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Topic CB3 Genetics – Revision Task 1. Can you name the units below used to measure growth. m = ………………………………………………… g = …………………………………………… Km = …………………………………… l = …………………………………………… mg = ………………………………………….. µm = ………………………………………… ml = …………………………………………. Kg ………………………………………… Task 2: Decide what kind of variation the following are and link to the correct variation, one has been done for you: Leaf size Height (of animal or plant) Genetic / discontinuous variation Leaf colour Environmental Eye colour / continuous Blood group variation Skin colour Mass (weight) Task 3. Answer the questions: 1. What do we need meiosis for? …………………………………………………………………… 2. Name a haploid cell and a diploid cell. ………………………………………………………… 3. Explain why gametes need to be haploid? ………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………………… 4. Define the following words: Allele: . …………………………………………………………………………………………………………………………… Gene: …………………………………………………………………………………………………………………………… Heterozygous: …………………………………………………………………………………………………………………………… Homozygous: …………………………………………………………………………………………………………………………… Genotype: …………………………………………………………………………………………………………………………… Phenotype: …………………………………………………………………………………………………………………………… Genome: …………………………………………………………………………………………………………………………… Mutation: …………………………………………………………………………………………………………………………… Task 4: Put these sentences in the correct order to give the process of meiosis. Give the correct order here …………………………………………………… 1. 2. 3. 4. 5. 6. Metaphase 1: chromosomes line up in pairs in the middle of the cell. Telophase 1 and cytokinesis 1: Cell splits into two. Interphase: chromosomes replicate Anaphase 1: Chromosome pairs move away from each other. Prophase 1: nucleus disappears The 2 cells then splits again – producing 4 haploid daughter cells. Task 5: Can you compare meiosis with mitosis? Give three differences between meiosis and mitosis. Mitosis Meiosis 1. 2. 3. Task 6: Describe the structure of DNA by filling in the gaps. DNA is a ………………………………………………… shape. This means it is made of 2 strands held together. DNA is made up of ………………… bases. Adenine always pairs with …………………… Cytosine always pairs with …………………………… We say the pairs are …………………………………… The DNA keeps its double helix shape because the bases are held together by weak …………………………… bonds. There are …………… hydrogen bonds holding adenine and thymine together. There are ……………………… hydrogen bonds holding cytosine and guanine together. The backbone of DNA is made of alternating sugar and …………………………… groups. Task 7: DNA extraction experiment 1. Why did we add the strawberry cells to detergent (washing up liquid)? ………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… 2. Why did you filter the mixture? ………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………… 3. Draw a scientific diagram of how you filtered the mixture. Draw this below. 4. Why did you use the ethanol at the end of the experiment? What did you see? ………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… Task 8: Cystic fibrosis is a nasty genetic disorder. It is inherited from parents passing down genes. It is a recessive disorder – you need two faulty recessive alleles to have cystic fibrosis (cc) Complete the punnet square to show if two heterozygous parents can have a cystic fibrosis child. Mother’s gametes Father’s gametes 1. What is the probability that the couple will have a cystic fibrosis child. …………………… 2. What is the percentage chance they will have a cystic fibrosis child……………………… 3. What is the ratio of normal offspring to cystic fibrosis offspring………………………… Task 9: Pedigree analysis Task 10: Describe how sex (gender) is determined in humans by completing the gap fill. To be a …………………………… you have two ……………… chromosomes. To be a male you have an ……… and a ………… chromosome. Female eggs can only contain an ………… chromosome. Male ……………… cells can contain an X or a Y chromosome. If an egg (X) is fertilised by an X sperm, the child will be a …………………… If an egg (X) is fertilised by an Y sperm, the child will be a …………………… Task 11: Complete the variation revision task – ask miss for the sheet.
