climate, diet, accidents, culture and lifestyle. For example, if you eat too much you will become heavier, and if you eat too little you will become lighter. A plant in the shade of a big tree will grow taller to reach more light.

Other examples of features that show environmental variation include:

• scars

• language and accent

• flower colour in hydrangeas as these plants produce blue flowers in acidic soil and pink flowers in alkaline soil

Genetic and environmental causes together

Some features vary because of a combination of genetic and environmental causes. For example, tall parents will pass genes to their children for height. Their children have the genetic potential to also be tall. However, if their diet is poor then they will not grow very well: their environment also has an impact on their height.

Multiple Choice

What is a mutation?

• Change that helps a living thing survive in its environment

• Change in DNA structure

• Natural differences in traits (like color)

Multiple Choice

What is an adaptation?

• Change that helps a living thing survive in its environment

• Change in DNA structure

• Natural differences in traits (like color)

Multiple Choice

What is this?

• Variation

• Adaptation

• Mutation

Mutation and variation

Extensive genetic variation is contained within any species. This is clearly visible in the domestic dog species.

Variation within genes leads to different genotypes, and this can be seen by a different phenotype. Genetic and environmental variation combine together to produce these different phenotypes. All variants arise from mutations and most have no effect on the phenotype.

A mutation is a change in a gene or chromosome. Mutations arise spontaneously and happen continually.

Multiple Choice

Homozygous is defined as....

• Two of the same alleles

• Two of the same genes

• Two different alleles

• The characteristic shown by the gene

Multiple Choice

What are small stretches of DNA that code for traits

• Nucleus
• Chromosomes
• Gene
• Centromeres

Natural Selection

Natural selection is a process where organisms that are better adapted to an environment will survive and have more offspring. This means their genes are passed on to the future generations.

This is associated with the term 'survival of the fittest'. A famous example is the peppered moth.

Multiple Choice

Individuals that are well adapted to their environment will survive and produce:

• Fewer mutations
• Stronger genes
• More offspring
• Better traits

Multiple Choice

Horse breeding for specific desired traits is an example of which type of evolutionary evidence?

• Artificial selection
• Embryology
• Fossils
• Biochemical molecules

Multiple Choice

According to the theory of natural selection, some individuals more likely than others to survive and reproduce because they:

• pass on to their offspring their newly acquired traits.
• are better adapted to their environment than others and will pass on those adaptations to future offspring.
• do not pass on newly acquired traits.
• produce fewer offspring than others in the same environment.

Peppered Moths

​During the nineteenth century, pollution killed off some of the lichens and soot deposits caused the bark on trees to appear darker. Light coloured moths were no longer camouflaged and were eaten by birds. The dark moths had a better camouflage. As a result, dark moths had a greater chance of reproducing and passing on the phenotypes, and through this the alleles that made them dark. This led to a gradual increase in the proportion of dark moths until light moths became very rare in industrial areas. Note that this change was not due to pollution making the moths darker. The dark variety had always existed, but had an advantage when the environment changed.

Multiple Choice

Which of the following is a term for a group of similar organisms that can reproduce fertile offspring?

• individual
• population
• species
• fossil

Multiple Choice

What does evolution mean?

• changes to a species over time

• changes to one living thing in a life time

• changes in traits colors

Selective Breeding

Selective breeding or artificial selection is when humans breed plants and animals for particular genetic characteristics.

1. Decide which characteristics are important enough to select.
2. Choose parents that show these characteristics from a mixed population. They are bred together.

3. Choose the best offspring with the desired characteristics to produce the next generation.

4. Repeat the process continuously over many generations, until all offspring show the desired characteristics.

Selective Breeding

Characteristics can be chosen for usefulness or appearance:

Desired characteristics in plants:

• disease resistance in food crops

• wheat plants that produce lots of grain

• large or unusual flowers

Desired characteristics in animals:

• animals that produce lots of milk or meat

• chickens that lay large eggs

• domestic dogs that have a gentle nature

The new varieties may be economically important. For example, they may provide more or better quality food, or allow farmers to feed more people.

Multiple Choice

Selective breeding is...

• a process to create an organism with desired traits from parents with those desired traits

• natural method of producing offspring with desired traits

• creating a new species

• making organisms reproduce during times of stress

Multiple Choice

An example of selective breeding is

• a dog breeder mating 2 dogs to make more dogs

• a farmer grows bees to pollinate the plants on his farm

• a person pollinates 2 white rose plants to only create white roses

Multiple Choice

One problem with selective breeding is

• creating a new species

• gene variety is lost

• new food sources

• reduced genetic variation can lead to attack by specific insects or disease, which could be extremely destructive

• rare disease genes can be unknowingly selected as part of a positive trait, leading to problems with specific organisms, eg a high percentage of Dalmatian dogs are deaf

• can create physical problems in specific organisms, eg large dogs can have faulty hips due to not being formed correctly

• new varieties may be economically important, by producing more or better quality food

• animals can be selected that cannot cause harm, for example cattle without horns

Risks and Benefits of SB

Genetic Engineering

1. selection of the desired characteristic

2. the gene responsible for the characteristic is 'cut out' of the chromosome with enzymes

3. the gene is transferred and inserted into another organism (vector) using more enzymes

4. replication of the modified organism. or vector is used to transfer the gene into required cells

Multiple Choice

Genes found on DNA contain the instructions for making  

• pyrimidines 
  
• pyrimidines
• proteins
• purines

Multiple Choice

Choosing two closely related organisms from the same species to ensure desired traits are passed to their offspring

• inbreeding
• outbreeding
• hybridization
• pedigree

Multiple Choice

Which is used to cut DNA molecules at specific points?

• gel electrophoresis
• PCR analysis
• a restriction enzyme
• recombinant DNA

Multiple Choice

Rice modified to have more Vitamin A is an example of

• Genetic engineering

• Cloning

• Gene mutation

• Artificial selection

Multiple Choice

Putting the gene for bioluminescence into a fish is an example of...

• Genetic Engineering
• Selective Breeding
• Artificial Selection
• Gene Mutation

Uses

• diabetes

• GMO crops (to be herbicide resistant, increased yields, to contain more vitamins)

• to treat inherited disorders - CF (in the future)

• Transfer of the selected gene into other species. What benefits one plant may harm another.

• Some people believe it is not ethical to interfere with nature in this way. Also, GM crop seeds are often more expensive and so people in developing countries cannot afford them.

• GM crops could be harmful, for example toxins from the crops have been detected in some people’s blood.

• GM crops could cause allergic reactions in people.

• Pollen produced by the plants could be toxic and harm insects that transfer it between plants.

• Genetic modification is a faster and more efficient way of getting the same results as selective breeding.

• Improve crop yields or crop quality, which is important in developing countries. This may help reduce hunger around the world.

• Introduce herbicide resistance, which results in less herbicides being used, as weeds are quickly and selectively killed.

• Insect and pest resistance can be developed and inserted into the plants. The plant produces toxins, which would discourage insects from eating the crop.

• Sterile insects could be created such as a mosquito. They would breed, which would lead to infertile offspring. This may help with spread of diseases, such as malaria, dengue fever and the Zika virus.

Risks vs Benefits

Open Ended

Evaluate the use of genetic engineering to treat cystic fibrosis.