Living Environment Translated Arabic 2014 | Page 62

 An allele inherited on a sex chromosome is called a sex-linked gene.
o Sex-linked traits show up more often in one sex ( usually
males) than they do in the other sex.
o Examples: colorblindness; hemophilia
 A sex-limited trait is found on the sex chromosome and ONLY shows
up in one sex or the other.
 Recessive genes control many human genetic disorders.
 Pedigrees are visual tools used to trace a trait through several
generations of a family.
 Genetic Engineering - the process of changing an organism’s DNA to
give the organism new traits.
o Scientists work with biological and chemical methods to
change the arrangement of DNA that make up a gene.
o One method of genetic engineering is making recombinant
DNA. This is a method of inserting form one organism into
another organism. Usually the receiving organism is bacteria.
o Bacteria are used because of their rapid reproduction rates.