Chapter 14 The Human Genome

14-1 Human Heredity I. Karyotype A. Picture of chromosomes arranged in pairs from largest to smallest Page 341 II. Human Chromosomes A. 46 individual or 23 pairs 23 from egg and 23 from sperm 2. Fertilized egg = zygote B. Pairs 1-22 = autosomes C. Pair 23 = sex chromosomes 1. Female = XX 2. Male = XY

D. Total number of chromosomes are written as: 46,XX or 46, XY E. Female:Male Ratio = 50:50 1. Eggs only contain X’s (23,X) 2. Sperm contain an X or a Y (23,X or 23,Y) III. Pedigree A. Chart showing the relationship of traits within a family B. Uses Symbols = female Page 342 = male

A circle represents a female. Page 342 A circle represents a female. A square represents a male. A horizontal line connecting a male and a female represents a marriage. A vertical line and a bracket connect the parents to their children. A circle or square that is not shaded indicates that a person does not express the trait. A shaded circle or square indicates that a person expresses the trait.

IV. Genes and the Environment C. Some human traits are almost impossible to associate with single genes and can’t see in a pedigree 1. Traits, such as the shape of your eyes or ears, are polygenic 2. Traits only partially genetic  environment IV. Genes and the Environment A. Some traits phenotypes are strongly influenced by environmental, or nongenetic, factors. B. Example: Height 1. Nutritional improvements have increased the average height by about 10cm

V. Human Genes: A. Human Genome 1. Contains tens of thousands of genes 2. Human complete set of genetic information B. Blood Groups 1.Known as ABO blood groups 2. Three Alleles: IA, IB, i 3. IA and IB are codominant 4. Four Blood Types: A, B, AB, and O

Page 344 5. Produce antigens on the surface of Red Blood Cells (RBC’s) 6. Allele Combinations: A IAIA, IAi B IBIB, IBi (Universal Recipient) AB IAIB O ii (Universal Donor) Page 344

7. Rh blood group: a. determined by a single gene with two alleles b. Named after the Rhesus Monkey c. Positive allele (Rh+) is dominant (Rh+ Rh+ or Rh+ Rh-) d. Negative allele (Rh-) alleles are recessive (Rh- Rh-) e. Rh- can give to Rh+ but Rh+ cannot give to Rh- C. Recessive Alleles 1. TWO recessive alleles = disorder (aa) a. Carriers = do not have disorder but carry the allele for it (Aa) Examples: Phenylketonuria (PKU), Albinism, Cystic Fibrosis, Tay-Sachs

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Page 345 D. Dominant Alleles 1. ONE dominant allele = disorder (HH or Hh) Examples: Huntington’s, Dwarfism Page 345

E. Codominant Alleles 1. Both alleles are dominant = both alleles show in phenotype 2. Example: Sickle Cell Anemia a. Heterozygous for sickle cell = produce both types of RBC’s (round and sickle shaped) b. Sickle shaped can get stuck in blood vessels and cause LOTS of pain and block the flow of blood damaging tissues/organs

14-2 Human Chromosome VI. Human Genes and Chromosomes A. Smallest human autosomes 1. Chromosomes 21 and 22 a. 21 contains 225 different genes 1. Contains gene for Amyotrophic lateral sclerosis (ALS)-Lou Gehrig’s disease- degenerative neuromuscular disease b. 22 contains 545 different genes 1. Contains gene for leukemia and neurofibromatosis

Page 350 B. Sex-Linked Genes 1. Located on sex chromosomes (Pair 23) 2. More than 100 sex-linked disorders on X chromosome WHY not Y? because X is much larger than Y ; Y only 1 gene 3. Genetic disorders: a. colorblindness, hemophilia, Duchenne Muscular Dystrophy Page 350

4. Recessive sex-linked alleles more common in males than females because: a. To be expressed in females, there must be two copies of the allele, one on each of the two X chromosomes. XdXd b. Males have just one X chromosome. Thus, all X-linked alleles are expressed in males, even if they are recessive. XdY Page 350

VII. Chromosome Inactivation A. One X is randomly switched off and forms a Barr Body (This chromosome forms a dense region in the nucleus ) B. Barr bodies are generally not found in males because their single X chromosome is still active. C. Responsible for different color spots in female cats (Page 352) 1. In parts of the female cat one X is switched off resulting in black spots and in other parts of the cat the other X is switched off resulting in orange spots; therefore, orange and black spots 2. Good way to tell male from female: males only have one color spots

VIII. Chromosomal Disorders A. The most common error in meiosis occurs when homologous chromosomes fail to separate = NONDISJUNCTION B. If nondisjunction occurs, abnormal numbers of chromosomes enter the gametes, and a disorder of may result. Nondisjunction Page 352

C. If two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with three copies of a chromosome. Ex: Down Syndrome; occurs equally in males and females 47, XX, +21 or 47, XY, +21 Page 353 a. Also called Trisomy 21 b. Has three #21 chromosomes c. produces mild to severe mental retardation

D. Monosomy = missing a chromosome in a pair 1. Usually do not survive in humans except Ex. Turner Syndrome; 45,XO; normal intelligence female; short 3-4’ stature; sterile b/c never go through puberty E. Ploidy = entire sets of chromosomes 1. Results from total lack of separation of homologous chromosomes Nondisjunction-failure of homologous chromosomes to separate a. Gamete inherits a diploid set of chromosomes i.Triploidy- At fertilization, gamete fuses with a normal gamete and zygote is triploid. (3 sets of chromosomes)- banana, apples ii. Tetraploidy = 4 sets of chromosomes (day lily, wheat)

IX. Sex Chromosome Disorders A. Disorders that occur on the sex chromosomes B. In females, nondisjunction can lead to Turner’s syndrome. 1. usually inherit only one X chromosome (karyotype 45,X). 2. Usually are sterile C. In males, nondisjunction causes Klinefelter’s syndrome (karyotype 47,XXY). 1. The extra X chromosome interferes with meiosis and usually prevents these individuals from reproducing.

14-3 Human Molecular Genetics X. Human DNA Analysis A. There are roughly 6 billion base pairs in your DNA. B. Biologists search the human genome using sequences of DNA bases C. DNA testing can pinpoint the exact genetic basis of a disorder. DNA fingerprinting analyzes sections of DNA that have little or no known function but vary widely from one individual to another. 1. Only identical twins are genetically identical 2. DNA samples can be obtained from blood, sperm, and hair strands with tissue at the base.

Page 356 Letter D is on next slide for guided notes. ** Chromosomes contain large amounts of DNA called repeats that do not code for proteins. **This DNA pattern varies from person to person. ** Restriction enzymes from bacteria are used to cut the DNA into fragments containing genes and repeats.

D. DNA fragments are separated using gel electrophoresis. 1. This produces a series of bands—the DNA fingerprint. Gel Electrophoresis Page 356 2. Suspect ___ DNA Fingerprint

XI. The Human Genome Project A. Attempt to sequence ALL human DNA B. Completed in June 2000 C. Biotechnology companies are looking for information that may help develop new drugs and treatments for diseases. XII. Gene Therapy A. an absent or faulty gene is replaced by a normal, working gene. B. The body can then make the correct protein or enzyme, eliminating the cause of the disorder.

C. Viruses are often used because of their ability to enter a cell’s DNA. D. Virus particles are modified so that they cannot cause disease. E. A DNA fragment containing a replacement gene is spliced to viral DNA.

F. The patient is then infected with the modified virus particles, which should carry the gene into cells to correct genetic defects.

14–1 A chromosome that is not a sex chromosome is know as a(an) A. autosome. B. karyotype. C. pedigree. D. chromatid.

14–1 Whether a human will be a male or a female is determined by which A. sex chromosome is in the egg cell. B. autosomes are in the egg cell. C. sex chromosome is in the sperm cell. D. autosomes are in the sperm cell.

14–1 Mendelian inheritance in humans is typically studied by A. making inferences from family pedigrees. B. carrying out carefully controlled crosses. C. observing the phenotypes of individual humans. D. observing inheritance patterns in other animals.

14–1 An individual with a blood type phenotype of O can receive blood from an individual with the phenotype A. O. B. A. C. AB. D. B.

14–1 The ABO blood group is made up of A. two alleles. B. three alleles. C. identical alleles. D. dominant alleles.

14–2 The average human gene consists of how many base pairs of DNA?

14–2 Which of the following genotypes indicates an individual who is a carrier for colorblindness? A. XCX B. XCXc C. XcY D. XCY

14–2 Colorblindness is much more common in males than in females because A. the recessive gene on the male’s single X chromosome is expressed. B. genes on the Y chromosome make genes on the X chromosome more active. C. females cannot be colorblind. D. colorblindness is dominant in males and recessive in females.

14–2 The presence of a dense region in the nucleus of a cell can be used to determine the A. sex of an individual. B. blood type of an individual. C. chromosome number of an individual. D. genotype of an individual.

14–2 Nondisjunction occurs during A. meiosis I. B. mitosis. C. meiosis II. D. between meiosis I and II.

14–3 DNA fingerprinting analyzes sections of DNA that have A. little or no known function but are identical from one individual to another. B. little or no known function but vary widely from one individual to another. C. a function and are identical from one individual to another. D. a function and are highly variable from one individual to another.

14–3 DNA fingerprinting uses the technique of A. gene therapy. B. allele analysis. C. gel electrophoresis. D. gene recombination.

14–3 Repeats are areas of DNA that A. do not code for proteins. B. code for proteins. C. are identical from person to person. D. cause genetic disorders.

14–3 Data from the human genome project is available A. only to those who have sequenced the DNA. B. to scientists who are able to understand the data. C. by permission to anyone who wishes to do research. D. to anyone with Internet access.

14–3 Which statement most accurately describes gene therapy? A. It repairs the defective gene in all cells of the body. B. It destroys the defective gene in cells where it exists. C. It replaces absent or defective genes with a normal gene. D. It promotes DNA repair through the use of enzymes.