Inquiry into Life Twelfth Edition

Name: Inquiry into Life Twelfth Edition
Uploaded: 2017-08-11T20:53:00+00:00
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Description: Inquiry into Life Twelfth Edition

Inquiry into Life Twelfth Edition
Lecture PowerPoint to accompany Inquiry into Life Twelfth Edition Sylvia S. Mader Chapter 26 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

26.1 Counseling for Chromosomal Disorders
Genetic Counselors Help individuals understand modes of inheritance Medical consequences of genetic disorders Inform individuals of possible decisions they may need to make

Karyotyping A karyotype is a visual display of individual’s chromosomes Can be performed on any babies, children, teens, adults and on a fetus

Amniocentesis A prenatal test A sample of amniotic fluid is collected Fetal cells can be isolated and analyzed Risk of spontaneous abortion is %

Chorionic Villi Sampling A prenatal test Chorionic cells can be collected and analyzed Can be performed earlier than amniocentesis Risk of spontaneous abortion is %

Normal Karyotype (male) Down Syndrome Karyotype

Changes in Chromosome Number Too many or too few chromosomes Due to a process called nondisjunction Trisomy: An extra chromosome is carried by an egg or sperm Monosomy: An egg or sperm lacks a chromosome

Nondisjunction of Chromosomes During Oogenesis

Abnormal Autosomal Chromosome Number

Abnormal Sex Chromosome Number

Changes in Chromosomal Structure Chromosomal Mutations Radiation, certain chemicals, and some viruses can causes chromosomes to break apart Deletions Duplications Translocations Inversions

Chromosomal Mutations Deletions Williams Syndrome Chromosome 7 loses an end piece Individuals have a turned up nose and a wide mouth with small chin Poor academic skills but well-developed verbal and musical skills Cri Du Chat Syndrome Chromosome 5 loses an end piece Small head, mental retardation, cat-like cry

A Deletion

Chromosomal Mutations Duplication This example is characterized by poor muscle tone and autistic traits

Chromosomal Mutations Translocations The exchange of chromosomal segments between two nonhomologous segments A translocation of pieces of chromosomes 14 and 21 is another phenomena that results in Down syndrome (5% of all cases)

A Translocation Alagille Syndrome
Translocation of chromosomes 2 and 20

Inversion Segment is turned 180 degrees Leads to altered gene activity

26.2 Counseling for Genetic Disorders
Family Pedigrees Chart of Family’s History Key Males are indicated by squares Females are indicated by circles Shaded means individual is affected by disorder

Pedigrees for Autosomal Disorders
Autosomal Recessive Autosomal Dominant

Autosomal Recessive Pedigree

Autosomal Dominant Pedigree

Pedigrees for Sex-linked Disorders X-linked disorders X-linked recessive disorders To be affected, daughters must inherit it from both parents Sons can only inherit it from mother, therefore more males affected than females X-linked dominant disorders Affected males pass the trait only to daughters Females can pass trait to both daughters and sons Y-linked disorders Present only in males Fathers pass trait to all sons

X-linked Recessive Pedigree

Genetic Disorders of Interest Autosomal Recessive Disorders Tay-Sachs Disease Cystic Fibrosis (CF) Phenylketonuria (PKU) Sickle-Cell Disease

Tay-Sachs Disease Lack of Hex A enzyme Results in defective lysosomes (especially in the brain) Symptoms appear in the first year of life Disease is progressive and fatal

Cystic Fibrosis Most common genetic disorder in Caucasians in U.S. Defect in chloride channel proteins in cells Thick, abnormal mucus production Lungs, bronchial tubes, pancreatic ducts affected

Autosomal Recessive Disorders Phenylketonuria Lack enzyme for phenylalanine metabolism Affects nervous system development Can usually be controlled with diet Sickle-cell anemia Irregular red blood cells caused by abnormal hemoglobin Clog vessels- poor circulation Internal hemorrhaging Heterozygous individuals are normal unless dehydrated or experience mild oxygen deprivation

Autosomal Dominant Disorders Marfan Syndrome Defect in fibrillin-protein in elastic connective tissue Long limbs and fingers, weakened arteries, dislocated lenses in the eyes Huntington Disease Progressive degeneration of brain cells Gene for defective protein called Huntington Too many copies of the amino acid glutamine

Incompletely Dominant Disorders Familial hypercholesterolemia Affects the number of LDL-cholesterol receptors on cells Homozygous for defective gene- has no receptors and develops cardiovascular disease in teenage years Heterozygous individual has half the normal number of receptors

X-linked Recessive Disorders Color Blindness About 8% of Caucasian males have red-green color blindness Duchene's Muscular Dystrophy Absence of a protein called dystrophin Causes calcium to leak into muscle cells which actives enzymes that break down the cells Hemophilia Hemophilia A is due to a lack of clotting factor VIII Hemophilia B is due to a lack of clotting factor IX Blood clots slowly or not at all

Testing for Genetic Disorders Testing for a Protein Some mutations lead to disorders caused by a missing enzyme Tay-sachs disease-test for quantity of hex A enzyme present in a sample of cells can determine if individual is homozygous normal, a carrier, or has Tay-sachs PKU-blood test done on all newborns to detect the presence of phenyalanine

Use of a Genetic Marker to Test for a Genetic Mutation

Testing for Genetic Disorders Testing the DNA Testing for genetic markers-similar to DNA fingerprinting Restriction enzymes cleave DNA Used to test for Huntington disease Testing with DNA probes DNA probe-single stranded piece of DNA that binds to complementary DNA For genetic testing, the probe has a mutation of interest DNA chip can test for many abnormalities at once Has many DNA segments mutated genes bind if present and are detected by laser scanner

Use of a DNA Chip

Testing the Fetus Ultrasound The fetus is exposed to high frequency sound waves to produce a picture

Testing Fetal Cells Amniocentesis Performed at 15 weeks of gestation Can also test for alpha fetoprotein (AFP) which can indicate neural tube defects Chorionic Villi Sampling Performed earlier than amniocentesis no amniotic fluid taken so cannot test for AFP Fetal Cells in Mother’s Blood A small number of fetal cells enters the mother’s blood These can be isolated and analyzed

Testing the Embryo Following in vitro fertilization, the embryo is allowed to develop. At the 8-cell stage, a cell can be removed and tested. Only “normal” embryos are implanted Testing the Egg Test the polar bodies of women who are heterozygous prior to in vitro fertilization If the polar body has the defect, then the ovum is normal

Counseling for genetic disorders: the present cont’d.
Testing for genetic disorders cont’d. Testing the embryo If both parents are carrier, they may want assurance that embryo is normal Following in vitro fertilization, can remove a cell at 6-cell stage and test for defect, then implant only those embryos that are normal Testing the egg Test the polar bodies of women who are heterozygous prior to in vitro fertilization If the polar body has the defect, then the ovum is normal

26.3 Genomics Genomics is the Study of Genomes.
Humans have 20, ,000 genes that code for proteins Many other organisms have more genes than do humans

26.3 Genomics Sequencing the Bases Genome Comparisons
The Human Genome project was a project to sequence all of the base pairs in all of the DNA of human chromosomes. Genome Comparisons Scientists can compare the genomes of different species of organisms to gather data regarding the cause of many diseases.

26.3 Genomics The HapMap Project
The objective is to catalog common sequence differences that occur in human beings. People have been found to inherit patterns of sequence differences, these are called haplotypes. Information gained from this project will allow scientists to link haplotypes to the risk of specific illnesses.

26.3 Genomics Proteomics and Bioinformatics Proteomics
Study of structure, function, and interaction of cellular proteins Translation of all human genes results in a collection of proteins called the proteome Computer modeling provides information about the three-dimensional shape of protein molecules May be possible to correlate drug treatment to genetic profiles

26.3 Genomics Proteomics and Bioinformatics Bioinformatics
Application of computer technologies to the study of the genome Analysis of data produced by genomics and proteomics Cause and effect relationships between various genetic profiles and genetic disorders caused by multifactor genes Current genome includes gene “deserts” with no known function Bioinformatics may discover functions of these regions

26.3 Genomics Expanding Present-Day Genomics
The Human Genome is described as three-dimensional One dimension is the sections of DNA that encode proteins This accounts for less than 2% of the DNA A second dimension is what used to be called “junk” DNA This “junk” DNA may code for RNA, researchers are trying to determine what this RNA does A third layer of our genome lies outside DNA. It consists of proteins and other chemicals that surround and adhere to DNA. These may provide clues to the inheritance of certain diseases.

26.3 Genomics Gene Therapy Insertion of genetic material into human cells for treatment of a disorder Ex vivo gene therapy Cells are removed from the patient Treated outside the body and then returned to the patient Ex: SCID (Severe Combined Immunodeficiency) In vivo gene therapy Patient is given a foreign gene directly Gene is incorporated into the genome within the body Ex: Cystic fibrosis

Ex Vivo Gene Therapy in Humans

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