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Allelealternative forms of a gene found on the same locus on a chromosome |
Homozygous2 identical alleles | BB (homozygous dominant) | bb (homozygous recessive) |
Law of Segregation (Random Fertilization)two copies of each hereditary factor (allele) segregate | offspring acquire one factor from each parent |
Crossing Overthe reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis |
Codominanceblood groups | both alleles are expressed in the heterozygote | neither is dominant or recessive, but there is no blending |
Pedigree Analysispedigree: family tree | males: squares | females: circles | shaded: showing exhibited trait | half shaded: carrier |
Nature vs. Nurturenature: genetically determined | nurture: environmentally determined |
Genes Inherited Located on Sex Chromosomesin humans: | ~ females: XX | ~ males: XY | examples of sex linked disorders: | ~ duchenne muscular dystrophy | ~ hemophilia | ~ colorblindness |
Calculate Recombination Frequencyif RF is >50%, the traits are considered to be independently assorted and on DIFFERENT chromosomes | if RF is <50%, the traits are on the SAME chromosome (any variants from the parent type are due to crossing over) |
Asexual Reproductiontwo identical cells | "clones" |
Examples of Asexual ReproductionFission: bacteria | Fragmentation: starfish | Budding: coral |
Termshaploid: cells that contain a single set of chromosomes in an egg or sperm cell (23 gametes) | diploid: two complete sets of chromosomes (46 somatic) | triploid: Extra set of chromosomes (69 chromosomes) |
Why are triploid plants seedless?3 sets of chromosomes make it very unlikely for meiosis to successfully produce spores and gametophytes. Uneven number of chromosomes that won’t pair correctly |
Meiosis Results4 haploid cells | not genetically identical |
Mitosis vs. Meiosissimilarities: | ~ prophase, metaphase, anaphase, telophase (pmat) | ~ cell division | ~ cytokinesis: complete division of cytoplasmic contents | differences: | ~ mitosis: single set of divisions | ~ meiosis: two divisions | ~ mitosis: production of 2n cells | ~ meiosis: production of 1 n cells | ~ mitosis: production of 2 cells | ~ meiosis: production of 4 cells |
| | Dominanta trait is expressed when dominant allele is present | capital letter (B) |
Heterozygousone dominant and one recessive allele | aka hybrids or carriers | Bb |
Law of Independent Assortmenthereditary factors (alleles) assort into gametes independently from one another (every combination) |
Genetic Variationcrossing over | independent assortment | random fertilization |
Epistasisdifferent genes can interact to control the phenotypic expression of a single trait | nonallelic genes affect one another |
X-Inactivation in Femalesbarr bodies | DNA methylation |
Gene Linkage (Linked Genes)genes that are on the same chromosome | usually linked genes will be inherited together (unless separated by crossing over) | exhibit recombination frequencies less than 50% |
Recombination Frequency Equation (x100%)
Sexual Reproductiongametes (sperm and egg) | two parents |
Examples of Sexual Reproductioninternal fertilization: humans, sharks, turtles | external fertilization: frogs, many fish | hermaphrodites: most worms, flowering plants | pollination: flowers |
Meiosisreduces the chromosome number | 1) Interphase I | 2) Prophase I | ~ synapsis: the lining up of homologous chromosomes | ~ chiasma: exchange of genes between non sister chromatids | ~ crossing over: results in recombination of genes so they assort independently | 3) Metaphase I | ~ lining up of homologous chromosomes | 4) Anaphase I | ~ independent assortment | 5) Telophase I and Cytokinesis I | 6) Prophase II | 7) Metaphase II | 8) Anaphase II | 9) Telophase II and Cytokinesis II |
Nondisjunction in Meiosis 1(left) and 2(right)
Horizontal Gene Transferdonor to recipient cell | transformation (uptake of external DNA (plasmid)) | transduction (virus -> bacteria) | conjugation (bacteria -> bacteria) |
| | Recessivea trait is masked in the presence of a dominant allele | lower case letter (b) |
Phenotypephysical characteristic of a trait | color, size |
Genotypegenetic makeup of the chromosome | letters (B, b, G, g) |
Incomplete Dominanceneither allele is completely dominant | hybrids are in between the homozygous traits | blending |
Polygenic Inheritancemode of inheritance in which additive effects of two or more genes determines a single trait | quantitative characters that vary in degree | AABBCC: dark | aabbcc: light |
DisordersDominant disorders: | ~ anchondraplasia (dwarfism) | ~ huntington's (late acting lethals) | Recessive disorders: | ~ cystic fibrosis | ~ tay-sachs | ~ sickle cell |
Calculate Chi Squareif we accept the null hypothesis (1:1:1:1), then the genes independently assort on DIFFERENT chromosomes | if we reject the null hypothesis (1:1:1:1), then the genes are on the SAME chromosome |
Asexual vs. Sexual Reproduction | Advantages: | Disadvantages: | Asexual: | do not have to find a mate or expend energy to find a mate | not much genetic variation | Sexual: | genetic variation | must find a mate and expend energy to find and/or court a mate |
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