Chapter 1 What Is in a Human Genome?
What Information Is in a Human Genome?
Clinical Connection 1.1
Exome Sequencing Saves a Boy’s Life
Bioethics: Choices for the Future
Genetic Testing and Privacy
Chapter 1 provides a glimpse of the basic concepts of genetics and genomics, and offers examples of DNA information impacting daily life. In this new era of genomics, individuals have access to their own genetic information, and health care providers are learning how to incorporate DNA data into diagnostic and therapeutic medicine. Bioethics deals with issues of privacy, discrimination, ...view middle of the document...
1.2 Levels of Genetics and Genomics
The Instructions: DNA, Genes, Chromosomes, and Genomes
1. Genetic investigation of the mechanisms of heredity occurs at multiple levels: from smallest to largest are DNA, gene, chromosome, and genome.
2. A DNA molecule consists of “rails” of alternating sugars and phosphates and “steps” of adenine-thymine (A-T) and guanine-cytosine (G-C) base pairs. Each three contiguous base pairs encode one of 20 types of amino acids, which build proteins. Messenger RNA carries DNA information out of the cell’s headquarters (nucleus) to where it is used to synthesize proteins.
3. A portion of DNA that encodes a protein is a gene.
4. A DNA molecule replicates as the sides of the double helix part and fill in with new bases.
5. Different cell types express different subsets of genes.
6. The exome is the 1.5% of the 20,325 or so genes of the human genome that encodes protein.
7. Mendelian Inheritance in Man (MIM) catalogs disease-related gene variants.
8. Genes can exist in more than one form. Variants (alleles) arise by mutation.
9. Chromosomes consist of genes and associated proteins.
10. The human genome is 22 pairs of autosomes and one pair of sex chromosomes.
11. A karyotype is a photographic chart of an individual’s chromosomes.
12. A Mendelian trait is caused by a single gene. A multifactorial trait is caused by one or more genes and environmental influences. Most genes do not function alone.
13. Genetic determinism is the idea that our genes control everything about us, with little or no outside influences.
The Body: Cells, Tissues, and Organs
1. The human body is composed of about 37 trillion cells. All cell types except mature red blood cells contain the entire genome.
2. Differential gene expression creates more than 290 distinctive cell types, which combine to form four basic tissue types that interact to form organs and organ systems.
3. Many organs contain stem cells that “self-renew” as well as produce cells that specialize. These two properties are essential for growth, development, and healing.
Relationships: From Individuals to Families
1. Genotype is the allelic makeup of an individual; phenotype is the observable or measureable expression of an individual’s alleles.
2. Dominant alleles are expressed when one copy is present. Recessive alleles require two copies for expression.
3. Pedigree diagrams follow recessive and dominant traits through generations.
The Bigger Picture: From Populations to Evolution
1. Population genetics concerns allele frequencies in members of the same species in a specified geographic area.
2. “Gene pool” refers to all of the alleles in a given population.
3. Population genetics has applications in health care, forensics, and evolution.
4. Comparative genomics explores evolutionary relationships among species.
3. Applications of Genetics and Genomics
1. DNA profiling...