Genetic + Biodiversity Flashcards
What is a homologous pair?
Carry the same gene, but not the same alleles.
What is Mitosis?
Sexual reproduction, produces 2 identical daughter cells, with the diploid number (46)
What is Meiosis?
Asexual reproduction, produces 4 daughter cells, with the haploid number (23)
What is a zygote?
2 haploid cells fuse, randomly
Explain the process of Meiosis 1
(Separating homologous chromosomes)
-Before this, DNA replication happens, interphase
Prophase 1: chromosomes condense, nuclear membrane disappears, homologous pairs pair up.
Metaphase 1: chromosomes line up in the centre in the homologous pairs.
Independent assortment/segregation- which wat round the chromosomes are, maternal and paternal can line up differently.
Crossing Over- exchange small portions of genetic material (alleles) when chromatids cross over, now unique.
Anaphase 1: homologous chromosomes separate
Telophase 1: nucleus divides, become haploid so no homologous pairs of chromosomes, chromosomes uncoil.
Cytokinesis: cell divides, consists of 2 unique chromatids.
Explain the process of Meiosis 2
(Separating sister chromatids)
Prophase 2: chromosome condense, nuclear membrane breaks down
Metaphase 2: chromosomes move to the middle of the cell, spindle fibres attach to centromere
Anaphase 2: sister chromatids separate, moving to opposite poles.
Telophase 2: nuclear membrane reforms, chromosomes uncoil.
Define ‘Natural Selection’
Organisms that are best adapted to the conditions are able to survive, breed, and pass on their adaptations to the next generation causing a gradual change in the species.
Define ‘Species’
A group of organisms that share common morphological, physiological, and behavioural characteristics. Need to be able to interbreed and produce fertile offspring.
What are alleles?
Different versions of genes, causing genetic variation.
What is ‘Biodiversity’?
A measure of how varied an ecosystem is. It can be measured in terms of genes, species, or habitats.
Define ‘Genetic diversity’
A measure of how many variations there are in the genetic code between individuals of a particular or different species/ number of different alleles of genes in a population.
Define ‘Species diversity’
Measure of how many different species are present in an area, and how many individuals of these species there are.
Define ‘Habitat diversity’
Measure of how many different habitats are present in an area.
What is a ‘gene pool’?
The variation of alleles that are present in a population.
What are selection pressures?
Factors such as predators or the climate that may cause natural selection.
What happens if there are no selection pressures?
Each individual is equally likely to breed and pass on its alleles to the next gen; so the frequency of alleles in the gene pool remain unchanged.
What happens if there are selection pressures?
For example a predator, then those individuals that are better adapted and suited are more likely to survive, breed, and pass on them alleles to the next gen. The allele frequency in the gene pool will change as those who have less desirable/useful traits will not breed.
What are the 3 types of selection?
-Stablising
-Directional
-Disruptive
What is ‘Stabilising Selection’ and where is the mode?
-Reduces the frequency of the alleles for the extreme expressions of a characteristic
-No change in the environment
-e.g. human birth weight, a weight significantly higher or lower than 7lb will put mum and baby in danger.
-Mode is in the middle of the curve, range reduces.
What is ‘Directional Selection’ and where is the mode?
-Increases the frequency of alleles for an extreme expression of a characteristic, which becomes the new average.
-When there is a change in the environment
-e.g. antibiotic resistant bacteria
-Mode shifts.
How does evolution occur?
-Mutations in the gametes, makes them better adapted
-Natural selection
What is evolution?
Any change in the heritable traits/ allele frequency within a population across a generation.
Why does over production of offspring lead to natural selection?
Too many offspring for the available resources, competition.
What are Homologous Pairs sometimes called?
Bivalents
During crossing over, what is the point at which the chromatids meet called?
Chiasma
What is ‘Courtship’?
A behaviour in animals that eventually results in mating and reproduction.
What is courtship used for?
-Animals to recognise members of their own species
-To identify a mate capable of breeding (needs to be sexually mature)
-To form a pair bond, leading to successful mating
-Animals can synchronise mating, increased chance of offspring
Basically to be able to breed.
How is courtship useful in determining a females sexual activity?
Females of many species undergo a cycle of sexual activity in which they can only conceive during a very short time period.
What is ‘Taxonomy’?
The science and practice of biological classification. Involves naming organisms and organising them into groups.
There are 2 main forms.
What are the 2 forms of Taxonomy?
-The Phylogenetic Classification system
-Artificial classification system
What is the Phylogenetic classification system?
-Allows us to arrange species into groups based on evolutionary trees and relationships.
-Each group is called a taxon, there is no overlap between groups.
What is the Artificial classification system?
-Divides organisms according to differences that are useful at the time e.g. eye colour
Carl Linnaeus devised 7 taxa, each group is a taxon (phylogenetic), and Carl Woese divised 1 more taxa- what are the 8 taxa?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
To remember:
Danish Kids Prefer Candy Over Fresh Green Sprouts
How did Woese discover the 8th taxa ‘domain’ many years later?
-Due to advancements and discoveries in technology e.g. DNA/RNA sequencing, electron microscopes.
What are the 3 domains?
-Archaea
-Bacteria
-Eukaryota
What is ‘Archaea’?
-A ‘domain’
-Single celled prokaryotes that are adapted to live in extreme environments
-DNA has histones
-Cell walls made of protein, no murein
-Membranes have ether linkages rather than ester linkages (in phospholipids)
-No membrane bound organelles
-70s ribosomes
What is bacteria (true bacteria)?
-A domain
-No membrane bound organelles
-Unicellular
-70s ribosomes
-Cell walls made of muriein
-Single loop of DNA, no histones
-Membrane has ester linked lipids.
What is ‘Eukaryota’?
(protists, fungi, plants, animals)
-A domain
-Membranes have ester linked lipids
-80s ribosomes
-Unicellular or multicellular
-DNA has histones
-Not all have a cell wall, but if they do its made of chitin in fungi, and cellulose in plants.
What is the ‘Binomial Naming System’ and how does it work?
The scientific naming of organisms based on genus and species.
- The genus comes first
- Species is second
e.g Homo-sapiens
What are the rules for the binomial naming system?
-If its printed, needs to be in italics
-Handwritten, its underlined
-Genus is uppercase
-Species is lowercase
-If you don’t know a species its s.p
What is a ‘Phylogenetic tree’?
A diagram that represents evolutionary relationships among organisms.
The point of branch represents an ancestor.
What do the bio, species, genetics, and habitat diversities show us?
Measures that allow comparisons to be made between:
-Different areas
-The same areas at different times
What is ‘Species Richness’?
The number of different types of species in a particular area. The greater the number of species, the ‘richer’ the area.
What is ‘Species Eveness’?
Comparison of the population (number of individuals) of different species within a particular area.
What is the index of diversity?
D= N(N-1) / Sum of n(n-1)
N= total number of organisms of all species
n= total number of organisms of a particular species
D= diversity index, the probability that 2 randomly selected individuals will belong to the same species.
What is biomass?
The total mass of living material normally measured over a specific area, over a given period of time.
What is a habitat?
The place where an organism normally lives, and which is characterised by physical conditions and the types of other organisms present.
What is a community?
All the living organisms present in an ecosystem at a given time.
What is an ecosystem?
All the living and non-living components of a particular area.
What is a ‘Biodiversity hotspot’?
Regions of the world that have a particularly high level of biodiversity but are threatened with destruction. Around 34 in the world.
What are ‘agricultural ecosystems’?
Controlled by humans.
Destruction of biodiversity, loss of habitats, use of pesticides. Low index of diversity e.g destruction of hedgerows.
What are the destructive effects of farming?
-Creating monoculture ( replacing natural meadows with one type of crop)
-Filling in ponds or draining marshlands to create more fields or crops.
-Over-grazing areas of land preventing natural areas from regenerating.
-Use of pesticides which can enter waterways and food chains.
What are some management techniques in farming to maintain biodiversity?
-Maintain existing hedgerows at a beneficial height.
-Plant hedges rather than put up fences
-Leave wet corners of fields
-Plant native trees
-Reduce use of pesticides, biological control (natural predators)
-Organic fertilisers
What are the 4 ways scientists investigate biodiversity?
-Comparison of observable characteristics
-Comparison of DNA base sequences
-Comparison of mRNA base sequences
-Comparison of amino acid sequences in proteins
What is ‘comparison of observable characteristics’?
-Each observable characteristic is determined by a gene
-The variety within a characteristic depends on the number and variety of alleles of that gene.
-But, a large number of characteristics are coded for by more than one gene- polygenic
-Can be modified by the environment, so differences can be the result of this rather than different alleles.
This has been replaced by directly observing DNA sequences for these reasons.
What is ‘comparison of DNA base sequences’?
-We can determine the exact order of nucleotides on DNA using gene technology.
-Done by automatic machines, and analysed by computers.
-Each base can be tagged with a colour .
-We can measure the genetic diversity of a species by sampling the DNA of its members and sequencing it to produce a pattern of coloured bands.
-Find evolutionary relationships
-Mutations change the nucleotide sequence
What is ‘comparison of the base sequence of mRNA’?
-mRNA is coded for by DNA
-Base sequences are complementary
-It follows that we can measure DNA diversity, therefore genetic diversity.
What is ‘comparison of amino acids sequences in proteins’?
-Determined by mRNA-> DNA
-So we can compare amino acids
-Similarity will reflect how closely related they are
-Count similarities
What is Standard Deviation?
A measure of how spread out all your repeats are from the mean.
What is the advantage of using standard deviation over the range?
-SD shows the spread of data around the mean, range is just lowest and highest
-SD reduces effect of anomalies, range includes them.
-SD can be used to indicate whether a difference between results is significant.
How do we know something is significant (SD)?
No overlap
What is the process of natural selection?
- New alleles for a gene are created by random mutations
- If the new alleles increase the chances of survival in that environment, then they are more likely to survive and reproduce.
- This reproduction then passes on that advantageous allele to the next generation.
- Over many generations, that allele will increase in frequency over a population.
How do you work out the number of possible combinations of chromosomes in daughter cells?
2^n
n= the number of homologous pairs
e.g in a human, 2^23 = 8,388,608 combinations
Egg and sperm cells randomly fuse in fertilisation, how would you find the number of possible combinations of chromosomes for this zygote?
(2^n)^2
e.g humans, (2^23)^2
Name the fixed position occupied by a gene on a DNA molecule
locus/loci
What is Non-disjunction
A change in the number of chromosomes due to the failure of homologous
chromosomes to separate during meiosis. This may result in a gamete with one more or one
less chromosome.
What is phylogeny?
The relationship between organisms as a result of their shared characteristics which link them to a common ancestor
Outline the difference between index of diversity and species richness
Species richness is just the number of species, whereas index of diversity also takes into account the number of each individual in each species
