How? What? Where? When? Why?

What is a gene mutation and how do mutations occur?

A gene mutation is a permanent alteration in the DNA sequence that makes up a gene, such that the sequence differs from what is found in most people. Mutations range in size; they can affect anywhere from a single DNA building block (base pair) to a large segment of a chromosome that includes multiple genes.

Gene mutations can be classified in two major ways:

Hereditary mutations are inherited from a parent and are present throughout a person’s life in virtually every cell in the body. These mutations are also called germline mutations because they are present in the parent’s egg or sperm cells, which are also called germ cells. When an egg and a sperm cell unite, the resulting fertilized egg cell receives DNA from both parents. If this DNA has a mutation, the child that grows from the fertilized egg will have the mutation in each of his or her cells.

Acquired (or somatic) mutations occur at some time during a person’s life and are present only in certain cells, not in every cell in the body. These changes can be caused by environmental factors such as ultraviolet radiation from the sun or can occur if an error is made as DNA copies itself during cell division. Acquired mutations in somatic cells (cells other than sperm and egg cells) cannot be passed to the next generation.

Genetic changes that are described as new mutations can be either hereditary or somatic. In some cases, the mutation occurs in a person’s egg or sperm cell but is not present in any of the person’s other cells. In other cases, the mutation occurs in the fertilized egg shortly after the egg and sperm cells unite. As the fertilized egg divides, each resulting cell in the growing embryo will have the mutation. New mutations may explain genetic disorders in which an affected child has a mutation in every cell in the body but the parents do not, and there is no family history of the disorder.

Most disease-causing gene mutations are uncommon in the general population. However, other genetic changes occur more frequently. Genetic alterations that occur in more than 1 % of the population are called polymorphisms. They are common enough to be considered a normal variation in the DNA. Polymorphisms are responsible for many of the normal differences between people such as eye colour, hair colour, and blood type. Although many polymorphisms have no negative effects on a person’s health, some of these variations may influence the risk of developing certain disorders.

1. What is a gene mutation? ________________________________

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2. What are the kinds of gene mutations?

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3. Where can you find hereditary mutations?

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4. What are somatic mutations?

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5. How can new mutations be described? ______________________

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6. What are the differences between genetic and somatic

mutations?

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7. Why is it important to distinguish between hereditary and somatic

mutations?

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Vocabulary

Make each of the following words the subject of a sentence. Then

complete the sentence to describe or explain the meaning of the

word. The first one is given as an example.

Mutations are permanent changes in the structure of an

organism’s DNA.

A sequence describes ____________________________________

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Chromosomes are_______________________________________

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To classify things means that ______________________________

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Somatic describes _______________________________________

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An embryo is ___________________________________________

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Polymorphisms are ______________________________________

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PDHPE How does training affect performance?

When athletes train they are trying to improve the way their bodies function

and perform. To understand how training affects performance it is important to

have a knowledge and understanding of the energy systems, types of training

and training methods, principles of training and physiological adaptations in

response to training.

The human body requires a continuous supply of energy both to meet the

metabolic needs and to power muscular contraction for movement. There are

three energy systems which provide the working muscles with energy for

movement. These include:

anaerobic energy systems which operate without the presence of oxygen -

the alactacid (ATP/PC) system and the lactic acid system

the energy system that operates with oxygen - the aerobic system.

The predominance of any system or systems during activity is dependent on the

duration and intensity of the activity.

Physiological adaptations in response to training

While training will cause immediate physiological responses in the body,

athletes are looking for adaptations and long term responses to improve

performance. These adaptations allow the athlete to achieve higher levels of

work. They include changes to resting heart rate, stroke volume and cardiac and

cardiac output, oxygen uptake and lung capacity, haemoglobin level, muscle

hypertrophy, and effects on fast/slow twitch muscle fibres.

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