Question

What are cells, selective breeding and fleece.

Answer 1

What is selective breeding?

Selective breeding involves selecting parents that have characteristics of interest in the hope that their offspring inherit those desirable characteristics.

What is selective breeding?Selective breeding involves choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics.Humans have selectively bred plants and animals for thousands of years including:crop plants with better yieldsornamental plants with particular flower shapes and coloursfarm animals that produce more, better quality meat or wooldogs with particular physiques and temperaments, suited to do jobs like herd sheep or collect pheasants.Selective breeding aims to adapt an organism’s characteristics in a way that is desirable to the humans that breed them. 

Humans have selectively bred apples to create lots of different varieties.
Image credit: Shutterstock

How does selective breeding work?An organism’s characteristics are partly determined by the combination of gene variants? that are passed on from one generation to the next. For example, the children of tall parents may themselves be tall if they inherit a combination of ‘tall’ gene variants.We can take advantage of this to selectively breed animals or plants, choosing parents with particular characteristics to produce offspring that have those characteristics.For example, if we breed tall parents together and exclude shorter parents, the offspring should inherit “tall” gene variants that make them tall.Some of the offspring may even be taller than both of their parents, because they may inherit a combination of different “tall” gene variants from each parent and together these make the offspring taller.With repeated selective breeding over multiple generations this population will get taller and taller.

A diagram showing the effect of selectively breeding for height in plants.
Image credit: Genome Research Limited

 Problems with selective breedingSelective breeding often results in a population of animals or plants with very similar genetics?.Similar genetics means that the population will have the same strengths but also the same weaknesses.Infectious diseases? are more likely to spread through genetically similar populations because they are vulnerable to the same diseases.Selective breeding often involves breeding individuals that are closely related, known as inbreeding?.Inbred populations are more likely to suffer from genetic conditions? caused by recessive? gene variants because they are more likely to inherit two copies of the recessive variants, one from each parent. Types of selective breedingInbreedingIf we want to establish a population of organisms with predictable characteristics we tend to “inbreed”.Inbreeding is when the animals bred are very close relatives, such as siblings.Continued inbreeding results in offspring that are very genetically alike.After many generations of inbreeding, the offspring will be almost genetically identical, and will produce identical offspring. When this happens, an organism is described as inbred or purebred.Examples of purebred animals are Labrador Retriever dogs and Siamese cats.

Purebred dogs like the Labrador Retriever were originally established through many generations of inbreeding.

LinebreedingLinebreeding is a type of inbreeding.It involves breeding together more distant relatives, such as cousins.This reduces the rate at which the breed becomes ‘purebred’, reducing the risk of ill-health that can sometimes be seen with purebred individuals.  Self-pollinationMost plants have both male and female reproductive parts.Some species? are naturally able to transfer the male gametes?(sperm) in the pollen? to the female parts of the flower where the female gametes (eggs) are. This is called self-pollination.The offspring of plants that self-pollinate are not identical to the parent plant, because their genes are shuffled during reproduction.Plant breeders can use self-pollination as a type of inbreeding, creating plants that are genetically more identical and that produce identical offspring after many generations.


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Answer 2

Cells:- cells are the basic unit of structure and functions in all living beings.
Fleece:- thick covering of fine hair on the body of some animals.
Selective breeding :- it is a process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits.