NEL Molecular Genetics 679
Section20.3combat genetic disorders. The project also may open a Pandora’s box of ethical questions,
legal dilemmas, and societal problems. Who will own or control the information obtained
and how will we prevent potential misuse of the data?
Enzymes and Recombinant DNA
As you have seen in this section, DNA sequencing is one way to identify specific seg-
ments of DNA. Another way is by creating genetic linkage maps, as you saw in
Chapter 18. Once a particular segment of DNA has been identified, molecular biolo-
gists may use enzymes to isolate that segment or modify it. The DNA fragment may
then be used to create recombinant DNA or be transferred to another organism. We
will review some of the most commonly used enzymes.
miniInvestigation Examining the Human Genome
In this activity, you will go to an online map of the human
genome. On the map, you will find diagrams containing
information about every chromosome in the genome. The
magenta and green regions on the diagrams reflect the unique
patterns of light and dark bands seen on human chromosomes
that have been stained for viewing through a light microscope.
The red region represents the centromere or constricted
portion of the chromosome. On other chromosome diagrams,
you will see yellow regions that mark chromosomal areas that
vary in staining intensity. The chromatin in these areas is
condensed and sometimes known as heterochromatin,
meaning “different colour.” Some diagrams have yellow regions
overlaid by thin horizontal magenta lines. This colour pattern
indicates variable regions called stalks that connect very small
chromosome arms (satellites) to the chromosome.Go to the Nelson Web site, and follow the link for Mini
Investigation: Examining the Human Genome. On the genome
map, click on each chromosome diagram to discover the traits
and disorders located on that chromosome. For example,
Figure 3shows traits and disorders that are found on
chromosome 20.
Touch each chromosome pair to find the number of genes
mapped on that chromosome.
Use the information you find to answer the questions below.
(a) Which chromosome pair contains the greatest number of
genes?
(b) Which chromosome contains the fewest genes?
(c) Estimate the size of the human genome. Show how you
calculated your estimate.http://www.science.nelson.com GOCreutzfeldt-Jakob disease
Gerstmann-Straussler disease
Insomnia, fatal familial
Hallervorden-Spatz syndrome
Alagille syndrome
Corneal dystrophy
Inhibitor of DNA binding, dominant negative
Facial anomalies syndrome
Gigantism
Retinoblastoma
Rous sarcoma
Colon cancer
Galactosialidosis
Severe combined immunodeficiency
Hemolytic anemia
Obesity/hyperinsulinism
Pseudohypoparathyroidism, type 1a
McCune-Albright polyostotic fibrous dysplasia
Somatotrophinoma
Pituitary ACTH secreting adenoma
Shah-Waardenbourg syndromeDiabetes insipidus, neurohypophyseal
SRY (sex-determining region Y)
McKusick-Kaufman syndrome
Cerebral amyloid angiopathy
Thrombophilia
Myocardial infarction, susceptibility to
Huntington-like neurodegenerative disorder
Anemia, congenital dyserythropoietic
Acromesomelic dysplasia, Hunter-Thompson type
Brachydactyly, type C
Chondrodysplasia, Grebe type
Hemolytic anemia
Myeloid tumour suppressor
Breast Cancer
Maturity Onset Diabetes of the Young, type 1
Diabetes mellitus, noninsulin-dependent
Graves disease, susceptibility to
Epilepsy, nocturnal frontal lobe and benign neonatal, type 1
Epiphyseal dysplasia, multiple
Electro-encephalographic variant pattern
Pseudohypoparathyroidism, type IBFigure 3
Although chromosome 20 is one of the smallest chromosomes, it has a great number
of genes.CAREER CONNECTION
Biotechnologist
Biotechnologists are involved in
improving and developing
processes and products used in
agriculture, health care, and the
chemical industry. A
biotechnologist needs specialized
knowledge of biochemistry,
microbiology, and molecular
genetics. Find out more about
opportunities in this field.http://www.science.nelson.com GO