Mutations and gene expression

• What are mutations?

  Any change to the base nucleotide sequence of DNA.
• How can mutations be caused?

  Errors during DNA replication and mutagens.
• what are mutagenic agent

  they increase the rate at which mutations occur
• what are the 6 types of muttion

  - addition

  substitution

  duplication

  deletion

  inversion

  translocation
• What is a substitution mutation?

  One or more bases are swapped for another.

  eg. ATGCCT becomes ATTCCT
• What is a deletion mutation?

  One or more bases are removed.

  eg. ATGCCT becomes ATCCT
• What is a addition mutation?

  One or more bases are added.

  eg. ATGCCT becomes ATGACCT
• What is a duplication mutation?

  When one or more bases are repeated
• What is a translocation mutation?

  A sequence of bases is moved from one location in the genome to another. This could be movement within the same chromosome or movement to a different chromosome.
• Why would a mutation affect the function/production of a protein?

  The order of DNA bases determines the sequence of amino acids in a polypeptide. If a mutation occurs, the sequence of amino acids in the polypeptide that it codes for could be changed.

  Polypeptides make up proteins, so if there is a change in the AA sequence, it may change the final 3D shape of the protein causing it to not function properly.
• What are genetic disorders?

  An inherited disorder cause by abnormal genes or chromosomes eg. cystic fibrosis.
• What are hereditary mutations and how do they occur?

  Occur if a gamete containing a mutation for a type of cancer or genetic disorder is fertilised, causing the mutation to be present in the fetus.

  Mutations passed on to the offspring.
• What does the degenerate code mean?

  Some amino acids are coded for by more than one DNA triplet.
• Why do not all mutations affect the order of amino acids?

  Because of the degenerate nature of the genetic code. Not all types of mutation will always result in a change to the amino acid sequence.
• What is it called when a mutation doesn't cause a change in the amino acid sequence?

  Silent mutation.
• What is cystic fibrosis?

  A genetic disorder of the cell membranes, resulting in the body producing a lot of thick, sticky mucus in air passages and the pancreas.
• What is a frameshift mutation?

  A mutation that results in a misreading of all following nucleotides.

  Additions, duplications and deletions will almost always change the amino acid sequence of a polypeptide because these mutations cause a change in the number of bases in the DNA code.
• What are mutagenic agents?

  Outside factors that increase the rate of mutations.
• What are examples of mutagenic agents?

  UV radiation, ionising radiation, some chemicals and some viruses.
• what is the ame of the chemicalmutagenic agent whhich acts as a base

  base analogs
• What are 3 ways mutagenic agents can increase mutation rate?


  1. Acting as a base - chemicals known as base analogs can substitute for a base during DNA replication (changing base sequence of new DNA).

  2. Altering bases - some chemicals can delete or alter bases.

  3. Changing structure of DNA - some types of radiation can change the structure of DNA, which causes problems during DNA replication.
• What are acquired mutations?


  Mutations that occur in individual cells after fertilisation.
• How can acquired mutations cause a tumour?


  If mutations occur in the gene that control the rate of cell division (by mitosis) it can cause uncontrolled cell division.

  If a cell divides uncontrollably = tumour.
• How can acquired mutations cause a tumour?

  If mutations occur in the gene that control the rate of cell division (by mitosis) it can cause uncontrolled cell division.

  If a cell divides uncontrollably = tumour.

  it is uncontrolable mitosis
• What are the 2 types of gene that control cell division?

  Proto-oncogenes

  Tumour suppressor genes
• Tumour suppressor genes: NORMAL AND MUTANT


  NORMAL :Slow cell division by producing proteins that prevent cells dividing or cause them to self destruct.

  MUTANT: If mutation occurs in tumour suppressor gene, gene will be inactivated. The protein it cods for isn't produced and cells divide uncontrollably = tumour.

  
• Proto-oncogenes: NORMAL AND MUTANT

  NORMAL: Proto-oncogenes stimulate cell division by producing proteins that make cells divide.

  MUTANT: If mutation occurs in proto-oncogene, the gene can become overactive = stimulates cells to divide uncontrollably (rate of division increases) = tumour.

  Mutated proto-oncogene = oncogene.

  
• Proto-oncogenes: NORMAL AND MUTANT

  NORMAL: Proto-oncogenes stimulate cell division by producing proteins that make cells divide.• It is activated when growth factors bin to the receptors on the cell surface membrane

  MUTANT: If mutation occurs in proto-oncogene. The oncogenes become overactive and become permanently switch on meaning that is activating cell division even if the growth receptors have not binded with the cell surface membrane= stimulates cells to divide uncontrollably (rate of division increases) = tumour.

  Mutated proto-oncogene = oncogene.
• what is it called when a cell programed death and why does it occur


  apoptosis

  - happens when cell is infected

  - it has coming to the end of their functional life

  -they are damaged
• What are benign tumours?


  Benign = not cancerous

  Grow slower than malignant

  Pieces don't break of and start new tumours in other parts of the body

  They don't invade other tissues causing damage other than where it originated

  Produce adhesion molecules

  Contained inside a capsule
• what are malignant tumours


  -cancerous tumour

  -fast grow

  - it invades their tissues and damages them

  - when pieces break they can spread to other parts of the body and cause tumour to start growing

  -Metastises

  -Doesn't produce adhesion molecules
• WWhat is the name for when a piece of tumour cell breaks of and spreads to another part of the body and starting growing their

  METASTISIS
• Properties of tumour cells:


  - Larger and darker nucleus, may have more than one

  - Irregular shape

  - Don't produce all proteins needed to function correctly

  - Have different antigens on surface

  - Don't respond to growth regulating processes.

  - Divide by mitosis more frequently than normal cells

  
• What is methylation?


  The addition of a methyl group (-CH3) to a molecule.
• What causes tumour growth?


  Abnormal methylation of DNA

  Increased exposure to oestrogen

  mutations of gene that control cell division 1
• Why is methylation of DNA important?

  It is an important method of regulating gene expression - it can control whether a gene is transcribed (copied to mRNA) and translated (turned into a protein).

  - it controls how easily read a gene is
• what gene is mutated which incrases the likelyhood of breast cancer


  BRCA1
• What is too much or too little methylation known as?


  Too much - hypermethylation

  Too little - hypomethylation
• Hypermethylation of tumour suppressor genes:


  When TSG hypermethylated, the genes are not transcribed = proteins they produce to slow cell division aren't made = cells are able to divide uncontrollably by mitosis and tumours can develop.

  
• Hypomethylation of proto-oncogenes:


  Hypomethylation of proto-oncogenes = causes them to act as oncogenes = increases production or the proteins that encourage cell division = stimulates cells to divide uncontrollably = formation of tumour.