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Chapter 12

Classical and Modern Genetics

Genetic Lingo
An organism is diploid if it inherits two variants, or alleles, of each gene, one from each parent. These two alleles constitute the genotype for a…
Punnett Squares
A Punnett square displays the possible genotypes offspring can inherit from two parental genotypes. If a trait’s inheritance pattern (e.g.,…
Monohybrid Crosses
In the 1850s and 1860s, Gregor Mendel investigated inheritance by performing monohybrid crosses in pea plants. He crossed two plants that were…
Dihybrid Crosses
To determine whether traits are inherited together or separately, Gregor Mendel crossed pea plants that differed in two traits. These parental…
Law of Segregation
When crossing pea plants, Mendel noticed that one of the parental traits would sometimes disappear in the first generation of offspring, called the…
Law of Independent Assortment
While Mendel’s Law of Segregation states that the two alleles for one gene are separated into different gametes, a different question of how…
Test Cross
Alleles are different forms of the same gene. Humans and other diploid organisms inherit two alleles of every gene, one from each parent. An allele…
Pedigree Analysis
A pedigree is a diagram displaying a family’s history of a trait. Analyzing pedigrees can reveal (1) whether a trait is dominant or…
Probability Laws
The probability of inheriting a trait can be calculated using the sum and product rules. The sum rule is used to calculate the probability of…
Multiple Allele Traits
Multiple allelism describes genes that exist in three or more allelic forms. Although diploid organisms, like humans, normally possess only two…
Chromosomal Theory of Inheritance
In 1866, Gregor Mendel published the results of his pea plant breeding experiments, providing evidence for predictable patterns in the inheritance of…
Non-nuclear Inheritance
Most DNA resides in the nucleus of a cell. However, some organelles in the cell cytoplasm—such as chloroplasts and mitochondria—also have…
X-linked Traits
In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be…
Sex-linked Disorders
Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in…
X-Inactivation
The human X chromosome contains over ten times the number of genes as in the Y chromosome. Since males have only one X chromosome, and females have…
Epistasis
In addition to multiple alleles at the same locus influencing traits, numerous genes or alleles at different locations may interact and influence…
Polygenic Traits
When more than one gene is responsible for a given phenotype, the trait is considered polygenic. Human height is a polygenic trait. Studies have…
Pleiotropy
Pleiotropy is the phenomenon in which a single gene impacts multiple, seemingly unrelated phenotypic traits. For example, defects in the SOX10 gene…
Nature and Nurture
Many human characteristics, like height, are shaped by both nature—in other words, by our genes—and by nurture, or our environment. For…
High-Throughput Robotically Assisted Isolation of Temperature-sensitive Lethal Mutants in <em>Chlamydomonas reinhardtii</em>
Systematic identification and characterization of genetic perturbations have proven useful to decipher gene function and cellular pathways. However,…
Optogenetic Random Mutagenesis Using Histone-miniSOG in <em>C. elegans</em>
Forward genetic screening in model organisms is the workhorse to discover functionally important genes and pathways in many biological processes. In…
Mosaic Zebrafish Transgenesis for Functional Genomic Analysis of Candidate Cooperative Genes in Tumor Pathogenesis
Comprehensive genomic analysis has uncovered surprisingly large numbers of genetic alterations in various types of cancers. To robustly and…

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