Introduction to Genetics Flashcards
is the general process by which traits controlled by genes are transmitted through gametes from generation to generation
Transmission genetics
explains how genetic information is stored and expressed. This discovery is the foundation of molecular genetics.
The Watson–Crick model of DNA structure
a molecular complex found in bacteria that has the potential to revolutionize our ability to
rewrite the DNA sequence of genes from any organism
CRISPR-Cas
it represents the ultimate tool in genetic technology
CRISPR-Cas
Other systems have been developed aside from the CRISPR-Cas
zinc-finger nucleases (ZFNs) & transcription activator-like effector nucleases (TALENs)
CRISPR means
(clustered regularly interspersed short palindromic repeats)
How does CRISPR work
designates an RNA molecule, which in the laboratory can be synthesized to match any DNA sequence of choice
CRISPR RNA has two ends
- Recognizes and binds to a matching DNA sequence in the gene of interest
- The other binds to a CRISPR-associated
(Cas) nuclease, or DNA-cutting enzyme
What is the most commonly used Cas nuclease
Cas9
CRISPR-Cas systems have already been used to repair mutations in cells derived from individuals with several genetic disorders, including…
cystic fibrosis
Huntington disease
beta-thalassemia
sickle cell disease
muscular dystrophy
X-linked retinitis pigmentosa
For example, one research group was able to use this system to spread genes that prevent mosquitoes from carrying the parasite that causes malaria. Other researchers have proposed using CRISPR-Cas9 to engineer laboratory-grown human blood vessels and organs that do not express proteins that cause rejection of transplanted tissues and organs. The method has also been used to create disease-resistant strains of wheat and rice.
Between 8000 and 1000 b.c., horses, camels, oxen, and wolves were domesticated, and selective breeding of these species soon followed. Cultivation of many plants, including maize, wheat, rice, and the date palm, began around 5000 b.c. Such evidence documents our ancestors’ successful attempts to manipulate the genetic composition of species
The ————————-argued that active “humors” in various parts of the body served as the bearers of hereditary traits
The Hippocratic treatise “On the Seed”
He proposed that the male semen contained a “vital heat” with the capacity to produce offspring of the same “form” (i.e., basic structure and capacities) as the parent
He believed that this heat cooked and shaped the menstrual blood produced by the female, which was the “physical substance” that gave rise to an offspring
The embryo developed not because it already contained the parts of an adult in miniature form (as some Hippocratics had thought) but because of the shaping power of the vital heat
Aristotle
What is epigenesis?
an organism develops from the fertilized egg by a succession of developmental events that eventually transform the egg into an adult
What is the theory of preformation?
fertilized egg contains a complete miniature adult, called a homunculus
State the cell theory
all organisms are composed of basic structural units called cells, which are derived from pre-existing cells
What is the name of the published work of Charles Darwin
The Origin of Species, in 1859
What was the name of the ship boarded by Charles Darwin in his expedition
HMS Beagle (1831-1836)
Explain natural selection
natural selection is based on the observation that populations tend to contain more offspring than the environment can support, leading to a struggle for survival among individuals. Those individuals with heritable traits that allow them to adapt to their environment are better able to survive and reproduce than those with less adaptive traits.
heredity and development were dependent on genetic information residing in genes contained in chromosomes, which were then contributed to each individual by gametes—the so-called
chromosomal theory of inheritance
in most eukaryotes, members of each species have a characteristic number of chromosomes called the…
diploid number (2n)
Chromosomes in diploid cells exist in pairs, called…
homologous chromosomes
A colorized image of the human male chromosome set. Arranged in this way, the set is called a —–
karyotype
states that inherited traits are controlled by genes residing on chromosomes faithfully transmitted through gametes, maintaining genetic continuity from generation to generation.
chromosome theory of inheritance
any heritable change in the DNA sequence and are the source of all genetic variation
Mutation
defined as alternative forms of a gene
Alleles
The set of alleles for a given trait carried by an organism is called the
Genotype
By the 1920s, scientists knew that proteins and DNA were the major chemical components of chromosomes
Each linear strand of the helix is made up of subunits called
nucleotides
In eukaryotic cells, the process leading to protein production begins in the nucleus with
Transcription
The synthesis of proteins under the direction of mRNA is called
Translation
The information encoded in mRNA (called the ———) consists of a linear series of nucleotide triplets. Each triplet, called a ——-
genetic code
codon
There are how many different amino acids commonly found in proteins
20
Protein assembly is accomplished with the aid of adapter molecules called
transfer RNA (tRNA)
tRNAs recognize the information encoded in the mRNA codons and carry the proper amino acids for construction of the protein during translation
They form the largest category of proteins
Enzymes
Enzymes serve as biological catalysts, lowering the energy of activation in reactions and allowing cellular metabolism to proceed at body temperature
Examples of proteins
- hemoglobin, the oxygen-binding molecule in red blood cells
- insulin, a pancreatic hormone
- collagen, a connective tissue molecule
- actin and myosin, the contractile muscle proteins
caused by a mutant form of hemoglobin
a mutation in the gene encoding β-globin causes an amino acid substitution in 1 of the 146 amino acids in the protein
a change in codon 6 in mRNA from GAG to GUG, which in turn changes amino acid number 6 in β@globin from glutamic acid to valine
mutant β-globin proteins cause hemoglobin molecules in red blood cells to polymerize when the blood’s oxygen concentration is low, forming long chains of hemoglobin that distort the shape of red blood cells
Sickle-cell anemia
recombinant DNA began in the early ——
1970s
used by bacteria to cut and inactivate the DNA of invading viruses, could be used to cut any organism’s DNA at specific nucleotide sequences, producing a reproducible set of fragments
restriction enzymes
Large amounts of cloned DNA fragments can be isolated from these bacterial host cells. These DNA fragments can be used to isolate genes, to study their organization and expression, and to study their nucleotide sequence and evolution
Collections of clones that represent an organism’s genome, defined as the complete haploid DNA content of a specific organism, are called
genomic libraries
The use of recombinant DNA technology and other molecular techniques to make products is called
biotechnology
What was the name of the Finn Dorset sheep that was cloned in 1996
Dolly the sheep (a Finn Dorset sheep)
What was the name of Dolly the sheep’s offspring
Bonnie
the Human Genome Project, began in 1990 as an international effort to sequence the human genome.
(the study of genomes), studies the structure, function, and evolution of genes and genomes
Genomics
identifies the set of proteins present in a cell under a given set of conditions, and studies their functions and interactions
proteomics
To store, retrieve, and analyze the massive amount of data generated by genomics and proteomics, a specialized subfield of information technology called
Bioinformatics
the DNA sequence for a particular gene of interest is known, but the role and function of the gene are typically not well understood
reverse genetics
Render targeted genes non-functional in a model organism or in cultured cells, allowing scientists to investigate the fundamental question of “what happens if this gene is disrupted?” The ultimate goal of this biotechnology technique is to determine the function of the gene
Gene knockout
defined as organisms used for the study of basic biological processes
model organisms
Gradually, geneticists added other species to their collection of model organisms: viruses (such as the ——————————) and microorganisms (the bacterium ————-
and the yeast ——————-)
namatode: —————-
T phages and lambda phage
Escherichia coli
Saccharomyces cerevisiae
Caenorhabditis elegans
The first generation of model organisms in genetic analysis included..
(a) the mouse, Mus musculus and
(b) the fruit fly, Drosophila melanogaster.
Sensitive genetics-related issues include
- prenatal testing
- genetic discrimination
- ownership of genes
- access to and safety of gene therapy
- genetic privacy
This organism was chosen as a model system to study the development and function of the nervous system because its nervous system contains only a few hundred cells and the developmental fate of these and all other cells in the body has been mapped out
also used to study diabetes
nematode Caenorhabditis elegans
a far-reaching methodology used in molecular genetics, allows genes from one organism to be spliced into vectors and cloned, producing many copies of specific DNA sequences
Recombinant DNA technology
One example of genomics
The Human Genome Project
In this approach geneticists relied on the use of naturally occurring mutations or intentionally induced mutations (using chemicals, X-rays or UV light as examples) to cause altered phenotypes in model organisms, and then worked through the lab intensive and time-consuming process of identifying the genes that caused these new phenotypes
classical or forward genetics
This organism has become a model organism for the study of many aspects of plant biology
Arabidopsis thaliana, a small plant with a short life cycle
This organism is used to study vertebrate development: it is small, it reproduces rapidly, and its egg, embryo, and larvae are all transparent.
also used in studying cardiovascular diseases
zebrafish, Danio rerio
Model organism used to study colon cancer and other cancers
Escherichia coli
Model organism used to study cancer and Werner syndrome
S. cerevisiae
Model organism used to study disorders of the nervous system and cancer
Drosophila melanogaster
Model organism for studying Lesch-Nyhan disease, cystic fibrosis, fragile-X syndrome, and many other diseases
Mus musculus
a hereditary growth disorder that results in curved bones, short limbs, and hand deformities
diastrophic dysplasia
diastrophic dysplasia is a disorder due to a defect in chromosome number
other genetic disorders encoded in this chromosome are the following:
~ Laron dwarf
~ Susceptibility to diphtheria
~ Limb-girdle dystrophy
~ Low-tone deafness
Chromosome #5
Carolus Linnaeus believed that animal and plant groups remain unchanged in form from the moment of their appearance on earth
Fixity of Species
This states that all cells of an organisms release gemmules found in the different parts of the body and travels to the reproductive organs where it is transferred to the gametes:
- physical units representing each body part that were gathered by the blood into the semen
Pangenesis
According to this theory, germ-line tissue in the reproductive organs contain a complete set of genetic information that is transmitted directly to the gametes
Germ-plasm theory
The proposed ancestor of giraffes has characteristics of modern-day…
Okapi
What is the center of heredity in eukaryotic organisms, prokaryotic organisms, and viruses
Eukaryotic organisms = nucleus
Prokaryotic organisms = nucleoid region
Viruses = protein coat (viral head or
capsid)
histones found in between nucleosomes
H1 histone (together with spacer DNA
Subunit of DNA
Nucleotide
Characteristics of a genetic material
- Stable * does not easily denature
- Replicable * sequence can be copied
- Translatable * sequence can be converted into a different language
- Mutable * can be changed to yield variations
informational storage unit capable of undergoing replication, mutation, and expression
Gene
- heritable units that are passed on from parent to offspring
Genes
Describe a eukaryotic chromosome
- Many chromosomes composed of linear DNA molecules intimately associated with proteins
How can chromosomes be visualized?
Electron microscope (viruses)
Light microscope (eukaryotes)
* Mitosis
* meiosis
When an organism has more than 2 sets of chromosomes, they are called
Polyploid
- What are the sources of genetic variation?
Chromosomal Mutations (chromosome segments)
Gene Mutations (in nucleotides)
• Are there exceptions where proteins are not the end product of a gene?
mRNA
tRNA
RNA is sometimes the end product of stored genetic information
• Why are proteins so important to living organisms that they serve as the end product of the vast majority of genes?
Serve as highly specific biological catalysts or enzymes
Perform non-enzymatic roles
• What are the other protein products which are critical components of cells and organisms?
- Hemoglobin • oxygen-binding pigment in red blood cells
- Insulin • pancreatic hormone
- Collagen • the connective tissue
molecule - Keratin • the structural molecule in hair
- Histones • Proteins integral to chromosome structure in eukaryotes
- Actin and myosin • the contractile muscle proteins
- Immunoglobulins • the antibody molecules of the immune system
Genetics can be subdivided into 3 interrelated fields
- Transmission genetics
- Molecular genetics
- Population genetics
Patterns of inheritance are determined through planned breeding experiments
Transmission genetics
Study of the cellular or physical basis of heredity (chromosomes)
Cytogenetics
Characterization of the chemical nature of the genetic materials (DNA and RNA) as well as the mode by which they bring about the traits they control
Molecular genetics
Describes the behavior of genes in large groups of individuals with passage of time
Population genetics
Methods of studying genetics
- Planned experimental breeding
- Pedigree analysis
- Statistical analysis
- Twin study
- Karyotyping
- DNA testing/profiling
• Mating of individuals exhibiting contrasting expressions of a given trait and observe their offspring through several generations
Planned experimental breeding
CHARACTERISTICS OF A GOOD TEST ORGANISM FOR GENETIC STUDY
- Observable traits → highly variable
- Sexual reproduction or recombination is present
- Controlled mating not within bounds of ethical concerns
- Short generation time
- Produces large number of offspring
- Easy to handle/maintain
With diagrams showing the ancestral relationships and transmission of genetic traits over several generations
Pedigree analysis
Used mostly in tandem with planned experimental breeding
Tests for significant difference in variations
Statistical testing
Determines which plays a more significant role in the expression of a trait: heredity or environment
Uses identical twins that are separated from birth
Twin study
Metaphase chromosomes of an organism is arranged according to size and centromere location
Can detect chromosomal aberrations
Karyotyping
Detects differences at the molecular level (DNA/RNA or protein)
DNA testing/profiling
Relies on the use of naturally occurring mutations
Intentionally induced mutations (chemicals, x-rays, UV light) to cause altered phenotypes in model organisms
Lab-intensive and time consuming process of identifying genes that caused new phenotypes
MODERN APPROACH: CLASSICAL GENETICS
DNA sequence of gene of interest is known but not well understood
Gene knockout render targeted genes nonfunctional in a model organism or cultured cells, to investigate and answer “what happens if gene is disrupted?”
MODERN APPROACH: REVERSE GENETICS
Forward vs. Reverse genetics
Forward genetics
Known phenotype > discover gene underlying phenotype
Reverse genetics
Known genes > discover phenotype resulting from alteration (gene silencing, gene targeting, TILLING)
Tests that can be done under genomics
- Genetic paternity test
- Genetic compatibility test
- Genetic ancestry test
- Genetic fingerprinting
- Genetic disease risk
Apply genetic knowledge for the improvement of human existence
Eugenics
• Encourage parents displaying favorable characteristics to have large families
• Superior intelligence, intellectual achievement, artistic talent
Positive eugenics
• Restrict reproduction of parents displaying unfavorable characteristics
• Low intelligence, mental retardation, criminal behavior
Negative eugenics
• Medical and/or genetic intervention designed to reduce the impact of defective genotypes on individuals
• Insulin by diabetics, dietary control of newborn phenylketonurics
Euphenics
• study of the improvement of human functioning and well-being by improvement of living conditions.
• altering external factors such as education and the controllable environment, including the prevention and removal of contagious disease and parasites, environmentalism, education regarding employment, home economics, sanitation, and housing
Euthenics
• enzymes that cut viral DNA at specific sites
• could be used to cut any organism’s DNA at specific nucleotide sequences, producing a reproducible set of fragments
Restriction enzymes
DNA Fragments + DNA Vector = Recombinant DNA
donor cells removed from mammary gland of an adult Finn Dorset ewe
Donor cells starved
Fused with an egg cell with its nucleus removed
Fertilization and development of Dolly the sheep
1988 a strain of mice modified by recombinant DNA technology to be susceptible to cancer was patented for the first time
Created for studying cancer development and anticancer drugs
GENETIC ADVANCES IN AGRICULTURE
Improvements in Plants
- Enhanced potential for more vigorous growth and increases yields (hybrid vigor-heterosis)
- Increase resistance to natural predators and pests, including insects and disease causing microorganisms
- Production of hybrids exhibiting a combination of superior traits derived from two different strains or even two different species
- Tangelo (tangerine + grapefruit/pomelo)
- Rabbage (radish+cabbage)
- Selection of genetic variation with desirable qualities
- increased protein value
- Increased content of limiting amino acids
- Smaller plant size, reducing vulnerability to adverse weather conditions
Some genetically altered traits in crop plants
Herbicide resistance
- corn, soybeans
Insect resistance
- corn, cotton
Virus resistance
- potato, papaya
Nutritional enhancement
- golden rice
Altered oil content
- soybeans, canola
Delayed ripening
- tomato
GENETIC ADVANCES IN AGRICULTURE
Improvements in Animals
- Development of superior breeds in livestock
Chickens - Grow faster
- Produce more high-quality meat
- Lay greater number of egg
Larger animals (pig and cow) - Artificial insemination
GENETIC ADVANCES IN MEDICINE
- Genetic basis of disorders are documented
- Advances in cancer research
* Effective early detection and more effective approaches to treatment - Genetic Counseling
* Provides couples with objective information on which they can base rational decisions about child-bearing - Immunogenetics
* Compatible blood transfusions and organ transplants
- Genetic disorders are treated by inserting normal copies of genes into cells of afflicted individuals
Gene therapy
- The entire genetic complement (genome) of several species is being sequenced
Human Genome Project
Gene therapy procedure:
- Cells are removed from the patient
- A new or corrected version of a gene is added to the cell, usually with the use of genetically engineered virus
- The cells are then grown in a culture and implanted into the patient
