Genetics And Evolution Flashcards
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?
Mutagens
What are all the nucleotide level mutations?
- Silent
- Missense
- Nonsense
- Insertion
- Deletion
What is a point mutation?
When one nucleotide in DNA is changed for another
What are the three types of point mutations?
- Silent
- Missense
- Nonsense
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