Flashcards in Genetics And Evolution Deck (77):
What are genes?
DNA sequences that code for heritable traits that can be passed from one generation to the next.
What is a genotype?
The genetic combination possessed by and individual
What is a phenotype?
The manifestation of a given genotype as an observable trait
What does it mean if a gene is dominant?
Only one copy of the allele is needed to express the phenotype. It is usually represented with a capital letter.
What does it mean if an allele is recessive?
Two copies are needed of the allele in order to be expressed and is usually represented with a lower case letter.
What does homozygous mean?
That both alleles are the same for a given gene
What does heterozygous mean?
That the alleles are different
What does hemizygous mean?
A situation where there is only one allele for a gene, such like the X chromosome in males
What is complete dominance?
When there is only one dominant and one recessive allele for a given gene. The dominant gene will mask the recessive one.
What is codominance?
When there is more than one dominant allele for a given gene, both genes will be expressed simultaneously
What is incomplete dominance?
When a heterozygote expresses a phenotype that is in between two alleles. An example is a red flower crossed with a white flower will produce a pink flower
What is penetrance?
The amount of individuals in the population that carries the genotype and expresses the phenotype
Explain full penetrance
100 percent of individuals with this allele will show the phenotype
What is high penetrance?
When most but not all of the individuals in a population show the phenotype
What is expressivity?
When there are different phenotype that come from the same genotype
What happens if expressivity is constant?
Then all the individuals with the same genotype will have the same phenotype
If expressivity is variable then?
The individuals with the same genotype could have different phenotypes
Compare and contrast penetrance and expressivity.
Penetrance is the proportion of the population with a genotype who actually express the phenotype. (Population parameter)
Expressivity is the different manifestations that come from the same genotype throughout a population. (Individual parameter)
What is Mendel's first law?
The law of segregation which states that there are two alleles for each gene and they segregate during meiosis resulting in gametes that have only one allele for each trait.
What is Mendel's second law?
Law of independent assortment which states that the inheritance of one allele does not influence the probability of inheriting an allele for another trait
What allows for greater genetic diversity?
Segregation and independent assortment
What is a mutation?
A change in the DNA sequence that results in a mutant allele
What does wild type mean?
It's the normal or natural version of an allele
What are substances that cause mutations called?
What are all the nucleotide level mutations?
What is a point mutation?
When one nucleotide in DNA is changed for another
What are the three types of point mutations?
What is a silent mutation?
Is when the change in the nucleotide has no effect on the final protein that's produced. Most likely occurs in the third nucleotide
What is a missense mutation?
The change in the nucleotide causes a different amino acid in the final product
What is a nonsense mutation?
The change causes a stop codon instead of the normal amino acid in the final protein
What are frameshift mutations?
When nucleotides are inserted or deleted from the genome
What results from a frameshift mutation?
When a nucleotide is inserted or deleted it will shift the reading frame which will change the amino acid sequence
What are the two frameshift mutations?
Insertions or deletions
What are chromosomal mutations?
They are larger scale mutations where large DNA segments are affected
If expressivity is variable, then
Individuals with the same genotype could have different phenotype
What are the types of chromosomal mutations?
What is a deletion mutation?
When a large segment of DNA is lost from a chromosome.
What is a duplication mutation?
When a segment of DNA is copied multiple times in the genome
What is an inversion mutation?
When a segment of DNA is reversed within the chromosome
What is an insertion mutation?
When a segment of DNA is moved from one chromosome to another
What is a translocation mutation?
When a segment of DNA from one chromosome is switched with a segment from another chromosome
What are inborn errors of metabolism?
They are defects in the genes that are needed for metabolism
What is leakage?
It is the flow of genes between species.
What is genetic drift?
The changes in the composition of the gene pool due to chance
Genetic drift is more heavily seen in what kind of populations?
What is the founder effect?
A more extreme case of genetic drift where a small population will become reproductively isolated from other populations
What does bottleneck mean?
It's a drastically and sudden reduction in the size of a population
What is inbreeding?
Mating between two genetically identical individuals
What are three ways that genetic diversity is reduced?
1. Genetic drift
2. The founder effect
What is inbreeding depression?
The loss of genetic variation that this a reduction in the fitness of the population
What is outbreeding or outcrossing?
The introduction of unrelated individuals into a breeding group
What is a Punnett square?
A diagram that predicts the relative genotypic and phenotypic frequencies that will result from the crossing of two individuals
What is a monohybrid?
When only one trait is being studied
What is the P generation and the F generation?
P generation are the individuals being crossed and the F generation is the offspring
What ratio is produced when two heterozygotes are crossed?
What is a test cross or a back cross?
A test used to determine the genotype of the parent based on the phenotype of the offspring
What is a dihybrid cross and what are the ratios?
A dihybrid cross is on that accounts for two different genes.
Which gender is more popular for sex linked traits?
Males because they only have one X chromosome
What is recombination frequency?
The likelihood that two alleles are separated from each other during crossing over. The closer the genes are to each other, the less likely they will be separated.
What is allele frequency?
How often an allele appears in a population
What criteria must be met in order for a population to be in hardy-Weinberg equilibrium?
1. The population is very large
2. There are no mutations that affect the gene pool
3. Mating between individuals is random
4. There is no migration if individuals into or out of the population
5. The genes in the population are all equally successful at reproducing
What is natural selection?
Theory that there are certain characteristics that are possessed by individuals within a species that may help those individuals to have a greater reproductive success and thus are passed on to offspring
What is differential reproduction?
When a mutation or recombination results in a change that is favorable to the organism's reproductive success, and that chance is more likely to be passed onto the next generation
What is inclusive fitness?
A measure of an organism's success in the population. It is based on the number of offspring, success in supporting offspring, and the ability of the offspring to then support others.
What is punctuated equilibrium?
It suggests that changes in some species occur in rapid bursts rather than evenly over time
What is directional selection?
It moves the average phenotypes towards a more extreme one
What is disruptive selection?
It moves towards two different phenotypes at the extremes and can lead to speciation
What is adaptive radiation?
Is the rapid emergence of multiple species from a common ancestor, each of which occupies its own niche.
What is polymorphism?
Naturally occurring differences in form between members of the same population
What is the definition of a species?
The largest group of organisms capable of breeding to form fertile offspring
What is speciation?
The formation of a new species through evolution
What is divergent evolution?
The independent development of dissimilar characteristics in two or more lineages sharing a common ancestor
What is parallel evolution?
The process of how related species evolve in similar ways for a long period of time in response to analogous environmental selection pressures
What is convergent evolution?
The independent development of similar characteristics in two or more lineages not sharing a common ancestor
How is the rate of evolution measured?
By the rate of change of a genotype over a period of time and is related to the severity of the evolutionary pressures put on the species
What is the molecular clock model?
The degree of similarity in the genome is correlated to the amount of time since two species split off from the same common ancestor