genetic info variation and relationship between organisms 3.4 Flashcards
aqa as level biology
what is a genome?
complete set of genes in a cell
what is a proteome?
complete set of proteins a cell can produce
what are the structural differences between mRNA and tRNA
mRNA
- linear single shape
- triplet code (codon)
- less stable
- no amino acid region
tRNA
- clover shaped
- triplet code (anticodon)
- more stable
- amino acid region
what is transcription?
production of mRNA from DNA
what is translation?
production of polypeptides from the sequence of codons carried by mRNA
what happens in transcription?
- DNA helix unwinds to expose bases and on strand acts as a template
- catalysed by DNA helicase
- DNA helicase breaks the hydrogen bonds between bases
- free mRNA nucleotides in the nucleus align with complementary bases on strand
- A/U C/G G/C T/A
- RNA polymerase bonds the nucleotides together to form RNA chain
- once copied mRNA is modified and leaves nucleus through nuclear pores
how is pre-mRNA modified?
- introns are spliced out of pre-mRNA by protein splicesome
- leaves behind just coding regions (exons)
what happens in translation?
- mRNA attaches to ribosome in the cytoplasm
- ribosome attaches at start codon
- tRNA that has complementary anticodon lines up with mRNA codon and binds
- tRNA brings specific amino acid
- amino acids joint together by peptide bonds using ATP (condensation reaction)
- tRNA released after amino acids joint to polypeptide
- ribosome moves along polypeptide until reaches stop codon
- polypeptide formed and now enters Golgi apparatus
what is genetic diversity?
the number of different alleles of genes in a population
what is the enabling factor for natural selection to occur?
genetic diversity
what does natural selection lead to?
evolution
what is evolution?
change in allele frequency over many generations in a population
what are the advantages of natural selection?
leads to species being better adapted to their environment (anatomically, physiologically or behaviourally)
how does natural selection occur?
- random mutations lead to new alleles to form
- if the allele increases the chances of survival in the environment they are more likely to reproduce
- this passes on advantageous allele to offsprings
- over many generations allele frequency increases in population
what is directional selection?
one of the extremes are favoured and have an advantage
when does directional selection occurs?
when there is a change in the environment (modal trait changes)
what is stabilising selection?
modal trait remains the same and is favoured
when does stabilising selection occur?
when there is no change in environment
what happens to the standard deviation of stabilising selection over time?
decreases as extreme traits decrease
what is an example of directional selection?
antibiotic resistance in bacteria
what is an example of stabilising selection?
human birth weight
what is the binomial naming system
all organisms universally named by their genus and species
what is the taxonomy system?
domain, kingdom, phylum, class, order, family, genus and species - each group called taxa
what is a hierarchy?
smaller groups within a larger group with no overlaps
what are modern ways for accurate classification?
through DNA and mRNA sequence and immunology
what are the three domains?
archaea bacteria and eukarya
what are the five kingdoms?
animal plants fungi monera and protists
what are species?
organisms are able to breed and produce fertile offspring
what are courtship rituals?
sequence of actions that are specific to each specie and this is how members identify their own species to reproduce with
what are the importance of courtship behaviours?
- ensures successful reproduction
- enables animals to recognise their own species
- synchronise mating behaviour (indicated mating season)
when species have similar courtship behaviour what does this suggest?
they’re closely related since courtship behaviour is genetically determined
what is species diversity?
number of different species and individuals within species within a community
what is species richness?
number of different species in a particular area in a specifc time
how does farming reduce biodiversity?
- destroying hedgerows
- selective breeding
- monoculture
- over grazing
- filling in ponds and draining wetlands
what is index of diversity?
measures the relationship between the number of species in a community and the number of individuals in each species
what is the formula for index of diversity?
D = N(N-1)
———-
total n (n-1)
what does N and n represent in index of diversity?
N is the total number of organisms of all species
n is the total number of organisms in a specifc species
how can genetic diversity within species or between species be made and compared in early times?
the frequency of measurable or observable characteristics
how can genetic diversity within species or between species be made now after advanced gene tech?
1) studying base sequence of DNA
2) studying base sequence of mRNA
3) the amino acid sequence of proteins encoded by DNA and mRNA
why does evolution occur?
random mutations in genetic material
what does two distantly related species suggest?
it has been a long time since they shared common ancestor so more time allowing mutation to occur
how to compare DNA or mRNA sequence?
the less similar in base sequence the less closely related species are
how to compare amino acid sequence?
the more differences in amino acid sequence the less closely related species are
what are the problems with comparing amino acid sequence?
two organisms may have same amino acid sequence but different DNA sequence because amino acid codes are degenerate. so less useful to compare close related organisms
how do you investigate diversity?
take random sample of a population
collect data
calculate mean
calculate standard deviation
what is standard deviation?
the spread of means
what does a large or small standard deviation suggest for diversity?
large - large diversity
small - small diversity
