Inheritance Flashcards
What are gametes?
Haploid (1n) sex cells.
Describe sexual reproduction in animals, and what the n (number of sets of chromosomes) is in each stage.
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Describe sexual reproduction and the alternation of generations in plants, and what the n (number of sets of chromosomes) is in each stage.
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What is the alternation of generations?
A pattern of reproduction occurring in the life cycles of many lower plants and some invertebrates, involving a regular alternation between two distinct forms. The generations are alternately sexual and asexual.
What does meiosis do?
It produces haploid gametes, being sperm or egg cells.
What happens during the first division of meiosis (M1)?
The chromosome number is reduced from diploid to haploid by separating homologous chromosomes.
What happens during the second division (similar to mitosis) of meiosis (M2)?
The chromatids are separated into four haploid gametes per starting cell.
What is ‘crossing over’ and when does it occur?
Crossing over is a recombination event that occurs at different sites along the chromosome. It occurs during meiosis I.
What happens if meiosis goes wrong?
In some cases chromosomes fail to separate properly during meiosis 1 and 2, this results in gametes having +/- 1 chromosome meaning the zygote will be aneuploid (2n +/-1) which can lead to things such as down syndrome.
What are the principles of heridity?
- Inherited characteristics are determined by genes
- All individuals of a species have the same base set of genes (variation due to gene mutation)
- Variants of the same gene - alleles - account for variant traits.
What are Mendel’s principles?
Dominance - phenotypes depend on inheritance of dominant and recessive alleles.
Segregation - the two alleles separate from each other in gametes
independent assortment - genes segregate independently when gametes are formed.
What is a test cross?
When an unknown individual is crossed with a recessive homozygous individual to determine the genotype of the unknown individual.
What is true breeding?
An organisms that always passes down a particular phenotypic trait to its offspring.
What is the P generation, F1 generation, and f2 generation?
P generation - Parental generation
F1 generation - First filial generation
F2 generation - second filial generation
What is additive (polygenic) inheritance?
When multiple genes can exert additive effects on the same trait - quantitative traits.
What is genetic mapping? and what are the concepts that it relies upon?
Genetic mapping is a part of genetic analysis used to determine the location and relative order of genes on a chromosome. It relies upon genetic linkage and genetic recombination.
What are the ratios between recombinant and parental phenotypes in genes that are tightly linked, weakly linked, and unlinked?
Tightly linked genes - Recombinant genotypes are rare, parental genotypes are abundant
Weakly linked genes - Recombinant genotypes are less rare, parental genotypes are less abundant
Unlinked genes - “Recombinant” and parental genotypes are equal
What is the equation to determine recombination frequency?
Recombination frequency = # of total recombinants/# of total offspring x 100%
What is incomplete dominance?
When heterozygous individuals exhibit an intermediate phenotype
What is a co-dominant trait?
When heterozygous individuals exhibit both phenotypes
What is epistasis?
When two or more genes interact to yield a trait.
What is the extension locus?
In relation to epistasis the extension locus is the locus on the chromosome where colour is altered.
What is the equation for phenotypic variation of a population? and what do each of the terms mean?
Vp = Vg +Ve +Vge
Vg - Variation due to genotype
Ve - Variation due to environment
Vge - Variation due to the interaction between genotype and the environment
What is the equation for heritability? and what do it’s values correspond to?
H^2 = Vg/Vp
When H^2 = 1 genotype completely determines phenotype
When H^2 = 0 genotype has no effect on phenotype
