Chapter 12  CHROMOSOMES and HUMAN GENETICS

1. Textbook website: http://www.brookscole.com/biology
   1. chapter by chapter resources
      1. chapter/outlines/ch12.html
      2. chapter/quizzes/ch12
      3. flash cards-select from resources for chapter 12.
2. Mendelian Genetics many excellent links from Ken House's BioWeb
3. On-Line Biology Book by M. J. Farabee 
   1. Genes and Chromosomes 
   2. Chromosome abnormalities
   3. Human Genetics
4. Kimball's Biology Pages
   1. Genetic Linkage and Genetic Maps from Kimball's Biology Pages
   2. Phenylketonuria (PKU) from Kimball's Biology Pages
   3. Screening for Genetic Disease
   4. Polyploidy
5. The Biology Project  an interactive online resource for learning biology, developed at The University of Arizona
   1. Sex Linked Inheritance1
   2. Sex Linked Inheritance 2
   3. Color Blindness
   4. Human Genetics
6. MIT Biology Hypertext 
   1. Linkage Mapping
   2. sex linkage
   3. Pedigrees
   4. The future of genetic research
   5. An Exercise in Genetic Counseling
7. North Harris College Genetics Tutorials
8. Mendel Web

CHROMOSOMES AND HUMAN GENETICS Chapter 12 

The Philadelphia Story

1. the Philadelphia chromosome
   1. The first abnormal chromosome associated with cancer 
   2. chromosome number nine to which a piece of number twenty-two is attached. [Fig. 12.1]

12.1 – THE CHROMOSOMAL BASIS FOR INHERITANCE – AN OVERVIEW 

Genes and Their Chromosome Locations 

1. Genes
2. Homologous chromosomes
3. Alleles
4. Crossing over

Autosomes and Sex Chromosomes 

1. autosomes
   1. homologous pairs whose chromosomes are similar
   2. 44 in humans
2. Sex chromosomes
   1. Female mammals have two X chromosomes
   2. Male mammals have one X and one Y. 

12.2 – KARYOTYPE ANALYSIS 

1. karyotype [fig. 12.3]

12.3 – CHROMOSOMAL SEX DETERMINATION IN MAMMALS 

1. sex chromosomes (fig 12.4)
2. Functions of the Sex Chromosomes [fig 12.5]
   1.  SRY - sex determining region of Y
   2. Before week 7, embryo is neither male nor female 

12.4 – EARLY QUESTIONS ABOUT GENE LOCATIONS 

Linked genes -- Clues to Inheritance Pattterns

1. X-linked genes
   1. genes on X have no alleles on Y 
   2. heterozygous carriers do not express trait, but pass it on to 50% of their sons 
   3. eye color in Drosphila [fig 12.6] 
2. Autosomal Linkage 
   1. linkage group

12.5 RECOMBINANT PATTERNS AND CHROMOSOMAL MAPPING 

1. alleles for certain fruit fly characteristics on the same chromosome tend to remain together during meiosis because they are positioned closer togther [Fig. 12.9] 
2. genetic mapping [fig. 12.10]: gene order is determined by the percent of recombination between each of the possible pairs 

12.66 – HUMAN GENETIC ANALYSIS 

Analysis of Patterns of Inheritance 

1. nonhuman research 
2. humans: small families, long generation time 
3. pedigree [fig. 12-11]

Genetic Disorders [table 12.1] 

1. genetic abnormalities
2. Genetic disorders
3. Syndrome
4. Genetic disease

12.7 – INHERITANCE PATTERNS 

Autosomal Recessive Disorders [fig. 12.12] 

1. Either parent can carry the recessive allele on an autosome.
2. Carriers: symptom-free
3. Examples
   1. Phenylketonuria (PKU)
   2. Cystic fibrosis
   3. Tay-Sachs
   4. Galactosemia

Autosomal Dominant Disorders [fig. 12.13] 

1. dominant allele is nearly always expressed 
2. Examples
   1.  Neurofibromatosis 
   2. Huntington Disease
   3. Achondroplasia

X-Linked Recessive Inheritance [fig. 12.14]

1. Heterozygous females are phenotypically normal 
2. males are more often affected 
3. Examples
   1. color blindness: in men 6% green gene; 2% red
   2. Hemophilia A: lack of clotting factor VIII [fig. 12.14b]
      1. A Pedigree of Hemophilia in the Royal Families of Europe by Robert J. Huskey;  BIOL 121: Human Biology Web Site
      2. Hemophilia: "The Royal Disease" by Yelena Aronova-Tiuntseva and Clyde Freeman Herreid University at Buffalo, State University of New York
   3. Muscular Dystrophy
   4. fragile X syndrome[Fig. 12.15] 

12.8 – PROGERIA – TOO YOUNG TO BE OLD 

1. Progeria: a heritable (genetic) disorder
2. Hutchinson-Gilford syndrome [fig. 12.16] 

12.9 – CHANGES IN CHROMOSOME STRUCTURE

1. Major Categories 
   1. duplications:
   2. inversions 
   3. translocations [Philadelphia chromosome]
   4. deletions
      1. cri du chat syndrome  [fig 12.17] 
2. Evolutionary significance
   1. usually selected against
   2. duplications create new genes 
   3. Duplications, inversions, and translocations figured in human evolution [fig. 12.18]

12.10 – CHANGES IN CHROMOSOME NUMBER 

1. Categories
   1. Aneuploidy [fig. 12.19]
      1. abnormal meiotic (or mitotic division) 
      2. trisomy: (2N+1) one extra; Down Syndrome, trisomy 21.
      3. Monosomy: (2N-1) one fewer. 
   2. Polyploidy: http://www.ultranet.com/~jkimball/BiologyPages/P/Polyploidy.html
      1. more than 2N chromosome sets
      2. lethal in humans;
      3. many (47%) flowering plants, especially grasses are polyploid
2. Autosome Abnormalities
   1. few trisomies in humans, no live birth monosomies 
      1. Down syndrome [fig. 12.20]
      2. translocation form of Down syndrome 
      3. Patau Syndrome
      4. Edwards Syndrome 
3. Sex Chromosomes [fig.12.16]
   1. Turner syndrome: XO, monosomy of X
   2. Klinefelter syndrome XXY
   3.  XYY

12.11 – DETECTING GENETIC ABNORMALITIES 

1. Phenotypic Treatments 
2. Genetic Screening
3. Genetic Counseling
4. Prenatal Diagnosis
   1.  amniocentesis
   2. chorionic villus sampling
   3. genetic probes 
5. regarding abortion 
6. Preimplantation diagnosis for in vitro fertilizatio

KEY TERMS FOR CHAPTER 11

Genetics Problems that have been asked on previous exams

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