16. Inheritance
A section of Biology, 9700
Listing 10 of 199 questions
Spermatogenesis, the production of male gametes, occurs in the testes of a human male from the age of puberty. outlines the sequence of events that occur during oogenesis. germinal epithelium process A one spermatogonium process B many spermatogonia process C primary spermatocyte process D secondary spermatocyte process E spermatid process F spermatozoan With reference to , state what is happening to cells during: process B process D process F. Female gametes develop inside follicles. shows a section through a mature (Graafian) follicle in a human ovary. H G J K Table 3.1 below lists a number of statements about the mature follicle. Each statement refers to one of the letters G, H, J and K shown in . Complete the table using the letters G, H, J and K. Table 3.1 statement letter contains protective fluid produces oestrogen has glycoprotein receptors contains 23 chromosomes A man and a woman may be described as infertile if they have failed to conceive a child after 12 months of trying. They may opt for in-vitro fertilisation (IVF) if the woman is producing some normal eggs. Outline the technique of IVF. Not all pregnancies due to IVF treatment result in live births. In the USA in 2008 the figures were: • 85% of these pregnancies result in live births for women under 35 years old • 66% of these pregnancies result in live births for women between 38–40 years old. Suggest reasons for the difference in percentage for the two groups of women.
9700_w11_qp_43
THEORY
2011
Paper 4, Variant 3
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Flowers of the common morning-glory plant, Ipomoea purpurea, can have several different phenotypes. An example of these flowers is shown in . Flower colour in I. purpurea is controlled by two genes on different chromosomes. Gene R/r, which codes for a protein involved in pigment production, has 2 alleles: • the dominant allele, R, allows pigment production • the recessive allele, r, prevents pigment production of any colour, resulting in white flowers. Gene T/t, which determines the type of pigment produced, has two alleles: • the dominant allele, T, results in purple flowers • the recessive allele, t, results in red flowers. Define the term allele. Suggest ways in which the expression of allele R allows pigment production. Complete to show the results of a cross between two I. purpurea plants that are heterozygous at both loci. parental genotypes: parental gametes: parental gametes results of cross: phenotypic ratios: show parental gametes in first column and top row • show offspring genotypes and phenotypes in square boxes •
9700_m20_qp_42
THEORY
2020
Paper 4, Variant 2
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shows two chromosomes in one stage of meiosis. The letters G to M represent the dominant alleles of seven genes and the letters g to m represent the recessive alleles of the same seven genes. G H I J K L M G H I R J K L M g h i j k l m g h i j k l m S S Name the structures labelled R and S on . R S State three features visible on that identify the chromosomes as a homologous pair. shows the same two chromosomes a little later in the same stage of meiosis. Crossing over is beginning to occur at point T. G H I J K L M G H I T J K L M g h i j k l m g h i j k l m shows an outline of the same two chromosomes after crossing over has occurred. Complete by writing in the letters of the alleles along both chromosomes. Take care to clearly show the difference between letters representing dominant alleles and letters representing recessive alleles. State the stage in meiosis in which crossing over occurs. Crossing over results in genetic variation. Explain how random assortment of homologous chromosomes also results in genetic variation.
9700_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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Questions Discovered
199