Unit 10 Test Flashcards
Reproduction Division
Meiosis splits the chromosomes in half, therefore, creating a haploid gamete. The diploid number is then reconstituted by fertilization and/or sexual reproduction.
Haploid vs. Diploid
Haploid cells have one set of chromosomes and diploid cells have two sets of chromosomes.
Genetic Rearrangement (Crossing Over vs. Random Assortment)
Crossing over is the exchange of DNA between non-sister homologous chromatids. Random Assortment is when chromosomes line up in a random orientation during metaphase I.
Phases of Meiosis
Meiosis I: The first meiotic division functions to separate the homologous chromosomes. Reduction division that results in the formation of 2 haploid daughter cells.
Meiosis I Phases: Prophase I, Metaphase I, Anaphase I, and Telophase I
Meiosis II: The second meiotic division functions to separate the sister chromatids.
Meiosis II Phases: Prophase II, Metaphase II, Anaphase II, and Telophase II
S-Phase What happens?
This is a phase in interphase in which DNA is replicated and chromosomes will consist of genetically identical sister chromatids.
What kinds of cells does meiosis make?
Meiosis produces four haploid gametes that are genetically unique.
Synapsis and the Chiasmata
Synapsis is the stage during prophase one in which homologous chromosomes become connected. Chiasmata are physical connections in which non-sister chromatids may recombine with their homologous partner.
Mendel’s Law of Segregation
All sexually reproducing organisms inherit one copy of a gene (i.e. allele) from each parent
Mendel’s Law of Independent Assortment
Inheritance of alleles for one gene occurs independently of all other genes
Dihybrids
Gametes use the foil method:
F- First
O- Out
I- In
L- Last
Linked vs. Unlinked
Linked genes are genes whose loci are all on the same chromosome.
Consequently, linked genes function as a single inheritable unit during meiosis.
Unlinked genes- These will form all phenotypic combinations via random assortment.
Linked genes- These will only produce recombinant phenotypes when crossing over occurs
Thomas Morgan
Thomas Morgan developed the concept of gene linkage via breeding experiments with fruit flies (Drosophila).
Monogenic vs Polygenic traits
Monogenic traits- are controlled by a single gene and show discrete variation. Examples of monogenic traits include the presence of attached earlobes / freckles.
Polygenic traits are controlled by multiple genes and show continuous variation. Examples of polygenic traits include human height, weight and skin colour.
Gene Pools
Gene pools represent the sum total of alleles for all genes present in a population. Gene pools change via evolution.
Genetic Drift
Genetic drift is a change in the composition of a gene pool due to chance events.
Population Bottle Necks
Population bottlenecks occur when an event reduces population size by an order of magnitude.The surviving population is smaller and has less genetic variability.
Founder Effect
The founder effect occurs when a new population is established by a small subset of a larger population (resulting in less genetic variation and greater genetic drift).
Speciation: Allopatric vs Sympatric
Types of Selection-
Stabilising: An intermediate phenotype is favoured over the extremes
Directional: One phenotypic extreme is selected at the expense of another
Disruptive: Both extremes are selected over an intermediate phenotype
Allopatric speciation: Divergence due to geographical isolation
Sympatric speciation: Divergence within the same geographical location
Polyploidy
If sex cells fail to undergo cytokinesis, chromosome number doubles in gametes.
Phyletic Gradualism vs Punctuated Equilibrium
This is the pace of speciation:
Phyletic Gradualism-Speciation results from continuous change occurring at a constant pace.
Arises as a result of the gradual accumulation of genetic mutations over time.
Punctuated Equilibrium-Speciation results from abrupt bursts that intersperse periods of stability.
Equilibrium is punctuated by rapid environmental changes.
Chi Squared Test
The Steps in a Chi Squared Test are:
1. Identify a hypothesis (null hypothesis versus alternative hypothesis)
- Construct a table of frequencies (observed versus expected data)
- Apply the chi-squared formula to test for differences in the phenotypic ratios
- Determine the degree of freedom and identify the p value (should be p<0.05)
Equation for test: (O-E)²/E
