Genetics Chapter One: Gene Transmission

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Genetics

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The study of how genetic material gets from one generation to the next

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Classical genetics

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Concentrates on readily observable characteristics of an organism

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Cytogenetics

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Observations of the cellular mechanisms using microscopic techniques; used to study characterics

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Eukaryotes

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Organisms composed of cells containing nuclei

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Gene

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Unit of information that controls one particular characteristic

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Allele

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Particular form of a gene

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Wildtype allele

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Most common form of a gene

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Mutation

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Process by which one allele is converted to another; very rare

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Genotype

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Listing of the particular alleles present in an individual

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Phenotype

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Characteristic controlled by a particular gene

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DNA (deoxyribonucleic acid)

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Molecules composed of genes; controls many different phenotypes

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Chromosome

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DNA packaged with proteins

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Locus

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Location of a particular gene on a particular chromosome

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Genome

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Complete set of genes/chromosomes for an organism

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Karyotype

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Picture of the chromosomes of an organism; the human genome consists of 24 chromosomes

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Autosomes

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Chromosomes found in all cells

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Sex chromosomes

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X and Y chromosomes; present in individuals in different numbers depending on sex

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Haploid

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Cell that contains one set of chromosomes; most common haploid cells are egg and sperm, or gametes

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Diploid

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Cell containing two sets of chromosomes

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Fertilization

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Fusion of egg and sperm

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Zygote

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Diploid cell containing a maternal and paternal copy of each chromosome from the fusion of sperm and egg

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Homologues

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Maternal and paternal pair of chromosomes

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Polyploid

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Cells that carry more than two copies of the genome

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Mitosis

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Process by which zygotes divide to produce a multicellular organism; parent nucleus divides into two nuclei

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Cell cycle

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Determines how chromosomes get from one generation to the next

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Centromere (primary constriction)

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Point of attachment for spindle fibers

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Kinetochore

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Part of the chromosome within the centromere that actually attaches to the spindle fibers

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Telomeres

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Special structures at the ends of chromosomes

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Arms

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Parts of the chromosome between the centromere and telomere

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Chromatid

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The centromere and two arms; chromosomes consist of either one or two chromatids attached to each other

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Spindle organizing region

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Defines where th spindle will be produced

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Centriole

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Spindle organizing region in animals

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Spindle

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Complex structure composed of microtubules, which are composed of the protein tubulin; Connect the kinetochore to the spindle organizing region to move chromosomes during nuclear division

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Interphase

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Period of cell cycle before mitosis during which the cell grows and chromosomes are duplicated

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Cytokinesis

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Cytoplasmic division; takes place after nuclear division

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S phase

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Period of interphase during which synthesis of genetic material takes place

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G1 phase

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First period of cell growth during interphase

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G2 phase

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Growth period during interphase during which cells have twice as much genetic material as in G1

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Sister chromatids

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Exact duplicates of chromosomes formed during S phase

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Chromatin

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Diffuse haze of chromosomal material in the nucleus of a cell about to enter mitosis from G2

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Prophase

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Stage of mitosis during which the nuclear membrane disintegrates, the chromosomes condense, and the spindle organizing region moves to opposite ends of the cell

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Metaphase

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Stage of mitosis during which the chromosomes move to the metaphase plate between the poles

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Anaphase

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Stage of mitosis during which the centromere splits and two identical single chromatid chromosomes are created

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Disjuntion

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Process by which the spindle fibers pull the single chromatid chromosomes to the poles during anaphase

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Telophase

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Stage of mitosis during which chromosomes reach the poles and decondense and nuclear membranes reform into two nuclei

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Meiosis

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Mechanism by which haploid gametes are formed from a diploid parent cell

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Meiosis I

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Reduces the number of chromosomes in each nucleus by half

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Recombination

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Exchange of genetic material between homologous chromosomes

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Meiosis II (equational division)

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Separates products of recombination into separate nuclei; the number of chromosomes is not changed

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Prophase I

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Stage of meiosis I during which the nuclear membrane disintegrates, the spindle forms, and homologous pairs condense and undergo synapsis

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Synapsis

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Process in prophase I by which chromosomes condense as homologous pairs of double chromatid chromosomes (4 chromatids)

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Chiasmata

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Points where two chromatids are crossed over one another during recombination

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Metaphase I

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Stage of meiosis I during which the homologous paris move to the metaphase plate

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Anaphase I

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Stage of meiosis I during which one chromosome from each homologous pair is pulled to each pole

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Telophase I

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Stage of meiosis I during which chromosomes are decondensed, nuclear membranes and formed, and the spindle is dissolved

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Interkinesis

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Period between divisions of meiosis during which there is no growth or S phase

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Prophase II

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Stage of meiosis II during which chromosomes condense, the spindle forms, and the nuclear membrane disintegrates; chromosomes consist of two chromatids

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Metaphase II

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Stage in meiosis II during which the chromosomes line up at the metaphase plate

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Telophase II

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Stage in meiosis II during which chromosomes decondense, the spindle disintegrates, nuclear membranes form, and cytokinesis takes place

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Gametogenesis

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The process of making gametes