science form 4 chapter 3 3.4 mutation

Quick test (15 minutes)Sex determination and the occurrence of twins in human beings

Answer the following question.1.Compare the characteristics given and

complete the following table.Characteristic Male Female Number of chromosome Gamete formedChromosome make up in somatic cellChromosome make-up in gamete

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2. what causes identical twins to have the same genetic make-up?

3. Why is sex of a child determined by the father?

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Elicit studEnts iDeaElicit studEnts iDeaDo you ever see someone who

down’s syndrome out there?

Today we are going to learn Today we are going to learn about about

3.4 Understanding mutation

Learning outcomeLearning outcomeAt the end of the lesson, you are

able to 1. State what mutation is2. State the types of mutation3. List examples of mutation4. Identify the causes of mutation5. State the advantages and disadvantages of mutation

What is mutation?What is mutation?Mutation is a change in the

amount or the chemical structure of DNA.

Types of mutation?Types of mutation?Chromosome mutation Gene mutationsChanges in arrangement of genes or number of chromosomes.

Changes in the structure of a gene

Down’s syndrome (extra chromosome 21), Klinefelter’s syndrome (XXY) and Turner’s syndrome (XO).

Colour blindness AlbinismSickle cell anaemiaHaemophilia

Causes of mutationsCauses of mutations1. Agents which cause mutation

are called mutagens. 2. Chemical substances

- pesticide, nicotine in cigarrettes, drugs, nitrous acid and some presevertives, colouring and artificial sweetener can cause mutation.

3. Radioactive substances- Alpha, beta and gamma radiation.

- UV rays and X-rays can cause skin cells to mutate and this may cause cancer.

4. Temperature -which are too high or low can cause mutation.

Advantages Disadvantages•Mutation causes variations in organisms which allow them to adapt to the environment.

•Some mutation cause disease like colour blindness and haemophilia cannot be cured.

•Species that are more resistant to diseases, weather and polluted environment can be produced.

•Klinefelter’s syndrome causes infertility.•Disease like haemophilia and sickle cell anaemia can lead to death

ExerciseExerciseDefine the following terms

a) Mutation b) AlbinismState two diseases caused by

a) chromosome mutationsb) gene mutations

Name one advantages and one disadvantages of mutations.

Homework Homework Do exercise in science process

skills book on page 30

Learning outcomeLearning outcomeAt the end of the lesson, you are

able to 1. State what mutation is2. State the types of mutation3. List examples of mutation4. Identify the causes of mutation5. State the advantages and disadvantages of mutation

ConclusionConclusionMutation is a change in the genetic

information of an individual.Mutation can cause genetic

disorders in the descendants such as haemophilia and albinism.

Down’s syndrome is caused by an extra chromosome in the body cell, as a result of mutation.

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Down’s syndromeDown’s syndromeThis heredity disease in general is

caused by the presence of one extra chromosome at chromosome 21 in somatic cells.

Incomplete separation of chromosome during meiosis causes the zygote to have extra chromosome. 47 in total.

Give characteristics of down’s syndrome patient????? Bac

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Klinefelter’s syndromeKlinefelter’s syndromePatient has one extra X

chromosome, i.e XXY.Normally males suffer from this

hereditary disease. They posses some feminine features and fail to produce sperms. Therefore they are infertile.

Patient have 47 chromosomes and posses special features i.e narrow shoulder and small testes. Bac

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Turner’s syndromeTurner’s syndromeA person who suffer from this

heredity disease lacks one X chromosome.

People with Turner’s syndrome have only one sex chromosome which is XO.

Only female suffer from this heredity disease.

They posses the following features;◦Infertility◦Short stature◦Do not experience menstrual cycle Bac

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Colour blindnessColour blindnessSex-linked disease determines by

a recessive gene on the X chromosome

A colour blind person cannot see or diffrentiate the colours of red and green.

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Albinsm Albinsm The change in the gene that

control skin colourThe newly produced gens are

unable to produce skin pigmentCan u state the colour of skin and eyes of albinos patient????

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Sickle cell anaemiaSickle cell anaemiaDisease caused by the change in

the genes that produce hemoglobin

Hemoglobin that has undergone mutation is inefficient in transporting oxygen.

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Blood smear (normal)Image Credit: http://lifesci.rutgers.edu/~babiarz/

Sickle cell anemiaImage Credit: http://explore.ecb.org/

Haemophilia Haemophilia Deficiency of a type of protein in

the blood required for blood clotting.

A patient who has a wound will experience continuous bleeding or will take a long time for the blood to clot. This condition can lead to death.

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Quick test (15 minutes)

Answer the following question.1.Compare the characteristics

given and complete the following table.Characteristic Male Female

Number of chromosome 46 46Gamete formed Sperm Ovum Chromosome make up in somatic cell

44+XY 44+XX

Chromosome make-up in gamete

22+X and 22+Y

22+X

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2. what causes identical twins to have the same genetic make-up?

Identical twins originate from one ovum and one sperm which are the same.

3. Why is sex of a child determined by the father?

The sex of a child depends on the type of X chromosome or Y chromosome in the sperm which fertilises the ovum.

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