Ch. 1OVERVIEW

OF GENETICS

Is the study of inherited traits and their variation

Is a life science that should not be confused with genealogy

Is also an informational science that is having a huge societal impact

GENETICS

Figure 1.1

Contain the instructions within the cells for protein production

Genes are composed of deoxyribonucleic acid (DNA)

Traits are produced by an interaction between the genes and their environment

GENES

Figure 1.1

Is the complete set of genetic information for an organism

It includes all of the genes present in an organism

And also DNA sequences that do not encode genes

Genomics is a field that analyzes and compares genomes of different species

THE GENOME

LEVELS OF GENETICS

A double-stranded polymer consisting of a chain of nucleotides

Deoxyribonucleotide components:- Phosphate- Sugar: Deoxyribose- Base: Adenine A Guanine G Thymine T Cytosine C

The sequence of the bases code for the amino acid sequence in a protein

DEOXYRIBONUCLEIC ACID (DNA)

Reading1.1, Figure 1

Box, Figure 1

A single stranded polymer of ribonucleotides

Ribonucleotide components:- Phosphate- Sugar: Ribose- Base: Adenine A Guanine G

Uracil U Cytosine C

Exists in several types

Uses information on DNA to construct proteins

RIBONUCLEIC ACID (RNA)

Reading 1.1, Figure 2

Box, Figure 2

Only 1.5% of our DNA encodes protein- About 20,325 protein-encoding genes in all

Rest of the human genome includes highly repeated sequences with unknown functions

Genes known to cause disorders or traits are cataloged in a database

- Online Mendelian Inheritance in Man (OMIM)

Proteomics is a field that studies the proteins made in a cell

THE HUMAN GENOME

Alleles are variants of genes

They form by mutation

Mutations in sperm or egg cells are passed on to the next generation

Mutations may be positive, negative, or neutral

GENES

Polymorphisms are variations in the DNA sequence that occur in at least 1% of the population

Single nucleotide polymorphisms (SNPs) are single base sites that differ among individuals

- Can cause disease or act as genomic markers

VARIATIONS

Genome-wide association studies track SNP patterns among individuals who share a particular trait or disorder

Gene expression profiling measures which genes are more or less active in particular cell types

RESEARCH

Composed of DNA and protein

Found in the nucleus of the cell

Human somatic cells have 46 chromosomes

- 22 pairs of autosomes- A pair of sex chromosomes

- Females have two X chromosomes

- Males have one X & a Y

CHROMOSOMES

Figure 1.2

KaryotypeA chart displaying the chromosome pairs

from largest to smallest

Figure 1.2

A human body contains approximately 50-100 trillion cells

- All cells except RBCs contain the same genome

Differentiation causes cells to differ in appearance and function

- Controlled by variation in gene expression

Stem cells are less specialized and can become many different cell types

CELLS

The genotype of an individual refers to the alleles they carry

The phenotype is the visible trait

A dominant allele is expressed if the individual carries just one copy

A recessive allele is only expressed if the individual carries two copies

INDIVIDUAL

Individuals are genetically connected into families

A pedigree is a diagram used to study traits in families- Can be used to trace multiple genes or genes with large environmental component- Will be discussed in detail in Chapter 4

THE FAMILY

Is a group of interbreeding individuals

The gene pool is the sum of all alleles in a population

Evolution is the changing allelic frequencies in populations over time

A POPULATION

Genome comparisons among species reveals evolutionary relationships- The more similar the sequences are, the more recent the divergence from a common ancestor

98% of human DNA sequences are shared with chimpanzees

Humans share genes with mice, pufferfish, fruit flies, yeast, and even bacteria

EVOLUTION

Figure 1.4

Figure 1.4

Mendelian traits are determined by a single gene- Their recurrence is predicted based on Mendel’s laws

Multifactorial traits are determined by one or more genes and the environment- Predicting their recurrence is much more difficult

Most traits are multifactorial

MENDELIAN VS. MULTIFACTORIAL TRAITS

MENDELIAN VS. MULTIFACTORIAL TRAITS

Figure 1.5

Genetic determinism is the idea that the expression of an inherited trait is inevitable

This may be harmful or helpful, depending on its application

- As part of a social policy, it is disastrous- Knowing genetic risks can help us make good choices

GENES AND DISEASE RISK

Genetics impacts many areas of our lives

DNA profiling (DNA fingerprinting) looks at SNPs and short repeated DNA sequences- It has applications in:

- Forensics- History and ancestry

APPLICATIONS OF GENETICS

Identification of victims of natural disasters or terrorist attacks

Matching the DNA of suspects to samples left at the crime scene

Helping adopted individuals locate blood relatives

FORENSICS

DNA analysis can flesh out historical details

- Revealing the offspring of Thomas Jefferson and Sally Hemmings

- Revealing the origins of the Jewish Lemba of South Africa

HISTORY AND ANCESTRY

Figure 1.7

HISTORY AND ANCESTRY

Figure 1.6 Figure 1.7

Pharmacogenomics is a field that identifies individual drug reactions based on genetics

HEALTH CARE

Analysis of single-gene illnesses reveals many differences from other diseases

HEALTH CARE

Diseases are increasingly being described in terms of gene expression patterns

Tracking gene expression can reveal new information about diseases and show how diseases are related to each other- This is not obvious via traditional medicine

HEALTH CARE

GENETIC TESTING AND TREATMENT

Tests to identify about 1,200 single-gene disorders have been available for years- Direct-to-consumer (DTC) genetic testing

The Genetic Information Non-discrimination (GINA) act was passed in the US in 2008

Genome information is useful for developing treatment to genetic and infectious diseases

Gene therapy attempts to correct certain genetic disorders.

AGRICULTURE

Traditional agriculture is the controlled breeding of plants and animals

Biotechnology is the use of organisms or their parts to produce goods and services

Genetically-modified (GM) organisms have new genes or over- or under-express their own genes

Goats produce spider silk protein in their milk

Transgenic rice manufactures beta-carotene and stores twice as much iron as unaltered rice.These animals

make glowing fluorescent protein (gene from a jellyfish)

A transgenic organism harbors a gene or genes from a different species.

A GLOBAL PERSPECTIVE

Genetics and genomics are spawning technologies that may vastly improve the quality of life

Human genome information has tremendous potential for the entire globe- Individual nations are using approaches that exploit their particular strengths

A GLOBAL PERSPECTIVE

Nation Program

China The genome of 100 people are being sequenced.

Gambia A DNA databank has samples from 57,000 people.

India A national databank stores DNA from 15,000 people. A company is genotyping the entire Parsi population of 69,000. Law prevent foreign researchers from sampling tissue from Indians without permission.

Mexico The National Institute of Genomic Medicine has genotyped 1,200 people o look for correlations to common diseases. Legislation requires approval for foreign researchers to sample DNA from Mexicans.

South Africa Studies of human genetic diversity among indigenous tribes and susceptibility to HIV and tuberculosis among many populations are underway.

Thailand A database stores information on genetic susceptibility to dengue fever, malaria, other infectious diseases, and posttraumatic stress disorders from the 2004 tsunami.