7th Grade Science-Chapter 11 Test Study Guide: Human Genetics and Genetic Technology
LESSON 11.1
Carrier-a person who has one recessive allele and one dominant allele for a trait
The carrier will not have the trait if the characteristic is determined by a recessive allele.
Sex chromosomes-the chromosomes that carry the genes that determine the sex (gender) of the
individual, as well as other genes (XX-female; XY-male)
The likelihood a couple will have a boy vs. girl is 50%/50%.
Sex-linked gene-a gene found on the X or Y chromosome
Some traits are controlled by a single gene with only two alleles. EX: widow’s peak and dimpled chin
Some traits are controlled by a single gene with multiple alleles. EX: human blood type
Some traits are controlled by multiple genes. EX: human height
You must be able to use a Punnett Square to determine the probability of passing on sex-linked
characteristics. See pgs 417 and 420 in the textbook for sample problems.
LESSON 11.2
Genetic disorder-an abnormal condition a person inherits through genes or chromosomes
Some genetic disorders are caused by gene mutations in the DNA; others are caused by a change in the
overall structure or number of chromosomes.
EX: cystic fibrosis and sick-cell disease are caused by a mutation in one’s genes/DNA
EX: hemophilia-caused by a recessive allele on the X chromosomes (sex-linked)
EX: Down’s syndrome-caused by the addition of an extra chromosome #21
Doctors use pedigrees, karyotypes, and genetic testing to trace and diagnose genetic disorders.
People with genetic disorders are helped through medical care, education, and job training.
Genetic counseling helps couples understand their chances of having children with a genetic disorder.
Pedigree-a chart or family tree that tracks which members of a family have a certain trait
Karyotype-a picture one all the chromosomes in a person’s cell (23 pairs = 46 total chromosomes)
You must be able to draw and analyze a simple pedigree, given example information. See pgs 421 and
432 for textbook samples.
LESSON 11.3
Selective breeding, cloning, and genetic engineering are three different methods for developing
organisms with desired traits.
Selective breeding-process of selecting organisms with desired traits to be parents of the next
generation. Ex: plants and animals can sometimes be bred in this way to get the desired traits in the
offspring.
Two techniques for selective breeding are: inbreeding and hybridization.
Inbreeding- breeding technique that involves crossing two individuals that have similar desirable
characteristics. This process produces organisms that are genetically very similar. This type of breeding
leads to a greater chance for genetic disorders.
Hybridization-breeding technique where breeders cross two genetically different individuals. The hybrid
is bred to have the best traits of both parents.
Clone-an organism that is genetically identical to the parent; the offspring has the same genes as the
organism from which it was produced.
Genetic engineering-process where genes from one organism are transferred into the DNA of another
organism. Many positive things result from genetic engineering, such as producing medicines and
improved food crops.
Gene therapy-a process that involves inserting copies of a gene directly into a person’s cells. This
process may be used one day in the future for the purpose of correcting genetic disorders.
LESSON 11.4
Genetic information can be used positively (to identify individuals and to learn about health and disease)
and negatively (to discriminate against people.
Ethics-the study of principles about right vs. wrong and fair vs. unfair.
The Genetic Information Nondiscrimination Act (GINA) makes it illegal for health insurance companies
and employers to discriminate against individuals based on genetic information. Also, it is illegal for
them to require you to have a DNA test done.
Genome-an organism’s fill set of DNA
The Human Genome Project was a research project completed in 2003 with the purpose of identifying
the DNA sequence of the entire human genome. Scientists still continue to research the functions of the
tens of thousands of human genes.
DNA “fingerprinting” is a process where scientists take a person’s DNA and break it into fragments,
which are used to produce a unique pattern, which is called a DNA fingerprint. DNA fingerprints can be
used to identify individuals because no two people have the same DNA fingerprint, except for identical
twins. There is much debate about whether or not the US should obtain people’s DNA fingerprint to
keep on file.