Ch. 12.1: DNA stores Information Objectives: 1.Describe how DNA is packed within the nucleus. 2.Explain the significance of the Human Genome Project. Vocab:  Genome  Histone

DNA Structure Review Genome: Complete set of genetic material in an organism (order of bases).  Can fit into nucleus b/c of packing system.  Coiled around proteins (spools): HISTONES  Coiled are coiled into helical fiber to make CHROMOSOME

Human Genome Project Goal: Determine … 1. Sequence of bases in the human genome. 2.Sequences code for proteins (exons). 3.Function of resulting proteins.  Began in 1990  1st Draft completed in 2000  Government funded agency cooperated w/ private companies  Results published on web and available to scientists.

12.2: Chromosomal Disorders Objectives: 1. Relate Down syndrome and non-separation of chromosomes. 2.Describe how chromosomes can be damaged. 3.Explain how a “jumping gene” can affect other genes. Vocab.:  Trisomy  Down syndrome  Non-disjunction  Duplication  Insertion  Deletion  Inversion  Translocation  Transposon

Non-disjunction Homologous chromosomes or sister chromatids fail to separate during meiosis. Result: Gametes with abnormal # of chromosomes… Offspring with abnormal # of offspring

Non-disjunction  Most embryos with abnormal chromosome # result in miscarriage.  Cause: Random  Increased risk with age (35 +)

Trisomy Having 3 of a particular chromosome. - Chromosome # = 47 Examples Trisomy 21: Down syndrome 1 in 700 births Most common Cognitive and physical impairments Trisomy 18: Edwards syndrome (more lethal)

Trisomies & Maternal Age  Pre-egg cells in girls have gone through Meiosis I.  Meiosis II happens b4 ovulation.  Longer time lag = increase chance of nondisjunction

Trisomies of Sex Chromosomes XXX Female XXY: Klinefelter Male XYY: Male Turner’s Syndrome XO Female 45 Chromosomes

Chromosomal Duplications  Part of a chromosome is repeated.  Vary from fatal to developmental abnormalities.

Chromosomal Deletions  Part of a chromosome is deleted.  Very serious damage Ex: Williams Syndrome Partial deletion of chromosome 7

Chromosome Inversion Fragment breaks and reverses on the same chromosome.  Not as lethal.

Chromosome Translocation List of Chromosome DisordersList Fragment of one chromosome attaches to ANOTHER, DIFFERENT chromosome. If there is an UNEQUAL swap of segments, results can serious.

Transposons: Jumping Genes List of Chromosome DisordersList Discovered by Barbara McClintock Experimented w/ corn; Jumping genes interfered w/ corn pigments.

Transposons  Single genes that can move around.  “Jump” from one chromosome to another.  If they insert in the middle of an existing gene, that gene will be disrupted.