Science form 4 Mutation

7/29/2019 Science form 4 Mutation

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Do you ever see someone who

downs syndromeout

there?


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Why do these happen to them?


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3.4 MUTATION


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Learning outcomesAt the end of the lesson, you are able to

1. State what mutation is

2. State the types of mutation

3. List examples of mutation

4. Identify the causes of mutation

5. State the advantages anddisadvantages of mutation


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Mutation: the spontaneous

change to the structure of genes orchromosomes / genetic information.

Occurs in

Somatic/body cells

(can be passed downthrough mitosis)

Gametes/reproductivecells

(inherited)


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TYPES OF MUTATION

Gene mutation

Change in the

structureofDNA

Chromosome mutation

A change in the

numberand thestructureof

chromosomes.


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Downs syndrome: an extra chromosome in

autosome 21 (47 chromosomes)

Klinefelters syndrome: a male with extra X

chromosome (XXY)

Turners syndrome: a female with one less Xchromosome (XO)

Polyploidy: having one or more chromosomes ina set of chromosome


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Colour blindness: a mutated gene in theXchromosome

Sickle cell anemia: mutation in gene that

produces haemoglobin; inefficient in transportingoxygen in the blood

Albinism:the gene for skin colouris mutated;

unable to produce black pigment (melanin)

Haemophilia: mutation in gene that is importantfor blood-clotting


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Downs syndrome

Additional or EXTRA

chromosome at autosome 21.(47 Chromosomes)

Physical retardation

Thick neckSlanted eyes

Protuding tongue

Reduced resistance to diseases

Need Special Care.


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Klinefelters syndrome

A male with extra X chromosomes

(having XXY)

Infertile

Underdeveloped testes

Narrow shoulder

Some female characteristics

Enlarged breasts


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Turners syndromeA female having one less X

chromosome (XO)Infertile

Short

Mentally retardedHas no ovaries

Small breasts

Folded skin on neck

No menstrual cycle


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Polyploidy

The number of chromosomes is increased by one

or more sets. More common in plants.


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Colour blindness

Mutant gene (recessive gene) on the Xchromosome.

Not able to differentiate colours

especiallygreen and red

More common in

males because male has onlyone X chromosome


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Albinism

The gene for skin colour is mutated

(recessive gene)

Unable to produce melanin (black

pigment)

White hair

Pink eyes and pinkish skin

Skin is sensitive to sunlight


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Sickle-cell anemia

Mutation in gene that produce

haemoglobin

Sickle-cell shaped of red blood cells

Not efficient in transporting oxygen

Facing painful crises such as chest pain,

bone pain,Yellowing of eyes

Inherited from both parents


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Haemophilia

Mutation in chromosome X (for blood

clotting)

Have problem in blood clotting

May bleed continuously or for a longer

period

A woman carrier may inherit thedisease to a son


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Spontaneous changes

during cell division

Exposure to physicalmutagens: UV radiation,

X-rays, radioactiveradiation

Environmental change: thechange of temperature for along period causes genetic

evolution in organism

Exposure to chemicalmutagens: Benzene,

formaldehyde, nicotine,sodium nitrite, pesticides


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Give rise to variationwhich leads todifferences in traits

Better chance of

survival when newspecies are moreresistant to diseases

Advantages

Cause physical

defects/deformities

Causes geneticdiseases

Some chromosome

mutations and genemutation are lethal(fatal)

Causes mental

defects

Disadvantages


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QUIZPlease take a pieceof paper and write

your answersclearly.


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1. State the sex chromosomes for

i) male

ii) female 2. State 1 advantage and 1 disadvantage of

mutations.


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Documents

Science form 4 Mutation