genetic diversity and adaptation Flashcards
prokaryotic DNA is…
short, circular and NOT associated with proteins
eukaryotic DNA is…
long, linear and IS associated with proteins called HISTONES
mitochondria and chloroplasts have DNA too, which is…
like prokaryotic: short, circular, not associated with proteins
DNA bases are…
A + T (2 hydrogen bonds)
C + G (3 hydrogen bonds)
what is a gene?
base sequence of DNA that codes for: amino acids sequence of a polypeptide, functional RNA (rRNA + tRNA)
occupies a fixed position on a DNA molecule called locus
3 DNA bases form a codon which is…
triplet of bases that encodes for a specific amino acid
properties of genetic code…
universal= same for all organisms
degenerate= more codons that amino acids, so some encode the same amino acid
non-overlapping= each base is only part of one code so each codon is read as a discrete unit
features of DNA are…
most in non-coding
only about 2% of DNA codes for amino acids
coding part called exons
non-coding part called introns
a genome is…
a complete set of genes in a cell
a proteome is…
full range of proteins that a cell is able to produce
the stages of protein synthesis are…
- transcription
- splicing (eukaryotic only)
- translation
transcription is…
DNA to pre-mRNA/mRNA
splicing is…
pre-mRNA to mRNA (eukaryotic only)
translation is…
mRNA to protein using (tRNA)
mRNA structure
short, single-stranded linear chain of ribonucleotides
groups of 3 adjacent bases called codons
tRNA structure
silly polynucleotide strand with a clover shape
has an amino acid attached to it and an anticodon that’s complementary to an mRNA codon
the steps of transcription are…
- DNA helicase unwinds 2 DNA strands by breaking hydrogen bonds between complementary base pairs, one strand acts as a template
- free mRNA nucleotides align and pair with complementary bases
- RNA polymerase joins mRNA nucleotides together to form pre-mRNA
the steps of splicing are…
- introns are removed
- exons attached back together via condensation reaction
- mRNA is formed, m exits nucleus through nuclear pores into cytoplasm
the steps of translation are…
- ribosome attach to start codon of mRNA
- tRNA molecule with complementary anticodon aligns with mNA
- ribosomes move along mRNA, allowing another tRNA to attach to next codon
- 2 amino acids attached to tRNA molecules are joined by peptide bonds (requires ATP)
- process keeps occurring until ribosome reaches a stop codon, where it detaches and translation ceases
- peptide chain/protein has now been created
genetic diversity is…
the no. of different alleles of genes in a population, enables natural selection to occur
an allele is…
variations of a gene
what is natural selection and its steps
leads to evolution of populations
1. random mutation can result in new alleles of a gene
2. in certain environments, new allele is advantageous, so possessor is more likely to survive + reproduce
3. advantageous allele inherited
4. over generations, new allele incr. in frequency in the population
adaptations can be anatomical, physiological or behavioural, examples are…
hedgehogs
spikes-anatomical
hibernation- physiological
ball when scared- behavioural
directional selection is…
selection favours one extreme phenotype
normal distribution curve shifts in direction of this phenotype
(directional selection) the steps of antibiotic resistance in bacteria are…
- random mutation creates allele in bacterial population
- when exposed to antibiotic, only those with resistance will survive and reproduce
- resistance allele frequency incr. over generations
stabilising selection is…
‘middle trait’ or ‘average phenotype’ has selective advantage
variation of traits decreases over generations
(stabilising selection) the steps of human birth weights…
- average birth rate has selective advantage
- more likely to survive and reproduce to pass on allele to offspring
a species is…
similar organisms that can reproduce to produce fertile offspring
courtship behaviours are…
behaviours animals exhibit to attract a mate
species specific, so essential for successful mating
display when sexually mature + fertile
ritual forms a pair bond
allows female to select strong + healthy male
phylogenetic classification system…
arranges species into groups based on evolutionary origins and relationships
determines how closely related different species are
all organisms have evolved from shared common ancestors
hierarchies are…
smaller groups placed in larger groups with no overlap in between
each group is called a taxon
order is: domain, kingdom, phylum, class, order, family, genus, species
binomial system…
universal- avoids use of different names in other countries, leading to errors in counting no. of individual of each species
uses the genus + species
biodiversity is…
can relate to a range of habitats from small, local, Earth
a habitat is…
range of physical, biological and environmental factors that a species can live in
species richness is…
measure of no. of different species in a community
index of diversity is…
describes the relationship between the no. of species in a community and no. of individuals in each species
biodiversity reduced by farming techniques include…
monoculture= wheat reduce species diversity (one species present in field)
ploughing
crop spraying with pesticides, fungicides and insecticides
balance between conservation and farming include…
uncultivated strips of land alongside hedges provide food source and habitat
delayed harvesting allows seed dispersal
meadow conservation conflicts with grass planting
diversity can be investigated through…
frequency of observe + measurable characteristics
DNA sequence
mRNA sequence
amino acid sequence
(last 3 more accurate)
features of investigating diversity
smalls taken because would be impossible to record data for every individual in the population
must be large to be representative of population as a whole
must be random to avoid bias
mean average is…
sum of all values/ no. of values
standard deviation is…
hoe much results differ from mean average
says if differences are significant or not
a gene mutation is…
change in base sequence of DNA
can occur during DNA replication
substitution is…
single substitution of one base for another
change in amino acid sequence
change in primary and tertiary structure, so possibly affecting protein structure and function
single amino acid change is more likely to have less of an effect on protein structure and therefore function
deletion is…
deletion of a base in DNA structure
causes frameshift
has larger impact on amino acid sequence
chromosomal mutation is…
mutation in no. of chromosomes can arise by chromosome non-disjunction in meiosis
can result in trisomy (extra copy if chromosomes) or aneuploidy (missing copy/part of chromosome)
whole extra set of chromosomes= polyploidy
overview of meiosis
form of cell division that produces 4 daughter cells that are genetically different
involves 2 separate divisions
haploid (n) cells formed from diploid (n) cells
produce gametes (sex cells)
steps of meiosis are…
meiosis 1= prophase 1, metaphase 1, anaphase 1, telophase 1 and cytokinesis (homologous chromosomes separate
meiosis 2= prophase 2, metaphase 2, anaphase 2, telophase 2 and cytokinesis (sister chromatids separate)
crossing over…
occurs in prophase 1
homologous chromosomes pair to form bivalents
sections of chromatids break + re-join/ exchange with chromatids on homologous chromosomes
result= now combination of allele/recombination of alleles
independent segregation is…
homologous pairs line up at equator randomly
chromosomes separate randomly
gametes receive different combination of maternal + paternal chromosomes
random fertilisation of gametes…
increase genetic variation within a species
