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01 Variation FT 2 Answer all the questions. 1 All people are different. Some of our characteristics are inherited from our parents. Some are caused by our environment. Some are a combination of both. (a) Complete the table by writing down one example of each type of characteristic. inherited from our parents caused by our environment a combination of inheritance and environment [3] (b) Genetic characteristics are determined by our genes. These statements are about genes. Some of the statements are correct and some are not. Put ticks (✓) in the boxes next to the three correct statements. Genes are instructions for making proteins. Some genes are instructions for making enzymes. Genes are made up of chromosomes. Some characteristics are controlled by several genes working together. Genes are instructions for making carbohydrates. Some genes are instructions for making fats. [2] © OCR B1B2B3 Jan 2012 3 (c) Sex is determined by the X and Y chromosomes. Complete the Punnett square to show how sex is inherited in humans. You should write something in each of the empty boxes. X X X [3] [Total: 8] © B1B2B3 Jan OCR 2012 Turn over 2 Answer all the questions. 1 Body cells and sex cells have similarities and differences. (a) Put ticks (✓) in the boxes next to the three correct statements. A sex cell usually has two alleles of each gene. Body cells contain pairs of chromosomes. Sex cells contain alleles that can be dominant or recessive. Body cells contain half the normal number of chromosomes. A sex cell usually contains one allele of each gene. Body cells in males have only Y sex chromosomes. Sex cells in humans always have both X and Y chromosomes. [3] (b) Body cells and sex cells both contain chromosomes. Put ticks (✓) in the boxes next to the three correct statements. Chromosomes are made from very long DNA molecules. A person only has one allele for each gene. Genes are sections of DNA molecules. Genes are instructions for making fats and carbohydrates. All DNA is found in the cytoplasm of cells. All our characteristics are determined by genes. Genes with a recessive allele always express that allele. Many characteristics are produced by several different genes working together. [3] B1B2B3 June 2012 OCR 3 (c) Two parents each have a dominant allele (A) and a recessive allele (a) for the same gene. Draw a genetic diagram to show how these alleles can be passed on to their children. Explain your genetic diagram. The quality of written communication will be assessed in your answer. .............................................................................................................................................. [6] B1B2B3 June 2012 OCR Turn over 2 Answer all the questions. 1 Steve and Jane are expecting a baby. (a) Jane’s sex chromosomes are XX. Complete the Punnet square to show the possible combinations of sex chromosomes in their baby. Jane X X Steve [2] (b) Steve and Jane already have two baby boys. Steve says there is a higher chance that the new baby will be a girl. Explain why Steve is wrong. .............................................................................................................................................. [2] B1B2B3 June 2013 OCR 3 (c) Steve and Jane’s baby is born. Some features of the baby are like Steve and some are like Jane. However some features look different to both Steve and Jane. Use ideas about genes, alleles and the environment to explain these observations. The quality of written communication will be assessed in your answer. .............................................................................................................................................. [6] [Total: 10] B1B2B3 June 2013 OCR Turn over