University:
Sam Houston State University
Course:
BIOL 1406 | General Biology I
Academic year:

2022
Views:

497

Pages:

16
Author:

SpaceCadet101

Fundamental Principles of Genetics •Genetics – study of heredity •Gene – determinant of heredity •Chapter is outline of basic principles of genetics Cell Theory of Inheritance •Plants and animals composed of cells •Plant cell – surrounded by cell wall •Animal cell – surrounded by cell membrane •Nucleus – location of chromosomes in cell •Chromosomes – carrier of genes Chromosomes • Carriers of genetic material – genes • Occur in pairs • Homologous chromosomes – members of a pair • Number of chromosomes constant among normal members of a species Chromosome Number • Diploid (2N) numbers donkey 62 horse mule 63 swine sheep 54 cattle human 46 mink dog 78 cat chicken 78 64 38 60 30 38 • Normal body cells have diploid (2N) number • Gametes (sperm and egg) have haploid (1N) number Chromosomes • Two major types –Sex chromosomes – one pair which influences sex of organism –Autosomes – all pairs other than sex chromosomes Sex Determination • Mammals –Sex chromosomes are: • female • male XX XY • Chickens and turkeys –Sex chromosomes are: • female • male ZW ZZ homogametic heterogametic heterogametic homogametic Chromosomal Abnormalities • Changes in number of chromosomes (nondisjunction of sex cell) –Aneuploidy – extra or missing chromosome(s) –Polyploidy – extra sets of chromosomes • Usually lethal in animals –Except aneuploidy of very small chromosomes (eg Down Syndrome in humans is extra #21) Chromosomal Abnormalities • Changes in chromosome structure –Deletion – piece of chromosome removed –Duplication – piece of homologous chromosome duplicated –Translocation – exchange of material between different (nonhomologous) chromosomes –Inversion – segment of chromosome reversed Chromosomal Abnormalities • Changes in chromosome structure –Cause loss of fertility –Amount of loss dependent on type of change and importance of the affected segment of the chromosome Cell Division • Two types –Mitosis – division of normal body cells –Meiosis – division of germinal cells to produce gametes (sperm and egg) Cell Division • Mitosis –Cell division of normal body cells –Each daughter cell has same genetic complement as original cell Cell Division • Mitosis –Four phases • Prophase • Metaphase • Anaphase • Telophase –Interphase – period between cell divisions Cell Division • Meiosis –Division in germinal cells to produce sperm and egg –Each cell that results has 1N number of chromosomes (half of number of chromosomes in body cells Cell Division • Meiosis –Two cycles of: • • • • Prophase Metaphase Anaphase Telophase –Results in four cells with 1N number Cell Division • Meiosis –During late prophase I • homologous chromosomes wrap together (synapsis) – Crossing over – exchange of genetic material between homologous chromosomes Cell Division • Meiosis –Spermatogenesis – meiotic production of sperm cells –Oogenesis – meiotic production of egg cells