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99 Cards in this Set
- Front
- Back
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gene regulation
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cells' ability to control their level of gene expression; unicellular organism responds to changes in the environment; multicellular regulates the body as a whole, not responding to cell's environment
maintaining a relatively constant environment is homeostasis in multicellular organisms |
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structural genes
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proteins only produced at certain time and in specific amount
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constitutive genes
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unregulated and have essentially constant levels of expression
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functions achieved through regulation of gene expression
Eukaryote |
development, maintain homeostasis, function as a whole
- genes organized individually, regulated by small effector molecules, more intricate and requires more coordination and integration |
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functions achieved through regulation of gene expression
Prokaryote |
can adapt to changing environments (temp, salinity, UV radiation, specific substrate presence)
- genes are grouped for common functions |
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Points of control Eukaryotes
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NA processing, translation, transcription, post-translational
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Points of control in Prokaryotes
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transcription (most common for both bacteria and eukaryotes), rate of mRNA translated, or post-translational
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cell differentiation
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leads to cells with same genome but with different proteomes (set of expressed proteins)
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activators
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bind to DNA to increase transcription or turn on a gene
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transcriptional control
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most common mechanism for gene expression regulation; for transcription to be initiated RNA polymerase must have access to the DNA double helix and must also be capable of binding to the gene's promoter.
Consider: Homeostasis is the tendency of a system, especially the physiological system of higher animals, to maintain internal stability. When an activator (regulatory transcription factor) binds to DNA and increases the transcription of a gene, it is imposing positive control. Considered to be a hallmark of multicellular organisms. |
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regulatory proteins
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possess DNA binding motifs (structural motifs that are specific bends in protein chains) that allow them to bind to where the edges of the nitrogen bases protrude from DNA at the major groove without unwinding the helix
Consider: The structural motifs include helix-turn-helix (most common), homeodomain, zinc finger, and leucine zipper. The homeodomain contains a nearly identical sequence of 60 amino acids in may eukaryotic organisms. |
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effector molecules
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regulate gene transcription by binding a regulatory protein
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operators (operator site)
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site immediately in front of promoter region; regulatory proteins (repressors imposing negative control) can bind to this site to reduce or shut off transcription; so it is a site of negative genetic regulation; binding by repressor blocks transcription
Consider: The promoter region (site at the 5' end of a gene to which RNA polymerase attaches to initiate transcription) of DNA is where general transcription factors are required for proper binding of RNA polymerase to the DNA helix for transcription to be initiated. |
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repressors
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bind to DNA in vicinity of promoter and impose negative control by inhibiting transcription.
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enhancers
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DNA sequences to which specific transcription factors (control-proteins) bind to increase the rate of eukaryotic transcription
Consider: Those specific transcription factors are known as activators and have two domains; one for DNA binding and another for activation. Imposing positive control, they increase the rate of transcription. |
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operon
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cluster of functionally-related genes encoded into a mRNA molecule; a mode of prokaryotic gene regulating unit
Consider: Within a bacteria, it permits the coordinated regulation of a group of genes that encode proteins with a common function |
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polycistronic mRNA
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mRNA that contains the coding sequence for two or more structural genes
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lac operon
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DNA region that contains genes for use of lactose as energy source; contains 3 structural genes: lacZ, lacY, lacA (identify products from lecture material)
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lacP site
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upstream to the 3 genes and is the lac promoter site where RNA polymerase binds
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2 regulatory sites near lac promoter
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lacO – operator – provides binding site for repressor protein & CAP site – activator protein binding site (cAMP is effector molecule responsible for ability of glucose to repress lac operon)
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lacI
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codes for lac repressor (not part of lac operon; strictly a regulatory gene)
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allolactose
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(small effector molecule) can bind to lac repressor thereby preventing repressor binding and triggering induction...an increase in allolacose levels leads to an increase in gene transcription within the lac operon
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Regulation of this region is important to bacteria because of limited availability of lactose and the high metabolic cost of constantly producing enzymes. 3 points to consider:
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The lac operon will not be induced in the presence of both glucose and lactose
-Control of the lac operon is negative, mediated by a repressor -The lac operon controls the expression of three downstream genes. |
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inducible
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When gene expression is turned on in a bacterium by adding a substance (such as lactose) to the medium, the genes involved are said
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inducer
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The regulatory substance that brings about this gene induction
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induction
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phenomenon of producing a gene product in response to an inducer
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glucose vs/ lactose
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when presented with both, bacterial cells prefer to use glucose
Consider: Glucose prevents induction (initiation of gene transcription) of lac operon because high glucose levels cause low cAMP levels which limits the binding of CAP-cAMP complex to CAP binding site (requirement for lac operon induction). |
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CAP
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A protein that initiates the transcription of genes which allow the use of non-glucose molecules
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trp operon
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5 gene cluster involved in the biosynthesis of tryptophan
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mediator
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facilitates interactions between RNA polymerase II and regulatory transcription factors
controls the rate at which RNA polymerase transcribes mRNA partially wraps around RNA polymerase and the general transcription factors and is composed of several proteins |
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repressor
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protein that down-regulates transcription by binding to the operator
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inducer
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molecule that can inactivate a repressor protein by binding to it, thereby allowing transcription to proceed
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core promoter
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site at the 5' end of a gene to which RNA polymerase attaches to initiate transcription; includes transcriptional start site and TATA box
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operator
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site of negative genetic regulation; binding by repressor blocks transcription
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inducer exclusion
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main form of glucose repression of the lac operon; high glucose levels cause low cAMP (inducer) levels
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miRNA (micro RNA)
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small RNA that regulates gene expression by binding directly to mRNA to prevent translation
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development
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series of changes in the state of the cell, tissue, organ, or organism that gives rise to the structure and function of living organisms; organization phases regulated by morphogens, transcription factors, and segmentation genes
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cadherins
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cell adhesion proteins may be used by some cells during the process of differentiation
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cytoplasmic determinants
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different developmental signals within cells created by cleavage
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morphogens
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signal molecules that determine relative positions during development; asymmetric distribution throughout cell, give positional information and promote cellular changes to resident cell and can act on neighboring cells, are concentration dependent, and can cause apoptosis (cell death)
morphogen development involves the initial cells formed by cleavage containing different determinants and those determinants directing the path of development. |
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zygote
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diploid cell resulting from fertilization of sperm and ovuum
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clevage
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zygote initially dividing into smaller cells each called a blastomere; dividing cells of an early embryo lack the G1 & G2 cell cycles seen in adult somatic cells
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blastula
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the structure (hollow ball of cells) that forms from the zygote resulting from a huge increase in the number of blastomeres (cells), but with a corresponding decrease in individual cell size
Consider: blastomers of the animal pole for the ectodermal tissues and blastomeres of the vegetal pole form the endodermal tissues. |
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genome
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set of genes that constitute the program of development
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model organism
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ideal characteristics include small body size but large oocytes with many offspring and a short generation time
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Drosophila melanogaster
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model organism that meets criteria; mutant strains (resulting from homeotic gene mutations) are used to determine specific gene functions
Consider: Stages of Drosophila development are syncytial blastoderm formation, cellular blastoderm formation, germ cell layers form, body divides into segments (majority of which will become part of abdomen), larva hatches, pupa forms, metamorphosis. Specific segments formed during normal Drosophila development will always form the same structure in adult flies and maternal genes determine the initial course of development after fertilization. |
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organization of animal bodies
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fall along dorsoventral, anteroposterior, and right-left axes
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limb formation
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follows the path of cell division, cell migration, cell differentiation, and cell death
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zygote
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diploid cell formed by egg and sperm (fertilized) which undergoes mitosis to become a blastomere (solid ball of cells that is the result of an increase in cell numbers with a decrease in individual cell size --> cleavage)
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totipotent
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cell capable of expressing all its genes and produce all adult cell types; zygote and up to 8 cell division; fertilized egg is example
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pluripotent
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descendants of the totipotent stem cells of the embryo; can differentiate into almost any cell (except totipotent stem sells and cells of the placenta) but a single cell has lost the ability to produce an entire individual
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cell death
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necrosis is when injured cells swell and then burst releasing contents into extracellular fluid; apoptosis is programmed cell death when cells shrink and shrivel because material is being absorbed by neighboring cells
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stem cells
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have the capacity to divide and daughter cells can differentiate into 1 or more cell types
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meristems
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special groups of self-renewing cells in plants used to build themselves outward through cell division at both the tip of the shoots and roots; this process is used instead of cell migration to determine the morphology of plants
apical meristem can differentiate into stems, leaves, or flowers |
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seed germination
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results from responses to changes in its environment
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suspensor
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elongated structure that links the embryo of a developing plant to its nutrient sources
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metamorphosis
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passage from one body form to another in insects; involves total rearrangement of all larval cells which are used in growth and development of adult
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CAMs
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(surface receptors) that position a cell within a multicellular organisms with influences by combination of contacts with other cells and with the extracellular matrix
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differential gene regulation
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certain genes expressed at specific phase of development in a particular cell type
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colinearity rule
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describes spatial arrangement of homeotic genes along the chromosome;
order of homeotic genes along chromosome corresponds to their expression along the anteroposterior axis of body |
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homeotic genes
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are found in complexes (clusters) and encode transcription factors and activate developmental genes . A portion of the proteins they encode can bind DNA. Expression of these genes occurs after pattern formation along the A/P axis has been successfully established.
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homeobox
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sequence of 180 nucleotides that codes for 60 amino acids; typically found in fruit fly homeotic genes
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bicoid & nanos proteins
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associated with activating genes that code for the first mRNA transcribed in Drosophila embryos
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nurse cells
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transcribe bicoid mRNA and then transport it to the embryo
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population genetics
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Study of the distribution of alleles in populations and the factors that alter the frequency of alleles and genotypes. The total of all alleles of all the genes in a population is a gene pool.
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alleles
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Alternate forms of the same gene. Because they are different, their action may result in different expressions of a trait. Upper case letter designates dominant allele, lower case letter designates recessive allele; AA is homozygous dominant, aa is homozygous recessive, Aa is heterozygous; when considering dominant/recessive traits, genotype determines phenotype
Example: sickle cell |
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polymorphic gene
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2 or more alleles and each allele must occur at a frequency greater than 1%; a polymorphic locus exhibits more variation than is expected by mutation
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How do populations evolve? (4 Ways)
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*Certain individuals survive to reproduce more than others.
*Mutations can spread *Genes enter and leave the gene pool *Random Chance changes in gene pool (genetic drift) |
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population
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A more or less distinct group of individuals within a species who are reproductively isolated from other groups. In other words, they restrict their mate selection to members of their own group. This is usually due to geographic and/or social barriers to mating with outsiders.
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evolution
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The sum total of the genetically inherited changes in the individuals who are the members of a population's gene pool. In other words, change in frequencies of alleles in the gene pool of a population.
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Do individuals evolve?
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No. Only Populations evolve over time.
*Certain individuals survive to reproduce more than others. ---Features that increase the likelihood of survival and reproduction by an organism in a particular environment are called adaptations. The genetic contribution of an individual to succeeding generations, compared with that of other individuals in the population, is known as fitness |
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How do populations evolve?
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*Mutations can spread (but this would be expected to have the smallest potential to produce evolutionary change in a given period of time)
*Genes enter and leave the gene pool (but this would be expected to have the greatest potential for producing evolutionary change in a given period of time) *Random Chance changes in gene pool |
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gene pool
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The gene pool is all of the alleles at all of the gene loci in all of the individuals in a breeding population.
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Hardy Weinberg
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The name of the equation (p²+2pq+q² = 1) used by population geneticists to determine genotype frequencies of a population for specific traits. By comparing these frequencies for subsequent generations, it is possible to document the direction and rate of evolution. The Theory is based on the assumption that the frequency of alleles and genotypes in a populations gene pool remain constant from generation to generation and no evolution is occurring. For a population to be in equilibrium, all the Hardy-Weinberg assumptions must be met. (The assumptions are below)
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What are the three main goals of population genetics?
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1- To explain the origin and maintenance of genetic variation
2-To explain the patterns and organization of genetic variation 3-To understand the mechanisms that cause changes in allele frequencies in populations |
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How do you calculate the Genotype Frequency of a population?
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GENOTYPE / TOTAL # of INDIVIDUALS
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How do you calculate the allele frequency of a population?
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Total Number of Dominant (or Recessive) Alleles / Total number of all alleles in population.
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What are the nine assumptions of the Hardy Weinberg Theorem?
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1-Organism is Diploid
2-Reproduction is Sexual 3-Generations are non-overlapping 4-Mating is Random 5-Population size is large 6-Migration is negligible 7-Mutation can be ignored 8-Natural Selection does not affect alleles under consideration 9-The alleles are not on the sex chromosomes. |
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How is the Hardy-Weinberg Theorem useful? (Two Ways)
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It explains how genetic variation is preserved
It provides a benchmark to compare to other populations. Example: No change in frequencies, evolution is not occurring |
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What are the two basic equations of the Hardy-Weinberg Theorem?
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p + q = 1
p²+2pq+q² = 1 |
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In the Hardy-Weinberg equation p + q = 1, what does p stand for?
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p is the variable for the frequency of the dominant allele
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In the Hardy-Weinberg equation p + q = 1, what does q stand for?
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q is the variable for the frequency of the recessive allele
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In the Hardy-Weinberg equation p²+2pq+q² = 1, what does p² stand for?
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p² is the frequency of the homozygous dominant genotype (AA)
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In the Hardy-Weinberg equation p²+2pq+q² = 1, what does 2pq stand for?
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2pq is the frequency of the heterozygous genotype (Aa)
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In the Hardy-Weinberg equation p²+2pq+q² = 1, what does q² stand for?
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q² stands for the frequency of the homozygous recessive genotype (aa)
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What causes microevolution?
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Relaxing the conditions of the Hardy-Weinberg Equilibrium.
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Name five causes of microevolution.
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1- Small Population Size- Genetic Drift
2-Immigration/emigration 3-Mutation 4-Nonrandom Mating 5-Natural Selection |
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What is Natural Selection?
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Natural selection is when genes that instill features (adaptations) that are needed for reproductive survival are passed down, when those without the genes are less likely to reproduce; caused by factors in the environment and leads to evolutionary change.
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- What is directional selection?
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When selection acts to eliminate one extreme from an array of phenotypes while selecting for in the other direction.
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- disruptive selection
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results in the population being strongly selected for in two directions (phenotype extremes e.g., very tall and very short)
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- stabilizing selection
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when the midrange of an array of phenotypes is favored
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What is Gene Flow?
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When individuals migrate from the population taking their alleles, also when new individuals enter the population with new alleles leading to hybridization
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What is Sexual Selection?
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Selection which arises from differences in mating success. From both Male-Male Competition and also Female Choice
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What is genetic drift?
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Happens in a small population, where alleles could be lost or changed due to chance. Causes loss of genetic variability.
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Does random mating affect all alleles?
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No, it could affect only a few alleles. For example, random mating would not affect blood type, or other phenotypes that are not outwardly seen. It would affect others like intelligence, or physical appearance.
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What are two effects of migration?
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1-To increase variability within a population
2- To prevent a population of that species from diverging to the extent that it becomes a new species. Consider: Migration would be expected to produce the largest evolutionary change in a given period of time in a population of birds...mutation would be expected to produce the smallest evolutionary change in a given period of time in a population of birds |
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What is the bottleneck effect?
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When a large number of individuals die or are removed from the population, changing drastically the genotype/and or allele frequency which leads to low heterozygosity in the descendant population.
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What is the founder effect?
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A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have:
reduced genetic variation from the original population. a non-random sample of the genes in the original population. |
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fitness
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is determined by how long it survives, how often it mates, how many viable offspring it produces per mating; the genetic contribution of an individual to succeeding generations, compared with that of other individuals in the population
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