CLASSIFICATION + DIVERSITY Flashcards
TOPIC 4
GENE
section of DNA that contains code for making polypeptide + functional RNA
LOCUS
location of particular gene on chromosome
ALLELE
location of particular gene on chromosome
CHROMOSOME
threadlike structure composed of tightly coiled DNA + wrapped around histones
HOMOGLOUS CHROMOSOMES
pair of chromosomes that have same genes therefore- same size
PROKARYOTIC DNA
Shorter
Circular
Not associated w/histones
No nucleus
May have plasmids
Only exons
EUKARYOTIC DNA
Longer
Linear
Associated w/ histones
Contains nucleus
No plasmids
Have introns + exons
CODON
3 bases on mRNA- code for amino acid
START CODON
3 bases at start of mRNA sequence which help initiate translation
STOP CODON
3 bases at end of every gene that don’t code for amino acid- ribosomes to detach + therefore stops translation
UNIVERSAL
code universal for all living things
GENETIC CODE
amino acid is coded for by 3 DNA bases which- described as “triplet code”
ADVANTAGE OF THE CODE BEING UNIVERSAL
genetic engineering is possible human gene can be inserted into another organism
e.g human gene for insulin inserted to bacteria to make insulin
NON-OVERLAPPING
each triplet is read separately
ADVANTAGE OF THE CODE BEING NON-OVERLAPPING
if point mutation occurs, it will only affect one codon and therefore one amino acid
DEGENRATE
each amino acid is coded for by
more than one triplet of bases
ADVANTAGE OF THE CODE BEING DEGENERATE
if substitution mutation occurs new triplet of bases may still code for same amino acid
therefore mutation will have no impact on final protein produced
MUTATION
change in DNA can be gene or chromosome mutation
INTRON
non-coding sequence of DNA
EXON
sequences in gene that code for amino acid sequences
MRNA
.Single stranded
.Linear chain
.Longer chain/ has more nucleotides
.Corresponds to genetic sequence of gene
.Unpaired bases
MRNA FUNCTION
copy of gene from DNA created in nucleus, and it then leaves nucleus to carry copy of genetic code of one gene to ribosome in cytoplasm
TRNA
.Single stranded folded into a clover shape
.Hydrogen bonds
.Anticodon
.Amino acid attachment site
.All similar lengths
TRNA FUNCTION
single-stranded, folded to create cloverleaf shape held in place by hydrogen bonds
has an anticodon and amino acid binding site
GENEOME
complete set of genes in cell
PROTEOME
full range of proteins that cell is able to produce
POLYPEPTIDE SYNTHESIS
.sequence of nucleotides on gene on DNA acts as template
.complimentary copy is transcribed onto mRNA in nucleus
.At ribosomes mRNA acts as template that is translated to chain of amino acids using complementary tRNA which carry specific amino acids which are linked together
TRANSCRIPTION FROM DNA TO MRNA
1.H bonds between complementary base pairs of gene to be transcribed are broken DNA nucleotide bases are now exposed
2.One strand acts as template to make an mRNA copy
3.Free RNA nucleotides alongside their complementary base pair on template strand of DNA-Uracil replaces thymine on mRNA
4.RNA polymerase joins adjacent nucleotides together w/phosphodiester bond
5.RNA Polymerase continues until it reaches stop signal and then it detaches + introns are removed
PRE-MRNA + SPLICING
.eukaryotic cells, mRNA produced during transcription contains both introns and exons-this is pre-mRNA
.introns need to be removed because they don’t contain any genetic information that can be translated into an amino acid sequence
.introns are “spliced” out of mRNA sequence by an enzyme
.produces strand of mRNA that contains only exons - coding regions- known as mature mRNA
TRANSLATION OF MRNA TO FORM POLYPEPTIDE
- mRNA attaches to ribosomes
- tRNA anticodons bind to complementary mRNA codons
- tRNA brings a specific amino acid
- Amino acids join by peptide bonds
- use of ATP
- tRNA released after amino acid joined to polypeptide
- ribosome moves along mRNA to form polypeptide
HAPLOID
one copy of each chromosome in cell
DIPLOID
two copies of each chromosome in cell
MEOSIS
Meiosis I is reduction division separation of homologous pair of chromosomes:
.Homologous pairs are separated
.Variation is introduced
Meiosis II is similar to mitosis w/separation of sister chromatids
Four haploid cells are produced, each w/ half diploid number of chromosomes
CROSSING OVER
occurs in prophase I w/ formation of chiasmata
1.Homologous pairs of chromosomes associate and form bivalent
2.Chiasmata forms
3.Equal lengths of non-sister chromatids or alleles are exchanged
4.Producing new combinations of alleles
INDEPENDANT SEGREGATION
1.Metaphase 1, homologous pairs line up either side of equator
2.completely random which side of equator maternal and paternal chromosomes line up on
3.When separated, one of each pair ends up in daughter cell
4.‘shuffling’ leads to different combinations of maternal and paternal chromosomes in daughter cells
OTHER SOURCES OF VARIATION
.Fertilisation: random mating w/random gametes –results in random fusion of gametes and produces new allele combinations/new maternal and paternal chromosome combinations
.mutations may occur
INSERTION
extra base is added during DNA replication results in frame shift – all codons after mutation are affected
MITOSIS VS MEOISIS
Same number of chromosomes VS Half number of chromosomes
Genetically identical VS Genetically different
Two cells VS Four cells
DELETION
One base is left out during DNA replication results in frame shift – all codons after mutation are affected
SUBSITUTION
One base is changed for another during DNA replication-Only codon w/mutation is affected
CHANGE IN CODON RESULTS CHANGE IN PROTEIN
.amino acid sequence changes
.hydrogen/ionic/disulphide bonds between R groups changes
.tertiary structure changes
NON-FUNCTIONAL ENZYME
change is in active site of an enzyme then active site is no longer complementary to substrate and enzyme cannot form enzyme-substrate complexes
MUTAGENIC AGENTS
increase rate of gene mutation eg. UV radiation
CHROMSOME MUTATION
.Most likely to occur in meiosis – not being shared equally between daughter cells in metaphase and anaphase
.Changes in numbers: Non-dysjunction where one daughter cell gets both of homologous pair and other none
DEFINE GENE MUTATION + EXPLAIN HOW GENR MUTATION CAN HAVE NO EFFECT OR POSITIVE EFFECT ON AN INDIVIDUAL
- change in base sequence
- formation of new allele
NO EFFECT - genetic code is degenerate
- does change amino acid but no effect on tertiary structure
- recessive so doesn’t influence phenotype
POSITIVE EFFECT - change in polypeptide that positively changes protein
- may result in increased reproductive success
THINGS THAT AFFECT GENETIC DIVERSITY OF POPULATION
- Population size – smaller populations generally have lower genetic diversity and larger populations larger one
- Inbreeding – reduces genetic diversity
- Migration – increases genetic diversity
- Mutations – increases genetic diversity
- Genetic Bottlenecks – reduces genetic diversity
- Founder effect – reduces genetic diversity
- Natural selection – increases frequency of beneficial alleles
BOTTLENECK EFFECT
previously large population suffers dramatic fall in numbers
major environmental event can massively reduce number of individuals in population which in turn reduces genetic diversity in population as alleles are lost
surviving individuals end up breeding and reproducing w/close relatives
FOUNDER EFFECT
only small number of individuals from large parent population start new population
new population is made up of only few individuals from original population only some of total alleles from parent population will be present
not all of gene pool is present in smaller population
gene pool is complete range of DNA sequences that exist in all individuals of population or species
NATURAL SELECTION
.random mutation result in new alleles of gene
.selection pressures exist in environment
.increase/decrease in chance of survival and reproduction
.advantageous alleles pass on to offspring
.many generations-increasing allele frequency in population and change in gene pool
DIRECTIONAL SELECTION
.Individuals w/alleles for an extreme type are more likely to survive and reproduce
.Some bacteria have alleles that give them resistance to an antibiotic
.normal population of bacteria are killed by antibiotic
.Resistant bacteria survive and reproduce w/X competition passing on allele for antibiotic resistance to their offspring
.After some time most of population will have antibiotic resistance allele
STABILISING SELECTION
.Individuals w/alleles for middle of the range are more likely to survive and reproduce
.Small babies find it hard to maintain their body temperature so less likely to survive
.Large babies less likely to survive also
.So conditions most favourable for medium sized babies
.weight of human babies shifts towards middle of range
HOW NATURAL SELECTION BETTER ADAPTS SPECIES
.Anatomical adaptations: Structural features eg. whales have thick layer of blubber to keep warm in cold sea
.Physiological adaptations: Processes in organism eg. Hibernation over winter reducing metabolic rate to conserve energy when food is scarce
.Behavioural adaptations: way an organism acts eg. possums playing dead near to predators
RP6-USING ASEPTIC TECHNIQUES
.Set up petri dish w/nutrient agar
.Use sterile technique to transfer bacteria from liquid broth to agar
.Spread bacteria over plate using spreader
.Use sterile forceps to place paper discs soaked w/different concentrations of antibiotic
.Also add negative control disc just soaked in sterile water
.Incubate at 25oC for 48 hours Inhibition zones are clear: Anywhere bacteria can not grow
.size of inhibition zone is how well antibiotic has grown
RP6-TYPES OF ASEPTIC TECHNIQUES
.Avoids contamination of cultures from unwanted microorganisms, particularly disease causing
.Heat glassware, petri dishes and agar in an autoclave in steam under pressure at 121oC for 15 minutes
.Sterilise work surfaces before and after using disinfectant
.Use Bunsen to set up an air flow upwards to carry bacteria away
.Lift petri dish lids w/just enough angle to allow entry of loop and for short time
.Secure petri dish lids w/ 2 pieces of tape
.Sterilise plastic material using gamma radiation
PHYLOGENETIC CLASSIFICATION
attempts to arrange species to groups based on their evolutionary origins and relationships
HIERACRCHY
Smaller groups are placed in larger groups w/no overlap between groups
Domain → kingdom → phylum → class → order → family → genus → species
BINOMAIL SYSTEM
genus and species name
PROBLEMS W/USING OBSERVABLE FEATURES IN CLASSIFICATION
Some organisms will look alike due to convergent evolution 2 organisms evolve similar features but are not closely related
live in similar environments and are exposed to similar selection pressures Similar alleles will provide similar selective advantages
ADVANCES TECHNIQUES CAN HELP TO CLARIFY EVOLUTIONARY RELATIONSHIPS BETWEEN ORGANISMS
.DNA sequences – more similarities between base sequences more closely related organisms are e.g same genus
.Amino acid sequences – more similarities in amino acid sequence more closely related organisms are
.Immunology- Similar proteins in organisms will bind same antibodies eg. see if antibodies that bind to human version of protein will also bind to mouse version of protein
PHYLOGENETIC TREE
Phylogeny is study of evolutionary history of groups of organisms It tells us who’s related to who and how closely
Phylogenetic trees show these evolutional relationships
Each branch is common ancestor
BIODIVERSITY
variety of organisms living in an area
relate to range of habitats from small local habitats eg. pond
measure of species richness and
abundance
COURTSHIP BEHAVIOUR
organisms to attract mate of right species
essential for successful mating so that organisms can pass on advantageous alleles and species can survive
It could be releasing chemicals or series of displays
Behaviours and actions which are unique to each species- allows species identify individuals of their own species to mate and reproduce w/
normally performed by males eg. dance, song+ Females choose individual they wish to mate w/
Courtship ensures successful reproduction - Enables individuals to recognise others of their own species and individuals of opposite sex- also synchronises mating behaviour – mating occurs only when individual is sexually mature and in season
Courtship increases survival of offspring - Formation of pair bonds – 2 parents looking after offspring increases its survival
COMMUNITY
all species in particular area at particular time
HABITAT
range of physical, biological and environmental factors in which species can live
SPECIES RICHNESS
measure of number of different species in community It can be calculated by taking random samples of community and counting number of different species
INDEX OF DIVERSITY EQUATION
d=N(N-1)/n(n-1)
.N = total number of organisms of all species
.n = total number of organisms of each species
.higher number d, more diverse an area is
AGRICULTURE
cultivation of soil to grow crops
usually involves clearing of land to allow more space for crop growing- It often includes use of herbicides to kill weeds and pesticides to kill insects which may feed off of crops-These practices reduce biodiversity of areas
WHY REMOVING WOODLANDS REDUCES BIODIVERSITY
Less habitats, less variety of food sources
WHY USING PESTICIDES REDUCES BIODIVERSITY
Kills insect species- reduction in variety of food sources for organisms higher up food chain
WHY USING HERBICIDES REDUCES BIODIVERSITY
Kills species of weeds- reduction in variety of food types for herbivores
WHY GROWING 1 TYPE OF CROP REDUCES BIODIVERSITY
Less variety in food sources- less variety of habitats
CONSERVATION
balance between need for agriculture and maintaining biodiversity
COMPARING GENTIC DIVERSITY IN OR BETWEEN SPECIES
mode is number that appears most median is middle value
mean is total of numbers divided by how many numbers there are
GENE TECHNOLOGY CAUSING CHANGE IN METHODS OF INVESTIGATING GENETIC DIVERSITY
.Inferring DNA differences from measurable or observable characteristics has been replaced by direct investigation of DNA sequences
STUDENT T-TEST
comparing mean values of two data sets
INTERPRETING DATA RELATING ON DNA BASE SEQUENCES + AMINO ACID SEQUENCES
.Suggest relationships between different organisms in species and between species
.More similarities mean that organisms are more closely related
GENE TECHNOLOGY ALLOWING GENETIC DIVERSITY IN OR BETWEEN SPECIES TO BE INVESTIGATED
.By comparing base sequence of DNA
.By comparing base sequence of mRNA
.By comparing amino acid sequence of proteins
COLLECTING DATA FROM RANDOM SAMPLES OF POPULATION
.Divide area into grid
.use random number generator or random number table to generate coordinates
.use large number of samples to collect reliable and representative sample
