Mixture of topics

  • Created by: Maisie
  • Created on: 21-01-11 21:31

proteins made in protein synthesis- important in cell function they can be:

  • structural proteins-(keratin/collagen walls of blood vessels),  
  • proteins in cell membranes (receptors, antigens of ABO blood groups, CFTR protein),
  • proteins with specific biochemical adaptations( haemoglobin)
  • enzymes(respiration RNA polymerase in protein synthesis)
  • important genes are regulated because only some genes needed in certain cells/and stages of life and they dont need to be made al the time as its a waste of resources so they are switched on/off
  • testosterone-males main sex hormone in contact with every cell as it circulates the blood only affects target cells- steroid hormone-can move easily across membranes.
  • inside a cell testosterone combines with receptor molecule in cytoplasm= receptor molecule complex- travels into cell nucleus binds to recpter on chromatin- stimulates specific genes to be transcribed into mRNA
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Acetylation and Methylation

adding acetyl groups to histone proteins - stimulates transcription

removing acetyl groups from histone proteins- represses transcription

DNA methylation occurs when methyl groups are added to cytosine bases on DNA-represses transcription of DNA- the pattern of methylation can be passed on to daughter cells (important for epigentics-inherited changes in DNA)- switches genes on/off during embryo developement when cells are differntiating

prada willi syndrome- methylated groups added.. when defective chromosome inherited from fatherdsyndrome inherited whereas its not from mother

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Genes and Cancer

tumour suppressor gene cause a tumor when they are turned on/off

  • may inherit a mutated tumour suppressor gene- may be heterozygous for TSG as long as they have normal allele no cancer - but normal allele can mutate
  • mutatations in tumour suppressor genes can be left uncorrected - cancer develops
  • TSG with badly damaged DNA commit apoptosis
  • some tumour suppressor genes act as signal transducers- proto oncogene mutates the signal transducer is permanently switched on  stimulating cell division
  • code for transcription factors which act on DNA and control which genes are transcribed into RNA to synesise proteins if PO mutates transcription factors produced in large amounts
  • code for proteins which cause cells to commit apoptosis when abnormal if TSG mutates abnormal cell may carry on growing
  • gene mutations changes in the DNA base sequences in TSG and PO-  increasing methylation in DNA represses transcription
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genes have a promoter region - where RNA polymerase attaches- this determines the strand of DNA that becomes the template for mRNA transcription- if a promotor region has too many methy groups added gene cant be transcribed

methylation may be increased by certain environmental factors.

oestrogen and cancer

  • oestrogen is a steriod hormone so it stimulates gene transcription.
  • oestrogen passes through plasma membrane and binds to a specific oestrogen receptor protein in cytoplasm this binds to a corregulator and the whole complex binds to a chromatin= gene transcription
  • breast cancer that is oestrogen + can be treated with tamioxifen
  • tamioxifen is similar shape so it binds to oestrogen receptor protein - corregulator doesnt bind but complex still binds to chromatin but no transcription is timulated
  • treats it well but can develop resistance - different drug given which reduces oestogen
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