Biology Unit 5
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This 4 page Study Guide was uploaded by Stacy Downing on Saturday January 30, 2016. The Study Guide belongs to BIOL 190 at Towson University taught by preeti shah in Spring 2016. Since its upload, it has received 30 views. For similar materials see Introductory Biology for health professions in Biology at Towson University.
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Date Created: 01/30/16
Unit 5 Review- Genetics Human Chromosome 46 (23 pairs) Pairs= one from mom and one from dad Autosomal: #1-#22, non sex chromosome Sex Chromosome: (x and y) Homologous Chromosome Pairs Eukaryotic chromosome that is linear and comes in pairs Are present in all stages of cell cycle Can be in chromatin or chromosome (fully compacted) form depending on the stage “Homologous” because… o Same length o Same centromere position o Same sequence of genes o But NOT same alleles b/c each comes from a different parent HCP SC Same length, centromere position, One side (1/2) of a replicated genes chromosome Not same allele sequence b/c one is Each contains 1 of 2 daughter DNA mat and pat molecules Never attached to centromere Are identical in goth gene and allele sequence Appear in metaphase, replicated Always held together by centromere Separated at anaphase, becoming independent chromosomes Diploid Haploid # of chromosomes in a body cell Gametes (required to restore)= 23 chromosomes Characteristics of a species Animals egg and sperm Always even # b/c chromosomes occur On half the diploid number in pairs Both HC members of each pair present 1 member of each type/pair present (m in the cell or p) Abbreviation: 2N Two haploid cells fuse = diploid state is restored Abbreviation: N Asexual Reproduction Sexual Reproduction 1 parent (cell) 2 parent (multicellular) Mitotic division Requires: Meiosis division and fertilization Parents no longer exist after Parents still exist after reproduction reproduction Minimal genetic variation Maximal genetic variation (mixing of DNA) Gene Allele Specific location on the chromosome of Actual base sequence present at 1 DNA location on DNA Where info is stored to produce protein Starting cell for Meiosis/Products of Meiosis/ Meiosis division Only selected cells go through meiosis which are diploid cells Product: haploid cells egg and sperm cells Meiosis has 2 consecutive nuclear division Produces 4 haploid gametes from one 1 diploid parent cell Half the amount of DNA as parent cell, 1 copy of each gene Gametes do not divide, will fuse with gamete from other parent Meiosis 1 Separation of homologous chromosome Sister chromatids still together, but daughter cells are haploid Reduction division Made from one diploid parent cell Prophase 1: tetrad formation, homologous chromosome come together and line up, tetrad are held together w/ protein glue, spindle fibers attach to both sides of whole tetrad , crossing over Metaphase 1: tetrads line up at equator Anaphase 1: no centromere division, protein glue dissolves, mat and pat chromosome separate, result: 2 haploid cells Telophase 1: nuclear membrane reforms, each daughter contains 2 sister chromatids Meiosis 2 Separation of sister chromatids Each daughter cell gets just one copy of either mat or pat chromosome 4 cells made (gametes) Prophase 2: nuclear membrane breaks down, spindle fibers bind to both side of centromere Metaphase 2: chromosome line up at equator Anaphase 2: spindle fibers pull sister chromatids apart to opposite poles Telophase 2: nuclear envelope reforms resulting in 4 haploid cells Origin of genetic variation Gene mutation (very rare) Chromosomal aberration (very rare) Sexual reproduction (main source) o Meiosis crossing over in prophase 1 o Fertilization Crossing over Prophase 1 of meiosis Even exchange of genetic material between each tetrad Chiasma: point at which non sister chromatids Results: 4 different possible combos of mat and pat genetic info at metaphase 1 in gametes Independent Assortment Tetrad of different type of chromosome line up independently of each other at metaphase 1 Position of mat and pat chromosome is random Nondisjunction Error in chromosome/chromatid separation in meiosis 1 or 2 they didn’t separate Result are abnormal gametes Terms/Definitions Genotype: combo of alleles present from existing alleles Dominant allele: always expressed if present Recessive allele: will be masked or hidden by dominant allele if both are present Phenotype: the physical appearance conferred by the genotype Tay-Sachs Chromosome 15 HEXA gene involved 4 copies of HEX in each of your cells (H=healthy and h = unhealthy) HH= homozygous normal Hh= heterozygous hh= homozygous mutated Mendel True breeding Self-pollinating Crossing: Self pollinations Fertilization Germination Development Law of gene segregation: o in each diploid individual there are 2 copies of every gene, one from each parent, that reside on homologous chromosomes, these genes copies are separated into separate gametes during gamete formation (meiosis) Law of independent assortment: o 2 different genes assort independently of each other during gamete formation (mitosis), resulting in a mixture of mat and pat genes Monohybrid: one gene heterozygous, 100% Pp genotype, 100% all purple Monohybrid Cross: 1PP:2Pp:1pp genotype, 3 purple and 1 white phenotype Examples of Mendel Inheritance in humans o Tay-Sachs, PKU, cystic fibrosis, sickle cell anemia, Huntington disease Multiple Allele o ABO blood type I : dominant, codes for CHO A B I : dominant, codes for CHO B i : recessive, codes for an inactive enzyme Incomplete dominance: neither allele appear fully dominant over the other o Example: red and white make pink o Example: Hypercholesterolemia HH: low blood cholesterol level, healthy Hh: high cholesterol, needs to be careful with diet, drugs to lower hh: dangerously high cholesterol levels, prone to stroke/ heart attack Codominance: both alleles are fully expressed , example: AB blood type Polygenic Inheritance: 1 character controlled by 3 or more distinct genes, example: human skin color Sex-linked o Genes located on X or Y chromosome but not both o Phenotype appears frequentAy in male a o Example: color blindness X codes for normal vision and X codes for colorblindness Level of Products of Products of # of # of Examples Dominance Allele 1 Allele #2 Genotype Phenotype Complete Large No protein or 3 2 Peas, quantity of a non- heterozygous Humans functional functional has protein protein DOMINANT Incomplete Small No protein or 3 3 Snapdragon quantity of a non- heterozygous Humans functional functional has protein protein intermediate Codominance Large Large 3 3 Human: quantity of quantity of a heterozygous ABO blood functional different has additive types protein protein that is phenotype also functional
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