16. Inheritance
A section of Biology, 9700
Listing 10 of 199 questions
Yeasts are unicellular organisms from the kingdom Fungi. Saccharomyces cerevisiae is one species of yeast that can carry out either asexual reproduction by mitosis or sexual reproduction by meiosis. Budding in S. cerevisiae is a process where a small daughter cell forms as a bud on the parent cell. The bud contains a copy of the parent cell nucleus and it eventually separates from the parent cell to form a new cell. S. cerevisiae can exist in two forms: haploid cells or diploid cells. • Haploid cells can be one of two different mating types: a and α. • Haploid cells can only mate with other haploid cells of the opposite mating type. shows the life cycle of S. cerevisiae with its asexual and sexual reproductive stages. a a a α α α α mating type a mating type α Key: a a a α α aα aα α a a a a α a α aα aα α α lack of nutrients budding an ascus - a sac containing four spores mating budding budding formation of zygote germination when conditions have improved With reference to , state the numbers of the stages 1–5 that: involve mitosis involve meiosis produces new genetic variation shows only haploid cells shows only diploid cells When there is a lack of nutrients, cells made in stage 3 will carry out stage 4 to make spores, which germinate only when conditions improve. Suggest and explain how the type of reproduction that makes spores during stage 4 is advantageous for S. cerevisiae in a changing environment. Haploid and diploid cells of S. cerevisiae can carry out asexual reproduction. Suggest why a new harmful recessive mutation may not have a damaging effect on: • an asexually reproducing population of haploid cells of S. cerevisiae • an asexually reproducing population of diploid cells of S. cerevisiae. State two features, other than reproduction using spores, of the kingdom Fungi.
9700_w23_qp_42
THEORY
2023
Paper 4, Variant 2
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Lunularia cruciata is a primitive plant. Its body consists of a flattened sheet of photosynthetic tissue called a thallus. shows L. cruciata with two different types of reproductive structure, labelled A and B, on its surface. A B Structures A and B and the thallus of L. cruciata are haploid. Explain what is meant by haploid. Structure A contains pale discs of tissue, C, that can germinate into new L. cruciata. The new plants that develop from C are genetically identical to the parent plant in . Structure B contains male sperm that are chemically attracted to swim to female eggs on a neighbouring parent plant. When the egg and sperm fuse, they form structure D. Structure D develops to produce spores that grow into new plants that are genetically different from the two parent plants. Identify which of the structures A, B, C and D are: associated with sexual reproduction ………………………………………… produced by mitosis ………………………………………… the site of meiosis ………………………………………… Each letter may be used once, more than once, or not at all. shows a horse, Equus caballus. Horses are diploid animals that reproduce sexually. Male and female horses produce gametes, which fuse to form genetically different offspring. Explain the need for a reduction division during meiosis in the production of gametes in animals such as horses.
9700_w24_qp_41
THEORY
2024
Paper 4, Variant 1
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Lunularia cruciata is a primitive plant. Its body consists of a flattened sheet of photosynthetic tissue called a thallus. shows L. cruciata with two different types of reproductive structure, labelled A and B, on its surface. A B Structures A and B and the thallus of L. cruciata are haploid. Explain what is meant by haploid. Structure A contains pale discs of tissue, C, that can germinate into new L. cruciata. The new plants that develop from C are genetically identical to the parent plant in . Structure B contains male sperm that are chemically attracted to swim to female eggs on a neighbouring parent plant. When the egg and sperm fuse, they form structure D. Structure D develops to produce spores that grow into new plants that are genetically different from the two parent plants. Identify which of the structures A, B, C and D are: associated with sexual reproduction ………………………………………… produced by mitosis ………………………………………… the site of meiosis ………………………………………… Each letter may be used once, more than once, or not at all. shows a horse, Equus caballus. Horses are diploid animals that reproduce sexually. Male and female horses produce gametes, which fuse to form genetically different offspring. Explain the need for a reduction division during meiosis in the production of gametes in animals such as horses.
9700_w24_qp_43
THEORY
2024
Paper 4, Variant 3
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Meiosis is described as a reduction division because the number of chromosomes in the daughter cells is reduced by half. Table 5.1 describes some of the events that take place during four of the different stages of meiosis in an animal cell. Table 5.1 stage of meiosis spindle fibres diagram metaphase I attach to centromeres and arrange homologous pairs of chromosomes at the equator of the cell anaphase I re-form spindle in daughter cells telophase II disassemble Complete Table 5.1 by: • outlining the behaviour of the spindle fibres during anaphase I • identifying the stage of meiosis in which spindle fibres re-form the spindle in daughter cells • drawing a diagram to show telophase II. You do not need to add labels to your diagram showing telophase II. Explain the need for a reduction division during meiosis.
9700_m23_qp_42
THEORY
2023
Paper 4, Variant 2
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Use is a photomicrograph of a section through the ovary of a mammal. Name A and B. A B B A Examiner’s Use shows part of the sequence of processes by which female gametes are produced. cells in germinal epithelium oogonia C P Q secondary oocyte With reference to , name the cell at stage C; draw a label line on to a cell at stage C; name the types of cell division that take place at P and Q. P Q Describe one way in which genetic variation between secondary oocytes is achieved during meiosis.
9700_s07_qp_4
THEORY
2007
Paper 4, Variant 0
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Meiosis is a type of nuclear division, which produces gametes for sexual reproduction. shows diagrams of the stages of meiosis, A to J, but they are not in the correct order. A B C D E F G H I J Complete the table below by writing the stages of meiosis in the correct order. Some of the stages have already been written in the table. nuclear division letter of stage meiosis I B D meiosis II Explain how meiosis can result in genetic variation amongst offspring.
9700_s11_qp_42
THEORY
2011
Paper 4, Variant 2
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Questions Discovered
199