VARIATION2003 SECTION A (NO 3) :

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2007 A(4)

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SKEMA JAWAPAN.

2003. A(5)

NO MARKING SCHEME MARK5 (a)(i)

(ii)

(iii)

(b) (i)

(ii)

(c)

(d)

Whorl: composite

Genetic factor

Arrangement and recombination of genes during crossover will produce gametes that are different genetically.

Discontinuous variation

Ability to roll tongueBlood group

Thumbprint is discontinuous variation and the photograph is continuous variation for individual that has same face.i.e for identical twin.

The body mass is continuous variation whereas thumbprint is discontinuous variation.

Body mass is influenced by genetic factor and environment whereas thumbprint is only influenced by genetic factor.

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3

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1 (12)

5 (a) (i)

(ii)

(b)(i)

(ii)

(e)

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The male karyotype will have a pair of homologous chromosome that have different sizes, i.e chromosome pair XY.The female karyotype will consists of all chromosome pairs with the same size and homologous.

Gametes Q : 22 + XGametes R : 22 + YGametes J : 22 + X

Process P is meiosis, i.e. the homologous chromosome pairs is separated to different daughter cells.

The female carrier of colour blind gene has genotype XBXb and the male colourblind has genotype of XbXY

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A great possibility that during fertilization of gametes that

NO MARKING SCHEME MARK

5 c (i)

(ii)

Carries the allele Xb is not fertlised because fertilization that occurs is random.Hence , genotype XBXb and XbY cannot be obtained

Father motherParent XBY XBXbgenotype

gamete XB Y XB Xb

offspring XBXB XBXb XBY XbYgenotype

offspring girl girl boy boy phenotype: normal normal normal colour-blind

= ¼ x 100 % = 25%

2004 Section C

5 (a)

(b)

(c)

(d)

Follicle Stimulating Hormone (FSH)Role : Sent from the pituitary gland to stimulate the formation of follicles in the ovary.Hormone P is oestrogen whereas hormone Y is luteining hormone. Hormone P cause the rejuvenation of uterus wall, whereas hormone Y will cause ovulation. If hormone P is not balanced with Y, hence the ovulation process will be delayed or decreased(i) day 26

(ii) structure T is corpus luteum that secreted progesterone, Q and oestrogen. When reaches day 26, the structure will degenerate. Hormone P and Q will decrease.

The pituitary gland will secrete FSH, LH, oxytosin and prolactin. If the menstruals persists, hence FSH and LH will play their part. If fertilization occurs, and during pregnancy, FSH and LH will not be secreted. Progesterone will be high.

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The menstrual cycle will not occurs. Oxytosin and prolactin

NO MARKING SCHEME MARKhormone will be produced when the baby is born.

Section C3 (a)

3 (b)

(a) female ( ) Male ( )

Parents HH X hh

Black, HWhite, h

In the parents, a pair of alleles code for colours at the same locus on the pair of homologous chromosomes. From the pair of allele, only one allele exits in the gametes due to meiosis. This occurs in Mendel’s First Law.

Gamete : H H h h

If the first generation is cross-breed between themselves, the rat in F1 will obtain a pair of alleles for black colour at the same locus at the pair of homologous chromosomes after fertilization.From the pairs of alleles, only one allele exists in the gamete.The rat from F2 will obtain a pair of alleles for coloured body at the same locus on the pair of homologous chromosome.

Chemical K, a mutagen will cause mutation on the genes or the chromosomes of the rat naturally during replication of the chromosome and segregation of the chromosome to the gamete cells in the reproductive organs. Mutation will be passed down to the zygote. Mutation of the chromosome cause changes in the structure of the chromosome which includes :

(i) loss of several genes(ii) addition of genes(iii) transfer of genes

Changes in the number of chromosomes is also a part of mutation of chromosome, i.e . loss of chromosome or addition of chromosomes. Genes mutation causes changes at the base of DNA molecule and this affects the production of protein.Degeneration will exists in the rats. There will be sterile rats, their offsprings will defected. The rat population will decrease

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until a state of equilibrium where they are able to adapt themselves and live as a mutant

4 (a)

(b)

Charactersistics

Father Mother Child- curly hair- black hair- has dimple- thick lips- oval face

-straight hair-brown hair-no dimpler- thin lips- round face

- curly hair and black- has dimpler- thick lips- round face

Based on the differences above, can be concluded that the child inherit a lot of characteristics from the father who is dominant.The combination of characteristics of the father and mother can be inherited by the child by (i) cross- over at meiosis 1(ii) choosing of dominant characteristics through Mendel’s First law.

Haemophilia is a sex linked disease on chromosome X only. The characteristics is carried by the recessive gene.Haemophilia can occur in men because men only need one recessive gene on chromosome X to cause the haemophilic characteristicsA woman who has family pedigree of haemophilia does not necessarily has it because she can still exist in heterozygous condition which means that the female is normal but she is a carrier for the next generation. Two recessive genes are needed to show the haemophilic characteristic. The inheritance of haemophilia can be avoided by making sure that every marriage of the grandchildren do not invo lve carriers of haemophilic individuals, and eventually after generations by elimination, the recessive genes will disappear.

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NO MARKING SCHEME MARK2005 Section B7 (a)

(b)

(c)

The process of producing sperms is known as spermatogenesis-the primordial germ cells undergo cell division by mitosis to produce a large number of spermatogonium which is diploid-The spermatogonium enlarges to become primary spermatocyte.- each primary spermatocyte divides by meiosis I and then produces a pair of secondary spermatocyte which is haploid (n)-Every pair of secondary spermatocyte divides by meiosis I to produced 4 haploid spermatids.-finally, the spermatid will differentiate to produce a sperm that can move and swim-when injected with HCG in female, primary oocyte will undergo meiosis I which is incomplete and it will complete the process of meiosis I before ovulation occurs, producing secondary oocyte and polar bodies.- the women is incouraged to produced secondary oocyte that surrounded by follicle cells known as secondary follicle and will form Graffian follicle when it is matured. The the Graffian follicle will burst to release secondary oocyte by ovulation.- pregnancy will occurs when the ovulation is stimulated- as soon as the sperm gets into the uterus, the secondary oocytes will complete meiosis II when the sperm penetrates the oocyte.- ovum will then be produced and the union of the two nucleus from ovum and sperm will occur- fertilization has occurred and the woman is pregnant

(i) Similarities - identical - same age - formed from the same zygote - same sex - similar in all aspects and number or type of chromosomes Differences - twin P is attached at a part of body whereas Q is not attached - the zygote is perfect at P - twin P shares with a part of body that is attached - the life of P is restricted because has to move together - twin Q lives as a separate individual - twin Q is identical and P is Siamese twin

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NO MARKING SCHEME MARK(ii)

Twin R Twin SType of win Identical twins Fraternal twinsProcess of formation of pairs

One zygote produced from fertilization of one ovum and one sperm to form a blastula and divides into two spontaneously to form two individual

Two zygotes produced from fertilization of two ovum and two different sperms to form two zygotes separately and divides to form two individuals

Characteristics of pairs

-identical in all aspects-same physical appearance-same sex-same in number of chromosomes-genetically same

-not identical because they are two different individuals-like sisters/brothers-can be same or different sex-genetically different

Section C8 (a) Mendel’s First Law of segregation, i.e one gene

characteristic is carried by one allele in every gamete and forms a monohybrid in the genotype ratio of 3:1.Key : T : tall, t : short/dwarfParent TT X tt

Gamete T T t t

1 st generation Tt Tt Tt Tt

Parent gamete Tt X TtGamete T t T t

2 nd generation TT Tt Tt tt

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Tall : dwarf

(b) Dura X pisifera

hhFF HHff

Tenera H : F ( Thick husk : thick kernel)

Tenera X Tenera HhFf HhFf

Gamete HF Hf hF hf

Generation HF HHFF HHFf HhFF HhFfCrossbreed Hf HHFf HHff HhFf HhffOf Tenera hF HhFF HhFf hhFF hhFf (genotype) hf HhFf Hhff hhFf hhff

Phenotype : Thick : Thick : Thin : Thin Husk husk husk husk Thick thin thick thin Kernel kernel kernel kernel

9 : 3 : 3 : 1

Only 9/16 X 100 = 900/16 of generation = 56 .25 % crossbreed between Tenera will produces thick nhusk, thick kernel, not 100 %

(c) There are advantages and disadvantages in the development of genetic engineering. Advantages.

1. Contribution in agriculture - the crops are resistant to diseases and changes in the environmentExample: Resistant to viral attack, herbicides and pesticides. Able to fix nitrogen efficiently Can withstand climatic changesExample of crops: tomatoes,soybean,corn,wheat,barley,

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paddy,carrot,cauliflower,watermelon and apples

2. contribution to medicine(a) produce insulin to treat diabetes. The gene from DNA is responsible to produce insulin in the cell is placed into a DNA of bacteria E coli. The bacteria are left to breed in the nutrient and produces insulin.

(b) Other hormones formed are important for human such as somatotropin to treat dwarfness of interferon, to treat disease by virus and cancer, also vaccine for hepatitis B

(c) To detect the foetal condition in the uterus whether there are genetic disorder such as Thalasemia, Huntington disease, cystic fibrosis, Down Syndrome, Duchennes’s muscular destrophy and other.

3. Other contribution DNA fingerprinting can be use to identify the parents of an individual, to identify criminals, genetic diseases, cancer and other diseases caused by virus.4. Human Genome Project is aimed to identify all genes on the chromosomes so that human can : - identify genetic diseases - identify diseases caused by interaction between gene and the environment - treat dangerous diseases - identify genetic changes at old ages

Disadvantages

1. maybe can create many issues from social,religious, economic and moral aspects2. Food that is modified genetically maybe not safe to consume and can arise side effects on humans. This also encourages mutation of virus, bacteria and organisms causing new genes to be formed which can adversely affect the health of human.3. Normally the projects will involve a lot of money hence rich people will only be paid. This will causes problem to poor people.4. If the scientist are unethical . they create a lot of social problems and political problems by creating clones that are under human control.

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NO MARKING SCHEME MARK2006 Section B4 (a)

(b)

(c)

P : pollen tube Q : male gametesR : ovary S : embryo sacs

(i)

Polar nucleus

Egg cell/ ovum

(ii) - one male gamete fuses with the egg cell- another polar male gamete fuses with the two polar

nucleus- double fertilization occurs.

(i) Place in dry/cool place which is air tight(ii) Place in sugar solution.

5 (d)This is substitution mutation where the amino acid valine replace glutamic acid. The amino acid sequence in the polypeptide is altered. This changes the structure of the protein which loses its to original function

2007 Section A

4 (a)

(b)

P : PhosphateQ : Nitrogenous baseComplete diagram:Criteria:1. correct pairing for all the nitrogenous base (shape)2. position of pentose sugar// pentagon shape3. complete chain (phosphates are bonded to pentose molecules)

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(c)

(d)

(e)

(i) Mutation/chromosomes mutation/deletion

(ii) exposure to radioactive substances/X Ray/alpha radiation/ gamma ray / beta ray /ultra violet light/ laser ray / carcinogenic chemicals(i) Girl/Female/woman

(ii) Down Syndrome Chromosomes number 21 has three chromosomes1. allele for black fur is dominant//black fur2. each gamete carries one allele (for the fur colour) from the parents//each offspring receives one allele from each parents3. Each offspring produced is heterozygous// carries one dominant allele and receive allele.

2008 Section A3 (a)

(b)(i)

(ii)

(c)(i)

(ii)

Genotype : Bb/heterozigygous//heterozigusPhenotype : Black fur // bulu hitam

1. Different / alternative form of gene/ same gene2. Occupy the same locus on a pair of homologous chromosomes3. Each allele is responsible for the expression of the contrasting trait/black fur /white fur Alleles B and b / both alleles are separated/ segregated

Bb or BB // Bb // BB

P1 : gamete from R carry allele B or b // R has Bb

: gamete from S carry allele B only (if S is homoziguot) // S carry BB

: gamete from S carry allele B or b (if S is heterozigot) S carry BbP2 : V received one dominant allele/ gene from R and one allele from S during fertilization of gametes

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(d) (i)

(ii)

Parent Bb X bb

Gamete B b b

Offspring Bb bb

Black fur white fur

50 % / ½ / 0.5

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4 (a) (i)

(ii)

(b) (i)

(ii)

(c)

Fraternal twins / non identical twins // kembar tak seiras

P1 : Two ovum /ova/eggs are released from the ovary at the same timeP2 : each ovum is fertlised/fuse by a different spermP3 : two different zygotes/ embryos are formed

Placenta

P1 : Provide/supply/transport/give nutrients/Oxygen/glucose Hormone, antibody for the growing foetusP2 : Secretes hormonea that are essential in pregnancyP3 : help to remove the waste /excretory products of the foetusP4 : Forms a selective barrier/separate membrane between the mother’s blood and the foetal bloodP5 : Allows substances to pass from mother to foetus/vice Versa

P1 : Twins P shares the same placenta whereas twins Q have separated placentasP2 : Twins P are formed by a single pair of sperm and ovum but twins Q are formed by two pairs of sperm and ovum// P is form from 1 zygote but Q is form from different zygote.P3 : Twins P posses identical genetic constituent/ content/material whereas twins Q have different genetic constitution/content/materialP4 : Twins P are similar in physical appearance / feature/ characteristic but not in twins QP5 : Twins P have the same sex / gender but twins Q are not

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4(d)

(e)

necessarily of the same sex/gender

P1 : Different eating habit P2 : Different daily activities

C1 : Chemicals like nicotine can diffuse through the placenta to the foetusE1 : This will cause brain damage / retarded growth of the foetus/ decrease the size of foetus

C2 : Carbon monoxide can diffuse through the placenta to foetusE2 : This will deprives/ lack its tissues of oxygen/reduce its growth

C3 : Carcinogensubstance/ example : benzene/acetone/ formaldehydeE3 : cause mutation // explanation

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