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Asexual reproduction
One parent produces genetically identical offspring (clones); no gametes are involved (e.g., bacteria, some plants).
Sexual reproduction
Two parents contribute gametes (sperm and egg) that fuse to form a genetically unique zygote.
Gametes
Haploid sex cells (sperm or egg) with 1 set of chromosomes (n).
Zygote
A diploid cell (2n) formed by the fusion of two gametes; first cell of a new organism.
Haploid
One set of chromosomes (gametes)
Diploid
Two sets of chromosomes—one from each parent (somatic cells and zygote).
Meiosis I (Reduction Division)
Prophase I: Homologous chromosomes pair up and cross over; synapsis and formation of tetrads.
Metaphase I: Tetrads align at metaphase plate.
Anaphase I: Homologous chromosomes (not chromatids) are pulled to opposite poles.
Telophase I + Cytokinesis: 2 haploid cells form, each with duplicated chromosomes.
Meiosis II
Prophase II: New spindles form in each haploid cell.
Metaphase II: Chromosomes line up in each cell.
Anaphase II: Sister chromatids are pulled apart.
Telophase II + Cytokinesis: 4 genetically unique haploid cells are produced.
Duplicated chromosome
A chromosome with two sister chromatids.
Tetrad
A pair of homologous chromosomes (4 chromatids total) formed during prophase I.
Allele
Different versions of a gene (e.g., blue vs. brown eyes).
Mutation
A change in the DNA sequence that can create new alleles.
Synaptonemal complex
Protein structure that holds homologs together during synapsis
Synapsis
Synaptonemal complex proteins help each Homologue form a tight pair with its other Homologue
Chiasma
Point where homologous chromosomes cross over
Recombinant chromosomes
Chromosomes that contain new combinations of alleles due to crossing over.
Oogenesis
makes 1 viable egg and 3 polar bodies (die)
Spermatogenesis
Production of sperm in testes; makes 4 functional sperm.
Random Mutations
occur in gametes during DNA Replication
(also occurs in Mitosis) makes different forms of a gene
Crossing over
gives new unique Recombinant Chromosomes
Independent Assortment
at Metaphase I 2^23 possible combinations = 8.39 million genetically unique
gametes from 1 person
Fusion of egg and sperm
creates > 70 trillion genetically distinct combinations of zygotes
Gonads
organs that produce gametes – Ovaries & Testes
Germ Cells
cells in gonads that produce gametes
Pluripotent stem cells
capable of reproducing and becoming any human cell
Differentiated cells
change from one cell type to another by changing their gene expression pattern, becoming more specialized
Embryonic stem cells
pluripotent stem cells in blastocyst
Adult stem cells
In bone marrow, skin, and brain, they can form a limited number of cell types. Red cells are pluripotent stem cells
Fungi life cycles
Can reproduce sexually and asexually
Haploid cells make up tissue of dominant multicellular stage
Algae life cycles
Can reproduce sexually and asexually
Haploid cells make up the tissue of the dominant multicellular stage
could also be like plants life cycle
Plants life cycles
Have both Haploid and Diploid multicellular organisms
Gametophytes: haploid multicellular plants
Sporophyte: diploid multicellular plants