Inheritance

Key Issues

Titles

Chapters

• Alternative forms of a gene (allele) cause variation
• An understanding that crop plants can be genetically modified
• Asexual Reproduction
• Benefits and dilemmas of genetic engineering
• Body cells divide by mitosis to produce additional cells during growth or to produce replacement cells
• Body cells have two sets of genetic information; sex cells (gametes) have only one set
• Cell Division in Mature Animals
• Cells from human embryos and adult bone marrow, called stem cells, can be made to differentiate into many different types of cells eg nerve cells
• Cells in reproductive organs - testes and ovaries in humans - divide to form gametes
• Characteristics depend on both genetic and environmental influences
• Chromosomes
• Cloning
• Cystic Fibrosis
• Cystic fibrosis - a disorder of cell membranes - must be inherited from both parents
• Cystic fibrosis is caused by a recessive allele of a gene and can therefore be passed on by parents, neither of whom has the disorder
• describe the process of selective breeding involving cross breeding
• describe the process of selective breeding involving the selection and rejection of suitable offspring over many generations
• describe the process of selective breeding involving the selection of parents with desired traits and characteristics
• Determination of sex in humans
• Embryos can be screened for the alleles that cause these and other genetic disorders
• explain how selective breeding can contribute to improved agricultural yields
• explain that a selective breeding programme may reduce the gene pool leading to problems (accumulation of harmful recessive characteristics)
• explain that a selective breeding programme may reduce the gene pool leading to problems (reduction in variation)
• Gametes
• GENE TECHNOLOGY
• Genes as part of chromosomes and DNA
• Genetic modification (engineering)
• Homozygous and heterozygous genotypes and phenotypes
• Huntington's disease - a disorder of the nervous system - is caused by a dominant allele of a gene and can therefore be passed on by only one parent who has the disorder
• Huntington's Disease
• Implications of the outcome of the Human Genome Project
• In body cells the chromosomes are normally found in pairs
• In females the sex chromosomes are the same (XX) in males the sex chromosomes are different (XY)
• In human body cells, one of the 23 pairs of chromosomes carries the genes which determine sex
• In mature animals, cell division is mainly restricted to repair and replacement
• Inheritance of genetic disorders
• Inherited diseases
• know that cloning results in genetically identical offspring, for example, cuttings and runners in asexual reproduction in plants, tissue culture and splitting of early embryos in agricultural animals
• Meiosis
• Mitosis
• Monohybrid crosses and genetic diagrams
• Monohybrid inheritance using crossing diagrams
• Most types of animal cells differentiate at an early stage whereas many plant cells retain the ability to differentiate throughout life
• Objectives of the Human Genome Project
• Prediction of ratios of genotypes and phenotypes
• Probabilities of inheritance from parents
• recognise that some diseases (cystic fibrosis; Huntington's chorea) have genetic causes
• Screening and Genetic Disorders
• Selective breeding
• Sex Chromosomes
• Sexual Reproduction
• Sexual reproduction gives rise to variation because, when gametes fuse, one of each pair of alleles comes from each parent
• Techniques of genetic engineering
• The cells of the offspring produced by asexual reproduction are produced by mitosis from the parental cells. They contain the same genes as the parents
• The parents may be carriers of Cystic fibrosis without actually having the disorder themselves
• The parents of Cystic fibrosis may be carriers of the disorder without actually having the disorder themselves
• The type of cell division in which a cell divides to form gametes is called meiosis
• Treatment with these cells may help conditions such as paralysis
• understand that people can select the characteristics they want to breed in plants and animals
• use a knowledge of genetics to explain the inheritance of single gene disorders caused by dominant alleles (Huntington's chorea)
• use a knowledge of genetics to explain the inheritance of single gene disorders caused by recessive alleles (cystic fibrosis)
• use a knowledge of genetics to explain why some people are carriers of single gene disorders
• When a cell divides to form gametes copies of the chromosomes are made and then the cell divides twice to form four gametes, each with a single set of chromosomes
• When gametes join at fertilisation, a single body cell with new pairs of chromosomes is formed. A new individual then develops by this cell repeatedly dividing by mitosis