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alternative forms of a gene found on the same locus on a chromosome
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2 identical alleles
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BB (homozygous dominant)
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bb (homozygous recessive)
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two copies of each hereditary factor (allele) segregate
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offspring acquire one factor from each parent
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the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis
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blood groups
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both alleles are expressed in the heterozygote
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neither is dominant or recessive, but there is no blending
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pedigree: family tree
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males: squares
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females: circles
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shaded: showing exhibited trait
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half shaded: carrier
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nature: genetically determined
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nurture: environmentally determined
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in humans:
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~ females: XX
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~ males: XY
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examples of sex linked disorders:
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~ duchenne muscular dystrophy
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~ hemophilia
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~ colorblindness
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if RF is >50%, the traits are considered to be independently assorted and on DIFFERENT chromosomes
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if RF is <50%, the traits are on the SAME chromosome (any variants from the parent type are due to crossing over)
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two identical cells
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"clones"
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Fission: bacteria
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Fragmentation: starfish
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Budding: coral
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haploid: cells that contain a single set of chromosomes in an egg or sperm cell (23 gametes)
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diploid: two complete sets of chromosomes (46 somatic)
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triploid: Extra set of chromosomes (69 chromosomes)
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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
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4 haploid cells
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not genetically identical
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similarities:
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~ prophase, metaphase, anaphase, telophase (pmat)
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~ cell division
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~ cytokinesis: complete division of cytoplasmic contents
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differences:
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~ mitosis: single set of divisions
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~ meiosis: two divisions
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~ mitosis: production of 2n cells
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~ meiosis: production of 1 n cells
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~ mitosis: production of 2 cells
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~ meiosis: production of 4 cells
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parent to daughter cell
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a trait is expressed when dominant allele is present
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capital letter (B)
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one dominant and one recessive allele
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aka hybrids or carriers
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Bb
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hereditary factors (alleles) assort into gametes independently from one another (every combination)
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crossing over
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independent assortment
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random fertilization
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different genes can interact to control the phenotypic expression of a single trait
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nonallelic genes affect one another
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barr bodies
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DNA methylation
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genes that are on the same chromosome
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usually linked genes will be inherited together (unless separated by crossing over)
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exhibit recombination frequencies less than 50%
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gametes (sperm and egg)
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two parents
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internal fertilization: humans, sharks, turtles
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external fertilization: frogs, many fish
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hermaphrodites: most worms, flowering plants
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pollination: flowers
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reduces the chromosome number
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1) Interphase I
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2) Prophase I
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~ synapsis: the lining up of homologous chromosomes
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~ chiasma: exchange of genes between non sister chromatids
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~ crossing over: results in recombination of genes so they assort independently
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3) Metaphase I
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~ lining up of homologous chromosomes
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4) Anaphase I
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~ independent assortment
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5) Telophase I and Cytokinesis I
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6) Prophase II
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7) Metaphase II
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8) Anaphase II
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9) Telophase II and Cytokinesis II
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donor to recipient cell
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transformation (uptake of external DNA (plasmid))
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transduction (virus -> bacteria)
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conjugation (bacteria -> bacteria)
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a trait is masked in the presence of a dominant allele
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lower case letter (b)
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physical characteristic of a trait
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color, size
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genetic makeup of the chromosome
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letters (B, b, G, g)
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neither allele is completely dominant
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hybrids are in between the homozygous traits
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blending
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mode of inheritance in which additive effects of two or more genes determines a single trait
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quantitative characters that vary in degree
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AABBCC: dark
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aabbcc: light
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Dominant disorders:
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~ anchondraplasia (dwarfism)
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~ huntington's (late acting lethals)
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Recessive disorders:
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~ cystic fibrosis
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~ tay-sachs
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~ sickle cell
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.jpg)
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if we accept the null hypothesis (1:1:1:1), then the genes independently assort on DIFFERENT chromosomes
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if we reject the null hypothesis (1:1:1:1), then the genes are on the SAME chromosome
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Advantages:
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Disadvantages:
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Asexual:
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do not have to find a mate or expend energy to find a mate
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not much genetic variation
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Sexual:
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genetic variation
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must find a mate and expend energy to find and/or court a mate
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.jpg)
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