1. Topic 3.4

2.  14 Explain how a phenotype is the result of an interaction between genotype and the environment (e.g. animal hair colour, human height, monoamine oxidase A (MAOA) and cancers), but the data on the relative contributions of genes and environment is often difficult to interpret.  15 Explain how some phenotypes are affected by alleles at many loci (polygenic inheritance) as well as the environment (e.g. height) and how this can give rise to phenotypes that show continuous variation.

3.  What is a phenotype? The characteristics of an organism.  What determines phenotype? Genotype, environment, or combination of both  What is a gene? A length of DNA which codes for a certain protein The same gene is always found at the same location on the same chromosome (same locus) and on its homologous pair

4.  What is discontinuous variation? distinct groups:  Give examples blood type Sex (gender), tongue rolling, attached ear lobes  Cause? one gene at a single locus

5.  What is continuous variation: Many possibilities within a range, but no distinct groups.  Examples? height in humans, length of feet, weight  Cause? several genes at different loci and/or environmental influences.

6. Define: locus, allele, polygenic, susceptibility, multi-factorial Complete questions 3.18 and 3.19 in your notebook or in the textbook.

7.  Locus: specific location of a gene on a chromosome.  Allele: one form of a gene  Polygenic: relating to a inheritable characteristic that is controlled by several genes at once.  Susceptibility:  You may inherit a gene making you susceptible to a certain disease. You may or may not get the disease - environmental factors will play a role  Multi-factorial: Conditions where several genes and environmental factors are involved.

8.  Human height  Hair colour  MAOA (monoamine oxidase A)  Cancer

9.  People in the UK are on average 8cm taller than in 1850.  What is the evidence that the environment plays a role? Improved nutrition  Increased protein in diet leading to more muscle and bone growth leading to increased average height.  Increased Calcium in diet leading to more bone growth Improved health (less infectious diseases, cleaner water, increased use of vaccinations, antibiotics…etc) leading to more energy for growth. More energy available for growth  End of child labour  Better insulation

10.  People in the UK are on average 8cm taller than in 1850.  What evidence is there from the graph below to suggest that height is affected by genotype as well as the environment?  Maximum height potential

11.  People in the UK are on average 8cm taller than in 1850.  How could the gene pool (collection of all alleles in a population) change? Note: in this time period there can be no significant change due to evolution. Migration- emigration or immigration from or to countries where more people are on average taller/shorter

12.  Activity 3.16 Many Genes can affect a single characteristic  Activity 3.17 Are we still getting taller?  Collect data for homework  Analyse data using laptops  Describe the shape of the graph. What does this show about the type of variation? If the shape is not what you expected explain.  What is meant by standard deviation? How can calculating it for a set of data help us?

14.  Check you understand these words  Melanin: A dark pigment (light absorbing chemical)  Melanocytes: Cells that make melanin. These cells found in the skin and in hair follicles.  Melanocyte stimulating hormone (MSH) regulates the production of melanin  MSH receptors: MSH bind with them to activate melanin producing genes in the melanocytes  Melanosomes: Organelles, melanocytes place melanin into them. They transfer the melanin to nearby skin or hair follicle cells

15.  Genetic component? Different alleles for different number of MSH receptors- more receptors results in darker colour  Environmental factors? UV light increases the amount of MSH and number of MSH receptors UV light destroys the melanin in hair

16. Arctic Foxes What happens in summer? In summer white fur grows under the brown fur because fewer MSH receptors are produced Therefore, MSH has less effect Less melanin in hair results in (almost)white fur.  What happens in autumn? In autumn the dark fur is shed

17. Describe the colouration of the Himalayan rabbit. Why does the fur have this pattern?

18.  Monoamine oxidase A: What is it? This enzyme speeds up the breakdown of neurotransmitters and has been linked to dealing with stress  What is the link between low levels of this enzyme and aggressive behaviour in humans? Studies have shown no/little link between low levels and aggressive behaviour However, low levels combined with maltreatment of children has been linked to aggressive behaviour/violent crime

19.  What is a tumour? A mass undifferentiated of cells. The cells multiply faster than they die.  What causes cancer? Damage to DNA.  How does DNA get damaged?  https://www.youtube.com/watch?v=8LhQllh46yI

21.  Tumours more likely to develop in the lungs, bowel, skin, bone marrow: why? In these areas there is more mitosis and more chance of mutation  What are the steps of the cell cycle? How is the cell cycle controlled? G1, S, G2, Mitosis (pages 114-117) The cell cycle is controlled by regulatory proteins. When these proteins are present they either stimulate or inhibit the cell cycle from progressing.

23. What are oncogenes? Genes which code for regulatory proteins - stimulate the progression from one stage to the next of the cell cycle. What happens when there are mutations in oncogenes? Cell cycle occurs uncontrolled and without stopping.

24.  What are tumour suppressor genes? They code for proteins which stop the cell from moving from one stage to the next in the cell cycle.  What happens when there are mutations in tumour suppressor genes? Mutations can stop these proteins from working properly and mean that the cell cycle continues (cell moves from one stage to the next) without stopping.

26.  Give an example of an gene which a person can inherit which makes them susceptible (predisposes) them to cancer?  Describe the function of the protein which this gene codes for.

27.  How can you reduce your risk of getting cancer? don’t smoke avoid excessive sunlight eat a diet high in antioxidants

28. 1. Describe the relationship between UV light and the production of melanin in human skin cells. (3) 2. Explain how differential gene expression could result in the specialisation of cells.(3) 3. Describe the distribution of colour in a Siamese cat. (2) 4. Suggest an explanation for the distribution of dark-coloured fur in a Siamese cat.(3) 5. Define the following terms- 1. Polygenic(1) 2. Allele(1) 3. Multifactorial (1) 4. Phenotype(2)

29. 1. UV light increases the amount of MSH/ MSH receptors; In melanocytes; Causing them to produce more melanin (3) 2.

30. 3. Black tips; white body(2) 4. idea that ears etc., have a lower temperature (than the rest of body); (therefore) enzyme is {active / not denatured / eq}; pigment produced / eq; no pigment produced in other parts because enzyme is {inactive / denatured} / eq;max 3 5. 1. When a number of genes code for one characteristic 2. different form of a gene 3. Conditions where several genes and the environment are involved in its development 4. characteristics of an organism; can be affected by the genotype and/or the environment (5)