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11.1
- Genetics : scientific study of heredity
- trait : specific characteristic of an individual
- hybrid : offspring of crosses between parents with different traits
- genes : sequence of dna that determines a trait / factors that R passed from parent 2 offspring
- alleles : the different forms of a gene
- principle of dominance: some alleles R dominant & others R recessive
11.2
- Probability : the likelihood that a particular event will occur.
- Homozygous : 2 identical alleles 4 a trait / TT , tt
- Heterozygous : 2 different alleles 4 a trait / Tt
- Phenotype: physical description of the allels
- Genotype : alleles letter combination / TT , Tt , tt
- The principle of independent assortment : genes 4 different traits can segregate independently during the formation of gametes
11.3
- Incomplete dominance : when the offspring’s phenotype is a combination of the parents phenotype / red(RR) * white(WW) = pink (RW)/1 allele is not completely dominant over another
- Codominance: when both alleles can be observed in a phenotype / phenotypes produced by both alleles are clearly expressed / a chicken that has black & white feathers
- multiple alleles : A gene with more than two alleles / blood groups
- polygenic traits : Traits controlled by two or more genes / when multiple genes determine the phenotype of a trait / skin color : white and black
11.4
- Diploid Cells : A cell that contains both sets of homologous chromosomes / 2 sets of chromosomes
- Haploid cell: A cell that contains one set of homologous chromosomes / 1 set of chromosomes
- Meiosis :is a process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
17.1
- evolution : any change in the relative frequency of alleles in the gene pool of a population over time.
- Genepool : all genes that are present in a population
- Allele frequency : the percentage of a specific allele of a given gene locus
- single-gene trait : a trait controlled by only one gene
- Polygenic traits : traits controlled by two or more genes.
17.2
- Directional selection : when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end
- Stabilizing selection : when individuals near the center of the curve have higher fitness than individuals at either end
- Disruptive selection : when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle
- Genetic drift : random change in allele frequency
- bottleneck effect : change in allele frequency following a dramatic reduction in the size of a population.
- founder effect : when allele frequencies change as a result of the migration of a small subgroup of a population.
17.3
- Speciation: the formation of a new species.
Key points :
11.1
- Gregor Mendel founded the modern science of genetics
- An individual’s characteristics are determined by factors that are passed from one parental generation to the next.
11.3
- Environmental conditions can affect gene expression
17.1
- Natural selection acts directly on phenotype, not genotype.
- Three sources of genetic variation are:
- 1 mutation
- genetic recombination during sexual reproduction
- lateral gene transfer
17.2
- conditions required to maintain genetic equilibrium:
- The population must be very large;
- There can be no mutations;
- There must be random mating;
- There can be no movement into or out of the population
- No natural selection.
17.3
- Reproductive isolation :when a population splits into two groups and the two populations no longer interbreed
- behavioral isolation : when two populations that are capable of interbreeding develop differences in courtship rituals or other behaviors
- geographic isolation : when two populations are separated by geographic barriers such as rivers, mountains, or bodies of water
- Temporal isolation : when two or more species reproduce at different times.
11.4
Lesson 11-1
1. Where does an organism get its unique characteristics?
An individual’s characteristics are determined by factors that are passed from one parental generation to the next.
2. How are different forms of a gene distributed to offspring?
During gamete formation, the alleles for each gene segregate from each other, so that each gamete carries only one allele for each gene.
Lesson 11-2
1. How can we use probability to predict traits?
Punnett squares use mathematical probability to help predict the genotype and phenotype combinations in genetic crosses.
2. How do alleles segregate when more than one gene is involved?
The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes.
3. What did Mendel contribute to our understanding of genetics?
Mendel’s principles of heredity, observed through patterns of inheritance, form the basis of modern genetics.
geographic isolation, changes in the new population’s gene pool, behavioral isolation and ecological competition
Lesson 11-3
1. What are some exceptions to Mendel’s principles?
I) Incomplete Dominance
II) Codominance
III) Multiple alleles
IV) Polygenic Traits
2. Does the environment have a role in how genes determine traits?
Environmental conditions can affect gene expression and influence genetically determined traits.
Lesson 11-4
1. How many sets of genes do multicellular organisms inherit?
The diploid cells of most adult organisms contain two complete sets of inherited chromosomes and two complete sets of genes.
2. What events occur during each phase of meiosis?
I) Prophase I – each replicated chromosome pairs with its corresponding homologous chromosome.
II) Metaphase I – pairs homologous chromosomes line up across the center of the cell.
III) Anaphase I – spindle fibers pull each homologous chromosome pair toward opposite ends of the cell.
IV) Telophase I – a nuclear membrane forms around each cluster of chromosomes. Cytokinesis follows telophase I, forming two new cells.
V) Prophase II – chromosomes become visible.
VI) The final four phases of meiosis II are similar to those in meiosis I, however, the result is four haploid daughter cells.
3. How is meiosis different from mitosis?
In mitosis, when two sets of genetic material separate, each daughter cell receives one complete set of chromosomes. In meiosis, homologous chromosomes line up and then move to separate daughter cells.
Mitosis does not normally change the chromosome number of the original cell. This is not the case for meiosis, which reduces the chromosome number by half.
4. How can two alleles from different genes be inherited together?
Alleles of different genes tend to be inherited together from one generation to the next when those genes are located on the same chromosome.
Lesson 17-1
1. How is evolution defined in genetic terms?
Evolution is any change in the relative frequency of alleles in the gene pool of a population over time.
2. What are the sources of genetic variation?
I) Mutation
II) Genetic recombination during sexual reproduction
III) Lateral gene transfer
3. What determines the number of phenotypes for a given trait?
The number of phenotypes produced for a trait depends on how many genes control the trait.
Lesson 17-2
1. How does natural selection affect single-gene and polygenic traits?
Natural selection on single-gene traits can lead to changes in allele frequencies and, thus, to changes in phenotype frequencies.
Natural Selection on polygenic traits can affect the distributions of phenotypes in three ways: Directional Selection, Stabilizing Selection, Disruptive Selection.
2. What is genetic drift?
In small populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time, a series of chance occurerences can cause an allele to become more or less common in a population.
3. What conditions are required to maintain genetic equilibrium?
I) Large population
II) No mutations
III) Random mating
IV) No movement in or out of the population (immigration or emigration)
V) No natural selection
Lesson 17-3
1. What types of isolation lead to the formation of new species?
When populations become reproductively isolated, they can evolve into two separate species. Reproductive isolation can develop in a variety of ways including:
I) Behavioral isolation
II) Geographic isolation
III) Temporal isolation
2. What did the Grants’ scientific investigation show about Galapagos finches?
The Grants documented that natural selection takes place frequently – and sometimes rapidly.
The Grants’ work also shows that variation within a species increases the likelihood that the species can adapt and survive environmental change.
3. What is a current hypothesis about Galapagos finch speciation?
Speciation in Galapagos finches occurred by founding of a new population,