Download Life Science Study Sheet

Life Science Study Sheet
Modern Genetics Study Sheet
Know this information (Also: Study the vocabulary sheet, your homework answers,
and handouts/worksheets.) Be sure to know how to "read" a pedigree. Know the
meanings of the symbols used (circles, squares, shading, lines, etc.)
Section 1. Human Inheritance
1. Some human traits are controlled by a single gene that has more than two
alleles or forms. These three or more forms of a single gene are called multiple
alleles. Human blood type is an example of at trait controlled by multiple alleles.
2. Polygenetic traits are traits produced by multiple genes. Skin color, eye color,
and height are examples of polygenetic traits. These genes act together as a group
to produce a single trait.
3. Traits are often influenced by the organism’s environment. Height is an
example of a trait that can be modified by an organism’s environment. If a proper
amount of food is available, a person will probably reach his/her potential height.
If nutrition is poor the person may end up shorter that his/her potential height.
4. Males have one X chromosome and one Y chromosome. Females have two X
chromosomes. (Male = XY; Female = XX)
5. The X and Y chromosomes are the 23rd pair of chromosomes in the human
genome. These chromosomes are called the sex or gender chromosomes.
6. Males are more likely than females to have a sex-linked trait controlled by a
recessive allele such as colorblindness. This is because the Y chromosome is
shorter that the X chromosome. If the X chromosome has a defective gene, and
there is no homologous gene on the Y chromosome to override it, the male will
have the condition caused by the defective gene.
7. A pedigree is a chart that shows several generations of a family. Geneticists use
pedigrees to trace the inheritance pattern of a particular trait through a
number of generations of a family.
Section 2. Human Genetic Disorders
1. Genetic disorders are abnormal conditions that are caused by mutations or
changes in an organism’s DNA in a gene or chromosome. In some cases, these
mutations can be passed on from one generation to the next.
2. Commonly known genetic disorders include cystic fibrosis, sickle-cell anemia,
hemophilia, and Down syndrome. There are many others that are not well
known to the general public such as Williams disorder and Turner syndrome.
3. Amniocentesis is a test used to diagnose genetic disorders. During
amniocentesis a small amount of fluid (amniotic fluid) surrounding the
developing fetus is extracted and analyzed to see if any abnormalities are present
in the fetus’s chromosomes.
4. Karyotyping is another tool used to diagnose genetic orders. A sample of DNA is
taken from a white blood cell. The chromosomes are photographed, organized in
pairs, and examined for abnormalities.
5. Genetic counselors are professionals who help couples understand their chances
of having a child with a genetic disorder.
Section 3. Advances in Genetics
1. Selective breeding is the process of selecting a few organisms with desired
traits to serve as parents of the next generation. Farmers and animal breeders
have used selective breeding to improve plants and animals for thousands of
years.
2. Cloning is a technique used to produce an organism that is genetically
identical to the organism from which it was produced. The process involves
removing the nucleus from an egg cell, replacing it with the nucleus of the
organism to be cloned, then placing the egg cell with the new nucleus into
compatible female organism for gestation.
3. Genetic engineering involves the transfer of a gene from the DNA of one
organism into another organism. Genetic engineering can be used to produce
medicines and to improve crops. Genetic engineering is responsible for tomatoes
with fish genes that can resist cold, and goats that produce spider silk or medicine
in their milk!
4. Gene therapy involves the insertion of working copies of a gene into the cells
of a person with a genetic disorder in an attempt to correct the disorder. Results
have been mixed regarding the success of this strategy for curing diseases.
5. DNA fingerprinting can be used to help determine whether material found at a
crime scene came from a particular suspect. DNA can be extracted from urine,
semen, saliva, blood, hair, and skin cells. DNA "fingerprints" are images of
sequences of DNA. No two individuals, except for identical twins, have the same
DNA sequences.
6. The goal of the Human Genome Project was to identify the DNA sequence of
every gene in the human genome. This has been accomplished. Scientists are
working on or have completed the genomes of other species such as bacteria,
fungi, many plants and some animals – many invertebrates and some vertebrates
like dogs, mice, etc.