Edexcel Biology 2105, also Science 2101, Additional Science 2103

Unit B1 a

Topic 2 — Genes

We are living in an age of an explosion in the use and understanding of genetics. The Human Genome Project may now be followed by many new medical treatments.
The activities of any organism are determined by the genes they possess. Chemical reactions in the cell depend on the cell’s proteins. The structure of these proteins is determined by the cell’s DNA.
Genes are passed from parent to child in predictable ways, but sometimes these mutate. Variation is produced by a combination of genes and environment. There is now even more genetic manipulation of living organisms for food production. Scientists are able to extract and modify genes in order to change the properties of crops and animals used as food. Scientists are also able to clone organisms and some scientists hope to produce cloned body parts for transplantation surgery.
Studying this topic gives students opportunities to interpret data produced through breeding experiments. Students can use various kinds of resources to consider the benefits, drawbacks and risks of scientific opportunities in gene therapy, cloning and genetic modification. Students can also investigate how scientific decisions are made and how the ethical concerns of society can be considered, for example in relation to cloning.

Guidance for students

Have you ever wondered?
Why can we not just breed a racehorse that will win every race?
Are clones really like they are in the movies?
Is it possible that Old English Sheepdogs and Yorkshire Terriers both came originally from wolves?
How can cows make drugs in their milk?
When will I be able to get medicines especially made for just me?
How can genetics be used to cure diseases?
Learning objectives
• Characteristics of organisms are dependent on their genes.
• Sexual reproduction leads to variation.
• Genetic modifications are used for a range of purposes.
• There are many ethical considerations associated with advances in genetic modification.
Glossary
You will be expected to be able to recall, explain, describe and use appropriately the following words and phrases:

allele    clone gene recessive
antibody  cystic fibrosis   generation sexual reproduction
asexual reproduction    DNA genetics transgenic
cancer   dominant Human Genome Project  transplant
cell    environment inheritance variation
characteristic   fertilisation nucleus
chromosome  forensic
carrier diploid haploid gamete
gene therapy heterozygous homozygous genotype phenotype
      Information for teachers
ICT is an integral part of the way science works, and students should be given opportunities to experience and explore its use. It is expected that ICT will be used where it enhances the learning and teaching of science and helps to make scientific concepts easier to understand.
Some of the learning outcomes have been written deliberately in order to promote discussion and expression of opinion. Where contentious, unresolved or other scientific issues are discussed, it is expected that students will be exposed to the facts, evidence and opinions from all sides of the argument.
Learning outcomes
Learning outcomes, words or statements in bold indicate that this content is designated for Higher tier students only.
Students will be assessed on their ability to:
• describe genes as parts of chromosomes which are found within the nucleus and which control the cell’s activity  B1 a 2.1
• explain that the unit of inheritance is the gene which is a section of a long chain (DNA) molecule  B1 a 2.2
•   appreciate the emerging outcomes of the Human Genome Project (HGP) and discuss some of their implications, including the use of DNA evidence in forensic science and medicine B1 a 2.3
• discuss how gene therapy could change the lives of two people, one suffering from cystic fibrosis and the other from breast cancer, if these diseases could be treated genetically  B1 a 2.4
• describe how asexual reproduction leads to genetically identical individuals called clones, including Chlorophytum (spider plant) 
B1 a 2.5
• explain how sexual reproduction, involving fertilisation, leads to variation in the new generation (including the use of a monohybrid cross diagram)   B1 a 2.6
• explain how some inherited characteristics can be modified by environmental conditions, including the influence of diet on human growth and mineral resources on plant growth  B1 a 2.7
• explain, how alternative forms (dominant and recessive alleles) of a gene cause variation in a characteristic   B1 a 2.8
• demonstrate an understanding of how some alleles can cause diseases which can be inherited, for example, sickle cell anaemia, Huntington’s disease and haemophilia B1 a 2.9
• evaluate the potential for using transgenic animals, including the production of ‘designer milk’, for example milk containing human antibodies and low cholesterol milk  B1 a 2.10
• describe the social and ethical concerns of cloning mammals, including the possibility of the cloning of human body parts for transplant surgery  B1 a 2.11
• consider the contemporary scientific theory of ‘designer babies’ and explain why today’s scientists are finding so much opposition to the use of this approach being publicly acceptable   B1 a 2.12