Unit 4 Flashcards
Gene mutations
Any random changes to bases in DNA.
Insertion/deletion mutation
-A base is either inserted or deleted.
-Triplet codons change.
-Code for different amino acid.
-Different polypeptide chain is formed.
-Tertiary structure is different as hydrogen, ionic and disulfide bonds for elsewhere.
-Different protein with different function is formed.
Substitution mutation
Missense, Nonsense, Silent
Chromosome mutations
-Arise spontaneously.
-Changes in whole sets of DNA when there is more than 2 sets of DNA. Called polyploidy and occurs in plants.
-Changes in number of chromosomes. Non-disjunction of chromosomes so they don’t split properly resulting in one more or one less chromosomes. Leads to Down’s Syndrome.
Importance of meiosis
-During meiosis, homologous pairs of chromosomes separate so one chromosome from each pair enters the daughter cell.
-Known as haploid cell and has half the original number of chromosomes.
-At fertilisation, diploid number is restored.
Process of meiosis
-Meiosis 1- homologous chromosomes pair up and their chromatids cross over. By the end of it, homologous chromosomes split with one chromatid in each of the 2 daughter cells.
-Meiosis 2- chromatids move apart and cells are split again.
Prophase 1
Nuclear membrane breaks down and chromosomes condense.
Metaphase 1
-Homologous pairs of chromosomes line up next to each other on the equator.
-Spindle fibres attach at centromere.
-Crossing over occurs.
Anaphase 1
-Homologous pairs separate to each pole.
-Independent assortment occurs.
Telophase 1
-Nuclear membrane reforms
-Cell divides
Prophase 2
-Chromosomes condense
-Nuclear membrane breaks down
-Centromeres move apart
Metaphase 2
-Chromosomes line up on the equator
-Spindle fibres attach at centromere
Anaphase 2
-Centromeres split
-Chromatids move to opposite poles
Telophase 2
-Nuclear membrane reforms
-Chromosomes uncoil
-Cells divide
Independent assortment
-Random orientation of homologous chromosomes during metaphase 1.
-Production of gametes with different assortment.
Crossing over
-Prophase 2.
-Two chromosomes are joined at the synapse forming bivalent chromosomes.
-They have 4 arms or chromatids.
-Two non-sister chromatids get twisted and linked.
-Point of linkage is called chiasma.
-New combination of genes.
Gene
A length of DNA that codes for a polypeptide.
Locus
The position of the gene on a chromosome or DNA molecule.
Allele
One of the different forms of a particular gene.
Homologous chromosomes
A pair of chromosomes, one maternal, one paternal, they have the same gene loci.
Possible chromosome variations following meiosis
2^n
Genetic diversity
Total number of different alleles in a population.
Why are organisms different?
-Different alleles, more genetically diverse.
-Random fertilisation.
-Random fusion of gametes
Factors influencing genetic diversity
-Mutations
-Fertilisation
-Environment
-Meiosis (crossing over and independent assortment)
-Gene flow
How reproductive success affects allele frequency in a gene pool
-More advantageous characteristics can be passed on.
-When the offspring inherits them, the frequency of that advantageous allele increases.
Natural selection
-Genetic variation within a population of the same species.
-Environmental change occurs which means that some are more suited to the environment than others.
-Better suited have advantageous allele.
-Those with the advantageous allele can survive and reproduce.
-Offspring inherit the allele.
-Overtime, frequency of advantageous allele increases.
Selection
Process by which organisms that are better adapted to their environment tend to survive and breed, while those who are less well adapted tend not to.
Types of selection
-Directional selection
-Stabilising selection
Directional selection
-Environmental change occurs.
-Organisms with favourable characteristics survive.
-Breed and pass on allele.
-One extreme is favoured.
Stabilising selection
-Environmental conditions remain same.
-Median is favoured.
Environmental factors that exert selection pressures
Types of adaptations
-Anatomical
-Behavioural
-Physiological
Anatomical adaptation
Structural features that an organisms which increases its chance of survival.
Behavioural adaptation
Something an animal does usually in response to some type of external stimulus in order to survive.
Physiological adaptation
Refers to the internal organs, tissues and cells.
Species
They are capable to breed together to produce fertile, living offspring.
Binomial system
-Proposed by Carl Linnaeus based on Latin or Greek words.
-First name- generic name- genus.
-Second name- specific name- species.
Courtship behaviour
-Recognise members of their own species.
-Identify a mate that is capable of breeding.
-Form a pair bond.
-Synchronised mating.
-Become able to breed.
Classification
Organisations of living organisms into manageable groups.
Taxonomy
The theory and practice of biological classification.
Artificial classification
A type of classification that divides organisms into groups based on analogous characteristics- same function but not the same evolutionary origins.
Phylogenetic classification
-Based on evolutionary relationships between organisms and their ancestors.
-Classifies species into groups using shared features derived from their ancestors.
-Arranges the groups into a hierarchy, in which the groups are contained within larger composite groups with no overlap.
-Homologous characteristics.
Domains
-Archaea
-Bacteria
-Eukarya
Bacteria
Group of single-celled prokaryotes with following:
-Absence of membrane bound organelles
-Unicellular
-70s ribosomes
-Cell walls present and made of murein
-Single loop of naked DNA made up of nucleic acid but no histones.
Archaea
Group of single-celled prokaryotes that were originally bacteria (resemble in appearance).
Differ from bacteria by:
-Genes and protein synthesis more similar to eukaryotes
-Membranes contain fatty acid chains attached to glycerol by ether linkages
-No murein in their cell wall
-Have more complex form of RNA polymerase
Eukarya
Group of organisms made up of more than one eukaryotic cells with the following features:
-Possess membrane-bound organelles
-Have membrane containing fatty acid chains attached to glycerol by ester links
-Not all possess cell wall, but ones that do are not made of murein
-80s ribosomes
Four kingdoms of Eukarya domain
-Protoctista
-Fungi
-Plantae
-Animalia
Order of classification
-Kingdom
-Phylum
-Class
-Order
-Family
-Genus
-Species
Phylogeny
The evolutionary relationship between individuals or group of organisms indicating common ancestors.
Species diversity
The number of different species and the number of individuals of each species within any one community.
Genetic diversity
The variety of genes possessed by the individuals that make up a population of a species.
Ecosystem diversity
The range of different habitats.
Species richness
A measure of the number of different species in a community at a given time. Measure of species diversity.
Index of diversity
d= N(N-1)/Σn(n-1)
d=index of diversity
N= total number of organisms of all species
n= total number of organisms of each species
Σ= the sum of
Biodiversity
The variety of genes, species and habitats within a particular area.
Impact of agriculture
Balance between conservation and farming
Comparison of observable characteristics
Comparison of DNA base sequences
Comparison of base sequence of mRNA
Comparison of amino acid sequences in proteins
