16. Inheritance
A section of Biology, 9700
Listing 10 of 199 questions
The process of gametogenesis in male and female vertebrates, including humans, involves meiosis. Describe how gametogenesis differs between human males and females. shows a Komodo dragon, Varanus komodoensis. This species of lizard is only found on five Indonesian islands. Using Table 4.1, identify the gene locus that shows the most genetic variability and name the process that gives rise to the different lengths of the alleles. locus process Using Table 4.1, state and explain which animals are heterozygous at one or more of the gene loci. Clones are organisms or cells that are genetically identical. Students made suggestions about the Komodo dragon offspring (1– 4) produced by a female that had never mated with a male. • Offspring 1 and 2 are clones of each other, and offspring 3 and 4 are clones of each other. • Offspring 1– 4 were produced by asexual reproduction using mitosis only. Explain, with reference to specific loci, whether the data in Table 4.1 support or do not support these suggestions. Offspring 1 and 2 are clones of each other, and offspring 3 and 4 are clones of each other. Offspring 1– 4 were produced by asexual reproduction using mitosis only. Reproduction without a male has evolved in a number of species that live on islands. Suggest advantages and disadvantages of this type of reproduction in an island habitat.
9700_m16_qp_42
THEORY
2016
Paper 4, Variant 2
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Outline the role of calcium ions in the transmission of nerve impulses. It has been suggested that during maturation of a sperm, the uptake of calcium ions is necessary to produce the vigorous movements of the sperm’s flagellum that allow it to penetrate the zona pellucida of an oocyte. Uptake of calcium ions can be measured by staining the sperm with a non-toxic fluorescent stain. Fluorescence increases as the concentration of calcium ions inside the sperm increases. Sperm from two types of mice were investigated: • wild-type mice, whose sperm have a particular protein, P. P is an ion channel found in the plasma (cell surface) membrane. • mutant mice whose sperm did not have protein P. The results of the investigation are shown in . sperm head sperm flagellum sperm from wild-type mice sperm from mutant mice mean percentage increase in fluorescence key: With reference to , describe and explain the different mean percentage increases in fluorescence of sperm from wild-type and mutant mice, sperm heads and flagella. The ability of sperm from wild-type and mutant mice to penetrate oocytes was tested using in-vitro fertilisation (IVF) of oocytes with and without a zona pellucida. The results are shown in . oocytes with zona pellucida oocytes without zona pellucida sperm from wild-type mice key: sperm from mutant mice percentage of oocytes penetrated by sperm Explain what is meant by in-vitro fertilisation. With reference to , explain the differences in the ability of sperm from wild- type and mutant mice to penetrate oocytes in IVF.
9700_s08_qp_4
THEORY
2008
Paper 4, Variant 0
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Canavan disease is a non sex-linked inherited condition that causes progressive damage to neurones of the brain. Symptoms of the condition include a loss of motor skills and mental retardation. The symptoms appear in early infancy and many children with this condition die by the age of four years. People with Canavan disease lack an enzyme called aspartoacylase which breaks down N-acetyl aspartate. The build up of N-acetyl aspartate can interfere with the formation of the myelin sheath, particularly in neurones of the brain. Enzymes such as aspartoacylase display specificity. Outline what is meant by specificity of an enzyme. Complete the genetic diagram below to show how an unaffected man and an unaffected woman could produce a child with Canavan disease. key to symbols parental phenotypes unaffected man unaffected woman parental genotypes gametes offspring genotypes offspring phenotypes Explain the importance of the myelin sheath in the functioning of a neurone.
9700_s11_qp_41
THEORY
2011
Paper 4, Variant 1
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shows a drawing of a section through an ovarian follicle. A B C D State the names of the parts labelled A-D in . A B C D Outline the biological basis of the effect of the oestrogen/progesterone contraceptive pill. The zona pellucida of an oocyte is made up of ZP proteins. ZP3, which does not occur anywhere else in the body, has a complex tertiary structure and acts as a receptor for sperm during fertilisation. A new method of contraception, which does not involve the use of hormones, is in the early stages of development. It involves blocking the expression of the gene coding for ZP3. Explain how blocking the expression of the gene coding for ZP3 acts as a contraceptive. Explain why it is desirable to devise a method of contraception that does not involve oestrogen and progesterone. Explain why it is important, when blocking the expression of the gene coding for ZP3, that ZP3 is only found in the zona pellucida.
9700_s11_qp_42
THEORY
2011
Paper 4, Variant 2
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shows a drawing of a section through an ovarian follicle. A B C D State the names of the parts labelled A-D in . A B C D Outline the biological basis of the effect of the oestrogen/progesterone contraceptive pill. The zona pellucida of an oocyte is made up of ZP proteins. ZP3, which does not occur anywhere else in the body, has a complex tertiary structure and acts as a receptor for sperm during fertilisation. A new method of contraception, which does not involve the use of hormones, is in the early stages of development. It involves blocking the expression of the gene coding for ZP3. Explain how blocking the expression of the gene coding for ZP3 acts as a contraceptive. Explain why it is desirable to devise a method of contraception that does not involve oestrogen and progesterone. Explain why it is important, when blocking the expression of the gene coding for ZP3, that ZP3 is only found in the zona pellucida.
9700_s11_qp_43
THEORY
2011
Paper 4, Variant 3
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Questions Discovered
199