16.1. Passage of information from parents to offspring
A subsection of Biology, 9700, through 16. Inheritance
Listing 10 of 75 questions
Describe the maturation of a spermatid into a spermatozoon . A method of sorting damaged from undamaged sperm has undergone trials at an in vitro fertilisation (IVF) clinic in Australia. It is hoped to use the procedure when attempting IVF with sperm from men with fertility problems. The sorting process is shown in . sperm sample placed in upper chamber plate with negative charge filter with 5 µm holes about 20 % of the sperm move into the lower chamber plate with positive charge Sperm left in the upper chamber have, on average, twice as much damage to their DNA as those that move into the lower chamber. In the body, sperm which mature normally move slowly through the epididymis, gradually accumulating molecules of a negatively charged protein in their cell surface membranes. Other sperm move more quickly through the epididymis.
9700_w10_qp_43
THEORY
2010
Paper 4, Variant 3
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Outline the differences in the process of gametogenesis in a man compared with that in a woman. The hormone testosterone is secreted by Leydig cells in the testis. These cells form an endocrine gland. Explain what is meant by an endocrine gland. In 2009, a research laboratory for family planning in Beijing announced that it had injected 1000 healthy, fertile men with testosterone over a two-year period and found that only 10 of the men were then able to father a child. The men’s normal fertility was restored six months after their last injections. The injections, each of 500 mg of testosterone, resulted in a reduced production of follicle stimulating hormone (FSH) and of luteinising hormone (LH) in the injected men. Describe the similarities between the effect of these testosterone injections on a fertile man with the effect of the oestrogen/progesterone contraceptive pill on production of FSH and LH by a fertile woman.
9700_w11_qp_41
THEORY
2011
Paper 4, Variant 1
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Outline the differences in the process of gametogenesis in a man compared with that in a woman. The hormone testosterone is secreted by Leydig cells in the testis. These cells form an endocrine gland. Explain what is meant by an endocrine gland. In 2009, a research laboratory for family planning in Beijing announced that it had injected 1000 healthy, fertile men with testosterone over a two-year period and found that only 10 of the men were then able to father a child. The men’s normal fertility was restored six months after their last injections. The injections, each of 500 mg of testosterone, resulted in a reduced production of follicle stimulating hormone (FSH) and of luteinising hormone (LH) in the injected men. Describe the similarities between the effect of these testosterone injections on a fertile man with the effect of the oestrogen/progesterone contraceptive pill on production of FSH and LH by a fertile woman.
9700_w11_qp_42
THEORY
2011
Paper 4, Variant 2
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shows the stages in spermatogenesis in a mammal. A B W X Y E D spermatid C State the letterof the arrow or arrows that represent mitosis. Name the cells W, X and Y. W X Y is a light micrograph of a transverse section through a seminiferous tubule in a mammalian testis. use this sector On the sector indicated on , use label lines and letters to label: G a cell in the germinal epithelium M a maturing sperm cell Y an area where spermatids are found. In all animals so far studied, the production of fully functional sperm is sensitive to temperature. In the nematode worm, Caenorhabditis elegans, spermatogenesis takes place in a similar way to mammals. Two proteins known as argonaute proteins are important in the development of sperm. They are coded for by the genes alg-3 and alg-4. Table 4.1 shows the effect of mutations in one or both of these genes on the fertility of male worms, at temperatures of 20 °C and 25 °C. Fertility was measured as the mean number of offspring produced when the male worms mated with normal females. Table 4.1 male worms mean number of offspring produced at 20 °C at 25 °C normal at both gene loci mutation in alg-3 only mutation in alg-4 only mutations in both alg-3 and alg-4 Describe the effect of increased temperature on the fertility of normal male worms. Compare the effect of increased temperature on the fertility of alg-3 mutant male worms with the effect on fertility of alg-4 mutant male worms. An investigation showed that at 20 °C the number of spermatids produced in worms with both mutations, in alg-3 and alg-4, was the same as in normal worms. However, at 25 °C, these mutant worms produced 29% fewer spermatids than the normal worms. Microscopic examination of their testes showed that many of the secondary spermatocytes had failed to complete meiosis. Use this information to state the letter of one arrow on that represents a stage of spermatogenesis affected by mutations in both the alg-3 and alg-4 genes. Table 4.2 shows the effect of temperature on the percentage of spermatids that developed full motility at 20 °C and 25 °C in normal worms and in worms with mutations in both alg-3 and alg-4. Table 4.2 male worms percentage of sperms with full motility at 20 °C at 25 °C normal mutations in both alg-3 and alg-4 With reference to Table 4.2, and the information in , state the cause or causes of reduced fertility in these mutant worms at each temperature. at 20 °C at 25 °C
9700_w12_qp_41
THEORY
2012
Paper 4, Variant 1
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shows the stages in spermatogenesis in a mammal. A B W X Y E D spermatid C State the letterof the arrow or arrows that represent mitosis. Name the cells W, X and Y. W X Y is a light micrograph of a transverse section through a seminiferous tubule in a mammalian testis. use this sector On the sector indicated on , use label lines and letters to label: G a cell in the germinal epithelium M a maturing sperm cell Y an area where spermatids are found. In all animals so far studied, the production of fully functional sperm is sensitive to temperature. In the nematode worm, Caenorhabditis elegans, spermatogenesis takes place in a similar way to mammals. Two proteins known as argonaute proteins are important in the development of sperm. They are coded for by the genes alg-3 and alg-4. Table 4.1 shows the effect of mutations in one or both of these genes on the fertility of male worms, at temperatures of 20 °C and 25 °C. Fertility was measured as the mean number of offspring produced when the male worms mated with normal females. Table 4.1 male worms mean number of offspring produced at 20 °C at 25 °C normal at both gene loci mutation in alg-3 only mutation in alg-4 only mutations in both alg-3 and alg-4 Describe the effect of increased temperature on the fertility of normal male worms. Compare the effect of increased temperature on the fertility of alg-3 mutant male worms with the effect on fertility of alg-4 mutant male worms. An investigation showed that at 20 °C the number of spermatids produced in worms with both mutations, in alg-3 and alg-4, was the same as in normal worms. However, at 25 °C, these mutant worms produced 29% fewer spermatids than the normal worms. Microscopic examination of their testes showed that many of the secondary spermatocytes had failed to complete meiosis. Use this information to state the letter of one arrow on that represents a stage of spermatogenesis affected by mutations in both the alg-3 and alg-4 genes. Table 4.2 shows the effect of temperature on the percentage of spermatids that developed full motility at 20 °C and 25 °C in normal worms and in worms with mutations in both alg-3 and alg-4. Table 4.2 male worms percentage of sperms with full motility at 20 °C at 25 °C normal mutations in both alg-3 and alg-4 With reference to Table 4.2, and the information in , state the cause or causes of reduced fertility in these mutant worms at each temperature. at 20 °C at 25 °C
9700_w12_qp_42
THEORY
2012
Paper 4, Variant 2
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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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Questions Discovered
75