topic 8

• What is a mutation?


  A change in the DNA sequence
• What are the 6 types of mutation? (Things that happen with bases)

  Substitution

  Deletion

  Addition

  Duplication

  Inversion

  Translocation
• What is a hereditary mutation?

  When a gameate containing a mutation for a type of cancer or genetic disorder is fertilised then it will be present in new foetus
• What happens during frameshift mutations?

  Additions, duplications or deletions within a gene change amino acid sequence causing a shift in the base triplets
• What are mutagenic agents? 3 examples

  Things that increase the rate of mutations , uv radiation, ionising radiation, chemicals , viruses
• How can mutagenic agents increase the rate of mutation? ( 3 ways)

  Acting as a base- chemicals called base analogs can substitute for a base

  Altering bases - some chemicals can delete or alter bases

  Changing the structure of dna - some types of radiation can change the structure of dna
• What are acquired mutations ?

  Mutations that occur in individual cells after fertilisation
• What are the 2 types of gene that control cell division?

  Tumour suppressor genes

  Photo-oncogenes
• What do tumour suppressor genes do?

  Slow cell division by producing proteins that stop cells dividing or causing cell death if DNA copying errors detected
• What do proto-oncogenes do?

  Stimulate cell division by producing proteins that make cells divide
• What is a mutated protooncogene called?

  Oncogene
• State 6 ways in which tumour cells differ from normal cells?

  - nucleus larger, darker sometimes more than one

  - irregular shape

  - don't produce all proteins needed to function

  - different antigens on surface

  - don't respond to growth regulated processes

  - divide by mitosis more frequently
• What are 2 causes of tumour growth?

  Abnormal methylation of dna

  Increased exposure to oestrogen
• What is methylation?


  Adding methyl group
• Why is methylation important?

  It regulates gene expression - controls whether gene is transcribed and translated when happening normally
• What does hypermethylation of tumour suppressor genes cause?

  Increased number of methyl groups attached so genes are not transcribed so gene is turned off therefore proteins are not produced
• What does hypermethylation of protooncogenes cause?

  Causes them to act as oncogenes as it reduces the number of methyl groups attached resulting in the gene permanently switched on
• What are the risk factors for cancer?

  Genetic factors - inherited alleles

  Environmental- radiation, smoking, alcohol, high fat diet
• What would be useful for curing and treating cancer?

  Knowing which specific mutations cause which cancers so treatment can be made to target them specifically
• What are stem cells?

  The unspecialized cells from which differentiated cells develop
• Where are stem cells found?

  Embryo

  And in some adult tissue ( where they become specialised cells that need to be replaced)
• What are totipotent cells?

  Cells that can mature into any type of body cell and occur only for a limited time in mammalian embryos
• What are pluripotent cells?

  Cells that can mature into any type of body cell except placental cells and occur in mammalian embryos
• What are multipotent cells?

  Present in adult mammals and are able to differentiate into a few different types of cell eg, red and white blood cells
• What are unipotent cells?

  Present in adult mammals , only differentiate into one type of cell eg skin cells
• Why and how do stem cells become specialised?

  They only transcribe and translate part of the dna - some genes expressed and other turned off in different conditions
• What happens once a gene is expressed?

  MRNA transcribes and translates into proteins, proteins modify the cell, cell becomes specialised for particular function
• What are cardiomyocytes?


  Heart muscle cells that make up a lot of the tissue in our hearts
• How are stem cells currently used in medicine?

  In bone marrow transplants - contains stem cells which make healthy new blood cells for patient with leukaemia and lymphoma
• Which 5conditions could stem cells be used as treatment for in the future? How

  Spinal cord injuries - replace damaged nerve tissue

  Heart disease/damage- replace damaged heart tissue

  Bladder conditions- grow new bladder

  Respiratory condition- windpipes can be stripped down to collagen structure and new stem cells could generate new tissue for them

  Organ transplants - organs can be grown
• What are the 3 sources of stem cells and how are they obtained?

  Adult stem cells - from body tissue of adult

  Embryonic stem cells- from embryos at early stages of development

  Induced pluripotent stem cells (IPS) - created in lab , reprogramming adult cells so they become pluripotent
• What are the advantages and disadvantages of using adult stem cells ?

  - Can be obtained from simple operation

  - aren't as flexible as embryonic cells and can only specialise into a limited range of cells
• How can induced pluripotent stem cells be made?

  By reprogramming specialised adult body cells so that they become pluripotent - adult cell can be infected with modified virus which infects cell so genes passed on to the dna so will be able to produce the transcription factors that are associated with pluripotent cells
• What are transcription factors?


  Protein molecules that control transcription of genes
• In the nucleus, transcription factors bind to specific DNA sites called.....


  Promotors
• Where are promoters located?


  Near start of target gene
• what do activators do?

  Stimulate or increase the rate of transcription - help RNA Polymerase bind to the start of target gene and activate transcription
• What do repressors do?

  Inhibit or decrease the rate of transcription eg they bind to start of target gene preventing RNA polymerase from binding
• What is oestrogen and how does it affect expression of genes?

  Steroid hormone that can affect transcription by binding to a transcription factor called an oestrogen receptor , forming an oestrogen-oestrigen receptor complex - this complex can act as an activator of transcription
• What is RNAi and how does it affect gene expression?

  RNA interface- small double stranded rna molecules stop mRNA from target genes being translated into proteins molecules involved are siRNA small interfacing or miRNA micro