genetic info, variation and relationships between organisms Flashcards
What are the features of the genetic code?
Degenerate - most amino acids code for mores than one protein
Non-overlapping - each base is only read once
Universal - the same in all living things
What does the order of bases determine?
The sequence of amino acids that form proteins
What is a triplet?
sequence of 3 bases that code for an amino acid
what is a gene?
a small section of DNA that codes for a polypeptide or functional RNA
Describe DNA in prokaryotic cells
short, circular and not associated with proteins
Describe DNA in eukaryotic cells
long, linear and associated with proteins called histones
Describe mitochondrial and chloroplast DNA
short, circular and not associated with proteins
What is a locus?
a fixed position on a strand of DNA
What are exons and introns?
Exons- coding regions of a gene
Introns - non coding regions
What is a genome?
the complete set of genes in a cell
What is a proteome?
the full range of proteins that a cell is able to produce
What is mRNA and its structure ?
a single strand of RNA that reads 3 bases at a time
a single-stranded chain of ribonucleotides with a sugar-phosphate backbone. It contains exons and introns
What is tRNA and its structure?
carries amino acid to ribosomes
clover leaf shape and are composed of a single strand of RNA with several loop structures (sugar phosphate backbone)
Describe the process of transcription
-DNA helicase breaks hydrogen bonds between 2 strands
- one DNA strand acts as a template strand
- -gree floating RNA nucleotides attach to adjacent bases
- RNA polymerase binds 2 strands together making a double helix (dettaches when reaching a stop codon)
- results in the production of mRNA
in eukaryotes it will go through splicing to remove introns
What is splicing?
The use of a spliceometer to remove any non-coding regions in mRNA (introns)
What is the structure of tRNA?
hydrogen bonding between nucleotides creates a clover- leaf shape molecule that has an amino acid binding site and an anticodon
Describe the process of translation
- mRNA attaches to a ribosome
- tRNA anticodon attaches to codon on mRNA
- peptide bond forms after another tRNA is attaches
- cycle will continue until a stop codon is reached
-forms a polpeptide chain
What are gene mutations?
a change in the base sequence of
chromosomes
What are mutagenic agents + examples ?
factors that increase the rate of mutations e.g radiation, carcinogens, viruses
What is base substitution?
when one base replaces another - doesnt cause a frame shift, not the original protein created
What is base deletion?
the removal of a base causing a frame shift
What is base addition?
a new base is randomly inserted into the sequence, causing a frameshift
What is base duplication?
when a whole gene or section of it is duplicated , mutation isnt harmful, and it is a source for evolutionary change
What are advantages and disadvantages of mutations?
A- antibiotic resistence in bacteria, immunity to HIV, rare gene immunity protetctedx against cancer
D- can cause down syndrome, cystic fibrosis or cancers
What is meiosis?
type of cell division that results in 4 genetically different daughter cells - takes place in the gametes
What is crossing over?
when sections of sister chromatids swap geentic material resulting in genetic variation
What is independent variation?
When the side the chromatids face before being pulled apart is random resulting in genetic variation
What does homologous mean?
pair of chromosomes, one from the mother and one from the father that share similar characteristics
What is chromosome non-disjunction?
when chromosomes fail to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal - down’s syndrome
Describe the process of meiosis
- DNA unravels and replicates so there are two copies of each chromosome - chromatids
- DNA condenses to form chromosomes each made from 2 sister chromatids joined by a centromere
- Meiosis I - the chromosomes arrange themselves into homologous pairs
- The homologous pairs are separated, halving chromosome number and creating two cells
- Meiosis II - the pairs of sister chromatids that make up each chromosome are separated
- Four haploid cells that are genetically different are produced
What is genetic diversity?
the total number of different alleles in a population
What is a population?
A group of the same species that live in the same area and interbreed
What is a species?
one or more populations that can produce fertile offspring
What factors affect genetic diversity?
Random mutation
Environmental factors
Selection pressures
What is natural selection?
when species adapt to their environment. These adaptations may be anatomical, physiological or behavioural
What is intraspecific competition?
Competition within the same species
Describe the process of natural selection?
- Random genetic mutations can create multiple alleles of genes within a population (gene pool)
- Genetic variation within a population creates intraspecific competition
- Individuals with particular alleles are better able to face challenges
imposed by the environment. - Individuals possessing alleles which code for advantageous
characteristics will be more likely to survive - Individuals that survive are more likely to reproduce and pass on the advantageous allele to the next generation
-Therefore, over time, the frequency of the advantageous allele
increases in the population.
What are the 2 types of selection?
Stabilising - acts against the extremes and tries to reduce variation , preserves characteristics of a population
Directional - leads to a shift in mode, favouring a certain extreme , changes characteristics of a population
Who came up with binomial classification?
Carl Linnaeus
What are the 3 domains?
Eukaryota , Bacteria and Archaea
What is the order of classification?
domain
kingdom
phylum
class
order
family
gene
species
What is a taxon?
groups in the classification system
What is classification?
the arrangement of organisms into groups of various sizes on the basis of shared features
What is taxonomy?
form of classification that focuses on physical similarities between
different species, for ease of naming and identification
What is phylogeny?
the classification of organisms by these evolutionary relationships, so that every group shares a common ancestor
Each group is called a taxon (plural taxa)
What is binomial nomenclature?
naming system used for classification -
Genus starts with capital and is underlined or in italics
Species is lower case and is underlined or in italics
What is courtship behaviour?
pre-mating activities for stimulation, partner attraction and mating initiation
What is biodiversity?
a range of habitats, from a small local habitat to the Earth
What are the functions of courtship behaviour?
-For species recognition
-Identification of a mate that is capable of breeding
-Insures stimulation and synchronization of mating
-form a pair bond
Individuals of the same species show the
same courtship behaviours
What is species diversity?
The number of different species and individuals within a community
What is genetic diversity?
The variety of genes within a population of a species
What is ecosystem diversity?
The whole range of different habitats on all scales
What is species richness?
The number of different species in a particular area at a particular time
What is index of diversity?
Total number of organisms of all species/ Sum of number of
organisms of each species
What farming practices reduce biodiversity?
Removing hedgerows
Overgrazing
Creating monocultures
Use of pesticides & inorganic fertilisers
Not rotating crops/ lack of intercropping
Filling in ponds, draining wetland and marsh
What is gene sequencing?
determining the exact order of nucleotide bases present in a gene, from a sample of DNA
In computerised systems, each nucleotide base is
be tagged with a different coloured dye
How can genetic diversity in amino acids be measured?
by counting either the number of similarities or the
number of differences in each sequence
What is DNA fingerprinting?
Analysing individuals DNA base sequences to see what genes or specific alleles are involved
The DNA profile will produce coloured bands and these will be compared to see the similarities and differences between them
What is the difference between inter/intraspecific variation?
Interspecific- one species differs from another
Intraspecific - between members of the same species
Why might sampling not be representative ?
Sampling Bias
Chance – Even if sampling bias is avoided, the individuals chosen, by pure chance, may not be representative
Sample size
What does aseptic mean?
Free from contamination caused by harmful bacteria, viruses, or other microorganisms; surgically sterile or sterilized
Describe the practical for the use of antimicrobial substances on the effect of microbial growth
Glass Petri dishes and
agar gel must be sterilised before use in an autoclave or pre-sterilised plastic Petri dishes can be bought.
Pour the sterile agar plates and allow to set fully.
Sterilise the
inoculating loop by heating it in the Bunsen burner flame.
Dip the inoculation loop into the microorganism solution and make streaks on the surface of the agar plate.
Replace the lid as soon as possible, secure with tape. Label and invert the plate, and store upside down.
Incubate at a maximum temperature of 25°C
