17. Inheritance
A section of Biology, 0610
Listing 10 of 531 questions
The American writer Ernest Hemingway lived on the island of Key West in Florida, USA in the 1930s. During this time he was given a male cat by a sea captain. The cat had more toes than usual. This inherited condition is called polydactyly. The allele for polydactyly is dominant. Define the term inheritance. is part of a pedigree diagram for Hemingway’s cats. male cat with normal number of toes female cat with normal number of toes male cat with polydactyly female cat with polydactyly Key: State the genotypes of cats 5, 6 and 14 in the pedigree diagram in . Use the letters T and t. cat 5 cat 6 cat 14 Explain why none of the offspring of cats 3 and 4 have inherited polydactyly. Use the information in in your answer. Scientists published the results of an investigation into the DNA of cats with and without polydactyly. They compared the base sequence from a particular region of DNA that controls the development of the limbs. Table 3.1 shows the base sequences. Table 3.1 cats without polydactyly AGA CAC AGA AAT GAG Hemingway’s cats with polydactyly AGA CAC GGA AAT GAG cats with polydactyly from Oregon and Missouri in the USA AGA CAC GGA AAT GAG cats with polydactyly from the UK AGA CAC AGT AAT GAG Describe how the base sequences of the cats with polydactyly differ from the base sequence of cats without polydactyly. State the name of the process by which base sequences in DNA are changed. The base sequences in Table 3.1 provide evidence that indicates which country the male cat given to Hemingway in the 1930s came from. Suggest which country this cat came from and give a reason for your choice. shows part of a DNA molecule from a chromosome of a cat. Complete by writing the letters for the base sequence of the other strand of the DNA molecule. T A A T G C G T G Explain why polydactyly is an example of discontinuous variation.
0610_s20_qp_43
THEORY
2020
Paper 4, Variant 3
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Define the term genetic engineering. State one example of genetic engineering. is a diagram of a fruit fly with normal wings and a fruit fly with vestigial wings. normal wings vestigial wings A gene determines whether fruit flies have normal wings or vestigial wings. There are two alleles for this gene: • A is dominant and represents the allele for normal wings • a is recessive and represents the allele for vestigial wings. A homozygous dominant fruit fly was crossed with a heterozygous fruit fly. Complete the genetic diagram to predict the probability of the offspring having vestigial wings. parental phenotypes normal wings × normal wings parental genotypes ………… × ………… gametes …… , …… × ….…. , …… offspring genotypes ………… ………… ………… ………… offspring phenotypes ………… ………… ………… ………… probability of offspring having vestigial wings ………… State the genotype of a pure-breeding fruit fly that has normal wings. The binomial name for a fruit fly is Drosophila melanogaster. State the genus of this fruit fly.
0610_s21_qp_32
THEORY
2021
Paper 3, Variant 2
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There are four blood groups in the ABO system in humans: A, B, AB and O. The gene that determines blood group has three alleles: IA, IB and Io. Parents with the genotypes IAIo and IBIo are planning to have more children. Complete the genetic diagram to determine the probability that the next child will have blood group O. parental blood groups A B parental genotypes IAIo IBIo Punnett square phenotypes of the children probability that the child will have blood group O Explain why the ABO blood group system is an example of co-dominance. shows the percentages of the global population with the four different blood groups in the ABO system. A B AB blood group percentage of the global population O With reference to , explain why the ABO blood group system is an example of discontinuous variation.
0610_s21_qp_43
THEORY
2021
Paper 4, Variant 3
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The inheritance of coat texture in guinea pigs is controlled by a single gene. Define the term gene. shows a photograph of a guinea pig with a rough coat and a guinea pig with a smooth coat. smooth coat rough coat The allele for a rough coat is dominant and represented by the letter R. The allele for a smooth coat is recessive and represented by the letter r. is a pedigree diagram showing the inheritance of coat texture in some guinea pigs. Key: male RR male Rr male rr female RR female Rr female rr generation 1 generation 2 A B C D E F State the total number of guinea pigs with smooth coats in . State the letter of a guinea pig that has a homozygous dominant genotype in . State the total number of male guinea pigs in . Two guinea pigs are bred together. • The genotype of the male guinea pig is RR. • The genotype of the female guinea pig is Rr. Complete to show the: • possible genotypes of the offspring from this cross • the probability of offspring having a smooth coat. male female probability of offspring having a smooth coat Complete the sentence about breeding. Two identical homozygous individuals that breed together will be -breeding.
0610_s22_qp_31
THEORY
2022
Paper 3, Variant 1
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Red blood cells contain the protein haemoglobin. State the names of the four chemical elements that are found in all proteins. State the role of haemoglobin. shows a photomicrograph of some red blood cells from a person with sickle cell anaemia. Abnormal red blood cells occur because of a mutation in the gene for haemoglobin. abnormal red blood cell Suggest how the shape of the abnormal red blood cell shown in will affect blood flow. The allele for the normal form of haemoglobin is HbA. The allele for the abnormal form of haemoglobin is HbS. Draw a genetic diagram to determine the probability of two heterozygous parents having a child who does not have the HbS allele. parental phenotypes x parental genotypes x gametes , x , offspring genotypes probability of offspring not having the HbS allele and are maps showing some of the different regions in a country. Scientists studied the distribution of the HbS allele in the country. shows the estimated frequency of the allele within the population. shows the estimated number of babies born with sickle cell anaemia in each region. A C B low high estimated frequency of the HbS allele in the population A C B low medium high estimated number of babies born with sickle cell anaemia The scientists made a statement: ‘There is a relationship between the frequency of the HbS allele and the number of babies born with sickle cell anaemia in regions A, B and C.’ Using the information in and , discuss the evidence for and against this statement for regions A, B and C only. Suggest how the scientists would identify the presence of the HbS allele in tissue samples. Mutations are always inherited in single-celled organisms that reproduce asexually but are not always inherited in organisms that reproduce sexually. Explain why.
0610_s22_qp_43
THEORY
2022
Paper 4, Variant 3
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