State the number of chromosomes which would be present in the cells labelled A, Band C.

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1 M N&ll!Iif..t _ class

2 lviarks DO NOT WRITE IN TIllS MARGIN. The diagram below represents stages in the production of human sperm. (a) Name the type of cell division that produces sex cells. (b) State the number of chromosomes which would be present in the cells labelled A, Band C. A: _ B: C: _ (c) Compare the appearance of the chromosomes in cell B and cell C. (d) Name the two processes which increase variation during the st division of the sperm mother cell. 2 _ (e) State the location of sperm production in the testes.

3 2. Some stages in the process of meiosis are shown in the diagrams below. Murks THIS MARGIN Only 6 chromosomes are shown in each cell. A B c D,.. - (a) (i) Place the stages in the correct order. (ii) At which stage could chiasmata form? (iii) Why are chiasmata important? (b) The diagram below shows a gamete mother cell and four sperm which would result from meiosis. (i) Complete the diagram by writing in the normal number of chromosomes found in each of the cells. Gamete mother cell Sperm (ii) In how many of these sperm will an X chromosome be found? (iii) Where in the testes does meiosis occur? [Turn over

4 3. The graph below shows the mass of DNA present as gamete mother cells develop into sperm cells during meoisis in the testes. P and Q represent cells at intermediate stages in this process. 4 DO NOT WRITE IN THIS lvlargin 3 Mass of DNA (arbitrary 2 units) Gamete mother cells p Q Sperm cells (a) Explain why the mass of DNA changes between (i) the gamete mother cells and cell type P _ (ii) cell types P and Q. _

5 3. (continued) DO NOT WRITE IN THIS MARGIN (b) The diagram below shows a pair of chromosomes in a cell undergoing meiosis. cross-over point Letters Rand T represent dominant alleles of two different genes. (i) What name is given to the point on the chromosomes where crossmg over occurs? (ii) Assuming that crossing over does occur, give all the combinations of alleles that would be present in the resulting gametes. (iii) Crossing over leads to genetic variation. Name one other way in which meiosis increases variation. (c) State the exact location of meiosis in the testes. [Turn over

6 4. The family tree below shows the inheritance of a genetic disorder. margin Key to symbols o male o female Jack Gill affected male tit affected female Tony Mary (a) State whether the disorder is dominant or recessive and give a reason for your answer. Dominant/recessive () ~ Reason () (b) Using symbols Band b to represent the alleles, give the genotypes of Tony and Mary. Tony Mary () (c) Jack.and Gill are expecting a third child. What is the percentage chance of this child inheriting the disorder? 0/0 ()

7 5. Thalassaemia is an inherited blood disorder in which haemoglobin is affected. The condition illustrates incomplete dominance in which the recessive allele has a partial effect. Heterozygous individuals show mild symptoms. TH~ MARGIN The diagram below shows the incidence of thalassaemia family. ~ male with mild female with mild thalassaemia male with severe thalassaemia o unaffected female in three generations of a Philip Carla Charles (a) Using the symbol Hb A to represent the allele for normal haemoglobin, and the symbol Hb B to represent the recessive allele, complete the table to show the genotypes of Anne, Philip and Charles. Individual Genotype Anne Philip Charles 2 (b) Mark and Carla have a third child. What is the percentage chance that the child will have the same genotype as the parents? Space for calculation % (c) Haemoglobin is found in red blood cells. Where in the body are red cells manufactured and destroyed? Manufactured Destroyed 2 [Turnover

8 6. The diagram below shows the inheritance of tongue-rolling ability in a family. THIS MARGIN o Male tongue-roller o Female tongue-roller Male non tongue-roller Female non tongue-roller P S (a) (i) Using the symbol R to represent the allele for tongue-rolling, and the symbol r to represent the allele for non tongue-rolling, state the genotypes of individuals P and T. P _ T _ (ii) How many individuals, shown In this family tree, have a genotype which is homozygous recessive? (iii) Place a cross through a symbol in the family tree which represents a heterozygous male. (iv) Female S is pregnant. Using information from the family tree, is it possible to predict whether the child will be a tongue-roller or not? Give a reason for your answer. YES/NO Reason _... (b) Some characteristics are controlled by several genes. (i) State the term used to describe this type of inheritance pattern. (ii) Which two of the following human characteristics show this type of inheritance pattern? Underline the correct answers. blood groups cystic fibrosis height haemophilia skin colour

9 7. The Rhesus blood group system is determined by three pairs of alleles: Cc, Dd and Ee. However, only the D allele is important in blood transfusion and pregnancy. People with the dominant allele D are Rhesus positive and those with genotype dd are Rhesus negative. (a) What term is used to describe characteristics controlled by many pairs of alleles? (b) Name another blood group system which has to be matched for blood transfusion to be successful. WRITE IN THIS MARGIN...-:=:,---, (c) What part of a cell carries the Rhesus antigen? (d) A Rhesus negative woman and a Rhesus positive man are planning to have a child. They consult a genetics counsellor to find out whether their child is likely to be Rhesus positive or Rhesus negative. What genetic information could they be given? 2 (e) Describe a treatment which can be used to protect a child at risk from the Rhesus reaction. [Turnover

10 8. (a) The MN blood group system is determined by two alleles, M and N. Each of these alleles controls the production of a different antigen on the cell membrane of red blood cells. M and N are co-dominant. THIS MARGIN (i) Two parents, who are heterozygous for this blood group, have a son. Complete the Punnett square below to show the parental gametes and the possible genotypes of their son. Parents Genotype Mother MN x Father MN mother's gametes father's gametes MN (ii). The son has a different genotype to either of his parents. chances of this happening? Space for calculation What are the % (ill) Describe how the son's phenotype differs from his parents. (b) The immune system recognises antigens on the cell membrane as self or non-self. What term describes (i) an immune reaction to self antigens? (ii) an over-reaction to a normally harmless non-self antigen? [Turn over

11 9. Sickle-cell anaemia is a blood disorder in which haemoglobin is malformed. The diagram below shows the effect of this disorder on a red blood cell. Normal red blood cell Sickled red blood cell The condition is not sex-linked. The allele for normal haemoglobin (H) IS incompletely dominant to the sickle-cell allele (h). Heterozygous individuals are mildly affected, whereas those with genotype hh are. severely affected. Two mildly affected parents have two children who are mildly affected like their parents. The parents are expecting a third child. (a) Complete the Punnett square to show the possible genotypes of this child. 2 (b) From the Punnett square calculate the percentage chance of the child being unaffected 2 mildly affected 3 severely affected.

12 0. Three different alleles determine the ABO blood groups. Allele A and allele Bare both dominant to allele 0. (a) Alleles A and B are both expressed in heterozygous individuals who have blood group AB. What term is used to describe the relationship between alleles A and B? (b) (i) A man with blood group AB marries a woman with blood group O. State the genotypes of the parental gametes and use them to complete the Punnett diagram below. man woman parental phenotypes AB x o gamete genotypes Punnett diagram (ii) State the possible phenotypes of the children and the ratio in which they would be expected to occur. Phenotypes Ratio (iii). Which of the parents would be able to -donate blood safely to any of their children? Give a reason for your answer. Parent Reason

13 . The blood group of an individual is controlled by three alleles A, B- and O. Alleles A and B are co-dominant and completely dominant to allele O. The diagram below shows the blood groups of three generations of a family. r ra ro MARGIN Parents Mother Group B Father Group A Children Son Son 2 Group A Group 0 Daughter T Husband Group 0 Grandchildren Grandson Group B Granddaughter Group A (a) What is the blood group of the daughter? (b) State the genotypes of the grandchildren. Grandson Granddaughter _ (c) How many of the three children are homozygous? (d) Explain the meaning of the term co-dominant. (e) Only one of the sons can safely receive a blood transfusion from his brother. Indicate whether this statement is true or false and explain your decision. True/False Explanation.:.._ ---:- _ 2 [Turnover

14 2. Three different alleles determine the ABO blood groups. both dominant to allele 0. Allele A and allele Bare (a) Alleles A and B are both expressed in heterozygous individuals who have blood group AB. What term is used to describe the relationship between alleles A and B? (b) (i) A man with blood group AB marries a woman with blood group O. State the genotypes of the parental gametes and use them to complete the Punnett diagram below. man woman parental phenotypes AB x o gamete genotypes Punnett diagram (ii) State the possible phenotypes of the children and the ratio in which they would be expected to occur. Phenotypes Ratio (iii) Which of the parents would be able to ' lonate blood safely to any of their children? Give a reason for your answer. Parent Reason

15 3. The gene for this blood group has three alleles. Alleles A and Bare co-dominant to allele O. A man, heterozygous for blood group A, and a woman of blood group AB, have children. THIS MARGIN (a) (i) State the genotypes of the parents. female _ male _ (ii) Complete the Punnett square below to show the genotypes of their gametes and the genotypes of the children they may have. 2 (iii) What is the percentage chance that a child of these parents would have blood group A? % [Turn over..

16 4. The diagram below shows inheritance of the ABO blood group over three generations of a family. The letters represent the blood group of each individual. DO NOT WRITE IN THIS MARGIN DMale 2 ofemale B 7 8 (a) The ABO blood group system is controlled by three alleles: A, Band O. Alleles A and B are co-dominant and both are completely dominant to allele O. (i) State the genotypes of the following: Individual _ Individual 3 _ (ii) What is the blood group of individuals? Give a reason for your answer. Blood group _ Reason 2 (iii) How many of the individuals shown in the family tree have a genotype which is heterozygous? (b) During an operation, individual 4 needed a blood transfusion. Identify all the individuals her. in the family tree who could safely donate blood to

17 5. Polydactyly is an inherited condition in which individuals are born with extra toes. The allele for polydactyly is dominant and not sex-linked. The family tree below shows the incidence of the condition through three generations. TH: MAR ( Grandparents o unaffected male o unaffected female affected male affected female Parents x y Children (a) (i) Using the symbol D for the allele for polydactyly and d for the normal allele, give the genotypes of the two children. and (ii) Individuals X and Yare expecting another child. What-are the chances of this child inheriting the condition? (b) (i) What evidence from the family tree confirms that th~ grandfather is heterozygous?... (ii) What evidence from the family tree confirms that the condition is not sex-linked? (c) What term is used to refer to chromosomes which are not sex-chromosomes?

18 6. The family tree shows the inheritance of a bone disorder. THIS MARGIN Parents Affected female o Unaffected female Affected male D Unaffected male p Q R s The disorder is caused by a dominant sex-linked allele (B). (a) Using appropriate symbols, give the genotypes of individuals P, Q, Rand S. P Q R S _ 2 (b) (i) Explain why all the F, females in this family are affected. (ii) Explain why only some of the F2 females in this family are affected. (c) Is the ratio of affected offspring to unaffected offspring in the F, generation as expected? Give a reason for your answer. Yes/No _ Reason

19 7. The diagram below represents the two sex chromosomes. x y (a) Using the letter H, mark on the diagram the likely position of the sex-linked allele which causes haemophilia. () (b) What term is used to describe the other 44 chromosomes found in a normal diploid cell? () (c) Describe how a karyotype can be used to detect genetic disorders. ()...

20 5!:::S w:p 8. Achondroplasia is an autosomal disorder of bone growth that is caused by a gene mutation. A person with this condition has relatively short arms and legs. The incidence of achondroplasia in a family is shown in the diagram below. lviarks Key o = unaffected female D= unaffected male = affected female G H J = affected male (a) (i) In this family, the mutation occurred in an ovum. In which individual did the mutation take place? (ii) Describe a change which takes place in a gene when it mutates. (b) The allele which causes achondroplasia is dominant. What is the percentage chance that a child of Hand J would inherit achondroplasia? Space for calculation % (c) People who are affected by achondroplasia do not produce enough growth hormone. State the site of growth hormone production. (d) The list below contains a number of inherited disorders. Phenylketonuria Down's syndrome Huntington's chorea Haemophilia Cystic fibrosis Select a disorder from this list which is: (i) (ii) the result of non-disjunction; a sex-linked condition. 2

21 9. (a) The diagram below shows the base sequence in part of a DNA strand. A G G I I I T T I I c I (i) What two amino acids are coded for by this strand of DNA? and _ (ii) If the base A was replaced by the base C as a result of a mutation in the strand above, which two amino acids would result? and _" _ (iii) 'What name is given to this type of mutation? (iv) Why is this type of mutation potentially less harmful than an insertion or deletion mutation? 2 (b) Name bases A and C. A _ C

22 What you should know (Chapters -4). (See table 4.3 for word bank.) A cross is one that involves two parents who differ in one way with respect to a particular characteristic. 2 One member of a pair of alleles of a gene exhibits dominance if it completely ---- theexpression of the other allele in the phenotype resulting from the heterozygote. 3 The members of a pair of alleles show ---- dominance if the heterozygote results in a pheno type between those of the two homozygotes. 4 The members of a pair of alleles show if the heterozygote produces a phenotype where both alleles are expressed. 5 If three or more alleles of a gene exist, it is said to have alleles. What you should know (Chapters -4). Analysis of a family tree relating to a 6 Human females possess a pair of homologous sex chromosomes called X chromosomes; human males have one X and a Y chromosome which is to part of the X chromosome. 7 Genes present on an X chromosome but not on a Y chromosome are said to be _ 8 A characteristic which shows variation is controlled by alleles of more than one gene and is said to show inheritance. 9 Mutations are changes in the which involve an alteration of type or sequence in DNA or a change in of chromosomes. 0 Substitution and bring about minor changes and are called point mutations; insertion and lead to major changes and are called frarneshift mutations. genetic disorder enables a genetic to. help people make decisions about parenthood based on assessment of _ 4 A is a display of a complement of chromosomes showing their form, size and number. 5 and chorionic villus sampling enable ---- material to be karyotyped and inspected for chromosomal abnormalities. 6 Risk evaluation in cases of polygenic inheritance is usually _ 7 Post-natal is done to identify babies suffering phenylketonuria. WYSK - 4 Inheritance abnormalities foetal amniocentesis fully Mutations occur rarely and at. Their base geno~e frequency can be increased by agents. co-dominance homologous.2 occurs when a spindle fibre fails during complete incomplete meiosis and the members of a pair of homologous continuous intermediate chromosomes fail to separate. This results in some counsellor inversion gametes receiving one chromosome too many or deletion karyotype one chromosome too few and leads to the formation of individuals suffering chromosomal _ empirical Dlasks family tree monohybrid 3 A pattern of inheritance amongst the members of a family can be established by constructing a Table 4.3 Word bank for chapters -4 multiple mutagenic non-disjunction number polygenic random risk screening sex-linked smaller

23 What you should know (Chapters9-0) (See table 0.3 for word bank.) A is a unit of heredity which controls a characteristic. It consists of a region of _ on a chromosome. 2 A species' chromosome is the characteristic number of chromosomes that it possesses (46 in a human). These can be arranged into pairs which match one another gene for gene. 3 In a human, one pair of chromosomes determines the of the individual and are called the sex chromosomes. The other 22 pairs are called 4 A cell containing 46 chromosomes as 23 pairs is ; a cell containing 23 _ chromosomes is haploid. S is the process by which the nucleus of a diploid gamete mother cell divides htto four, resulting in the formation of four Prior to nuclear, the amount of chromosomal material doubles by DNA undergoing and reproducing itself exactly. 7 DNA replication allows genetic information to be passed on from cell to cell and from generation to 8 Meiosis involves two consecutive _ divisions and produces gametes in preparation for sexual reproduction. 9 During meiosis, new combinations of existing alleles arise by independent and _ between homologous chromosomes. 0 The meeting of two haploid gametes at fertilisation allows mixing of part of one person's _ with that of another. By producing diploid individuals who are genetically different from their parents, this process produces amongst the members of the human species. assortment DNA meiosis autosomes gametes nuclear chromosomes gene replication compliment generation sex crossing over genotype unpaired diploid haploid variation division homologous Table 0.3 Word bank for chapters 9-0

24 Essay Questions. Describe /low the process of meiosis brings about variation in the human population, under the following headings: i) PuTangementofcbromosomes (5) ii) Exchange of genes (5) (0) 2. Outline the main mechanism of sex-linked inheritance in humans bv naming a sex-linked characteristic and showing how it is transmitted {rom one generation to the next Maximum 8 marks mark coherence mark relevance (lu)

25 Record of Progress Question Date due Mark