Meiosis has an important role in sexual reproduction. Meiosis occurs during gametogenesis in humans and during the formation of pollen grains and embryo sacs in plants.

1. (a)(i)Complete Table 4.1 to compare meiosis with mitosis. For both columns, put a tick (✔) in the box if the statement is correct and put a cross (X) in the box if the statement is incorrect. Each box must contain either a tick or a cross. [Table 4.1] statement | meiosis | mitosis chromosome number is maintained | | homologous chromosomes pair up | | sister chromatids separate | | occurs in prokaryotes | |[2]
2. (a)(ii)Compare the role of meiosis in gametogenesis to produce sperm cells in humans with the role of meiosis in gametogenesis in producing pollen grains in flowering plants.[4]
3. (b)(i)Flower colour is important in sexual reproduction of insect-pollinated plants. In the rosy periwinkle, *Catharanthus roseus*, flower colour is controlled by three genes, R/r, D/d and P/p, which interact together to control flower colour. [Figure 4.1] Fig. 4.1 is a drawing of a rosy periwinkle. The presence of the R allele results in a red pigment in the centre of the flower (red eye). The D allele and the P allele are only expressed when the R allele is present. • When the D allele and the R allele are present, the flower has dark pink petals with a red eye. • When the P allele and the R allele are present, the flower has pale pink petals with a red eye. • When the D allele, the P allele and the R allele are all present, the flower has dark pink petals with a red eye. • The recessive alleles r, d and p result in no pigments being produced and the flower has white petals and no red eye. Deduce the phenotypes of these rosy periwinkle genotypes. RR dd PP ................................................................................................................ Rr Dd Pp ................................................................................................................ rr Dd Pp ................................................................................................................ RR dd pp ................................................................................................................[4]
4. (b)(ii)The pigments causing flower colour in the rosy periwinkle are formed by a biosynthetic pathway. The R allele mutated to produce the r allele. The r allele codes for a non-functional protein. Explain how the mutation that changes R to r results in no red pigment being synthesised in the flower of rosy periwinkle.[4]
5. (b)(iii)One mutation that changes the flower colour of rosy periwinkle occurs in a region of the DNA that does not code for a polypeptide. Suggest what function this region of DNA might perform.[1]

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