Chapters 11-13 Flashcards
Gene regulation
the turning on and off of genes
- gene being turned on: being transcribed into mRNA and translated into specific protein molecules
- can help organisms respond to environmental changes.
gene expression
the overall process by which genetic information flows from genes to proteins (from genotype to phenotype)
Prometer
a control sequence at a site where the transcription enzyme, RNA polymerase, attaches and initiates transcription
operator
between the promoter and the enzyme genes
- DNA control sequence that acts as a switch
- determines whether RNA polymerase can attach to the promoter and start transcribing the genes
operon
a cluster of genes with related functions and the control sequences
What is the key advantage to the grouping of related genes into operons?
A single “on-off switch” can control the whole cluster.
How is transcription turned off?
a protein called a repressor binds to the operator and physically blocks the attachment of RNA polymerase to the promoter.
regulatory gene
- located outside the operon
- codes for the repressor
- expressed continually, so the cell always has a small supply of repressor molecules
activators
proteins that turn operons on by binding to DNA and stimulating gene transcription
differentiation
what individual cells must undergo to become specialized in structure and function, with each type of cell fulfilling a distinct role.
histones
A chromosome contains DNA wound around clusters of small proteins
-account for about half of the mass of eukaryotic chromosomes
nucleosome
“bead” that consists of DNA wound twice around a protein core of eight histone molecules
epigenetic inheritance
inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
x chromosome inactivation
- a specific gene on the X chromosomes ensures that only one of the chromosomes will be inactivated
- initiated early in embryonic development when one of the two X chromosomes in each cell is inactivated at random
Barr body
inactive X in each cell of a female condenses into a compact object
alternative RNA splicing
an organism can produce more than one type of polypeptide from a single gene
-may generate two or more types of mRNA from the same transcript.
opportunities for regulation of gene expression
- breakdown of mRNA
- initiation of translation
- protein processing
microRNAs
small single-stranded RNA molecules
-can bind to complementary sequences on mRNA molecules
small interfering RNAs
-similar in size and function to miRNAs
RNA interference
blocking of gene expression by siRNAs
homeotic gene
master control gene that regulates groups of other genes that determine the anatomy of parts of the body.
nucleic acid hybridization
the base pairing of one strand of a nucleic acid to a complementary sequence on another strand
DNA microarray
consists of tiny amounts of a large number of different single-stranded DNA fragments
signal transduction pathway
series of molecular changes that converts a signal on a target cell’s surface to a specific response inside the cell.
totipotent
capable of producing every kind of specialized cell in the organism
regeneration
the regrowth of lost body parts
nuclear transplantation
DNA from a donor cell is inserted into a nucleus-free host egg, resulting in a clone of the DNA donor.
therapeutic cloning goal
produce ES cells to treat disease
oncogene
a gene that can cause cancer when present in a single copy in the cell
proto-oncogene
a normal cellular gene that helps control cell division that has the potential to become an oncogene
tumor-suppressor genes
genes whose normal products inhibit cell division
carcinogens
agents that alter DNA and make cells cancerous
transcription factors
proteins that promote the binding of RNA polymerase to a gene.
reproductive cloning
If the animal being cloned is a mammal, the blastocyst is then implanted into the uterus of a surrogate mother.
adult stem cells
both perpetuate themselves in culture and give rise to differentiated cells.
-normally give rise to only a limited range of cell types.
biotechnology
manipulation of organisms or their components to makes useful products
DNA technology
modern laboratory techniques for studying and manipulating genetic material
how is recombinant DNA formed?
when scientists combine pieces of DNA from two different sources to form a single DNA molecule
what does genetic engineering use?
recombinant DNA technology
plasmids
small, circular DNA molecules that replicate separately from the larger bacterial chromosome
DNA cloning
the production of many identical copies of a target segment of DNA
vector
gene carrier
gene cloning
- genes can be cloned in recombinant plasmids
- manipulate bacterial plasmids to that they contain genes from other organisms
- these recombinant DNA plasmids can then be inserted into bacteria
restriction enzymes
-cut DNA at specific sequences, forming restriction fragments
restriction site
a particular short DNA sequence that restriction enzymes recognize
restriction fragments
pieces of DNA that result from a restriction enzyme binding to its restriction site where it cuts both strands of DNA at precise points within the sequence
-DNA ligase “pastes” DNA fragments together.
nucleic acid probe
a short, single-stranded molecule of labeled DNA that can tag a desired nucleotide sequence.
reverse transcriptase
a viral enzyme that can synthesize DNA from RNA template
-cDNA can be used to identify the genes that are being transcribed by a particular cell at a given moment
vaccine
harmless variant (mutant) or derivative of a pathogen that is used to stimulate the immune system to mount a lasting defense against that pathogen
genetically modified organisms
organisms that have acquired one or more genes by artificial means
transgenic organism
when a gene is transplanted from one organism into another
gene therapy
changing of a defective gene to a normal one in a living human.
forensics
the scientific analysis of evidence for crime scene investigations and other legal proceedings
DNA profiling
analysis of DNA samples to determine whether they came from the same individual
polymerase chain reaction
technique by which a specific segment of a DNA molecule can be targeted and quickly amplified in the laboratory
primers
short (15-20 nucleotides) chemically synthesized single-stranded DNA molecules with sequences that are complementary to sequences at each end of the target sequence.
gel electrophoresis
method that separates macromolecules - usually proteins or nucleic acids - on the basis of size, electrical charge, or other physical properties.
repetitive DNA
consists of nucleotide sequences that are present in multiple copies in the genome
-much of the DNA that lies between genes in humans is of this type.
short tandem repeat (STR)
stretches of DNA that contain short nucleotide sequences repeated many times in a row.
STR analysis
method of DNA profiling that compares the lengths of STR sequences at specific sites in the genome.
-involves amplifying the 13 STRs
genomics
study of complete sets of genes
genomes
complete set of genes
human genome project
scientific endeavor to determine the nucleotide sequence of all DNA in the human genome and identify the location and sequence of every gene.
whole-genome shotgun
method that involves sequencing and arranging many small DNA fragments simultaneously.
bioinformatics
the application of computational methods to the storage and analysis of biological data
proteomics
systematic studies of full protein sets (proteomes) encocded by genomes
CRISPR-Cas9 system
allows researchers to target a specific gene in a living cell for removal or editing
what is the PCR method used for?
to amplify DNA sequences
what is gene cloning and editing used for?
used to produce medical and industrial products.
what can complementary DNA (cDNA) be used for?
identify the genes that are being transcribed by a particular cell at a given moment.
natural selection
individuals with certain traits are more likely to survive and reproduce than are individuals who do not have those traits
adaptations
mulated diverse modifications that fit them to specific ways of life in their environment
theory
a widely accepted explanatory idea that is
- broader in scope than a hypothesis,
- generates new hypotheses, and
- is supported by a large body of evidence
evolution
the idea that living species are descendants of ancestral species that were different from present-day ones
-is a process of descent with modification
fossils
- are imprints or remains of organisms that lived in the past
- document differences between past and present organisms, and
- reveal that many species have become extinct
strata
layers of rock that new layers of sediment cover older ones and are compressed
paleontologists
a scientist who studies fossils
fossil record
the chronicle of evolution over millions of years of geologic time engraved in the order in which fossils appear in rock strata.
homology
similarity resulting from common ancestry. can include:
- anatomical structure, or
- molecular structure
homologous structures
features that often have different functions but are structurally similar because of common ancestry
molecular biology
study of molecular basis of genes and gene expression
vestigial structures
remnants of features that served important functions in the organism’s ancestors
evolutionary tree
diagram that represents the patterns of descent
artificial selection
the selective breeding of domesticated plants and animals to promote the occurrence of desirable traits in offspring
3 key points about evolution by natural selection
- natural selection occurs through interactions between individual organisms and the environment, individuals do not evolve.
- natural selection can amplify or diminish only heritable traits.
- evolution is not goal directed; it does not lead to perfectly adapted organisms.
mutation
a change in the genetic information encoded in the nucleotide sequence of DNA
-results in new alleles
population
a group of individuals of the same species that live in the same area and can potentially interbreed
gene pool
consists of all copies of every type of allele at every locus in all members of the population.
microevolution
is a change in the frequencies of alleles in a population’s gene pool and evolution occurring on its smallest scale.
Hardy-Weinberg equilibrium
no matter how many times states that allele and genotype frequencies will remain constant if
- a population is large,
- mating is random, and
- there is no mutation, gene flow, or natural selection.
Five conditions for a population to be in Hardy-Weinberg equilibrium
- very large population
- no gene flow between populations
- no mutations
- random mating
- no natural selection
three main causes of evolutionary change
- natural selection
- genetic drift
- gene flow
genetic drift
process where chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next.
bottleneck effect
leads to a loss of genetic diversity when a population is greatly reduced
founder effect
the smaller the group, the less likely that the genetic makeup of the colonists will represent the gene pool of the larger population they left
relative fitness
the contribution of an individual makes to the gene pool of the next generation relative to the contributions of other individuals
3 types of natural selection
- directional selection
- stabilizing selection
- disruptive selection
directional selection
shifts the overall makeup of the population by acting against individuals at one end of the phenotypic extremes
stabilizing selection
favors intermediate phenotypes
disruptive selection
typically occurs when environmental conditions vary in a way that favors individuals at both ends of a phenotypic range over individuals with intermediate phenotypes.
sexual slection
a form of natural selection in which individuals with certain traits are more likely than other individuals to obtain mates
balancing selection
occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population.
heterozygote advantage
type of balancing selection in which heterozygous individuals have greater reproductive success than either type of homozygote, with the result that two or more alleles for a gene are maintained in the population.
reasons why nature abounds with organisms that seem to be less than ideally “engineered” for their lifestyles
- selection can act only on existing variation
- evolution is limited by historical constraints
- adaptations are often compromises
- chance, natural selection, and the environment interact.
Fresh assortments of existing alleles arise every generation from three random components of sexual reproduction:
- crossing over,
- independent orientation of homologous chromosomes at metaphase I of meiosis, and
- random fertilization.
intrasexual selection
individuals compete directly with members of the same sex for mates
intersexual selection
(between sexes) or mate choice, individuals of one sex (usually females) are choosy in selecting their mates.
