UNIVERSITEIT VAN PRETORIA GTS EKSAMEN / EXAMINATION

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1 UNIVERSITEIT VAN PRETORIA GTS EKSAMEN / EXAMINATION Tyd/Time: 3 h STUDENTE NR / STUDENT NR: VAN & VOORLETTERS (Opsioneel) / SURNAME & INITIALS (Optional): PUNT/ MARK 100 EKSAMINATORE: / EXAMINERS: Dr V van Staden Ms P de Waal (Intern / Internal) Dr WC Fick (Ekstern / External) HEREKSAMENS: Dit is u EIE verantwoordelikheid om vas te stel of u vir 'n hereksamen kwalifiseer. Name van kandidate sal Woensdag 17 November 2004 op die kennisgewingbord langs Kamer 7-33 in die Landbougebou sowel as op WebCT verskyn. SUPPLEMENTARY EXAMINATIONS: It is your OWN responsibility to find out whether you qualify for a supplementary examination. Names of candidates will appear on the notice board next to Room 7-33 in the Agricultural Building as well as on WebCT on Wednesday 17 November Beantwoord alle vrae. Moet asb nie in die regterkantste kantlyn skryf nie. Kopiereg voorbehou. / Answer all questions. Please do not write in the right hand margin. Copyright reserved. Vraag 1 / Question 1 [6] Is elkeen van die volgende stellings waar of vals? / Is each of the following statements true or false? a. n Toetskruis is n kruising tussen n individu met n onbekende genotipe en n heterosigotiese individu. / A testcross is a cross between an individual with an unknown genotype and a heterozygous individual. b. Gene wat ver van mekaar op n chromosoom geleë is mag dalk nie koppeling toon tydens genetiese kruisings nie. / Genes located far apart on a chromosome might not show linkage during genetic crosses. c. Die fisiese voorkoms van genetiese eienskappe in n organisme word die genotipe genoem. / The physical manifestation of genetic traits in an organism is called the genotype. d. n Resessiewe alleel word slegs uitgedruk wanneer dit homosigoties is. / A recessive allele is expressed only when homozygous. e. Onvolledige penetransie van n geen kan beïnvloed word deur die omgewingstoestande. / Incomplete penetrance of a gene can be influenced by the environmental conditions. f. Onlangse eksperimentele data dui daarop dat rekombinasie plaasvind voor die chromosome gerepliseer het. / Recent experimental data indicate that recombination occurs before the chromosomes have replicated. 1

2 Vraag 2 / Question 2 [6] Beskou n plant met die chromosoomformule 2n = 40 = 2x: / Consider a plant with the chromosome formula 2n = 40 = 2x: a. Wat verteenwoordig die simbool 2n? / What does the symbol 2n represent? b. Wat verteenwoordig die simbool x? / What does the symbol x represent? c. Hoeveel stelle chromosome is daar per gameet in hierdie plant? / How many sets of chromosomes are there per gamete in this plant? d. Hoeveel DNA molekules is daar per sel tydens die G 2 fase van die selsiklus? / How many DNA molecules are there per cell during the G 2 phase of the cell cycle? e. Hoe sal hierdie chromosoomformule verander moet word indien die plant n tetraploïed is, met 40 chromosome in sy blaarselle? / How would this chromosome formula need to be changed if this plant is a tetraploid, with 40 chromosomes in its leaf cells? f. Hoe sal hierdie chromosoomformule verander moet word indien die plant n tetrasoom is, met 40 chromosome in sy blaarselle? / How would this chromosome formula need to be changed if this plant is a tetrasome, with 40 chromosomes in its leaf cells? Vraag 3 / Question 3 [6] Gee een word of term vir elkeen van die volgende definisies: / Give one word or term for each of the following definitions: a. Die onvermoë van homoloë chromosome om te skei en na teenoorgestelde pole te beweeg tydens meiose I. / The failure of homologous chromosomes to separate and migrate to opposite poles during meiosis I. b. Twee chromosome wat dieselfde struktuur en grootte het en dieselfde gene dra, maar in nukleotiedvolgorde kan verskil. / Two chromosomes that have the same structure and size and carry the same genes, but can differ in nucleotide sequence. c. Chromosome wat gedeeltelik homoloog is, maar nie normaalweg met mekaar paar tydens meiose nie. / Chromosomes that have some homology, but do not normally pair with each other during meiosis. d. n Kruising tussen twee individue wat beide heterosigoties vir n spesifieke lokus is. / A cross between two individuals that are both heterozygous for a specific locus. e. n Outosomale eienskap waarvan die uitdrukking verskil in manlike en vroulike individue. / An autosomal characteristic of which the expression differs in male and female individuals. f. Oorerwingspatroon van gene wat op die homoloë gebiede van die menslike X en Y chromosome voorkom. / Inheritance pattern of genes that are found on the homologous region of the human X and Y chromosomes. 2

3 Vraag 4 / Question 4 [12] U bestudeer seldeling in twee verskillende organismes, een met 2n = 2, en die ander met 2n = 4, maar u mikroskoop plaatjies het deurmekaar geraak. / You are studying cell division in two different organisms, one with 2n = 2 and the other with 2n = 4, but you accidentally confused your microscope slides. Identifiseer vir elke sel hieronder gegee: / Identify for each of the cells given below: a. Die fase van seldeling wat u waarneem. Kies een van die volgende: metafase, metafase I, metafase II, anafase, anafase I, anafase II. / The stage of cell division that you observe. Choose one of the following: metaphase, metaphase I, metaphase II, anaphase, anaphase I, anaphase II. b. Die 2n aantal van die organisme (2n =2 of 2n=4). / The 2n number of the organism (2n = 2 or 2n = 4). a.... a.... a.... a.... a.... a.... Vraag 5 / Question 5 [7] Die genetiese siekte brachidaktilie, wat lei tot vervormde hande met kort, dik vingers, is outosomaal dominant. Twee individue wat beide brachidaktilie het trou, en hulle eerste kind is n seun met normale hande. Hulle beplan om nog vier kinders te hê. / The genetic disease brachydactyly, that leads to malformed hands with short, thick fingers, is autosomal dominant. Two individuals with brachydactyly marry, and their first child is a boy with normal hands. They plan to have four more children. a. Wat is die waarskynlikheid dat die volgende kind weer n seun met normale hande sal wees? / What is the probability that the next child will again be a boy with normal hands? (2)... b. Wat is die waarskynlikheid dat van hulle volgende vier kinders, ten minste twee van die kinders brachidaktilie sal hê? / What is the probability that of their next four children, at least two will have brachydactyly? (5) 3

4 Vraag 6 / Question 6 [9] a. Hoekom word die strukturele eienskappe van chromosome tydens metafase gedefinieer, en nie tydens interfase nie? / Why are the structural characteristics of chromosomes defined during metaphase, and not during interphase? (2) b. Verduidelik wat die C-waarde paradoks is, en waarom dit slegs ter sprake is by eukariote. / Explain what the C-value paradox is, and why it is only relevant in eukaryotes. (3) c. Verduidelik watter faktore belangrik is by bloedskenking. / Explain which factors are important in blood donations. (2) d. Wat is Rhesus onverenigbaarheid? / What is Rhesus incompatability? (2).. Vraag 7 / Question 7 [8] Aanvaar in alle gevalle volledige penetransie. / Assume complete penetrance in all cases. a. Watter van die volgende is n eienskap van n resessiewe menslike siekte? Omkring die nommer van die korrekte antwoord. / Which of the following is a characteristic of a recessive human disease? Circle the number of the correct answer. (1) (1) Indien beide ouers aangetas is, sal sommige van hulle nageslag die siekte vertoon. / If both parents are affected, some of their offspring will have the disease. (2) Indien beide ouers aangetas is, sal al hulle nageslag die siekte vertoon. / If both parents are affected, all of their offspring will have the disease. (3) Die eienskap word in elke generasie waargeneem. / The trait is observed in every generation. (4) Indien een ouer aangetas is, sal al hulle nageslag die siekte vertoon. / If one parent is affected, all of their offspring will have the disease. b. Watter van die volgende is n eienskap van n dominante menslike siekte? Omkring die nommer van die korrekte antwoord. / Which of the following is a characteristic of a dominant human disease? Circle the number of the correct answer. (1) (1) Ouers wat n alleel dra, is normaalweg nie aangetas nie. / Parents that carry an allele, are generally not affected. 4

5 (2) Die eienskap verskyn dikwels in nageslag van n huwelik tussen verwante individue. / The trait often appears in offspring of a marriage between related individuals. (3) Indien beide ouers aangetas is, word verwag dat n kwart van hulle nageslag die siekte sal hê. / If both parents are affected, it is expected that one quarter of their offspring will have the disease. (4) Ouers sonder die siekte kan nie aangetaste kinders hê nie. / Parents without the disease can not have affected children. c. Beskou die onderstaande stamboom van n siekte in n menslike familie: / Consider the pedigree below of a disease in a human family: I II III IV 1 Watter van die volgende sou moontlike oorerwingsmeganismes vir hierdie siekte kon wees? Antwoord in elke geval Ja of Nee. / Which of the following could be possible mechanisms of inheritance for this disease? Answer Yes or No in each case. (3) (1) Outosomaal dominant / Autosomal dominant. (2) Outosomaal resessief / Autosomal recessive. (3) X-gekoppel dominant / X-linked dominant. (4) X-gekoppel resessief / X-linked recessive. (5) Holandries / Holandric. (6) Geslagsbeperk / Sex-limited. d. Gebasseer op enige van u keuses in (c) hierbo, ken genotipes toe aan die volgende individue: / Based on any of your choices in (c) above, assign genotypes to the following individuals: (3) I 5 : II 8 : IV 1 : Vraag 8 / Question 8 [7] a. Defineer elk van die volgende terme kortliks: / Define each of the following terms briefly: (1) Aneuploidie / Aneuploidy: (1) (2) Poliploidie / Polyploidy: (1) (3) Endoploidie / Endoploidy: (1) b. Waarom is baie kommersiële piesang variëteite triploïede? / Why are many commercial varieties of bananas triploid? (2) 5

6 c. Hoe word nuwe triploïede piesang variëteite ontwikkel? / How are new triploid varieties of bananas developed? (2) Vraag 9 / Question 9 [10] In Drosophila is daar vier lyne wat fenotipies verskil in oogkleur: bruin, rooi, oranje en pienk. Kruisings tussen verskillende suiwertelende individue lewer die volgende resultate: / In Drosophila there are four lines that differ phenotypically in eye colour: brown, red, orange and pink. Crosses between different pure breeding individuals yield the following results: Ouers / Parents F 1 nageslag / F 1 progeny (1) bruin x rooi / brown x red almal bruin / all brown (2) bruin x oranje / brown x orange almal bruin / all brown (3) rooi x oranje / red x orange almal bruin / all brown (4) oranje x pienk / orange x pink almal oranje / all orange (5) bruin F 1 van kruising (3) x pienk / 1 bruin : 1 rooi : 1 oranje : 1 pienk / brown F 1 from cross (3) x pink 1 brown : 1 red : 1 orange : 1 pink a. Verduidelik in sellulêre of molekulêre terme waarom daar dikwels meer as een geen betrokke is by die bepaling van n kleur fenotipe. / Explain in cellular or molecular terms why there is often more than one gene involved in determining a colour phenotype. (2) b. Gee n genetiese verklaring vir die oorerwingspatroon van hierdie eienskap (oogkleur in Drosophila). / Give a genetic explanation for the inheritance pattern of this trait (eye colour in Drosophila). (2) c. Gee n volledige simboliese voorstelling van kruising (5) hierbo. / Give a complete symbolic representation of cross (5) above. (6)

7 Vraag 10 / Question 10 [6] In kanaries word die lokus vir veerkleur op die Z chromosoom gedra. U het twee suiwertelende kanarie lyne, een met blou vere en die ander met groen vere. In kruisings tussen hierdie twee lyne word die volgende resultate verkry: / In canaries, the locus for feather colour is carried on the Z chromosome. You have two pure breeding canary strains, one with blue feathers and the other with green feathers. In crosses between these two strains the following results are obtained: (1) P: blou / blue x groen / green (2) P: groen / green x blou / blue F 1 : almal groen / all green F 1 : blou / blue green / green a. Is veerkleur n geslagsgekoppelde, geslagsbeïnvloede of geslagsbeperkte eienskap? / Is feather colour a sex-linked, sex-influenced or sex-limited trait? (1) b. Gee n simboliese voorstelling van kruising (2). Gee die genotipes en geassosieerde fenotipes van die ouers en die nageslag. / Give a symbolic representation of cross (2). Give the genotypes and associated phenotypes of the parents and the progeny. (4) c. Watter alleel is dominant, blou of groen? / Which allele is dominant, blue or green? (1) Vraag 11 / Question 11 [4] Bespreek dosiskompensasie en die gevolge daarvan. / Discuss dosage compensation and its consequences. 7

8 Vraag 12 / Question 12 [14] Toon asb al u berekeninge. / Show all your calculations please. Gegee n chromosoomkaart: / Given a chromosome map: A 10 B 20 D Aanvaar die koppelingsverband soos hierbo gegee. Aanvaar dat die koeffisient van toevalligheid (KvT) = 0.5. / Accept the linkage setup as given above. Accept that the coefficient of coincidence (C) = 0.5. a. U gaan n toetskruis met n trihibried doen. Gee n skematiese voorstelling van die toetskruis ouers, sodat die koppelingsverband van die loki duidelik is. / You are going to do a testcross with a trihybrid. Give a schematic representation of the testcross parents, so that the linkage relationship of the loci is clear. (2) b. Deur KvT = 0.5 te gebruik, bereken die persentasie dubbeloorkruising verkry. / Using C = 0.5, calculate the observed percentage double recombination. (2) c. Bereken die verwagte grootte van elke dubbel rekombinasie klas in die toetskruis nageslag. / Calculate the expected size of each double recombination class in the testcross offspring. (2) d. Bereken die verwagte groottes van al die enkel rekombinasie klasse in die toetskruis nageslag. / Calculate the expected sizes of all the single recombination classes in the testcross offspring. (5) 8

9 e. Bereken die verwagte grootte van elke ouerlike klas in die toetskruis nageslag. / Calculate the expected size of each parental class in the testcross offspring. (3) Vraag 13 / Question 13 [5] Mnr P is n translokasie draer. Hy het 45 chromosome omdat die lang arm van n chromosoom 14 met die lang arm van n chromosoom 21 versmelt het. Hy produseer 6 tipes spermselle, wat die lot van sy en Mev P se nageslag sal bepaal. / Mr P is a translocation carrier. He has 45 chromosomes because the long arm of a chromosome 14 has joined to the long arm of a chromosome 21. He produces 6 types of sperm cells, which will determine the fate of his and Mrs P s offspring. Mev P / Mrs P Mnr P / Mr P a. Watter tipe translokasie het Mnr P? / What type of translocation does Mr P have? (1) b. Wat is die verwagte gevolge van die versmelting van die volgende gamete op die chromosoom samestelling en fenotipe van die nageslag? / What are the expected results of the fusion of the following gametes on the chromosome composition and phenotype of the progeny? (4) Eiersel van Mev P / Egg cell from Mrs P Spermsel van Mnr P / Sperm cell from Mr P Effek op die sigoot / Effect on the zygote

10 10 Totaal: / Total: [100]