Ch 3 Heredity

8/17/2019 Ch 3 Heredity

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www.sciencespmform4.blogspot.com 26

1. CELL DIVISION

1. The nucleus of a cell contains many small-thread like structures called chromosomes.2. Chromosomes are built from molecules called Deoxyribonucleic acids. (DNA)3. Each DNA molecules contains thousands of genes.4. Genes exist in pairs. One gene is inherited from the father and one from the mother.

MITOSIS & MEIOSIS

i. Mitosis occurs in all somatic cells, except in sex cells.ii. It produces 2 daughter cells.

iii. Meiosis occurs in sex organs to produce gametes.iv. One parent cell produces 4 daughter cells. The number of chromosomes is half of the

number in parent cell.v. There are 2 stages in meiosis, called meiosis_I _ and meiosis II_.

CELL NUCLEUS CHROMOSOME DNA GENE

CHAPTER 3 HEREDITY AND VARIATION

The chromosomes shorten, fatten andbecome clearly visible

Chromosome replication into thread –

like structures called chromatids.

Sister chromatids separate and moveto the opposite poles

Centromeres divide At the same time cell begins to divide

The new nuclear membraneis formed

Two daughter cells areproduced

Chromosomes align themselves at theequatorial plate

Parent cell

THE STAGES IN MITOSIS


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Replication and crossingover in chromatids occur

Chromosomes are arrangedat equatorial plate

Chromatids separate andmove to opposite poles

Chromosomes arearranged at the centre of

the cell

Each daughter cell contains halfthe number of chromosomes ofthe parent cell

Chromatids separate Cell begin to split

Chromosomes in nucleusshorten and fatten

2 daughter cells formed

Parent cell

THE STAGES IN MEIOSIS


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Compare and Contrast between Mitosis and Meiosis

Mitosis Meiosis

1 Cell division 2

2 Product 4

Same Number of chromosomes Half the number

Yes Genetically identical No

In somatic cells Place In sex cellsTo produce new cells for growthand to replace damaged cells

Purpose Gametes

MITOSIS

1.Mitosis form new cells for growth and to replace a damaged or died cells.2.To ensure that the number of chromosomes in daughter cell is identical to that of the parent cell.

MEIOSIS

1. To produce gametes with half the number of chromosomes of the parent cells.

2. It allows a species to maintain a constant number of chromosomes in the offspring.3. To form variation between species.

The Importance of Mitosis and Meiosis

Difference between mitosis and meiosis


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2. INHERITANCE

1. Inheritance is a process of passing genetic information of characteristics or traits from parents tooffspring.

2. Genes are divided into 2, dominant and recessive.3. Human beings have _46 chromosomes. This means that we have _23_ pairs of homologous

chromosomes.4. Combination of genes it possesses is called genotype.5. The characteristics that can be observed or determined is called phenotype.6. A dominant gene is a gene which can show the characteristics it controls when it pairs with a

recessive gen.7. The recessive gene only shows its characteristics when paired with another recessive gene.

CharacteristicsDominant

characteristicRecessive

characteristic

Tongue rolling Ability to roll the tongue Inability to roll the tongue

Ear-lobe Presence of ear-lobe Absence of ear-lobe

Eye colour Brown eyes Blue eyes

Skin pigment Normal skin pigment Absence of skin pigment(Albinism)

Mechanism of Inheritance of Traits

Father Mother

Parents (Free ear lobe) (Attached ear lobe)

EE ee

Meiosis

Gamet

Fertilization

Offspring

All free ear lobe

The schematic diagram shows the inheritance of ear lobe

Dominant genes are represented by capital letters whereas recessive genes are representedby small letters.

‘E’ represents the genes for free ear lobe, which is the dominant gene. ‘e’ represents the gene for attached ear lobe which is the recessive gene.

E E e e

Ee Ee Ee Ee


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Monohybr id cross

Y for dominant traits ( yellow seeds)y for recessive traits (green seeds)

Parents: YY X yy

Phenotype: __Yellow __ ___Green___

Gametes: Y Y y y

Genotype: ___Yy___ ___Yy__ Yy ____Yy___

Phenotype: __yellow___ yellow yellow yellow

________________________________________________________________________

F1 Generation: Yy X Yy

Phenotype: yellow seed _yellow seed__

Gametes: Y y Y y

Genotype: YY Yy Yy yyPhenotype: __yellow_ ___yellow __yellow _ _green

Phenotype ratio: ____3 yellow_____:_____1 green _____

3. SEX DETERMINATION AND THE OCCURANCE OF TWINS

1. Human has 23 pairs of chromosomes, 22 pairs are autosomes and 1 pairs is sexchromosomes.

2. Type of the sex chromosomes are _X_ and _Y_ _.3. Females have _XX_ sex chromosome, while male have _XY_ sex chromosomes.4. Female has contains 22 pairs of autosomes and 2 sex chromosomes XX(44 + XX) while

male has 22 pairs of autosomes and 2 types of sex chromosomes X and Y(44 + XY)5. The sex of a child is determined by the father according to the type of sperm.


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The schematic diagram below show how sex is determined.

Parents: Father MotherXY XX

Meiosis

Gametes: X Y X X

Fertilisation

Genotype: XX XY XX XY

Phenotype: Girl Boy Girl Boy

Genotype ratio: 1XX : 1XYPhenotype ratio: 1 girl : 1 boy

TWINS

1. There are two types of twins, identical and non-identical twins.2. Identical twins are formed from _1_ sperm and_1_ ovum, while non-identical twins are formed

from _2_ sperms and _2_ ova.

3. Identical twins have same genetic traits, sex_ and appearance _.4. Non-identical twins may have different_genetic traits and may have similar or different sex.5. In identical twins, if the two embryos do not completely separate, they are called

_siamese_ twins.The di f ferences b etween id ent ical twins and no n- ident ical twins .

Characteristic Identical twins Non-identical twins

Number of ovums involved 1 2

Number of sperms involved 1 2

Number of zygotes produce 1 2

Number of placentas 1 2

Sex of child (same / different) Same Same/different

Genetic traits (same / different) same different

6. The similarities between this two types of twins are born through pregnancy.

4. MUTATION1. What is mutation?

The spontaneous random change to the structute of genes or chromosomes of anorganism.

2. There are two types of mutation, gene mutation and chromosomes mutation.3. The change that occurs in chemical structure of a gene is gene mutation.4. The change of gene sequence in a chromosome or the change in the number of chromosomes

is chromosomes mutation.5. The examples of gene mutation are albinism, colour blindness and haemophilia.6. The examples of chromosome mutation are Down’n syndrome, Klinefelter’s and Turner’s

syndrome.7. The Down’s syndr ome is caused by the presence of one extra chromosome at chromosome 21

in the somatic cells.8. The characteristics of Klinefelter’s syndrome are narrow shoulders and small testes.9. The Tur ner’s syndrome is a women who lacks one X chromosome.10. There are some factors that can increase the chance of mutation : High frequency radiowaves,

toxic chemical and nuclear radiation.


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11. The advantages and disadvantages of mutation:

Advantages Disadvantages

Causes variations and organisms able to adaptto the environment

Causes infertility

More resistant to diseases, wheather and

polluted environment

Causes physical, mental and foetus

retardation

5. GENETIC RESEARCH

1. Genetic research have contributed to the field of _medicine_and agriculture_.2. The example of contribution in each field:

3. Selective breeding is very important. It is done on crops and livestock.

4. The importance of selective breeding in plants and livestock’s are: i. Resistant to diseases.ii. Shorter growth period.iii. Higher yield.iv. Better quality.

6. VARIATION

1. Variation is the difference among individuals of the same group.2. The examples of variation in human are fingerprints, ability to roll a tongue, ear lobe and

blood group.3. There are two types of variation, continuous and discontinuous.

4. The example of continuous variation are height, body weight, intelligence, skin colour, width

of shoulder and length of sole.5. The examples of discontinuous variation are blood group, fingerprint, ability to roll the

tongues, ear lobe, left-handedness and presence of dimples.6. The similarity of continuous and discontinuous variation is caused by crossing over in meiosis

and mutation.7. The differences between the two types of variation:

Type Continuous variation Discontinuous variation

Has distinct characteristics Small degree of variation Clear-cut differences

Environmental factors Affected Not affected

Can be inherited No Yes

8. There are two factors that cause variation, genetic and environmental.

9. Mutation may also be another factor of variation and it will produce new variety.10. Variation is very important for us. The example of the important of variation are:

i. Enable each individual to be different from others.ii. More resistant to changes in the surrounding.iii. To form new breeds.

7. CODE OF ETHICS IN GENETIC RESEARCHES

Misused of knowledge in genetics can cause various controversial issues concerning religion andhumanity. Code of ethics in genetic researches is important to ensure that genetic researches benefitmankind.

Example: Human cloning and the marketing of genetically modified products have become hotissues debated at present.If cloning is carried out on humans, serious problems would arise. Religiouspeople consider humans produced by cloning as not having souls.

Medical Agr icul ture

To make human insulin for diabetics Species Tenera a new breed of oil palm fruits

Sheep can produce milk which contains proteinthat can cure haemophilic

The sahiwal Friesian cows which produce moremilk


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PAPER 1

1. Which of the following is the unit of inheritance found in chromosomes?

A Gene C GameteB Sperm D Nucleus

2. What is the function of cell division through meiosis?

A Produces more siblingsB Replaces damaged tissuesC Increases the size of an organismD Creates variation in a population of organisms

3. The diagram below shows four stages of mitosis in a plant cell.

Which of the following is the correct sequence of mitosis process?

A P,R,Q,S C Q,P,R,SB R,P,S,Q D S,P,R,Q

4. A goldfish has 100 chromosomes in each body cell. How manychromosomes are found in each male gamete?

A 25 C 75

B 50 D 100

5. What is the number of chromosomes found in a female human skin cell?

A 22+ X C 44 +XXB 22+ Y D 44+XY

6. Which of the following processes in plants involves meiosis?

A Bud growth C Repair of tissue

B Root growth D Formation of pollen


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7. Chromosomes duplicate during cell division. How many times does replication ofchromosomes occur during mitosis and meiosis?

8. What is the name of the thread-liked structure found within the nuclei of a cell?

A Gene C NucleusB Autosome D Chromosomes

9. The diagram below shows a process in the human body.

Parent cell

Process Y

Daughter cells

What is the name of the process?

A Mitosis C MeiosisB Fertilization D Cross-over

10. Where does mitosis take place?

A Sperm C OvaryB Anther D Somatic cells

11. The diagram below shows cell division in an animal cell.

Which of the following statement is correct about the cell division?

A Cell divides once onlyB Four identical cells are producedC Have the same kind of chromosomesD Similar number of chromosomes as parent cell

Mitosis Meiosis

A once once

B once twiceC twice once

D twice twice


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Stage Y

12. The diagram below shows four stages of meiosis.

Which of the following shows the correct sequence?

A P,R,S,Q C Q,S,P,RB R,S,P,Q D Q,R,P,S

13. Which of the following statements is true about mitosis?

A Occurs in ovaryB Produces gametesC Produces two daughter nucleiD Chromosomes number is halved

14. What are dominant genes?

A Cannot reproduce themselvesB Fully express their characteristicsC Do not express their characteristicsD Multiply to produce more daughter cells

15. When can the recessive genes be expressed fully?

A Dominant genes are absentB Dominant genes are presentC Both dominant and recessive genes are absentD Both dominant and recessive genes are present

16. The diagram shows the stages in human reproduction.

Sperm

Zygote BabyOvum

What are stages X and Y?

X Y

A Mitosis Mitosis

B Meiosis Mitosis

C Meiosis Meiosis

D Mitosis Mitosis

Testes

Ovaries

Stage X


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17. Which of the following processes is involved in the formation of zygote?

A Mitosis C MutationB Meiosis D Fertilization

18. Which of the following is dominant trait in human?

A Curly hair C Left handedB Blue eyes D Attached ear lobe

19. The gene for tall characteristics T of a pea tree is more dominant than t, whichreveals the short characteristics. Which of the cross below will produce half of the filialwhich are tall?

A TT and tt C TT and Tt

B Tt and Tt D Tt and tt

20. Azman who has the ability to roll his tongue has gene Aa and marries Siti whohas the same ability and has gene Aa too.What is the percentage of having children that are not able to roll t tongue?

A 100% C 50%B 75% D 25%

21. The diagram shows sex determination in human

Parent 44+XY x 44+XX

Gamete P 22+Y 22+X 22+X

Offspring 44+XX Q 44+XY 44+XY

Which of the following chromosomes are found in gamete P and offspring Q ?

P Q A 22+Y 22+ XB 22+X 44+XXC 22+Y 44+XXD 22+X 44+XY

22 What is the chromosome in a normal human egg cell ?

A 22+ X C 22+YB 23+XY D 23+XX


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23. The diagram shows a first generation of cross breeding of two flowers

Parents red flower x white flower

First red red white whiteGeneration flower flower flower flower

R represents the dominant genes for red flowerr represent s the recessive genes for white flowerWhat are the genes for the parents?

Male Female A RR RrB RR rr

C Rr rrD rr Rr

24. Farid who is able to roll his tongue has the genotype Gg. He married Sara whois also able to roll her tongue and has the genotype Gg. What percentage of theirchildren will be able to roll their tongues?

A 25% C 75%B 50% D 100%

25. What determines the gender of a baby ?

A Chromosomes in the ovumB Type of sex chromosomes in the spermC Number of chromosomes in the spermD Number of chromosomes in the ovum

26. Which of the following is the correct genotype?

27. What is the percentage probability that a couple will have a baby girl?

A 25% B 50% C 75% D 100%

28. What is the chromosome number of a female foetus?

A 22+X C 44+XXB 22+Y D 44+XY

Male Female

A XX XY

B XY XX

C YY XXD XX YY


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29. How are identical twins formed?

A Two ova fertilized by two different spermsB One ovum fertilized by two different spermsC Two ova fertilized by one sperm before splitting into twoD One ovum fertilized by one sperm before splitting into two

30. Why can non-identical twins be of different sexes ?

A They arise from the same zygoteB The same sperm fertilizes two different ovaC Two different sperms fertilize two different ovaD Two different sperms fertilize the same ovum

31. Which of the following describes Siamese twins?

A Born separatelyB Have different genetic contentC Have underdeveloped body partsD Identical twins do not separate completely

32. Two children are identical twins. Which of the following characteristic is not commonbetween them?

A Sex C Blood groupB Height D Ability to roll tongue

33. What is the term used for the sudden and permanent changes in the DNA ?

A Mitosis C VariationB Mutation D Crossing over

34. Which of the following can cause mutation?

A Changes in the shapeB Random physical changesC Changes in the genes structure

D Random fusion of a sperm and an ovum

35. The nucleus of a boy’s skin cell has 47 chromosomes. What is the name of the geneticdisorder the boy is suffering from ?

A Albinism C Sickle cell anemiaB Down’s syndrome D Turner’s syndrome

36. What causes albinism?

A Virus infection C Hormone imbalanceB Mutation of a gene D Changes in chromosomes number


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37. Which of the following pairs is correct?

ABCD

38. What is the advantages of mutation?

A Form underdeveloped individualsB Produce more varieties of new speciesC Stop the process of growth in organismsD Encourage the process of growth in organisms

39. The information shows the characteristics of an individual.

What is the name of genetic disorder the individual is suffering from?

A Albinism C Colour blindnessB Haemophilia D Down’s syndrome

40. Which of the following is a result of gene mutation?

A HaemopliliaB Down’s syndromeC Turner’s syndromeD Klinefelter’s syndrome

41. The diagram shows the cross between two different varieties of mango

X

Mutation Characteristics

Down’s syndrome 47 chromosomes in the nucleus

Klinefelter’s syndrome XYY in the gene

Tur ner’s syndrome Lack of one Y chromosome in the gene Albinism Additional Y chromosomes in the gene

Lacks pigmentation in the skin

Has white skin, eye lashes and hair

Skin is sensitive to sunlight

Mango K-has thick flesh- sweet-small fruit

Mango L-slightly thinner flesh-not so sweet-big fruit

Mango M


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What is the purpose of crossing Mango K with Mango L?

A Plenty of fruitsB Big and sweet fruitsC Trees bear fruits fasterD Big fruits with thick flesh

42. What is the term used for the selection of plants or animals of desirable traits?

A Gene screeningB Artificial breedingC Natural selectionD Selective breeding

43. What is the production of genetically identical individuals called?

A Cloning C Back-crossingB Breeding D Hybridization

44. The diagram shows the breeding of two different types of oil palm

X

small fruit bigger fruitthin mesocarp thicker mesocarp

thin endocarp thicker endocarp

What is the result of breeding these oil palms ?

A Plenty of oil palmB Sweeter oil palmC Oil palm Z produces plenty of palm oilD Oil palm Z becomes more resistant to disease

45. Which of the following is an example of a continuous variation?

A Fingerprint C HeightB Blood group D Type of ear lobe

Oil Palm X Oil Palm Y

Oil Palm Z


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46. Which of the following graphs correctly shows the distribution frequency ofcontinuous variation?

A B C D

47. Which of the following is the example of discontinuous variation?

A HeightB Skin colourC Blood groupD Body weight

48. What is the meaning of variation?

A Sudden change in hereditary materialB Sudden change in external appearance caused by the environmentC Different expression of similar characteristics among individuals of

the same speciesD Different expression of similar characteristics among individuals of

the different species

49. Which of the following does not involve genetic engineering?

A Gene therapy for treating cancerB The production of Tenera oil palmC The production of insulin by bacteriaD The production of genetically modified food

50. What is the characteristics desired from the genetic research done on plants?

A Matures fasterB Produces less fruit

C Easy to get diseasesD Has short life span


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PAPER 2

SECTION A

1. Pupils in a certain class had their weight measured. The data obtained is shown below:

Weight of pupils ( kg )

36 41 45 46 45 43 44 40 53 5258 59 51 45 46 48 45 47 49 4447 50 43 51 38 47 49 48 54 46

(a) Complete Table 1 using the given data.

Weight of pupils (kg) 35-39 40-44 45-49 50-54 55-59

Number of pupils

TABLE 1

(b) Using the data in table 1, draw a histogram below to show the distribution ofthe weight of pupils.

Weight (kg)

Number of pupils

8

12

14

4

50-54 35-39 40-44 55-59 0 45-49


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[2 Marks](c) What type of variation is shown by a pupil’s weight ?

………………………………………………………………………………………… [ 1 Mark]

(d) Other than weight, state two examples that show the same type of variation.

……………………………………………………………………………………… [ 1 Mark]

SECTION B

1. Diagram 1 shows the process involved in the formation of twins

Ovum sperm Process Q

Two zygoteformed

DIAGRAM 1

(a) Name the process that takes place at Q

…………………………………………………………………………………….…………… [ 1 Mark]

(b) Name the type of cell division that takes place at R

………………………………………………………………………………………………… [ 1 Mark]

(c) State the type of twins formed in the figure shown above.

………………………………………………………………………………………………… [ 1 Mark]

(d) State two similarities found in the zygote formed after process R.

…………………………………………………………………………………….……………

…………………………………………………………………………………….…………… [ 1 Mark]

Process R


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(e) What type of twins that will be formed if process R is incomplete?

…………………………………………………………………………………….…………… [ 1 Mark]

(f) If the spermatozoa in the figure carries 22+Y chromosome,

(i) what will be the sex of the zygotes?

…………………………………………………………………………………….…………… [ 1 Mark]

(ii) state the number and the type of sex chromosomes in both the zygotes

…………………………………………………………………………………….…………… [ 1 Mark]

2. Diagram 3 shows the cross-breeding of pea plants. T represents the dominantgenes while t represents the recessive gene.

Parent Tall plant x Short plant

Genotype

Gamete

Genotype Tt

Phenotype Tall Tall Tall Tall

DIAGRAM 3

(a) What is meant by gene?

…………………………………………………………………………………….…………… [ 1 Mark]

(b) The above pea plant have a pair of Tt genes which show the tall trait. Explain this.

…………………………………………………………………………………….…………………

[ 1 Mark]

(c) Complete the above figure by writing the possible genotypes of the parent, gameteand offspring

[2 Marks]


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3. The bar chart below shows the result of a study in a group of students.2.

80

60

40

20

able unable

(a) Calculate the percentage of students who are able to roll their tongues.

…………………………………………………………………………………….…………… [ 1 Mark]

(b) i) What are the characteristics shown by the graph above?

…………………………………………………………………………………….…………

……………………………………………………………………….………………… [ 1 Mark]

ii) What is the type of variation in this situation?

…………………………………………………………………………………….………… [ 1 Mark]

(c) i) Is ‘ the presence or absence of ear lobes’ the same type of variation as (b)ii?

…………………………………………………………………………………….………… [ 1 Mark]

ii) Give reasons for your answer in (c) i.

…………………………………………………………………………………….……………

…………………………………………………………………………………….…………

[1 Mark]

Number ofstudents

Roll tongue


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4 (a) What does cell division refers to?

……………………………………………………………………………………….

………………………………………………………………………………………. [ 1 Mark]

(b) What is meiosis?

……………………………………………………………………………………….

………………………………………………………………………………………. [ 1 Mark]

(c) Compare the number of chromosomes in the daughter cells and in the parentcell

…………………………………………………………………………………………

………………………………………………………………………………………… [ 1 Mark]

(d) State two importance of meiosis in organisms

i) ………………………………………………………………………………………

ii) ……………………………………………………………………………………….

[2 Marks]


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SECTION C

1.

(a) Examine the above statement, then suggest a suitable hypothesis for aninvestigation to determine the weight of forty students (boys and girls) who are all18 years of age. [1 Mark]

(b) Describe an experiment that could be carried in the classroom to verify yourhypothesis.Your description should include the following:

(i) Aim of the investigation [1 Mark](ii) Identification of variables [3Marks](iii) List of apparatus [1 Mark](iv Tabulation of data [1 Mark](v) Conclusion [1 Mark]

2. Study the statement below

(a) Suggest a suitable hypothesis to investigate this statement. [1 Mark]

(b) Design an experiment to test your hypothesis this statement(i) Aim of the experiment [1 Mark](ii) Identification of variables [2 Marks](iii) List of materials and apparatus [1 Mark]

(iv) Method [3 Marks](v) Recording and analyzing [1 Mark](vi) Conclusion [1 Mark]

No two individuals are alike. Every person is unique in himself

The length of leaves is a type of continuous variation


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i f 4 bl t 49

HairSkin

Liver Red bloodcell

3. (a) State four differences between cell division through mitosis and meiosis.[4 Marks]

(b)

The cell division that takes place in the body parts of a student is shown above. Explainhow you would build a concept based on the information above. Your explanation shouldinclude the following.

(i) Identify two common features(ii) Build an initial concept(iii) Give one example of body part that undergoes this cell division and one

example of body part that does not undergo this cell division.Give reason for each example.

(iv) Explain the actual concept [6 Marks]

Cell division

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Ch 3 Heredity

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