Genes and Disease

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Phenylketonuria (PKU)

mutation in a gene can cause disease


inherited error of metabolism

defiency in enzyme Phenylalanine

Autosomal recessive disorder

caused by mutation in both alleles on chromosone 12

loss of enzyme results in poor mental ability and organ damage

occurs in both males and females

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Duchenne Muscular Dystrophy

X linked chromosone

encodes for Dystrophin protein

affects mainly males

If more than one gene is associated with a disease - more than one mutation is required

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Crohns disease and Atherosclerosis

occurs in lower small intestine

inflammation extends

causes pain and diarrhoea

chromosone 16 and one less copy of beta - defensin gene on chromosone 8


affects anyone

high blood pressure, cigarrette smoke

narrowing of arteries

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Apolipoprotein E

removes cholesterol from blood

carry cholesterol to liver cells

chromosone 19, many different forms

DNA base sequence varies - APO E produced differ from each other

defects result in inability to bind cholesterol, leading to increase in cholesterol

risk in Alzheimers

different responses to medicines

human genome - 3 billion nucleotides

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immunosuprressant used to treat children with lymphoblastic leukemia

broken down by thiopunne methyle transferase whose level is controlled by single gene

inheritence determines response to drug

Bioactive dietary components can influence gene expression

the fluctuations in food consumed 

infulences absorbptions, metabolism

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Cancer occurs when cell division is out of control

Mutations can seriously affect the cycle

Internal and external inputs trigger molecular events regulates normal progress - initiates of DNA synthesis

Assembly and integrity of mitotic spindle

check point molecules lead to cancer CDKs and cyclins

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Cancer triggers and Cancer mechanisms

Exposure to environmental factors

a genetic predisposition

Mechanisms for cancer

1. Impairment of Dna repair pathway

2.transformation of normal gene

3. malfunction of tumor suppressor gene

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DNA repair genes

Damage caused by number of potential carcinogens

spontaneous errors in dividing cells can be damaging

If errors accumilate cells are at risk of neoplastic transformation

Luckily we have genes that can repair the damage

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Breast, Ovarian and colon Cancer

Clear genetic link

BRCA1 - chromonsone 17

BRCA2 - chromosone - 13

gene repair radiation - induced breaks in double stranded DNA

Colon Cancer

vast cases not inherited

FAP - familial adenomatous polysis

HNPCC - heridetary nonpolyposis colorectal cancer

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FAP - many polyps in colon APC gene on chromosone 5

HNPCC - diagnosis based on family history - not detectable in most cases

HNPCC genes have been discovered

Protein products normally help to repair mistakes in DNA replication

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P53 and Oncogenes

Oncogenes - viruses that induce cancer

normal cellular genes responsible for cellular homeostasi, including growth and differentiation

referred to as proto- oncogenes in order to distinguish them from retroviral oncogenes

P53 - guardian of the genome

supresses abnormal cell proliferation

protection agaisnt cancer

mutated P53 molecule loses ability to supress abnormal growth

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