Genes are found on Chromosomes! Genes are found on Chromosomes! I. Types of Mutations

Transcription

1 Genes are found on Chromosomes! genes and chromosomes are made up of DNA, which is the genetic material for all life on earth genes are found on a specific region on a chromosome; called a locus (loci) Genes are found on Chromosomes! chromosomes are condensed coils of DNA that contain hundreds, if not thousands of genes when a change happens in the genetic code (that is, the DNA, gene, or chromosome), it is called a can happen in any cell of the body MUTATIONS IN BODY CELLS MUTATIONS IN SEX CELLS I. Types of Mutations A. Gene Mutations normally affect many less traits than chromosome mutations do albinism, height, dwarfism, blood type, eye color, skin color, platelet production most are harmful! (harmful forms of a gene are called ) some are neutral (not good nor bad) can sometimes result in a beneficial change where the organism is better suited to fit in its environment this is

2 I. Types of Mutations B. Chromosome Mutations because chromosomes are made of thousands of genes, these mutations can have a very large (and usually detremental) impact on the organism 1. Chromosome Number normally, there are chromosomes in our diploid human body cells; and chromosomes in our haploid human gametes remember MEIOSIS? interphase synapsis crossing over??????? Nondisjunction when the chromosomes do not split correctly during meiosis, it is called gametes can have more or less than the n number of chromosomes n-1 n+1 n n Nondisjunction organism has wrong chromosome number trisomy monosomy n+1 n n-1 n Nondisjunction trisomy 2n+1 monosomy 2n-1

3 Human Chromosome Disorders high frequency in humans alterations are too disastrous developmental problems result from biochemical problems certain conditions are tolerated upset the balance less = characteristic set of symptoms = Down Syndrome a common example 3 copies of chromosome 21 1 in 700 children born in U.S. chromosome 21 is the smallest human chromosome but still severe effects: common facial features, Down Syndrome & age of mother Mother s age Incidence of Down Syndrome Under 30 <1 in in in in in in in in in in in in in 12 Rate of miscarriage due to amniocentesis: 1970s data 0.5%, or 1 in 200 pregnancies 2006 data <0.1%, or 1 in 1600 pregnancies Nondisjunction if an entire set of chromosomes fails to separate, you can have a organism (condition called polyploidy) in animals, polyploidy is usually lethal: this in animals, polyploidy is usually lethal: this is because so many genes are affected in plants, this is common can even make them hardier!

4 I. Types of Mutations B. Chromosome Mutations 2. Chromosome Structure when pieces of chromosomes are broken off or have other pieces added on can be very harmful, can be neutral, can have a beneficial effect, deletion _ duplication _ inversion _ translocation _ RADIATION cosmic rays, X-rays, UV rays, radon, radioactivity, microwave radiation, cell phones? CHEMICALS benzene, formaldehyde, asbestos, tobacco additives (all referred to as ) II. Effects of the Environment besides genes controlling our characteristics, there are many examples Color of Hydrangea flowers is influenced by soil ph Coat color in arctic fox influenced by heat sensitive alleles

5 II. Effects of the Environment 1) human skin color and sunlight some people s skin get darker with exposure to sunlight the sunlight activates the 2) sunlight and chlorophyll plants will produce, if not, will cease production and breakdown existing pigments 3) temperature and fur color in a species of Himalayan rabbit, warm temperatures yields white fur, cold temps turn the fur black! II. Effects of the Environment 4) identical twins identical twins are NOT truly identical over time since birth, they (probably) have had changes in their DNA, but not all in the same cells and same loci! III. Applications of Genetic Theory A. Artificial Selection (Selective Breeding) ex. dogs, apples, horses The raw genetic material is in all organisms, hidden in their genomes!

6 III. Applications of Genetic Theory B. Inbreeding crossing of two parents of the same species with very, very similar genetic backgrounds C. Outbreeding (Hybridization) crossing of two parents of the same species with different genetic backgrounds IV. Human Heredity A. Polygenic Inheritance when phenotypes are influenced by the additive effects of human height skin color intelligence eye color behaviors IV. Human Heredity B. Cancer and Genetics there are genes that control the cell cycle All cancer is genetic! We all have genes that could lead to cancer but it the genes might not be in the cancer mode, until mutated. this change can cause the cell to carry out repeated cell divisions and/or ignore the signals that normally tell it to stop

7 IV. Human Heredity C. Genetic Counseling by looking at the traits on your ancestors, you can learn more about your genotype techniques used are as follows: 1) using pedigrees, you can track a gene (either dominant or recessive) through a family IV. Human Heredity C. Genetic Counseling IV. Human Heredity C. Genetic Counseling 2) genetic screening if there is a history of a genetic disease in your family, can reveal the genotype 3) amniocentesis when pregnant, if a genetic screen has preliminary results of a possible problem, involves the removal of amniotic fluid Fluid is drawn from the amniotic sac. Here, some of the fetus cells are floating around the amniotic fluid. When you centrifuge the same, you can get a mass of cells. Then, you can stain the DNA and look for any chromosomal abnormalities. a picture of the chromosomes is called a

8 IV. Human Heredity C. Genetic Counseling 4) karyotyping can see abnormalities in chromosome number or structure Down syndrome (trisomy 21) Edward s syndrome (trisomy 18) Patau syndrome (trisomy 13) Jacob s syndrome (XYY) Klinefelter s syndrome (XXY) female / eg ggs A a Aa x Aa male / sperm A AA Aa a Aa aa Aa Aa People carry many of these recessive alleles if both parents are carriers, then these conditions develop 25% of the time. A a A a A. PKU (Phenyketonuria) caused by a recessive allele occurs when one gene of the enzyme that can metabolize the amino acid phenylalanine development of mental retardation as chemical builds up in brain can be treated with

9 B. Tay-Sachs Disease B. Cystic Fibrosis caused by a recessive allele (LETHAL) fatty material in brain accumulates due so it doesn t work! symptoms include seizures, blindness, and degeneration of mental and motor performance; child dies before 5 caused by a recessive allele ; so water doesn t follow results in a thick mucus in lungs (and other internal passageways) enlarged lysosomes in brain cells chloride channel normal lungs airway Cl- transports chloride through protein channel out of cell Osmotic effects: H2O follows ClCl- channel H 2O cells lining lungs cystic fibrosis ClH 2O bacteria & mucus build up thickened mucus hard to secrete mucus secreting glands D. Huntington s Disease caused by a DOMINANT allele; those that have this allele will develop this genetic disease symptoms do not usually develop until years old and include: involuntary movements uncoordinated gate irritability, depression, anxiety loss of short-term memory

10 E. Sickle-Cell Anemia both normal alleles normal protein both abnormal alleles abnormal protein one of each: 50% normal protein 50% abnormal protein E. Sickle-Cell Anemia under low-oxygen conditions, the abnormal hemoglobin causes the this has many effects on the person! here showing effects of hemoglobin on red blood cells here showing effects of hemoglobin on red blood cells