Topic 8 Inheritance, Variation And Evolution Flashcards
What does each gene code for?
Particular sequence of amino acids to make specific protein
What is the genome?
Entire genetic material of organism
What are 3 reasons understanding the human genome is important?
1) Search for genes linked to different types of disease
2) understanding and treatment of inherited disorders
3) tracing human migration patterns from past
Describe the structure of DNA?
Polymer made from 4 different nucleotides
What does each nucleotide consist of (3 things)?
Sugar, phosphate group, base
What is complementary base pairing?
A always pairs with T, C always pairs with G
What is each amino acid coded for by?
Sequence of 3 bases in gene
What does the order of bases control?
Order amino acids assembled to produce particular protein
What do long strands of DNA consist of?
Alternating sugar and phosphate sections, attached to each sugar is 1 of 4 bases
What can non-coding parts of DNA do?
Switch genes on and off, control whether or not gene is expressed
What happens when a protein chain is complete?
Folds up to form unique shape, enables proteins to do their job
What are 3 types/examples of proteins?
Enzymes
Hormones
Structural proteins (collagen)
What are proteins synthesised on?
Ribosomes
What effects do most mutations have on the protein?
None/slightly but appearance or function not changed
How do mutations occur?
Continuously
What do a few mutations code for?
Altered protein with different shape (enzymes/structural proteins)
What do mutations change in DNA?
Sequence of DNA bases in gene, produces genetic variant
What can a mutation in non-coding DNA alter?
How genes expressed
What does sexual reproduction involve in flowering plants?
Pollen and egg cells
How are gametes produced?
By meiosis
Where does meiosis occur in humans?
Reproductive organs
Want are the 3 stages of meiosis?
Genetic info copied
Cell divides twice to form 4 gametes, each with single set of chromosomes
All gametes genetically different
What happens after gametes join at fertilisation?
New cell divides by mitosis to produce lots of new cells in embryo, as embryo develops cells differentiate
What are 3 advantages of sexual reproduction?
Produces variation in offspring
If environment changes, variation gives survival advantage by natural selection
Natural selection can be speeded up by humans in selective breeding to increase food production
What are 4 advantages of asexual reproduction?
Only one parent needed
More time and energy efficient (do need to find mate)
Faster than sexual reproduction
Many identical offspring can be produced in favourable conditions
What are 3 organisms that reproduce both sexually and asexually?
Malarial parasites
Fungi
Plants
How can malarial parasites reproduce both ways?
Asexually in human host but sexually in mosquito
How can fungi reproduce both ways?
Asexually by spores but also sexually to give variation
What are 2 ways plants can reproduce asexually?
Runners
Bulb division
What are 2 inherited disorders?
Cystic fibrosis - genetic disorder of cell membranes
Polydactyl - extra fingers/toes
What type of allele is cystic fibrosis caused by?
Recessive
Why type of allele is polydactyl caused by?
Dominant
How can embryos be screened for genetic disorders?
In IVF before implantation, remove cell from each embryo and analyse genes
What are 3 arguments against embryonic screening?
Implies people with genetic problems are undesirable
Everyone may want to screen embryos to pick most desirable one
Expensive
What are 3 arguments for embryonic screening?
Stop suffering
Treat disorders cost tax payers money
Laws stop it going too far
What is variation?
Differences in characteristics of individuals in a population
What can mutations very rarely result in?
New phenotype in species
What is selective breeding?
Humans artificially select and breed plants and animals for particular genetic characteristics
What are 4 organisms that are selectively bred to develop features that are useful or attractive?
Crops with disease resistance
Animals that produce more meat or milk
Domestic dogs with gentle nature
Large or unusual flowers
What are the 4 steps in the process of selective breeding?
1) choose parents with desired characteristics from mixed population
2) breed together
3) select best offspring and breed together
4) continue process over several generations until all offspring show desired characteristic
What is the main drawback of selective breeding?
Lead to ‘inbreeding’, some breeds particularly prone to a disease or inherited defects
What is genetic engineering?
Modifying genome of organism by introducing gene from another organism to give desired characteristic
What are 2 examples of genetic engineering?
Bacterial cells genetically engineered to produce human insulin to treat diabetes
GM crops to be resistant to disease, insects, herbicides or produce bigger better fruits
Why is the transfer of a gene carried out when the organism is at an early stage of development?
Organism develops with desired characteristics
What are the 3 steps in genetic engineering?
1) enzymes used to isolate required gene
2) gene inserted into vector (usually bacterial plasmid or virus)
3) vector used to insert gene into required cells
What are 2 cons of GM crops?
Effect on populations of wild flowers and insects- reduce farmland biodiversity
Effects of eating GM crops on human health not fully explored
What is modern medical research exploring with genetic engineering?
Genetic modification to overcome some inherited disorders
What are 2 pros of GM crops?
Increase yields
Engineered to contain nutrients missing from diets in developing nations
What are 2 methods of cloning plants?
Tissue culture- using small groups of cells from part of plant to grow identical new plants
Cuttings- older, simpler method, produce many identical plants quickly and cheaply
What is tissue culture important for?
Preserve rare plant species or by plant nurseries to produce lots of stock quickly
What are 2 methods of animal cloning?
Embryo transplants
Adult cell cloning
What are the 2 steps in embryo transplants?
Splitting apart cells from developing animal embryo before become specialised
Cloned embryos implanted into host mothers
What are the 4 steps in adult cell cloning?
1) nucleus removed from unfertilised egg cell
2) nucleus from adult body cell (skin cell) inserted into egg cell
3) electric shock stimulates egg cell to divide to form embryo
4) when ball of cells, inserted into womb of adult female
What is an example of adult cell cloning?
Dolly the cloned sheep
What are 3 risks of cloning?
Reduced gene pool
Health problems in cloned animals
Human cloning in future?
What are 2 benefits of cloning?
Study of animal clones -greater understanding of development of embryo
Preserve endangered species
What were 3 reasons why the theory of evolution by natural selection was only gradually accepted?
Challenged idea God made all animals and plants
Insufficient evidence at time to convince many scientists
Mechanism of inheritance and variation not known until 50 years after theory published
What was the theory of Jean-Baptiste Lamarck?
Changes that occur in organism during its lifetime can be inherited
Which book did Darwin propose his theory in?
On the Origin of Species 1859
What is evolution?
Change in inherited characteristics of population over time through process of natural selection which may result in formation of new species
What does the theory of evolution state all species evolved from?
Simple life forms first developed more than 3 billion years ago
What is speciation?
Over time, phenotype of organism changes so much due to natural selection that new species formed
How are 2 new species formed?
2 populations of one species become so different in phenotype, can no longer interbreed to produce fertile offspring
What is a species?
Group of similar organisms that can reproduce to give fertile offspring
What 2 things lead to speciation?
Isolation and natural selection
What is isolation?
Populations of a species are separated
What is isolation occurring due to?
Physical barriers
How is a new species developed due to physical barriers separating populations?
Environment different on each side, different characteristics become more common in each population due to natural selection operating differently on populations
Who independently proposed the theory of evolution by natural selection and published joint writings with Darwin in 1858?
Alfred Russel Wallace
What was Alfred Russel Wallace best known for (2 things)?
Work on warning colouration in animals and his theory of speciation
What led to our current understanding of the theory of speciation (2 things)?
Observations of Alfred Russel Wallace
More evidence over time
Who carried out genetic experiments with pea plants in the mid 19th century?
Gregor Mendel
What 3 important conclusions did Mendel reach about heredity in plants?
1) characteristics in plants determined by ‘hereditary units’
2) hereditary units passed on to offspring unchanged from both parents, one unit from each parent
3) hereditary units dominant or recessive
Why did scientists not understand Mendels findings until after his death?
Didn’t know about genes, DNA and chromosomes
In the early 20th century what did scientists observe about chromosomes?
chromosomes and Mendels ‘units’ behaved in similar ways, led to idea ‘units’ (genes) located on chromosomes
What did scientists observe about chromosomes in the late 19th century?
How chromosomes behaved during cell division
What did scientists discover about genetics in the mid 20th century (2 things)?
Structure of DNA determined
Mechanism of gene function worked out
Why is the development of new antibiotics unlikely to keep up with the emergence of new resistant strains (2 reasons) ?
Costly and slow
What is an example of a ‘superbug’ ’ (resistant to most known antibiotics)?
MRSA
How are antibiotic resistant strains formed and easily spread?
Mutations of bacteria produce new strains
Antibiotics resistant strains survive and reproduce, population rises
Spread as people not immune and no effective treatment
What are 2 pieces of evidence for evolution?
Fossils
Antibiotic resistant bacteria
What are fossils?
Remains of organisms from millions of years ago, found in rocks
What are 3 ways fossils are formed?
1) preservation as one or more of conditions needed for decay are absent
2) parts of organism replaced by minerals as decay
3) casts and impressions
How are casts and impressions of an organism formed?
Buried in soft clay, clay hardens around organism as it decays leaving cast
What are 2 reasons scientists cannot be certain about how life began on earth?
Many early forms of life were soft bodied, left few traces
Fossils destroyed by geological activity
How were living things traditionally classified into groups?
Depend on structure and characteristics
Who developed the first classification system in the 1700s?
Carl Linnaeus
In the Linnaean system what are living things first divided into?
Kingdoms
What are kingdoms subdivided into (6 things) in the Linnaean system?
Phylum
Class
Order
Family
Genus
Species
Which 2 developments led to scientists putting forward new models of classification?
Knowledge of biochemical processes inside organisms developed
Microscopes improved
Who proposed the three domain system of classification?
Carl Woese
What evidence did Carl Woese use to develop the three domain system?
New chemical analysis techniques
What are the 3 domains organisms are divided into?
Archaea
Bacteria
Eukaryota
What are archaea?
Primitive bacteria living in extreme environments
What does Eukaryota include (4 things)?
Protists
Fungi
Plants
Animals
How are organisms named?
By binomial system- genus then species
What are evolutionary trees?
Method used by scientists show how believe organisms are related
What are 2 ways scientists work out evolutionary relationships?
Living organisms- current classification data
Extinct species- fossil data
