B5 Flashcards
Define “active site”
The part of the enzyme which is specific to the substrate and has a complementary shape to it
Define “allele”
A version of a gene (also known as a variant)
Define “antibiotic”
A type of medication that helps cure bacterial disease by killing infective bacteria inside the body
Define “antibiotic resistance”
The ability of a bacteria to become resistant to the treatment that is being used to kill it, i.e. antibiotics.
This provides evidence for evolution
Define “artificial classification”
The classification of organisms based on observable characteristics
Define “asexual reproduction”
A form of reproduction that only involves a single parent and creates genetically identical offspring
Define “biodiversity”
The variety of different organisms living in an ecosystem
Define “chromosome”
A long, coiled molecule of DNA that carries genetic information in the form of genes
Define “continuous variation”
Variation that can take any value between two extremes, e.g. height or weight
Define “DNA (deoxyribonucleic acid)”
A polymer that is made of two strands twisted around each other forming a double helix, and contains all the genetic information
Define “diploid”
A cell with a full set of chromosomes
Define “discontinuous variation”
Variation that can only take discrete values, e.g. eye colour
Define “dominant”
An allele that is always expressed when present, and is represented by a capital letter. Only one copy of it is needed for it to be expressed
Define “enzyme”
A biological catalyst that increases the rate of chemical reactions
Define “evolution”
A change in the inherited characteristics of a population over time, through the process of natural selection, which may result in the formation of new species
Define “extinction”
When all members of a species have died
Define “fossil record”
The remains or impressions of dead organisms found in rocks that are millions of years old.
They provide evidence for evolution
Define “gamete”
Sex cells (sperm and egg cells) with half the usual number of chromosomes.
They are involved in reproduction
Define “gene”
A section of DNA that codes for a specific amino acid sequence which is polymerised to make a specific protein
Define “genetic variation”
The variation in the genes of a species
Define “genome”
The entire genetic material of an organism
Define “genotype”
The genetic makeup of an organism
Define “haploid”
A cell that has half the number of chromosomes
Define “heterozygous”
When an individual has two non-identical alleles of a gene, e.g. Bb
Define “homozygous”
When an individual has two identical alleles of a gene, e.g. bb
Define “meiosis”
A form of cell division that produces gametes. They are not genetically identical and contain half the number of chromosomes
Define “messenger RNA (mRNA)”
An RNA subtype that carries genetic information from the nucleus to the ribosomes during protein synthesis
Define “molecular phylogenetics”
Finding evolutionary relationships between organisms on the basis of their DNA. This method can only be used on fossils that have DNA present
Define “mutation”
A random change in DNA which increases variation. They may have a neutral, beneficial or damaging effect on the phenotype
Define “natural classification”
The classification of organisms based on their evolutionary relationships
Define “natural selection”
The process by which advantageous alleles are passed down to offspring over many generations, increasing the allele frequency. These alleles give rise to phenotypes best suited to the environment
Define “nucleus”
An organelle found in most eukaryotic cells that contains the cell’s genetic material and controls the activities of the cell
Define “phenotype”
The physical characteristics of an organism. It is due to interactions between the genotype and the environment
Define “punnett square”
A grid used to determine potential outcomes of a genetic cross
Define “recessive”
An allele that is only expressed if two copies are present. It is represented by a small letter.
Define “seedbank”
A place where seeds are preserved in order to preserve genetic diversity
Define “sexual reproduction”
Reproduction that involves the fusion of male and female gametes. This method of reproduction produces genetic variation
Define “single gene inheritance”
Inheritance of characteristics that are controlled by a single gene
Define “speciation”
The formation of new species due to the evolution of two reproductively separated populations. This is usually due to geographic isolation
Define “transcription”
The unzipping of the DNA molecule around the gene, copying it to mRNA in the nucleus
Define “translation”
Translating the mRNA sequence to an amino acid sequence during protein synthesis
Give 3 advancements that have improved classification
-developments in microscopy
-developments in biochemistry
-new DNA evidence
Describe the process of natural selection
-populations are naturally varied due to random genetic mutations
-some of these mutations provide a selective advantage
-these organisms survive and reproduce, passing on the successful genes
Give 2 pieces of evidence for evolution
-fossils
-antibiotic resistance
Describe how antibiotic resistance arises
-a random genetic mutation causes bacteria to become resistant to the antibiotic
-when the antibiotic is used, all the bacteria that do not have the muration are killed
-the population containing just the resistant bacteria then begins to grow
Describe how two new species develop from one species
-a population is split where members of the population are isolated
-the environments become different and so natural selection will occur differently
-the two groups will become different enough that they cannot breed to produce fertile offspring anymore
Why was Darwin’s theory only slowly accepted?
Most people still believed God created all life on Earth
There was also insufficient evidence to support his theory
Describe how a mutation in a coding DNA sequence could be detrimental
-the mutation may change the sequence of amino acids in the protein which will change its structure
-this may affect the protein, particularly in specific molecules like enzymes and antibodies
What may happen if there is a mutation in non coding DNA
It may stop transcription and alter the expression of genes
Give one advantage and one disadvantage of sexual reproduction
Advantage: it introduces variation
Disadvantage: it is slower and produces a limited amount of offspring
Give one advantage and one disadvantage of asexual reproduction
Advantage:
-it produces lots of offspring quickly, as only one parent is needed
-if parents are well adapted, the offspring will share an identical set of characteristics, and will benefit
Disadvantage:
-it does not introduce variation and so all offspring are susceptible to the same environmental pressures as the parents
Give two differences between diploid and haploid cells
Diploid cells are body cells, whereas haploid cells are germ cells
Diploid cells have a full set of chromosomes, whereas haploid cells only have half this amount
Give 3 important findings of Gregor Mendel
-organisms inherit hereditary units from their parents
-offspring receive units from both parents and so share traits with both parents
-traits can be passed on but not visible
What discovery lead to people accepting Mendel’s ideas
The discovery of the gene
How does the cloning of a mammal work?
- Nucleus is removed from an egg cell, so it now an enucleated egg
- Nucleus from the body cell is inserted into the egg cell
- The egg cell is stimulated to initiate mitosis
- A genetically identical clone is created
What is the Linnaean System?
A system created by Carl Linnaeus, based on artificial classification. Living things were divided into kingdoms, phylum, class, order, family, genus, species.
What did Carl Woese add to the Linnaean System?
He added 3 large groups called domains above kingdoms:
-archaea: primitive bacteria which live in extreme environments such as hot springs
-bacteria: true bacteria (despite having similar features to archaea)
-eukaryota: organisms who have a nucleus enclosed in membranes, includes the kingdoms protists, fungi, plants and animals
What is the binomial system?
A system which gives each organism a name which is used worldwide. The first part is their genus and the second part is their species
3 ways in which fossils are formed
-parts of organisms that have not decayed because oxygen or moisture were not present, meaning that the microbes that cause decay cannot survive
-parts of the organism such as teeth, shells and bones are replaced by minerals as they decay, forming a rock structure of the original part
-preserved traces such as footprints, burrows and rootlet traces (plants roots) remain due to the ground hardening around them and forming a cast
Why are fossils useful as evidence for evolution?
-can be used to show how the anatomy of organisms have changed over time
-can be used to compare how closely related two organisms are, by looking at the number of similarities they have
-information can be used to create evolutionary trees
How is antibiotic resistance created?
-exposure to antibiotics creates a selection pressure, as those with antibiotic resistant genes survive and those without will die
-as a result, those with antibiotic resistance can reproduce and pass on the advantageous gene to their offspring
-population of antibiotic resistant bacteria increases over time as the gene becomes more common
Key ideas of Darwin’s theory:
-variation exists within species as a result of mutations in DNA
-organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully
-the beneficial characteristics are then passed on to the next generation
-over many generations the frequency of alleles for this advantageous characteristic increases within the population
Name of Darwin’s book?
On the Origin of Species
Define “survival of the fittest”
Only the organisms that have the best characteristics to adjust for that particular environment will survive and reproduce
According to Alfred Wallace, what is the process of speciation?
- Variation exists within a population as a result of genetic mutations.
- Alleles which provide a survival advantage are selected for through natural selection.
- Populations of a species can become isolated, for example through physical barriers such as a rock fall preventing them from breeding together.
- Different alleles may be advantageous in the new environment, leading to them being selected for.
- Over time the selection of different alleles will increase the genetic variation between the two populations.
- When they are no longer able to breed together to produce fertile offspring, a new species has formed.
How can scientists prove that bacteria is evolving?
Antibiotic resistance - they can choose a bacteria that is not resistant to antibiotics, and observe how the entire population will die. At the same time they can give antibiotics to a bacterial species where there is a mutation that allows them to be antibiotic resistant, and compare the differences
Compare continuous and discontinuous variation
Continuous:
-can take any value within a range
-genetic and environmental causes for variation
-controls multiple genes
Discontinuous:
-can only result in discrete values
-only genetic causes for variations
-controls only one or a few genes
How do potato plants reproduce asexually
They produce many tubers, each of which can grow into a new plant
How do spider plants reproduce asexually
They produce long stems with plantlets (tiny pkants) on the end
Give some examples of animals that reproduce asexually
sea anemones and star fish
Why are plant cuttings clones
Because they are genetically identical to its parent
What happens during fertilisation
2 haploid cells join together, to form a diploid cell, known as a zygote
How does the zygote develop into an organism
It divides many times through the process of mitosis
What happens in Stage 1 of meiosis?
Stage 1:
-chromosomes are copied
-chromosomes line up along the middle of the cell in pairs (one from each parent)
-one member of each pair is pulled to opposite ends of the cell
-often when they are pulled apart, sections of DNA are swapped
-the cell then splits in 2, and 2 separate cells are formed
What happens in Stage 2 of meiosis?
-chromosomes line up along the middle of each of the 2 new cells
-this time each chromosome is pulled in half
-a single copy of each chromosome goes to opposite ends of the cell
-each cell then divides into 2, resulting in 4 haploid cells
How does meiosis create genetic variation
It results in cells that are genetically different from each other and from the parent cell
