Humans have 23 pairs of chromosomes for 46 total. One pair is linked to sex. Males have XY sex chromosomes while females have XX. One X chromosome is inactivated in females, forming a Barr body. Pedigrees help track genetic inheritance, especially in the case of genetic disorders. These diagrams show a family tree along with the individuals that carry the phenotype for a particular trait. Some patterns are autosomal dominant, like in Huntingtons disease, and do not skip a generation. Some are autosomal recessive, like cystic fibrosis, Tay-Sachs disease, and phenylketonuria. These may skip a generation. Neither case is sex-linked. X-linked recessive inheritance is linked to the X chromosome, such as hemophilia, Duchene Muscular Dystrophy, and color blindness. Males are more commonly affected because females have two X chromosomes.
have 23 pairs of autosomes and one pair of sex chromosomes. Males
are XY and females are XX. Genes that are located on the sex
chromosomes are called sex-linked genes.
In females, one copy of the X-chromosome
is inactivated in each cell. The inactivated copy of the X
chromosome is called a Barr body.
A pedigree is a diagram of a family tree
that indicates the phenotype of individuals for a particular trait.
Pedigree analysis can help to determine the inheritance pattern of a
trait or genetic disorder.
Pedigrees for traits with an autosomal
dominant inheritance pattern show an approximately equal number of
affected males and females. Autosomal dominant traits do not skip
a trait is inherited in an autosomal recessive pattern, males and
females are approximately equally affected. The trait may skip a
are more frequently affected if a disorder has an X-linked
recessive inheritance pattern. Females may be carriers and these
disorders can skip a generation.
Sex-Linked Traits and Pedigree Analysis
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
The book and CD package include two full length practice exams that are presented with all questions answered and explained. The author also presents detailed reviews of all test topics and includes multiple-choice and free-response questions with answers at the end of each topic's chapter.
This book includes a review of the AP Biology exam format and scoring, proven strategies for answering multiple-choice questions, and hints for tackling the essay questions. The practice tests include answers and explanations and there is also proven test-taking strategies for both the multiple choice and essay parts.