BIO 143 Chapter Notes - Chapter 10: Triple X Syndrome, Siamese Cat, Genetic Linkage

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8 Jun 2018
Fall 2011BIO143 Study Guide: Chapter 10
Chapter 10: Patterns of Inheritance
I. What is the physical basis of inheritance?
A. Inheritance is the process by which characteristics of individuals are passed to their offspring
1. Genes are the units of inheritance
B. Gene are sequences of nucleotides at specific locations on chromosomes
1. A gene’s location on a chromosome is called what?
2. What are alleles?
3. Mutations are the source of alleles
C. An organism’s two alleles may be the same or different
1. If both homologous chromosomes have the same allele, the organism is referred to as
2. If both homologous chromosomes have different alleles, the organism is referred to as
II. How were the principles of inheritance discovered?
A. Gregor Mendel deduced the common patterns of inheritance
B. The secrets of Mendel’s success
1. Mendel chose pea plants as the subjects for his experiments
a. Reproductive structures are enclosed within petals, thus preventing cross-
b. Mendel artificially caused cross-pollination
i. Self-pollination is normal, simplifying self crosses
ii. True-breeding varieties were already available (what are true-breeding
2. Mendel chose to examine single traits individually
3. Mendel followed traits through several generations
III. How are single traits inherited?
A. Mendel’s early experiments involved flower color: purple and white true-breeding plants
1. In the parental generation (P), one parent was true-breeding for purple and the other true-
breeding for white
2. The first filial generation (F1) were the offspring
a. All were purple (how did this happen??)
3. Mendel self-fertilized the F1 generation to produce F2 generation
a. White flowers reappeared among the F2
b. About ¾ were purple and ¼ were white
i. White trait had “receded” into the background
ii. Purple trait had “dominated” white
B. The inheritance of dominant and recessive alleles on homologous chromosomes can explain the
results of Mendel’s crosses
1. Each trait is determined by discrete pairs of physical units called genes
2. When two different alleles are present in an organism, the dominant allele may mask the
expression of the recessive allele
3. Pairs of alleles on homologous chromosomes segregate from each other during meiosis
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