Mixture

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

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

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

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