CCHY 2020 Bio Yearly TYS ANS

6093 Biology Yearly TYS 2020 No Paper 1 Marks Remarks 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 1 10 1 11 1 12 1 13 1 14 1 15 1 16 1 17 1 18 1 19 1 20 1 21 1 22 1 23 1 24 1 25 1 26 1 27 1 28 1 29 1 30 1 31 1 32 1 33 1 34 1 35 1 36 1 37 1 38 1 39 1 40 1 Total 40

Paper 2 Section A 1a A: ovary B: oviduct/ fallopian tube C: cervix 1 1 1 1b X on one of the oviduct nearer to an ovary 1 1c Fertilised egg becomes a zygote + cilia sweep the zygote along oviduct + peristaltic movements help to move zygote along the oviduct to the uterus; Zygote divides by mitosis to form embryo + embryo embeds/implants itself in the uterine lining seven d ays after fertilisation; Amniotic sac begins to develop + encloses the embryo in the amniotic cavity containing amniotic fluid/ villi containing blood capillaries of embryo grow from embryo into the uterine wall making up a placenta + umbilical cord attaches embryo to placenta; 1 1 1 formation of amniotic sac/fluid or placenta 1di sweep the zygote along oviduct 1 1dii respiratory system 1 Total 9

2a D: interphase + each chromatin thread undergoing DNA replication, resulting in a pair of sister chromatids, causing the mass of DNA to double from 8 a.u. to 16 a.u.; E: cytokinesis + division of cell to produce two identical daughter cells each containing the same number of chromatin threads causing mass of DNA to decrease to 8 a.u.; 1 1 2bi anaphase 1 2bii before: metaphase after: telophase 1 1 2biii haploid number: 3 explanation: gametes are haploid means they contain half the number of chromosomes as normal plant cells produced when cells in the ovary or pollen grain/gonads undergo meiosis; 6 chromosomes will result in 3 homologous chromosomes + after meiosis, each daughter cell will contain 3 daughter chromosomes; 1 1 1 2c Homologous chromosomes may cross over in prophase I of meiosis + exchange of genes between the paternal and maternal chromosome producing new combinations of genes along the chromosomes which leads to genetic variation; Random arrangement of chromosomes in metaphase I in meiosis + chromosome randomly line up + random separation of homologous ch romosomes at anaphase I + independent assortment of chromosome + producing different combinations of genetic material in gametes + increasing genetic variation; Random fertlisation + nuclues of any sperm fuses with nucleus of any egg + producing offspring of different combination of genotypes + can lead to genetic variation; 1 1 1 Total 11

3a 1 1 1 3b codominance results when the two alleles controlling a trait both express themselves in the organism; multiple alleles is a term used for a gene that exists in more than two alleles for a