higher biology- unit 1

• what are stomatic cells?

  Body cells not including sex cells

  diploid (2n): two sets of chromosomes, one set from each parent , divide by mitosis

  mutations in stomatic cells can effect the individual but not its offspring
• What are gremline cells?

  Gametes and stem cells that divide to form gametes

  can sometimes divide by mitosis but usually divide by meiosis
• describe meiosis

  produces haploid gametes

  more divisions then mitosis and cells produced are not identical

  nucleus goes through two divisions

  1. separating homologous chromosomes

  2. separating chromatids
• what is cellular differentiation?

  the process by which a cell expresses certain genes to produce proteins characteristic for that type of cell

  
• Describe embryonic stem cells


  pluripotent- can make any type of cell

  removed early from embryo and all genes have the ability to be switched on
• describe tissue stem cells

  multipotent- can multiply into multiple cells (any cell found in that type of tissue)
• describe stem cells therapy

  stem cells are used for the growth and repair of damaged tissue

  examples of stem cell therapy-

  skin grafts

  cornea repair

  bone marrow transplantation
• describe stem cells research

  embryonic stem cells can self renew in right conditions which allow researchers to investigate gene regulation, differentiation and cell growth ie molecular biology of cancer

  can be used as model cells to see how disease and disorders develop in cells and how cells respond to drugs
• describe cancer

  cancer is an uncontrollable growth of cells as they do not respond to regulatory signals
• Describe how secondary tumours are formed

  tumours are a mass of abnormal cells

  secondary tumors form when cells which don't follow regulatory signals fail to attach to tumour and spread across the body
• Describe the structure of DNA


  DNA is made up of molecules called nucleotides.

  Each nucleotide contains a phosphate group, a sugar group (makes the backbone) and a nitrogen base.

  4 bases are: adenine (A), thymine (T), guanine (G) and cytosine (C).

  bases are joined by hydrogen bonds

  double stranded helix

  anti parallel

  always read from 5' end to 3' end

  
• describe DNA replication

  things that must be present for replication

  PEANUT - primers, enzymes (DNA polymerase and ligase), ATP, nucleotides and template strands

  Stages-

  1. Hydrogen bonds between bonds broken primers attach to 3' end

  2. DNA polymerase adds nucleotides using complimentary base pairing to 3' end of the new DNA strand

  - 3' end replicates continuously (leading strand)

  - 5' end replicates discontinuously (lagging strand) as nucleotides cannot be added to the phosphate because DNA polymerase can only add DNA nucleotides in a 5' to 3' direction. The lagging strand is therefore synthesised in fragments.

  3. fragments of DNA are joined together by ligase

  
• enzymes jobs


  Ligase joins fragments together

  DNA polymerase adds free nucleotide to growing DNA strand

  primers not and enzyme but short complimentary strands of DNA that allows DNA polymerase to add free nucleotides
• Describe PCR

  PCR artificially amplifies DNA

  can be used for paternity tests, screening/diagnosis of genetic disorders and forensics

  Stages-

  1. DNA is heated to 92-98 to sperate strands

  2. cooled at 50-55 to allow primers to bind to target sequence

  3. heated to 70-80 so heat tolerant DNA polymerase can replicate
• Explain gel electrophoresis


  technique used to separate DNA using an electric field applied to a gel matrix

  molecules are separated by being pushed through pores

  smaller fragments travel further vice versa
• describe RNA


  single stranded

  contains the base uracil (u)

  made up of nucleotides contain a base, deoxyribose sugar and phosphate
• Describe the three types of RNA (mRNA, tRNA and rRNA)

  -mRNA - Messenger RNA is a linear molecule which carries a copy of the gene to be expressed from the nucleus. Every group of three bases (a 'triplet') is described as a codon because each one codes for an amino acid.

  -tRNA - Transfer RNA has a cloverleaf shape. It is made from a single strand of RNA which folds due to base pairing to form this unusual shape. It has a triplet anti-codon site and an attachment site for a specific amino acid. carries specific amino acids to ribosome.

  -rRNA - Ribosomal RNA and proteins form the ribosome. The ribosome is the structure where protein synthesis takes place.

  
• Describe transcription

  Transcription- when information from the DNA sequence is copied and turned into a primary transcript

  1. RNA polymerase moves along the DNA unwinding the strand.

  2. Hydrogen bonds between base pairs break which allows the unzipping of the double helix.

  3. As RNA polymerase breaks the bonds, it synthesises a primary transcript of mRNA using RNA nucleotides. These form hydrogen bonds with the exposed DNA strand by complementary base pairing.
• Describe RNA splicing


  Introns (noncoding regions) are taken out of primary transcript and exons (coding regions) are kept in to make a mature transcript

  
• Describe Alternative RNA splicing


  The benefit of RNA splicing is that one gene can produce many different proteins as a result of what segments are treated as introns and exons. Different exons result in different mature transcripts and produce different proteins.
• Describe translation

  1. The mRNA molecule travels through the cytoplasm and attaches to the ribosome.

  2. tRNA molecules transport specific amino acids to the ribosome.

  3. Each mRNA codon codes for a specific amino acid.

  The first codon of an mRNA molecule is a start codon. This signals the beginning of translation.

  4. The anti-codons and codons match up and form complementary base pairs.

  5. Peptide bonds form between the adjacent amino acids to form the polypeptide (protein).

  
  

  The last codon of an mRNA molecule is a stop codon which signals the end of translation.
• What are codons and anticodons?

  Codons are three consecutive bases that responds to a single amino acid, found in mRNA, while anticodons are the three unpaired bases that a tRNA molecule has.
• describe the structure of a protein

  Amino acids joined by peptide bonds to form polypeptide chains and fold to form 3D structures, which are held together by hydrogen bonds
• What is a mutation?


  change in DNA sequence which leads to a protein being altered or not made.
• what are the types of mutations?

  singles gene- substitution, insertion, deletion

  chromosome structure- Deletion, Duplication, Inversion and translocation
• Describe single gene mutations

  1. Substitution

  >missense- alter to a single amino acid (non functioning protein/ little effect)

  >nonsense- Premature stop codon (shorter polypeptide chain)

  >splice site- some introns kept in and/or exons taken out (entirely different protein)

  2. Insertion

  3. Deletion

  Bothe are known as frame shift mutations and they shift all codons and change protein drastically
• Describe chromosome structure mutations

  1. deletion- gene section removed

  2. duplication- added gene section from its homologous partner

  3. Inversion- section is in revered order on the chromosome

  4. translocation- gene section is added to chromosome NOT HOMOLOGOUS PARTNER

  has substantial change and can be lethal
• What is a genome?

  an organisms entire hereditary information encoded in DNA

  both coding and non coding regions
• What is bioformatics?

  use of computers and statistical analysis to identify base sequences by looking for sequences similar to known genes.

  This information can be compared with the genes or genomes of other individuals or the genetic information of different species to look for similarities and differences

  this helps search for genes linked to particular types of disease, understand inherited disorders and their treatment and trace human migration
• What is genomic sequencing?

  the sequence of nucleotide bases can be determined for individual genes and entire genomes
• What is pharmacogenetics?


  The use of genome information in the choice of drugs

  Helps identify at risk patients and find the most effective drug for an individual
• What is personalised medicine?

  An individual's personal genome sequence can be used to select the most effective drugs and dosage to treat their disease
• describe the two types of metabolic pathways

  Catabolic- releases energy and breaks down large molecules

  Anabolic- Requires energy and builds up small molecules
• What are metabolic pathways?

  Integrated and controlled pathways of enzyme-catalysed reactions within a cell.
• what are the different pathways in a metabolic pathway ?

  Reversible, irreversible and alternative
• Why do alternative routes happen ?

  If the appropriate enzyme is absent then the pathway stop because of the possibility or harmful chemicals building up or follows an alternative route
• What is induced fit?

  when the substrate changes the shape of the active site for proper fit
• what is affinity?

  Attraction

  The active site has a high affinity to the substrate as well as being specific to the substrate. This orientates the reactants into the correct positions for the reaction to take place.

  The binding of the enzyme to its substrate also lowers the activation energy of the reaction (amount of energy needed to make a reaction happen).

  If an enzyme is present, the amount of energy needed to make a product is lowered. As the products are made, they are no longer specific to the active site (they have a low affinity to the enzyme) and so are released.
• Describe the control of a metabolic pathway

  Some metabolic reactions are reversible. The presence of a substrate or removal of a product will drive a sequence of reactions in a particular direction.
• What are inhibitors?

  stop an enzyme from binding to its substrate. As a result, inhibitors can directly control the progress of a metabolic pathway.

  There are three types of inhibition:

  competitive inhibition

  non-competitive inhibition

  feedback inhibition