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Differentiation in Germline Cells Higher Human Biology Unit 1 – Sub-Topic 1 (c) Learning Outcomes o The nucleus of a germline cell can divide by mitosis to produce more germline cells or divide by meiosis to produce haploid gametes. o Mutations that occur in germline cells will be passed to offspring whereas mutations in somatic cells will not. Germline cells Germline cells include the gametes and the cells that produce the gametes. Division of germline cells • Germline cells are diploid (23pairs of homologous chromosomes). • Germline cells can divide by mitosis to produce more germline cells. • Gamete mother cells divide by meiosis to produce gametes. Mutations • Mutations in germline cells are passed onto offspring. – For example: Cystic Fibrosis • A gene mutation on chromosome 7 may become the recessive form (leading to production of thick and sticky mucus). This mutant allele is passed onto gametes during meiosis. If the other parent is a carrier of the same recessive allele then the resulting zygote will be a cystic fibrosis sufferer. • A mutation in a somatic cell, even if it leads to a phenotypic change, is not passed onto offspring. Questions 1. What is the difference between the terms haploid and diploid? 2. What is a germline cell? 3. Describe how a diploid germline cell produces haploid gametes. 4. In which type of cell (somatic or germline) is a mutation not passed on to the members of the next generation? Answers 1. Haploid means a single set of 23 chromosomes. Diploid is a double set of chromosomes – 46 Chromosomes arranged as 23 pairs. 2. Germline cell is a cell that will eventually lead to the formation of sex cells (gametes). 3. By a form of nuclear division called Meiosis. The genetic material is doubled then it is divided between 4 nuclei. Each receives a set of 23 single chromosomes. 4. Mutations in Germline cells are passed onto members of the next generation.