Changes In Genetic Makeup Of A Population Flashcards
What is a dominant gene?
A gene where only 1 copy of the allele is required for the trait to be expressed
What is a recessive gene?
A gene where 2 copies of the allele are required for the trait to be expressed
Heterozygote gene
Ww, i.e. 2 different alleles
Homozygote gene
WW, i.e. 2 copies of the same allele
What determines if 2 organisms are part of the same species?
If they can sexually reproduce to create viable and fertile offspring
Define a population
A group of the same species living in a specific population
Define a Gene pool
All the different genetic material found within a population
Define allele frequency
The proportion of an allele in a population
Define Allele
An alternative form of a gene
What is the difference between a genotype and a phenotype?
Genotype is the genetic makeup of an organism for a specific trait, whereas phenotype is how that genotype interacts with the organism’s environment resulting in various characteristics
How is allele frequency calculated?
(Total number of alleles for a specific gene)/(total number of alleles for that gene in a population)
How are new alleles formed?
Through genetic mutations
Why is genetic variation in a species important?
It increases that species chance of survival, as diversity increases the chance not all the of the population will be killed by new selection pressures
What are genetic mutations?
Random unpredictable change that occurs to genetic material
Why are mutations important?
They provide a new source of alleles
Are mutations good or bad?
They can be good as they may provide a new source of alleles, but may also have negative effects like cancer.
What is the difference between a spontaneous and an induced mutation?
Spontaneous mutations occur randomly due to errors in DNA replication whereas induced mutations are brought on by environmental factors
What is the difference between a somatic and germline mutation?
Germline mutations occur in organisms reproductive tissue and can be passed down to the organisms offspring, whereas somatic mutations occur in a tissue other than reproductive tissue and cannot be inherited.
What type of mutation can be inherited and why?
Germline mutations as they occur in reproductive tissue and can be passed onto offspring during fertilization
What is the difference between a polyploidy and aneuploidy chromosomal abnormality?
Aneuploidy is the change in number of chromosomes by a factor of 1 and only affects 1 set, whereas polyploidy is the change in number of chromosomes in every set
What is the difference between block mutations and point mutations?
Block mutations are changes that occur to whole sections of chromosomes, whereas point mutations are changes to only 1 single base pair in the DNA sequence
What is a block inversion mutation?
When a section of a chromosome is flipped upside down/inverted
What is a block deletion mutation?
Where a section of a chromosome is deleted
What is a block duplication mutation?
Where a section of a chromosome is duplicated so that there are 2
identical sections joined together
What is a block insertion mutation?
when a section of DNA from one chromosome is inserted in the middle of
another
What is a block translocation mutation?
when a section of DNA from one chromosome switches with a section of
DNA from another chromosome
What is the difference between a substitution and frame shift mutation?
A substitution mutation is where a single base is substituted for another, whereas a frame shift mutation is where a single base is either added or deleted
What kind of mutation is a silent mutation?
A point substitution mutation
What is a silent mutation?
When a base is substituted in place of another, but the gene will still code for the same amino acid sequence as the original base
What is a Missense mutation?
A base is substituted for another, which results in a change in the amino acid
sequence
What is a nonsense mutation?
1 base is substituted for another, whereby the mutated triplet in the DNA now codes for a stop codon, resulting in a shorter amino acid chain.
What kind of mutation will result in a shortened amino acid chain?
A nonsense mutation
What effect do frame shift mutations have on the amino acid the gene codes for?
All the triplet codons after the mutation will be altered until the end of the chain, resulting in a drastically different protein.
How many amino acids do substitution mutations affect?
1
What is the first step in natural selection?
A variation existing in a trait within a population
What is the second step in natural selection?
A selection pressure act on the population and members with a selective advantage are more likely to survive
What is the third step in natural selection?
The members with a selective advantage are more likely to survive and reproduce with the frequency of the allele that correlates to the trait increasing over time
Why is variation important in a population?
It increases the chance the species will survive in the presence of a selection pressure, as some members may be able to survive due to their different traits
What is gene flow?
The movement of alleles between populations of the same species
What is immigration?
when individuals enter a population
What is emigration?
When individuals leave a population
Define genetic drift
When a populations allele frequency is changed due to a random event
What is the founder effect?
When a small group of organisms leaves the population to form a new one that isn’t genetically representative of the original
What is the bottleneck effect?
When there is a sudden change in allele frequency due to the reduction in a population as a result of a random event.
What occurs during allopatric speciation?
When part 2 groups from the same population become isolated from each other with no gene flow, and face different selection pressures resulting in the development of new traits
What are the 3 steps in allopatric speciation?
isolation -> divergence ->reproductive isolation
How is selective breeding different from natural selection?
Humans act as the selection pressure
What are the steps in selective breeding?
Genetic variation exists in a population resulting in different traits. Humans select members that have desirable traits and breed them together to produce offspring with that desirable trait. The gene pool is then reduced but a higher proportion of the population will have the desirable trait.
What are some reproductive isolating mechanisms?
• Temporal – species don’t have a chance to interact with each other because they may breed in different seasons or be nocturnal
• Behavioral – Species may have different mating calls or rituals
• Structural – species may have different genitalia that is not compatible with each other
• The chromosomes from the different species may be too different so that they would be unable to
pair up during meiosis, making the offspring sterile (hybrid sterility)
What size population are affected by genetic drift?
Small populations
