Genetics Flashcards
What is an allele?
Alternative types of genes
What is genetics?
The scientific study of heredity
What is a genotype?
The genetic makeup of an organism, visible and non-expressed alleles
What is a phenotype?
The physical traits show in an organisms
What is heterozygous?
When an organism has two different alleles for a given trait/gene
- Having two different alleles for the same trait
What is homozygous dominant?
When an organism has two identical alleles for a trait, this allele is dominant
What is homozygous recessive?
When an organism has two identical alleles for a trait, this allele is recessive.
What is incomplete dominance?
When a blended phenotype is created by one allele not being completely dominant over the other
What are the 4 types of cross diagrams?
- Monohybrid
- Dihybrid
- Test
- Reciprocal
What is the ratio for the combination AaBb x AaBb?
9:3:3:1
What is the dominance % of an offspring if one of its parents had AABB?
(AABB x n)
100% dominant
What is the ratio for AaBb x aabb?
4:4:4:4
What is a test cross?
Taking a dominant organism and finding if its other allele is recessive or dominant by comparing offspring to possible punnet squares
- Compares a dominant organism to a homozygous recessive: (An x aa)
What is a proto-oncogene?
A normal gene that when mutated, becomes an oncogene,
- Regulates the cell cycle
What is an oncogene?
A mutation of the proto-oncogene
What is locus?
The position of a gene in an allele
What are autosomes?
All of the numbered pairs of chromosomes in a karyotype,
- Humans have 22 pairs of autosomes and 1 pair of sex chromosomes
What does dihybrid mean?
The result of two parents breeding with two different traits.
What is a dominant trait?
A trait that becomes a phenotype if there is at least one allele for this trait
What is homozygous?
Having two identical alleles for a given gene on the homologous chromosome
What is hybridization?
Breeding two individuals of two different traits in the hope of a desirable result
What is independent assortment?
The randomness of having an allele is not affected by having another specific allele,
- Every combination of alleles is equally likely to occur
What is the law of segregation?
Genes are spread out equally across gametes so that offspring have an equal chance to have any random selection of alleles
What is monohybrid?
The combinations of alleles possible from two parents when looking at a single trait
What is a recessive trait?
Traits that are not expressed when paired with a dominant trait
What is a reciprocal cross?
2 Crosses, one representing the male gamete from an organism and the female gamete from the other (1st punnet square), and another when the first organism provides the female gamete instead and the second provides the male gamete (2nd punnet square)
What is a trait?
The variation in the physical appearance of a heritable characteristic
- Different types of inheritable characteristics
What is a pedigree?
A diagram showing the occurrence of a genetic trait in several generations of a family,
- Genetic family tree
What is recombination frequency?
The average number of crossovers between two alleles
What is X inactivation?
Condensation of X chromosomes into Barr bodies during embryonic development.
- This compensates for the double genetic dose
- A female with a phenotype in the X chromosome will deactivate the other X chromosome in order to prevent a double genetic dose
What is codominance?
When more than one type of allele has complete dominance
- Phenotypes for both traits are displayed: spotted cows have two colours with codominance so they are both displayed with patches of different colours
What is dominant lethal?
An allele that is dominant and lethal so affects individuals who are heterozygous or homozygous dominant
- Can be transmitted if offspring are fertilized before the individual’s death (the lethal phenotype displays)
What is epistasis?
When one gene affects the phenotype of a separate gene
What is incomplete dominance?
When neither allele is completely dominant so the phenotypes merge
- Red + white = pink
What is linkage?
When different traits are inherited together more often
- Freckles and ginger hair
What is a map unit?
In chromosomes mapping, an increment of 1% in the frequency of the crossing over
What is mitochondrial inheritance?
When a trait is inherited only from the mother, the trait is from mitochondrial DNA
What is pleiotropy?
The ability of a single gene to have multiple effects
What is recessive lethal?
When an allele carries a recessive trait that is lethal, only affecting the individual when homozygous recessive
- The heterozygous alternatives may have some other non-lethal changes to the phenotype
What are sex-linked alleles?
When a trait is controlled by genes from the sex chromosomes
What is a polygenic trait?
Characteristics that are influenced by more than one pair of genes
What are multiple alleles?
A gene that has more than two alleles:
- lots of different eye colours
What is an autosomal dominant trait?
Having a single allele of this trait is enough to display its phenotype
What is an autosomal recessive trait?
A trait that is recessive, though both alleles must be recessive for it to show its phenotype
What is the Hardy-Weinberg principle?
A population’s allele and genotype frequencies are constant unless there is some type of evolutionary force acting on them
What is a population?
- A group of the same species
- Can breed with each other
- Have fertile offspring
What are the 5 assumptions of the Hardy-Weinberg equilibrium?
- No selection
- random mating
- No mutations
- No migration
- Large population
What happens if the 5 assumptions of the Hardy-Weinberg are not met?
The allele frequency will change over time
Why do we use the Hardy-Weinberg even though it is unrealistic?
It is like a constant variable for an experiment, something that you can compare a real evolving population to.
- A baseline to compare how an evolving population to compare to one that remains constant without any evolution acting on it
What is the Hardy-Weinberg equation for allele frequency?
q + p = 1
q= dominant
p = Recessive
What is the Hardy-Weinberg equation for genotype frequency?
p^2 + 2pq + q^2 = 1 q = dominant p = recessive - q^2 = aa homozygous frequency - p^2 = AA homozygous frequency - 2pq = Aa Heterozygous frequency
What is true breeding?
When the offspring recieve the same phenotype as their parents every time, the parents must both be homozygous for that trait
