Changing Allele Frequencies (9.1) Flashcards
State what a particular species is defined by
Its’ genome
State whether or not the genome of individuals within a species varies
Yes.
State what the uniqueness in the genome for species is determined by
Unique allele combinations
State what changes in proportion to population changes
Percentage of individuals with particular alleles
Describe a gene
Sequence of DNA nucleotides
State what a gene codes for
Characteristics within a trait
Describe trait
A particular characteristic of organism
State what slight variations in the code of a gene result in
Different forms of a trait
State a term used to describe slight variation of a gene that result in different forms of a trait
Alleles
Describe alleles
Different forms of a gene
State what the various combinations of an allele in an individual make up
Its’ genotype
Describe genotype
The genetic composition of an individual
State what 2 factors determine the phenotype of an individual
- Genotype
2. Environmental conditions
Describe phenotype
Observable characteristics or traits of an organism, determined by genotype and environmental conditions
State what individuals within a species share
Genome
State whether or not individuals within a species are genetically identical
No
State what provides individuals within a species with genetic uniqueness
Different combinations of alleles
State a term used to describe traits that are controlled by one gene
Monogenic
Describe monogenic
Traits that are controlled by one gene
State the variation of monogenic traits
Discrete variation
Provide an alternative term for discrete variation
Discontinuous
State a term used to describe traits that are controlled by multiple interacting genes
Polygenic
Describe polygenic
Traits that are controlled by multiple genes
State the variation of polygenic traits
Continuous variation
State what a gene is referred to as when it has more than one allele
Polymorphic
Describe polymorphic
A gene that has more than one allele
Provide 1 example of polymorphic genes
Human blood groups
State why an individual can have two alleles for a trait
Diploid cells contain two copies of each chromosome
Describe homozygotes
Individuals with two copies of the same allele
Describe heterozygotes
Individuals with two different alleles
Describe gene pool
All alleles possessed by an entire population, which may be passed on to the next generation
State what the relative proportion of a particular allele in a population is referred to as
Allele frequency
Describe allele frequency
Relative proportion of particular alleles in a population
State how the allele frequency of a population is generally represented
- percentage
- decimal
State the equation to find allele frequency
allele frequency=2(no. homozygotes) + no. heterozygotes) /total no. individuals x100
State whether or not allele frequencies within a gene pol change over time
Yes.
State what all genetic variation between species and between individuals of the same species is a result of
Mutations
Describe mutations
Changes in DNA
State the 3 possible effects of mutations that cannot be repaired on an organism
- no effect
- beneficial effect
- harmful effect
State during what stage mutations often occur randomly
Replication
State 3 structures which may be affected by mutations
- single gene
- multiple genes
- whole chromosomes
State what mutations occur spontaneously as a result of
Mutagens
Describe mutagens
Factors that induce mutations
State what factors that induce mutations are referred to as
Mutagens
State whether or not mutations can be detected and repaired
Yes
State by what medium are mutations detected and repaired
Enzymes
Describe the effect of neutral mutations
No effect on organism survival
Describe the effect of beneficial mutations
Increase the likelihood of survival
Describe the effect of harmful mutations
Decrease the likelihood of survival
Describe somatic mutations
Mutations that occur in body cells
State whether or not somatic mutations can affect an entire species
No. Somatic mutations only affect the individual.
Describe germline mutations
Heritable mutations that affect gametes
State whether or not germline mutations can be passed from one individual to another within a species
Yes. These mutations affect gametes and therefore can be passed on to offspring.
State whether or not germline mutations may bring a new allele into a gene pool
Yes.
State whether or not germline mutations can influence allele frequencies
Yes.
State the 2 overall classifications of mutations (location)
- somatic mutations
2. germline mutations
State the 2 types of point mutations
- Substitution mutations
2. Frameshift mutations
State the 2 major groups of mutations (extensiveness of mutations)
- Point mutations
2. Block mutations
State the 3 major classifications of substitution mutations
- Silent mutations
- Missense mutations
- Nonsense mutations
Genetic sequences are read in sets of how many nucleotides?
Three nucleotides
State what a sequence of three nucleotides on a template DNA strand is referred to as
Triplet
State what a sequence of three nucleotides on a mRNA strand is referred to as
Codon
State what a triplet sequence codes for
Specific amino acids
State how many nucleotides exist
5
State how many possible codons exist
64
State how many amino acids can be produced
20
State whether or not amino acids can be coded for by more than one codon
Yes
State what a mutation that alters, adds or removes a single nucleotides from a sequence of DNA or RNA is referred to as
Point mutation
State what structure/s are affected by a point mutation
Single gene
Describe a substitution mutation
Point mutation - one nucleotide replaced by another
Describe a silent mutation
Substitution mutation - new codon still codes for the same amino acid
Describe a missense mutation
Substitution mutations - amino acid replacement
State whether or not missense mutations still produce a protein
Yes
State what the ability of a produced protein affected by a missense mutation to function correctly is dependent upon
Function of replaced amino acid
Describe a nonsense mutation
Substitution mutation - STOP codon
State the severest situation involving a nonsense mutation is
Mutation occurs early in sequence
Describe frameshift mutations
Nucleotides added/removed from sequence
State the affect of frameshift mutations
Alter every codon in sequence from impacted point onwards to change polypeptide produced
State what frameshift mutations results in a loss of
Functional protein
State the 2 types of frameshift mutations
- Nucleotide insertion
2. Nucleotide deletion
Describe nucleotide insertion
Addition of nucleotides in sequence to push nucleotides back
Describe nucleotide deletion
Removal of nucleotides that is pulled forwards in the sequence
Describe block mutations
Mutations that affect large sections of a chromosome
State whether or not block mutations typically affect multiple genes
Yes
State the 5 main forms of block mutations
- duplication
- deletion
- inversion
- insertion
- translocation
State when block mutations generally occur
During meiosis in eukaryotic cells
State whether or not block mutations can be triggered by mutagens
Yes
Describe duplication mutations
Mutations involving replication of sections of chromosomes
State what duplication mutations often result in
Increase in gene expression
Describe deletion mutations
Removal of section of a chromosome
State what deletion mutations lead to
Disrupted or missing genes
Describe inversion mutations
Section of sequence break off chromosome, rotate 180 and reattach to the same chromosome
State what inversion mutations involve
Two bases or several genes
Describe insertion mutations
Mutations that occur when a section of one chromosome breaks off and attaches to a different chrosome
State what the effects of insertion mutations are dependent on
The retainment of two copies of every gene
Describe translocation mutations
Whole chromosome/section of chromosome attached/exchanged with another chromosome
State what translocation mutations typically interrupt
Normal gene regulation
State what translocation mutations can result in
Cancer
State what always exists between individuals within a population
Variation
State what variation between individuals within a population is a result of
Different combinations of alleles
State what 4 factors influence the variation between individuals in a population
- random mating
- independent assortment
- recombination during gamete formation
- mutations
State what variation between individuals within a population can lead to
Differences in individuals’ phenotypes
Describe selection pressures
Conditions or factors that are likely to influence allele frequency in a population
State what selection processes along with mutation are combined considered
Driving forces of evolution
State the 2 classifications of evolution
- natural environment pressures
2. artificial pressures resulting from selective breeding
Describe natural selection
Influence of environmental pressures on allele frequency in a population
State what environmental selection pressures affect
Survival and reproduction of an organism
State what individuals with the most advantageous phenotypes have
Increased chance of producing fertile offspring
State what examples of environmental selection pressures include:
- climatic conditions
- competition for resources
- mate availability
- predator abundance
Environmental pressures influence allele frequencies of a gene pool because of a number of factors which include:
- variation
- reproduction
- survival
- environmental selection pressures
Describe adaptive value
A measure of how well suited a particular phenotype is to a particular environmental condition
State what high adaptive values provide an individual with
Advantage over individuals with a lower adaptive value
State what high and low adaptive value and the relationship to survival is often considered in parallel with
‘Survival of the fittest’ phenomenon
State what having an advantageous trait generally means for the individual
Individual is more likely to survive to reproduce and pass their alleles on to the next generation
State what alleles of the advantageous traits tend to do within the gene pool
Increase
State what alleles of disadvantageous traits tend to do within the gene pool
Decrease
State 3 examples of gene flow
- interbreeding between different populations
- seed dispersal in plants
- migration
State when gene pools may change
When new individuals join the population from a different gene pool or when some individuals leave a population
Describe gene flow
Movement of alleles between individuals of different populations
State what occurs when gene flow exists between two different populations
Gene pools may remain fairly similar
State what occurs when gene flow is not possible between two different populations
Gene pools are said to be ‘isolated’
State what may occur to allele frequencies in a gene pool
Change randomly over time as a result of chance events
Describe genetic drift
Random changes of allele frequencies in a gene pool due to chance events
State where genetic drifting is more clearly seen
Small population with little or no gene flow
State why genetic drifting is emphasised by small population with minimal gene flow
Death of one individual can significantly alter the allele frequencies
State what generally occurs as a result of genetic drift in small populations
Loss of genetic diversity over time as alleles are lost from the gene pool
State the 2 major types of genetic drift
- bottleneck effect
2. founder effect
State what the number of individuals in a population can be drastically and quickly reduced as a result of
Random event
Provide an example of a random event that can result in the dramatic and drastic reduction of the number of individuals in a population
Natural disaster
Describe the bottleneck effect
Result of removal of a large proportion of a population from their habitat by chance
State what the bottleneck effect results in
Reduced possible reproductive pairings
State what reduced reproductive pairings results in
High levels of inbreeding
State what high levels of inbreeding results in
Reduced variation in the population and increase in numbers of homozygous individulas
The smaller the population the _____ the effect of genetic drift
Greater
State whether or not alleles can be immediately lost from the gene pool after a natural disaster
Yes
State whether or not alleles can be ‘bred out’ of the gene pool in only a few generations after a natural disaster
Yes
State what the lowered variation in a gene pool as a result of the bottleneck effect will make the population more vulnerable to
Environmental change
Describe the founder effect
Dispersion of a small portion of a population to a new location which results in a genetic isolation
State what the founder effect results in
High levels of inbreeding
Describe interbreeding
Mating of two different species
Describe inbreeding
Mating of individuals that are genetically related
Describe heterozygote advantage
Heterozygous genotype has higher fitness than homozygous dominant/homozygous recessive genotype
Describe macromutation
Mutation producing phenotype well outside the range of variation previously existing.
State what natural selection acts upon
Organism’s phenotype
State when genetic drift is most likely to be observed
When the population is small
State the two things that can change allele frequencies
- Genetic mutations
2. Environmental pressures
Describe adaptive radiation
Organisms diversify rapidly from ancestral species into new forms
Describe biodiversity
A measure of variation at the genetic, species, and ecosystem level
State between what classification of chromosomes translocation mutations occur
Non-homologous chromosomes
