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Genetic Introduction.md

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+[[G11 Pre-AP Biology]]
+
+Human body cells have 46 chromosomes.
+
+Chromosome 23 is a sex chromosomes.
+First 22 chromosomes are autosomes.
+
+First chromatid of first pair is taken in metaphase, organised picture of chromosomes.
+
+DNA is the molecule that holds information.
+Chromosomes are structures that consist of DNA and associated proteins.
+
+DNA wraps around histones and forms nucleosomes.
+Nucleotide has 1 phosphate, base, and deoxyribose sugar.
+
+4 different bases.
+Adenine compliments thymine.
+Cytosine compliments guanine.
+
+Genes are sections of DNA that instructs cells to make proteins.
+Chromosomes are chromatins but more curly to be more condense and sturdy.
+
+Sperm and egg should have 23 chromosomes, zygote (fertilized egg) should have 46.
+
+Interphase is when all cell functions occur, DNA replicates, and the cell goes through G1, synthesis, and G2.
+Prophase is when chromatin condenses, nuclear membrane disappears, centrioles move, and spindle fibers form.
+Metaphase is when spindle fibers pull double stranded chromosomes to center of cells.
+Anaphase is when spindle fibers contract and pull sister chromatids apart. Single stranded chomosomes start migrating to opposite sides.
+Telophase is when single stranded chromosomes arrive at opposite sides, nuclear membrane and nucleolus reappear, and spindle fibers disappear.
+Cytokinesis is when cell splits into 2 identical daughter cells.
+
+Homologous chromosomes have the same gene but aren't identical. Same length, centromere location, and banding pattern. One from each parent.
+
+Allele are different version of a gene.
+
+Haploids (n) are one set of chromosomes.
+Diploids (2n) are two sets of chromosomes.
+One set from sperm, one from egg.
+Humans have 46 chromosomes, 23 chromosomes per set.
+
+Meiosis is the process of producing cells with half the number chromosomes of parent cells. Increases genetic variation, different combinations of alleles.
+
+Process of meiosis:
+Interphase involves growth of cell and replication of chromosomes.
+
+Prophase I.
+Synapsis is when the homologous chromosomes pair up.
+Crossover occurs. Non sister chromatids exchange information (homologous chromosome).
+Centrosomes move to opposite sides, spindle forms (nuclear membrane disappears, chromosomes coil).
+Tetrad is a pair of homologous chromosomes/bivalent.
+
+Metaphase I.
+Homologous pairs (tetrad) line up along equator of cells.
+![[Pasted image 20261013105105.png|496]]
+Cross over has already occured in prophase I.
+In mitosis they aren't lined up accross from their pair.
+Spindle fibers attach to centromeres of each homologous chromosome.
+
+Anaphase I.
+Homologous chromosomes separate from each other, homologues of each bivalent separate. Sister chromatids are still attached unlike mitosis.
+Double stranded chromosomes start moving to opposite sides.
+
+Telephase I.
+Double stranded chromosomes arrive at opposite ends.
+Spindle fibers disappear.
+Chromosomes uncoil.
+Nuclear membrane reforms.
+
+Meiosis part 2 is just like mitosis.