● Crossing over: homologous chromosomes exchange parts of their chromatids with each other
● Gene: unit of DNA that codes for RNA, proteins, and polypeptides
● Synapsis: the pairing of homologous chromosomes
o Line up gene by gene
● X chromosome: sex xhromosome; occurs twice in females, and once inmales.
● Y chromosome: sex chromosome present only in males
● Genetic recombination: the resulting regrouping of genes in an offspring that results from meiosis
● Haploid: cell containing only one set of chromosome (n)
● Diploid: cell containing two set of chromosomes (2n)
● Karyotype: display of a cell’s chromosomes, with homologues paired up and in order
● Genome: all of the cell’s DNA
● Somatic cell: diploid cells that undergo mitosis; also referred to as bodily cells
● Gamete: haploid cells that have already undergone meiosis; also referred to as sex cells
● Homologous chromosomes: chromosomes with the same length, shape, and genes (can have different alleles however in the same genes)
● Fertilization: when two haploid gametes contain to form a diploid cell
o Ex: the union between egg and sperm
● Zygote: result of fertilization; diploid cell produces somatic cells by mitosis
● Prophase I: occupies more than 90% of the time required for meiosis
chromosomes condense
synapse and crossing over
tetrads and chiasmata
● Sexual reproduction: the fusion of gametes
● Asexual reproduction: not involving the fusion of gametes.
● Chiasmata: point of crossover in homologous chromosomes
● Variation: difference of expressed alleles in gene pool
● Random fertilization: cause of genetic variation; refers to random process of fertilization between a random egg and random sperm
● Purpose
○ Produce gametes for sexual reproduction
○ Women: happens in ovaries
○ Men: happens in tests
● Nuclear division splits the amount of chromosomes in the parent cell into half
○ 2n → n
● Cellular division (Meiosis):
● Meiosis I
○ prophase
○ Metaphase
○ Anaphase
○ Telophase
○ Cytokinesis
● Meiosis II
○ prophase
○ Metaphase
○ Anaphase
○ Telophase
○ Cytokines
● Meiosis ends with four gametes each containing half the genetic complement of the parent
● Comparing Mitosis and Meiosis: MITOSIS: results in the production of 2 daughter cells IDENTICAL to the parent cell to make somatic cells(2n)
growth and repair of cell organisms
23 pairs of chromosomes in identical daughter cells
DNA replicated 1 time
creates 2 diploid cells
1 nuclear division
MEIOSIS: results in the reproduction of chromosomes number by half in the 4 new cells(used only in fertilization)
To make sex cells(n)
Production of sex cells for sexual reproduction
23 chromosomes in each 4 genetically different daughter cells
DNA replicates 1 time
Creates 4 haploid cells
2 nuclear division
● Genetic Diversity:
○ Crossing Over
○ Randomization
● Allele: Different forms of a gene
● Dominant: dominating allele
● Recessive: inferior allele; masked in the presence of a dominant allele
● Homozygous: two identical alleles for a trait
● Heterozygous: two different alleles for a trait
● Genotype: genetic makeup
● Phenotype: An organism's physical appearance
● Sex-linked: genes locatd on sec chromsomes
● Carrier: A person who has one recessive allele for a trait but does not have the trait.
● Pedigree: A diagram that shows the occurrence of a genetic trait in several generations of a family.
● Mendelian traits are traits that are passed down by dominant and recessive alleles of one gene.
● Not determined by the simplicity of dominant versus recessive
● Recombination Frequency: average amount of crossovers
● X Inactivation: Condensation of X chromosomes into Barr bodies
● Codominance: where both dominant, differing alleles are equally expressed in the phenotype
● Epistasis: when a gene also control the expression of other, independent genes
● Incomplete Dominance: where both dominate, differing alleles are blended; neither are expressed fully
● Linkage: Occurs when different traits are inherited together more often that they would have been by chance along
● Mitochondrial Inheritance: genes passed through the mother’s side
● Pleiotropy: The ability of a single gene to have an effect on multiple expressions in the phenotype
● Polygenic Traits: Characteristics that are influenced by more than one pair of genes
● Multiple Alleles: A gene that has more than two alleles
● Chromosome theory of inheritance:chromosomes contain genes, and the behavior of those genes during the process of meiosis affects the phenotype of the resulting offspring
● Genes close enough to each other on the chromosome that result in their constant inheritance as a pair
● Recombinant: new combination of inherited gene
● Linkage map: a map of genes on a chromosome depending on the genes’ recombination frequency
o Map units: a unit of measurement of the distance between genes. one map unit is equivalent to a 1% recombination frequency
● Nondisjunction: error that occurs in cell division in which homologous chromosomes do not detach from each other
o Aneuploidy: cell genome is missing a chromosome
o Polyploidy: cell genome contains an extra chromosome
● Genetic Mutations
o Deletion: one or more nucleotides are deleted or lost
o Duplication: portion of a chromosome is duplicated
o Inversion: fragment during crossover is moved in a reverse orientation to the chromosome
o Translocation: a chromosomal fragment is removed from a chromosome and attached to a different chromosome
● Disorders that result from Gene Abnormalities
o Klinefelter syndrome: XXY
o Turner syndrome: XO
o SRY gene: Y linked gene that triggers the male sexual development pathway in animals.
▪ A disorder occurs if this gene is deleted from the Y chromosome of a male; The individual is genetically male, but has female reproductive organs
o Trisomy X Syndrome: female has an extra X, resulting in XXX