16.1. Passage of information from parents to offspring
A subsection of Biology, 9700, through 16. Inheritance
Listing 10 of 75 questions
shows some of the steps involved in in-vitro fertilisation (IVF). Step 1 egg production stimulated Step 3 sperm sample provided Step 2 eggs retrieved from ovary Step 5 embryos introduced into uterus Step 4 eggs and sperm combined to allow fertilisation Explain how egg production is stimulated at step 1. Following step 3 in , the sperm sample is placed in a solution containing various nutrients and other substances, for up to one hour, before being added to the eggs. Explain why this is done. In 2010, researchers found that they could predict with 93% certainty which embryos produced by in-vitro fertilisation would develop into healthy babies when implanted into the uterus. Their technique involved the use of time-lapse microscopy. The successful embryos met three criteria: • the first cytokinesis lasted between 0 and 33 minutes • the time interval between the first and second cell division was between 7.8 and 14.3 hours • the time interval between the second and third cell division was between 0 and 5.8 hours. Suggest one advantage of the use of this new technique in the IVF procedure. Suggest one disadvantage of the use of this technique.
9700_s13_qp_42
THEORY
2013
Paper 4, Variant 2
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The sex chromosomes of domestic chickens are known as W and Z. • Male chickens have two Z chromosomes. • Female chickens have one W and one Z chromosome. A gene for feather colour in chickens is located on an autosome. This gene (C) has two alleles • black (CB) • splashed-white (CS). When a chicken with black feathers is mated with a chicken with splashed-white feathers, all the offspring will have blue feathers. A gene for feather pattern is located on the Z chromosome but not on the W chromosome. This gene has two alleles • barred feathers (A) • non-barred feathers . State the type of inheritance for feather colour and for feather pattern. feather colour feather pattern A male chicken with black, non-barred feathers was crossed with a female chicken with splashed-white, barred feathers. All the offspring had blue feathers, but the males were barred and the females were non- barred. Using the symbols given, draw a genetic diagram to show this cross. parents phenotype male, black, non-barred feathers female, splashed-white, barred feathers parents genotype gametes offspring genotypes offspring phenotypes male, blue, barred feathers female, blue, non-barred feathers Explain how the genotype of a male chicken with blue, barred feathers could be determined.
9700_s16_qp_42
THEORY
2016
Paper 4, Variant 2
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Meiosis is described as reduction division. Explain why meiosis is necessary in the life cycle of a sexually reproducing organism. Plants need mineral ions to grow and develop. For example, plants need phosphates and a deficiency inhibits cell division and root growth. Mutations in individuals of some plant populations allow them to survive in mineral-deficient soils. Name two examples of environmental conditions that affect plant phenotype, other than mineral deficiency. For each example, describe how it affects the phenotype. Explain why mutations are important in selection. A study compared root growth of thale cress, Arabidopsis thaliana, in two different soil types: • full nutrient • low phosphate. Two different populations of thale cress were used: • thale cress with a functional enzyme X • thale cress, with a non-functional enzyme X. 30 seedlings from each population were placed in each type of soil and left to grow for seven days. At the start all seedlings had a root of the same length. After seven days, the length of this root was measured again for each seedling. The mean final root length and standard deviation was calculated for each population of thale cress. The mean final root lengths are shown in . full nutrient low phosphate soil type mean final root length / mm Key population with functional enzyme X population with non-functional enzyme X With reference to , describe the effect of the low phosphate soil type compared to the full nutrient soil type on root growth, for both populations of thale cress. The null hypothesis states there is no significant difference between the mean final root lengths of the two populations of thale cress grown in low phosphate soil type. A t-test can be carried out to compare these two means. The critical value for t at the p = 0.05 significance level is 2.00. Table 3.1 population grown in low phosphate soil type mean final root length / mm standard deviation functional enzyme X 0.5 non-functional enzyme X 0.8 shows the formula for calculating the value of t. t n n x x s s = + - f p mean standard deviation sample size (number of measurements) x s n = = = Use the formula in to calculate the value of t. Show your working. t = Use your calculated value of t to explain whether the null hypothesis should be accepted or rejected. accept or reject explanation
9700_s18_qp_43
THEORY
2018
Paper 4, Variant 3
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Use Modern varieties of wheat have developed from numerous hybridisation events between different species of wild grasses. shows some of the possible steps that are believed to have been involved in the development of bread wheat, Triticum aestivum. The letters A, B and C represent three different sets of seven chromosomes. einkorn Triticum urartu 14 chromosomes AA × goat grass 1 Aegilops speltoides 14 chromosomes BB hybridisation and doubling of chromosome number emmer wheat Triticum turgidum 28 chromosomes AABB × goat grass 2 Aegilops tauschii 14 chromosomes CC hybridisation and doubling of chromosome number bread wheat Triticum aestivum 42 chromosomes Complete by writing letters to represent the sets of chromosomes in bread wheat. Write your answer on . Examiner’s Use Explain why hybridisation between emmer wheat and goat grass 2 would have produced a sterile hybrid, if doubling of chromosome number had not occurred. With reference to , suggest why Triticum urartu and Triticum turgidum are classified as different species. Triticum turgidum emerged as a new species without being geographically isolated from Triticum urartu. Outline how geographical isolation may result in speciation.
9700_w09_qp_41
THEORY
2009
Paper 4, Variant 1
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A recent development in fertility treatment is called in-vitro maturation (IVM). This is both cheaper and safer than the standard procedure used in in-vitro fertilisation (IVF), especially for women with polycystic ovaries. Hormone treatment can be dangerous for women with this condition, in which a number of ovarian follicles mature at the same time. IVF and IVM are compared in . In-vitro fertilisation (IVF) Women are given drugs for three weeks to suppress ovulation followed by hormones for two weeks. Mature secondary oocytes are harvested. In-vitro maturation (IVM) Immature secondary oocytes are harvested. Immature secondary oocytes are matured in laboratory culture for 24 to 48 hours. Oocytes from about 50% of women are fertilised by mixing the oocytes with a sample of sperm. Oocytes from about 50% of women are fertilised by injecting a single sperm into the cytoplasm of each oocyte. Fertilised oocytes are placed into the uterus. All oocytes are fertilised by injecting a single sperm into the cytoplasm of each oocyte. With reference to , explain why women are treated with hormones for two weeks after being given drugs to suppress ovulation at the beginning of IVF treatment. State the roles of mitosis and meiosis in producing an immature secondary oocyte. Suggest one advantage and one possible disadvantage of fertilising an oocyte by injecting a sperm into its cytoplasm instead of mixing the oocyte with a sample of sperm. advantage disadvantage
9700_w10_qp_41
THEORY
2010
Paper 4, Variant 1
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A recent development in fertility treatment is called in-vitro maturation (IVM). This is both cheaper and safer than the standard procedure used in in-vitro fertilisation (IVF), especially for women with polycystic ovaries. Hormone treatment can be dangerous for women with this condition, in which a number of ovarian follicles mature at the same time. IVF and IVM are compared in . In-vitro fertilisation (IVF) Women are given drugs for three weeks to suppress ovulation followed by hormones for two weeks. Mature secondary oocytes are harvested. In-vitro maturation (IVM) Immature secondary oocytes are harvested. Immature secondary oocytes are matured in laboratory culture for 24 to 48 hours. Oocytes from about 50% of women are fertilised by mixing the oocytes with a sample of sperm. Oocytes from about 50% of women are fertilised by injecting a single sperm into the cytoplasm of each oocyte. Fertilised oocytes are placed into the uterus. All oocytes are fertilised by injecting a single sperm into the cytoplasm of each oocyte. With reference to , explain why women are treated with hormones for two weeks after being given drugs to suppress ovulation at the beginning of IVF treatment. State the roles of mitosis and meiosis in producing an immature secondary oocyte. Suggest one advantage and one possible disadvantage of fertilising an oocyte by injecting a sperm into its cytoplasm instead of mixing the oocyte with a sample of sperm. advantage disadvantage
9700_w10_qp_42
THEORY
2010
Paper 4, Variant 2
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Questions Discovered
75