Higher unit 1 Flashcards
What dies DNA do
Stores genetic information
Determines the organism genotype
Structure of a protein
DNA strands are made of
Nucleotides
Nucleotides are made up of
Organic bases
Deoxyribose sugar
Phosphate group
Backbone is held by
Chemical bonds
Antiparallel
Sugar phosphate running in opposite directions
Bases are held by
Hydrogen bonds
3’ end
deoxyribose sugar
5’ end
Phosphate
Nucleotides can only add to the
3’ end
Genetic code
Formed by base sequence of DNA
Bonds in nucleotides
Covalent bonds
Charge of dna
Negative
Prokaryotes
Bacteria
Ring of DNA
Ribosomes
Eukaryotes
Fungi, green plants and animal Nucleus bound membrane DNA linear - nucleus Circular chromosomes - chloroplasts in plants Plasmids present in some yeast cells Mitochondria Ribosomes Introns present Response to antibiotic - growth not inhibited
Histones
Proteins DNA is tightly packaged around
Point of histones
So DNA doesn’t get tangled
DNA replication is controlled by
Enzymes
Primer
Short strand of nucleotides
Binds to the template DNA strand
Allows polymerase to ass nucleotides
Only binds to 3’ end
DNA polymerase
Adds DNA nucleotides
Using complementary base paring
Only adds nucleotides in one direction
What happens to DNA when it is unwound
Unzipped by enzyme helicase
Forms to template strands
Hydrogen bonds between bases are broken
Leading strand
Nucleotides are added continuously
Lagging strand
Neuceotides are added in fragments
Joined together by ligase
After neuceotides are added the primer is replaced by DNA
Steps of replication
Helicase - unzips (fork structure) Primer - starts replication DNA polymerase - adds neuceotides Ligase binds it together (onlyon lagging strand) Supply of ATP for energy
Polymerase chain reaction
Technique used to creat many copies of DNA
Primers in PCR
Short length of single stranded DNA
Complementary to its specific target sequence
Bind to target sequence
One primers is required to replicate each strand
Steps of PCR
Heated to between 92-98 degrees
To break the hydrogen bonds separating the two strands.
DNA is cooled to 50 - 65 degrees to allow each primer to bind to target sequence.
Tow primers can bind to each 3’ prime end (no lagging strand)
Heated between 70 - 80 degrees to allow a heat tolerant DNA polymerase to replicate each strand .
Assad nucleotides to 3’ prime ends
Must be heat tolerant so it does not denature
What is PCR used for
Crimes
Diagnosis of genetic disorder
Results of PCR experiment
gel electrphophsis
fragments of DNA are pulled through a gel matrix by an electric current, and it separates DNA fragments according to size.
The darker the colour the more dena there is
What is genotype determined by
Sequence of DNA bases in genes
What is phenotype determined by
Proteins that are synthesised when proteins are expressed
Can be affected by environmental factors
What are RNA molecules composed of
Ribose sugar
Organic base
Phosphate group
RNA
Nucleic acid
Single stranded
Uracil instead of thymine
What are enzymes made of
Proteins
What are proteins made of
Polypeptide chains composed of subunits called amino acids
What determines shape and function of a protein
Sequence of amino acids
Control of inherent characteristics via DNA
DNA controls structure of enzymes
And in doing so determines an organisms characteristics
MRNA
Carries a complementary copy of the genetic code from the nucleus to the ribosome
Codon - triplet of bases - codes for specific amino acids
TRNA
Carries specific amino acids to ribosome
Anticodon - complementary to an mRNA codon and correspond to a specific amino acid
Can’t bond to mor than 1 amino acid
One end has an anti coden the other ed has an attachment site
Found in cytoplasm
Composed of single strand of nucleotide
Folded back on itself creating 3D structure cause of the complementary base pairing
Hydrogen bonds
Transcription
Synthesis of mRNA from a section of DNA
RRNA
Made of protein + RNA to make ribosome
Site of protein synthesis
Anticodon
Exposed triplet of bases
Translation - anivodons Bond to coding by complementary base pairing translating the genetic code into a sequence of amino acids
Steps of transcription
RNA polymerase moves along DNA uncoiling the double helix and breaking the hydrogen bonds between the bases
Promoter region of DNA where transcription is initiated
MRNA gets a sequence of nucleotides complementary to one of the 2 DNA strands
RNA polymerase can only add nucleotides to 3’ end
Primary transcript forms - resultant mRNA strand becomes separated from the DNA
Introns
Non - coding regions
Exons
Coding region
What is the need for splicing
DNA transcribed to mRNA is about 8000 nucleotides long yet only 1200 nucleotides are needed to code for an average sized poly petite chain
Splicing
Intones are cut out and removed from primary trancript
Exons are spliced together to form mRNA with a continuous sequence of nucleotides
Mature transcript is formed - modified mRNA
MRNA after splicing
Moves from nucleus to cytoplasm
Translated into a protein
Translation
Synthesis of protein as a polypeptide chain under the direction of mRNA
Codon
Base triplet
Basic unit of genetic code
What does translation start and end
Begins at the start of a codon and ends at a stop codon
Result of alternating RNA splicing
Different mature mRNA transcript are produced from the same primary transcript depending on which exons are retained
What influences phenotype
Environmental factors
Genome
Sum of all genes in an organism
Proteone
All the proteins expressed by an organism
What percentage of genes are expressed
2%
3 types of rna
MRNA
TRNA
RRNA
RNA nucleotides are made of
Ribose sugar phosphate and a base
4 bases in RNA
Cytosine
Guanine
Adenine
Uracil
Where is mRNA trancribed
Nucleus
Where is mRNA translated
Ribosome in the cytoplasm
Where does RNA translation start and begin
Begins - start codon
Ends - stop codon
How anticodon and codons bond
By complementary base pairing
This when genetic code is translated into a sequence of amino acids
Peptide bonds join amino acids together
What catalyst is used for the formation of peptide bonds
Ribosome
What catalysed the formation of the sugar-phosphate backbone
RNA polymerase
What happens to the primary transcript
Introns are removed so the exon join together forming the mature transcript
Cellular differentiation
The process by which a cell expresses certain genes to produce proteins characteristics for that type of cell
Allows cell to carry out a specialised function
Meristems
Unspecialised cells in plants that can divide to self-renew or differentiate
Pluripotent
Cells in the early embryo can differentiate into all the cell types that can make up the organism
Tissue stem cells
Involved in the growth repair and renewal of the cells found in that tissue
Mutipotent - differentiate into any type of tissue stem cell
How do cells have specialise functions
By expressing particular genes into proteins
Where are stem cells in animals found
In the embryo and adult tissue
What can stem cells be used for
Skin graphs
Bone marrow transplant
Genome
An organisms entire hereditary information coded into DNA
Made up of:
Genes
Other DNA sequences that do not code for proteins
Hereditary information
The sequence of DNA which is inherited
Coding sequences
Sequences that code for a protein
Therapeutic uses of stem cells
Corneal repair
Regeneration of damaged skin
Bone marrow transplant
Why is stem cell research carried out
Information for cell processes
What happens to cells once diffreciated
Only expresses the gene that code for the protein specific to the working of that particular type of cell
Multipotent
Can differentiate into any cell type found in a particular tissue
Ethical issues
To use embryonic stem cells human embryo must be destroyed
Telomere
Repetitive DNA sequences that make up protective structure
At each end of a chromosome
What happens to the sequence of DNA that does not code for a protein
Forms of RNA:
TRAN
RRNA
Mutation
Change in the structure of an organisms genome
Random change to genetic material
Single gene mutation
Alteration of nucleotide sequence in a gene’s DNA
Types of mutations :
Substitution
Insertion
Deletion
Point mutation
Single-gene mutation that involves a change in one nucleotide in the DNA sequence of a gene.
Substitution
Change in only one amino acid
Insertion
Nucleotide is added into sequence causing amino acids to be altered because of the frame shift
Deletion
Amino acids are altered because of the frameshift
Where does splicing occur
Splicing is controlled by specific nucleotide sequence at splice site
What happened if their is a mutation at a a splice site
The codon for intron-exon splice may be altered
May lead to intron bring retained
Or
Essential exon may not be retained
Missense mutation
Substitution
Altered codon still codes for amino acids but not the original one
Causes small or no effect
If it happens at a critical position then it could be bad
Eg formation of haemoglobin S caused sicko cell anemia
Nonsense
Formation of a polypeptide chain that is shorter than the normal one and unable to function
Insertion
Deletion
Substitution - if coded for a stop codon - prematurely stops protein synthesis
Splice-site mutation
Mutation occurred during splicing where the wrong information is joined
If into a are retained or exons are not retained then this may cause the mature mRNA transcript to alter a protein during translation
Frameshift mutation
When the sequence of codons are changed because of a mutation causing a protein to be almost non-functional
Chromosome structure mutation
Breakage of one or more chromosomes
A broken end of a chromosome is sticky and it can join to another broken end
This can change the number or sequence of the gens in a chromosome
Types of mutation: Deletion Duplication Inversion Translocation
Deletion
Chromosome breaks in 2 places and the segment in between becomes detached
The 2 ends the join up giving a shorter chromosome which lacks certain genes
Duplication
A segment of a gene becomes detached to one end of the first chromosome or becomes inserted somewhere else
Translocation
Chromosome breaks in 2 places
The segment between the breaks turns round before joining up again
Causes normal sequence to reverse
Inversion
Section of one chromosome breaking off and becoming attached to another chromosome
Causes problems during pairing of chromosomes gamates
What does a tRNA anticodon become bound to at one of the attachment sites
To codon of mRNA
What happens to tRNA once the amino acids make a polypeptide chained
Discharged from ribosome and reused
Ways in which chains of amino acids can become arranged to form a protein
Chain coils to form a spherical shape
Arranged in long parallel strands
Functions of proteins
Structural - make up the membrane surrounding a living cell
Hormones - chemical messengers transported in the blood stream
Antibodies - white blood cells that provide a defence system for the body
Enzyme - speed up the rate of reaction
Differentiation
Unspealiased cells become specialised to a particular function
Types of stem cells found in humans
Bone marrow
Adult tissue
Embryonic
Why is duplication beneficial
Extra copies may mutate and produce new useful DNA sequences
Evalution
The changes in organisms over generations as a result of genomic variation
Natural selection
Non-random increase in frequency of DNA sequences that increase survival and the non random reduction in the frequency of deleterious sequences
Delirious sequences
Disadvantageous
Changes in phenotype frequency
Stabilising
Directional
Disruptive
Stabalising selction
An average phenotype is selected for and extremes phenotype range are selected against
Directional selection
One extreme of phenotype range is selected for
Disruptive selection
2 or more phenotypes are selected
Why is natural selection more rapid in prokaryotes
Prokaryotes can produce faster than eukaryotes
Transfer horizontally resulting in faster evolutionary change
Makes bacteria anti biotic resistance
Horizontal gene transfer
Genes are transferred between individuals in the same generation
Vertical gene transfer
Genes are transferred fromm parent to offspring as a result of sexual or asexual reproduction
Mainly in eukaryotes
Specisation
Generation of new biological species by evolution as a result of isolation, mutation and selection
Species
A group of organisms capable of interbreeding and producing fertile offspring
Does not normally breed with other groups
isolation barriers
Prevents interbreeding between sub populations so allow them to become genetically distinct
geographical barriers lead to
Allopathic speciation
Behavioural and ecological barriers lead to
Sympathic speciation
What causes the changes evolution
Changes to the genome sequence
What in bacteria passes genetic material
Plasmids are used to pass genetic material from the genome of one individual to the genome of another individual
Importance of isolation barriers
Prevent gene flow between sub-populations during speciation
Allopatric specisation
Split sub-populations into separate areas
Sympatric speciasation
Sub-populations live in the same place
Types of isolation barriers
Geographical - mountains - rivers
Behavioural - different courtships
Ecological - preference of different pH
RNA polymerase
Forms the primary transcript from RNA nucleotides
Ensures sequence of nucleotides is complementary to one strand of DNA
Stem cells in red bone marrow
Can differentiate into platelets and lymphocytes
Benefits horizontal gene transfer
High rate of gene loss
How could horizontal gene transfer be risky
Genetic sequence may be harmful
Genomics/bioformatics
Study of the genome
Determines the sequence of nucleotide base molecules i an organisms DNA
Relating it to gene function
Restriction endonuclease
Enzyme that recognises a specific short sequence of DNA nucleotides called a restriction sit on DNA
Cute DNA at this site
Shotgun approach
DNA cut into fragments using restriction endonuclease
Different restriction endonuclease cuts a copy of the genome
Order of bases established and put into computer
Virus and bacteria
Disease causing agents
Pest species
Eg mosquito
Act as vectors for Malerin and the unicellular organisms that causes malaria
Model organisms
Processes gene equivalents to genes in humans important for disease and disorder
Importance for research
Single nucleotide polymorphism
Variation in the DNA sequence that effects a single base pair in a DNA chain
Conservation
Same or very similar DNA sequences are present in the genomes
What causes differences in the base squwnce in genomes
Point mustations
How to tell how close organisms are
The grater the number of conserved DNA sequence that their genomes have in common
Phylogenetics
Study of evolutionary history and relatedness among different groups of organisms
If only a few bases differ what does it mean
They share a common ansestror
The grater number of differences, the longer sense the point of divergence
Molecular clocks
Shows when species diverged in history
Molecules of nuclei acid gradually change over time as they are effected by mustations such as nucleotide. Molecule of nuclic acid or a protein coded for by nucleus acid
What has been used as a molecular clock
RRNA
Why is rRNA used as a molecular clock
Constructing phylogenies
Genes that code for rRNA are ancient
Experienced little or no horizontal gene trasfer
Possess by living things
Three domains
Bacteria - traditional prokaryotes
Archea - mostly prokaryotes that inhabit extreme environments such as hot springs and salt lakes
Eukaryotes - fingi plants and animals
Fossils
Conservation of bone teeth or shells into rocks
Older the rock the less radioactivity it emits
Bacteria
1 RNA polymerase
Response to antibiotic - growth inhibited
Archaea
Introns present in some genomic sequencing
Several RNA polymerase
Response to antibiotics - growth not inhibited
Genetic disorder
Result of variation in a genomic DNA sequence
Risks of variations in DNA
Diabetics
Heat disease
Cancer
Pharmacogenetics
Personalised medicine
Uses of genome information in the choice of drugs
This is uses to select the most effective drugs and dosage to treat their disease
Sequence divergence
Used to estimate time since lineages diverged
Why do scientists normally express the length of a chromosome in number of base pairs
Constant reliable measurement whereas length measured in um varies according to the degree of coiling
Primer in PCR
Piece of single stranded DNA synthesised as the exact compliment of a short length of the DNA stand to which it is to become attached
What determines the distance travelled by DNA in the gel
Sizes and weight of molecule
E.g small molecule moves further than larger molecular
What must happen before translation can begin
Ribosome must bind to the 5’ end of the mRNA template so that the mRNA’s altert codon is in position at the binding site
What joins the mRNA coden and the complementary tRNA’s anticodon togther
Hydrogen bonds
Release factors
Frees the polypeptide from the ribosome
What type of energy does translation need
ATP
What causes a polypeptide chain to coil
Hydrogen bonds form between certain amino acids in a polypeptide chain
Corneal repair
Grown from patients own stem cells
Restores by replacing damaged tissue
Totipotent
Stem cell
Able to differentiate into any cell type and is capable of giving rise to the complete organism
When does specialisation occur
Circumstances that Interrupt gene flow between two populations curing there gene pools to diverge
Bioformatics
The fusion of molecular biology, statistical analysis and computer technology
