(1) Division and differentiation in human cells (F) Cancer Cells (A) Somatic cells Human Cells (E) Uses of stem cells (B) Differentiation in cells (D) Germline cells (C) Stem cells

Division and differentiation in human cells (D) State what is meant by germline cells Define the processes of mitosis and meiosis in a germline cell Compare the process of mitosis and meiosis Describe the effect of a mutation present in a germline cell Describe how the chromosome complement is maintained during cell division

Key Words Diploid Gamete Haploid Mitosis Meiosis Homologous Meiosis The term given to a ‘sex cell’ (Such as sperm or eggs) The term given to a cell containing 2 sets of chromosomes (Human somatic cells contain 46 chromosomes – 2 sets of 23 chromosomes) The term given to a cell containing 1 set of chromosomes (half the genetic information of the parent cell) (gametes contain 23 chromosomes – 1 set) Term used to describe 2 chromosomes which have the same genes (Diploid cells have 23 pairs of homologous chromosomes) Form of cell division, where by 2 identical diploid cells are produced Form of cell division where by 4 genetically different haploid gamete cells are produced

Germline cells Whilst somatic cells eventually form to create the different body tissues, germline cells eventually give rise to gametes (sex cells: eggs and sperm).

Matching set of chromosomes Every organisms has 2 matching sets of chromosomes. In humans, the 46 chromosomes can be arranged as 23 pairs. Each pair is known as a homologous pair (homologous = same)

What are the differences between the newly formed cells in mitosis and those formed in meiosis?

Division of germline cells Germline cells can divide by mitosis to produce more germline cells (the chromosome complement is maintained). They can also divide by meiosis to produce haploid gametes. meiosis video

All sex cells are haploid cells and contain only 1 set of chromosomes (23). After fertilisation, the complete 23 pairs of homologous chromosomes is restored in the new zygote that is formed (a diploid cell). ♀ Parent 46 chromosomes ♂ Parent 46 chromosomes Diploid (2n) Meiosis Egg 23 Chromosomes Sperm 23 Chromosomes Haploid (n) Fertilisation Zygote 46 chromosomes Diploid (2n)

What is a mutation? It is a change to the original genetic material (DNA, genes or chromosomes)

If a mutation occurs during meiosis it will be passed on to the offspring Normal division Mutation

If a mutation occurs during meiosis it will be passed on to the offspring Cells with a mutation Normal cells

TASK: Use your notes to complete the following table Mitosis VS. Meiosis Characteristic Mitosis Meiosis Purpose of division Number of cells produced Description of cells Number of chromosomes in each cell Types of cells that undergo this division Effect of mutations