Mutations What is a mutation A mutation is

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Mutations

Mutations

What is a mutation? • A mutation is a change in the DNA sequence

What is a mutation? • A mutation is a change in the DNA sequence that is not immediately and properly repaired. • Mutations are the only source of new alleles in a population. • They are rare and random. • Only mutations that occur in the formation of the gametes are passed onto the next generation. • Mutations are normally harmful and usually carried as a recessive allele.

Neutral mutations • Neutral mutations (or ‘silent’ mutations, as they have no observable effect

Neutral mutations • Neutral mutations (or ‘silent’ mutations, as they have no observable effect on the organism) are changes in DNA sequence that are neither beneficial nor detrimental to the ability of an organism to survive and reproduce. • They do not change the phenotype of the organism in anyway. • They don't harm an organism but they increase the genetic diversity that natural selection can work with later to drive evolution.

Causes of Mutations may occur randomly and spontaneously. They may also be induced by

Causes of Mutations may occur randomly and spontaneously. They may also be induced by environmental factors. Spontaneous mutations Arise from errors in replication Genes mutate at different rates Induced mutations Mutations can be induced by mutagens (environmental factors that cause a change in DNA): Examples of mutagens: radiation (e. g. UV rays) viruses microorganisms environmental poisons and irritants alcohol and diet

Effect of Mutagens on DNA After exposure to UV light (a potent mutagen) adjacent

Effect of Mutagens on DNA After exposure to UV light (a potent mutagen) adjacent thymine bases in DNA become cross-linked to form a 'thymine dimer'. This disrupts the normal base pairing and throws the controlling gene's instructions into chaos. UV Light Thymine dimer DNA of tumour suppressor gene

Location of Mutations Gametic Mutations Sperm The location of a mutation determines whether or

Location of Mutations Gametic Mutations Sperm The location of a mutation determines whether or not it will be inherited. Most mutations occur in somatic cells and are not inherited. Somatic Mutations Mutation Sperm Egg Fertilisation Cleavage. Prior to implantation Gametic mutations occur in the cells of the gonads (which produce sperm and eggs) and may be inherited. Mutation Fetus Baby Cells of tissues affected by the mutation Gametic mutations are inherited and occur in the testes of males and the ovaries of females. Somatic mutations occur in body cells. They are not inherited but may affect the person during their lifetime.

Harmful mutations • Any random change in a gene's DNA is likely to result

Harmful mutations • Any random change in a gene's DNA is likely to result in a protein that does not function normally or may not function at all. • Such mutations are likely to be harmful. • Harmful mutations may cause genetic disorders or cancer. A genetic disorder is a disease caused by a mutation in one or a few genes. • Good and bad mutations • Complete BZ pgs 104 -106

Harmful Mutations There are many examples of harmful mutations resulting from alterations to the

Harmful Mutations There are many examples of harmful mutations resulting from alterations to the DNA base sequence. Examples in humans include: Sickle-cell disease Cystic fibrosis An example in animals is albinism, which increases susceptibility to predation and disease (e. g. cancers). (Photo CDC) Thalassemias Sickle cell lesion These mutations are harmful because, by altering the DNA sequence, they upset the structure and function of the protein they code for. Normal red blood cells ‘Sickle-cells’

Beneficial mutations • A beneficial mutation is exactly what it says it is: a

Beneficial mutations • A beneficial mutation is exactly what it says it is: a mutation in an organism's genome that produces a beneficial effect. • It affects the organism in some way as to increase its chances of reproductive success, and therefore the chance of the mutation in question being passed along. • Example: antibiotic resistant bacteria

Beneficial Mutation Example Tolerance to high cholesterol levels in humans In the small village

Beneficial Mutation Example Tolerance to high cholesterol levels in humans In the small village of Limone, about 40 villagers have extraordinarily high levels of blood cholesterol, with no apparent harmful effects on their coronary arteries. The village has a population of 980 inhabitants and was, until recently, largely isolated from the rest of the world, with sheer cliffs behind the village, the lake in front of them, and no road access. The village of Limone, on the shore of Lake Garda, Italy Limone Brescia Lake Garda Verona

Beneficial Mutation Example The 40 villagers possess a point mutation which alters the protein

Beneficial Mutation Example The 40 villagers possess a point mutation which alters the protein produced by just one amino acid. This protein is ten times more effective at mopping up excess cholesterol. No matter how much excess cholesterol is ingested, it can always be disposed of. All carriers of the mutation are related and have descended from one couple who arrived in Limone in 1636. Generally, the people of Limone live longer and show a high resistance to heart disease. High blood cholesterol and dietary fat are implicated in the formation of plaques in the coronary arteries and in the development of cardiovascular disease.

Antibiotic Resistance Antibiotics are drugs that inhibit bacterial growth. With increased antibiotic use after

Antibiotic Resistance Antibiotics are drugs that inhibit bacterial growth. With increased antibiotic use after WWII, bacteria quickly developed resistance. A survey in five European countries showed that around 40% of hospital samples contained at least one antibiotic resistant strain. Resistant bacteria include: Klebsiella, Enterococcus, E. coli, Staphylococcus aureus, Enterobacter, Pseudomonas, and Mycobacterium tuberculosis. Colonies of bacteria are distributed evenly across the agar plate surface. Agar plate (nutrient growth medium) with bacterial colonies spread uniformly across its surface. Zone of inhibition where there is little or no bacterial growth. Petri dish Bacteria resistant to this antibiotic Photo CDC Paper disc saturated with antibiotic.

Complete BZ pgs 104 -106

Complete BZ pgs 104 -106