Environmental Impact on Phenotype

Section 8

Genotype, Environment & Phenotype

• The final physical appearance (phenotype) of an organism depends on the genetic information it carries (genotype) and the environment it is in

• This can be summed up in the following word equation:

Genotype + Environment Phenotype

Genotype & Phenotype

• Some characteristics that are solely based on genotype cannot be changed by the environment e.g. Having a widow’s peak

Sunny climate Rainy climate

Environment & Phenotype

• Other characteristics can be influenced by the environment they are in.

• E.g. If you are genetically predisposed to being tall, but you do not get enough food from your environment for growth, you may end up being smaller than your full potential

Twin Studies

• Identical twins are often used to determine the effects of genotype and environment on the physical appearance of an individual

• This is because identical or monozygotic twins have the same genotype

Factors That are and are not Inherited

• Genotypic traits are passed on to offspring because DNA is passed on from each parent to their child

• Environmental Factors ARE NOT passed on from one generation to the next because they usually do not help the species to evolve

• Environmental factors do not play any role in natural selection

Natural Selection

An introduction

Charles Darwin

“The Origin of Species”

Variation in characteristics

• All individuals in a species are different from each other.

• Some phenotypes are better suited to their environment.

• More likely that organisms with these phenotypes will survive to maturity and reproduce.

Environmental pressure

• Organisms produce more offspring than their environment can support.

• Predation, competition, overcrowding and disease resistance will limit the number of offspring surviving to maturity.

Inheritance

• Offspring often resemble their parents.

• Beneficial characteristics are passed on to offspring e.g. Ability to hide from predators

End Result

• Process is repeated generation after generation.

• Organisms with the more favourable phenotype are “selected” and survive.

• These organisms eventually become predominate in the population.

• SURVIVAL OF THE FITTEST

Variation in characteristics

Environmental pressures.

Only those with favourable characteristics survive.

Inheritance.

Favourable characteristics passed on to offspring.

Organisms with most favourable characteristics predominant in environment.

Natural Selection

Process by which only organisms best adapted their environment

survive and transmit their genetic characteristics in increasing

numbers to their offspring while those less well adapted tend to

become eliminated.

Over to you

• Read “Environmental impact on phenotype”

• Do check test 8.1

• Read “Natural selection” and do activity 6.

• Do check test 8.2

Peppered moth

2 types

Pre industrial revolution

• Air clean

• Lichen light coloured.

• Light coloured moth less easily spotted by predators.

• More light coloured moths survived to pass genetic information to offspring.

• Light coloured moth prevailed.

Post industrial revolution

• Air not as clean.

• Lichen and tree trunks darkened with soot.

• Dark coloured moth better adapted to environment.

• Dark coloured moth breeds and passes genetic information to offspring.

• Dark coloured moth prevailed.

SummaryBefore Industrial revolution• Air clean• Lichen light coloured.• Light coloured moth less easily spotted by predators - they are

camouflaged. • More dark coloured moths eaten by predators as easily seen.• More light coloured moths survived to pass genetic information to

offspring• Light coloured moth more common.

1840 – Industrial revolution • Air not as clean.• Lichens die.• Light coloured moth spotted by predators as trees darker• Dark coloured moth better adapted to environment.• Dark coloured moth survives, breeds and passes genetic

information to offspring.• Dark coloured moth more common.

Peppered moth game

• This link will allow you to be the bird eating the moths!

Evolution

• The biodiversity of Earth is thought to have occurred through a very slow process known as evolution.

• Evolution takes millions of years and involves the process of natural selection.

Selective breeding

An example of artificial selection

New varieties of plants have been produced through selective breeding by man. Most food plants bear little resemblance to their original wild variety.

Original wild variety of corn is shown on the left of this picture, and modern corn on the right. This was achieved through many generations of selective breeding.

Selective breeding in cabbage plants

Wild cabbage

Modern crop plants have been produced by selective breeding

Wheat Barley Potato

Plants have been selected for:

•Increased disease resistance

•Higher yield (of seeds, potatoes etc) per plant

Ornamental plants

Wild rose

Roses produced by selective breeding from the wild rose

Plants are selected for:

•Scent

•Colour

•Stem length

•Shape

•Longevity

Wild ox ancestor Modern cattle

Selective breeding in farm animals

Selective breeding has produced many varieties of cattle

Selective breeding in dogs

Collie

• Herding abilities

Husky

• Ability to pull a sledge

•Thick coat

Retriever

• ability to find and carry prey

All of these varieties of dog have been produced by selective breeding over thousands of years from their wild ancestor, the wolf.

Inbreeding regressionInbreeding can sometimes cause problems!

Shar pei

Bull dog

– Have breathing difficulties

– Difficult to give birth naturally to offspring

Golden Retriever

• Hip dysplasia

• Hereditary cataracts

• Other eye conditions

Selective Breeding Notes

• Selective breeding is the deliberate selection by humans of organisms which have some benefit to humans.

• Organisms with desirable characteristics are chosen to breed

• Undesirable organisms are not permitted to breed.

Characteristics which are often bred for

include:

– Increased milk yield in dairy cows.– Increased beef yield in cattle.– Increased disease resistance in crop

plants.– Increased yield in crop plants.

Advantages of selective breeding

Disadvantages of selective breeding

• Selective breeding takes a relatively long period of time.

• Results are not always guaranteed as there will always be some variation in the offspring.

Genetic Engineering

Insulin Production

• Insulin is a hormone made by the body to regulate the concentration of blood sugar.

• Diabetics are unable to produce this hormone. This can be treated by taking regular injections of insulin.

Insulin Production

• Insulin used to be extracted from pigs and cattle for human use because the hormone is similar, but not identical.

• Because the hormone is not exactly the same, it could sometimes cause allergic reactions.

• Producing insulin by genetic engineering overcomes this problem.

Insulin Production

• The gene for human insulin has been isolated and so the protein for insulin can be made by genetic engineering

Bacterial plasmids

Plasmid cut open

Part of human chromosome

Gene for insulin cut out of chromosome

Gene inserted into plasmid

Plasmid inserted into bacterium

Large circular chromosome

Notes!

• Using the previous diagram to help you, describe in words how human insulin can be produced by genetic engineering.

• List some advantages of genetically engineered insulin.

Applications of Genetic engineering

InsulinHuman Growth Hormone

Factor VIII

Insulin

• Made by pancreas cells

• Diabetes: where insulin is not made or the body doesn’t react properly to insulin

• Insulin given to diabetics

to relieve the symptoms of

diabetes

Better Blood

• Haemophilia is a condition where a person is missing a vital protein to clot their blood.

• Genetic engineering can resolve this potentially fatal problem.

• Genetically engineering blood proteins is better than other treatments because there is less risk of infections.

Human Growth Factor

• Made by cells in the pituitary gland.

• Required for children’s growth and development.

• Given to children who cannot

make enough of their own.

Prevents reduced growth

and dwarfism.

Applications of genetic engineeringProduct of genetic

engineeringNormal source and

functionMedical application

of gene

Insulin Made by pancreas cells; controls sugar levels in blood

Given to diabetics who cannot make insulin

Factor VIII Chemical In blood; require for blood clotting

Given by injection to sufferers of Haemophilia who lack Factor VIII and whose blood fails to clot

Human growth hormone Made by cells in pituitary gland; Required for children’s growth and development.

Given to children who cannot make enough of their own.

Prevents reduced growth

and dwarfism

Fighting Disease

• Antibodies are the body’s natural defence mechanism against foreign organisms such as bacteria and disease

• Antibodies give us immunity – the ability to protect ourselves from infection

• Oral vaccines are man made antibodies (proteins) that are absorbed into the body

Fighting Disease

• Simple bacterial cells cannot be used to make these oral vaccines because they are too simple

• Plant and animal cells are used because they can cope with making complex proteins

Fighting Disease

Organisms which can produce medically important proteins

Animals Plants

Cattle Soya Bean

Pigs Maize

Sheep Spinach

Goats Tobacco Plant

Rabbits Rubber Plants

Banana