Bio 1100 Test 3
What are the 4 alternates to dominance and recessiveness and their affects?
1) incomplete dominance - one of the alleles appears in the phenotype in the heterozygote, but not to the exclusion of the other, which can also be seen (ex.: a cross between a homozygous parent with white flowers and a homozygous parent with red flowers will have offspring with pink flowers); 2) codominance - both alleles for the same characteristic are simultaneously expressed in the heterozygote, heterozygotes express both phenotypes equally (ex.: type AB blood); 3) multiple alleles - individual humans only have two alleles for a given gene, multiple alleles may exist at the population level, such that many combinations of two alleles are observed (ex.: there are 3 types of blood that exist in humans A,B, and O, but an individual can only have a combo of two of these and A and B are dominant over O); 4) x-linked traits - when a gene being examined is present on the X, but not the Y, chromosome (ex.: the eye color of a fly)
*What is the process of DNA replication in eukaryotic cells?*
1. DNA unwinds at the origin of replication; 2. New bases are added to the complementary parental strands. One new strand is made continuously, while the other strand is made in pieces; 3. Primers are removed, new DNA nucleotides are put in place of the primers and the backbone is sealed by ligase;
*What are the steps of transcription?*
1. initiation - DNA double helix is partially unwound in the region of mRNA synthesis (this region is called a transcription bubble), the DNA sequence onto which the proteins and enzymes involved in transcription bind to initiate the process is called a promoter (determines whether the corresponding gene is transcribed all of the time, some of the time, or hardly at all); 2. elongation - RNA polymerase tracks along the DNA template, synthesizes mRNA in the 5 to 3 direction, and unwinds then rewinds the DNA as it is read; 3. termination - process of transcription is complete, in a prokaryotic cell, by the time termination occurs, the transcript wild already have been used to partially synthesize numerous copies of the encoded protein because these processes can occur concurrently using multiple ribosomes, in a eukaryotic cell, because of the presence of a nucleus, it precludes simultaneous transcription and translation
What is the difference between DNA and RNA?
DNA is double stranded and RNA is single stranded; DNA contains thymine and RNA contains uracil
Who were the scientists that discovered DNA and what was their contribution?
Francis Crick and James Watson determined the structure of DNA; Linus Pauling and Maurice Wilkins discovered the secondary structure of proteins; Rosalind Franklin used X-ray crystallography to understand the structure of DNA
Describe Mendel's experiment from P-F2 generation?
P - Mendel used pea plants that were true white and true violet, applied the pollen from a plant with violet flowers to the stigma of a plant with white flowers, and gathered and sowed the seeds that resulted from the cross; F1 - 100% of this hybrid generation had violet flowers, which contradicted regular thinking that the offspring would have been a light violet (continuous variation); F2 - he allowed F1 generation to self fertilize producing 705 violet and 224 white flowers (3:1)
*What are the steps of translation?*
Ribosome assembles on start codon of mRNA strand, tRNA anticodon pairs with mRNA codon, ribosome forms peptide bond between two amino acid and breaks bond between first tRNA and its amino acid, ribosome pulls mRNA strand the length of one codon — first mRNA shifts to exit site, when ribosome encounters a stop codon, it falls apart and the protein is released
What is adaptation?
a heritable trait that aids the survival and reproduction of an organism in its present environment; a "match" of the organism to the environment
What are the differences between allopatric and sympatric speciation?
allopatric speciation (means "other homelands") involves a geographic separation of populations from a parent species and subsequent evolution while sympratric speciation (means "same homeland") involves speciation occurring within a parent species while remaining in one location
What is the difference between homologous and analogous structures?
analogous structures are similar in function and appearance, but do not share an origin in a common ancestor while homologous structures share similarities (despite their differences resulting from evolutionary divergence)
What is the difference between continuous and discontinuous variation?
continuous - the range of small differences we see among individuals in a characteristic like human height (offspring are a blend of parents); discontinuous - the variation seen among individuals when each individual shows one of two (or very few) easily distinguishable traits, such as violet or white flowers (traits are not a blend of parents, but inherited as distinct traits)
What is the difference between convergent and divergent evolution?
divergent evolution is when two species evolve in different directions from a common point while convergent evolution is when similar structures arise through evolution independently in different species
What is the difference between dominant and recessive traits?
dominant - expressed traits, traits that are inherited unchanged in a hybridization; recessive - latent traits, traits that disappear in the offspring of a hybridization
What are the 6 common misconceptions about evolution?
evolution is just a theory, individuals evolve, evolution explains the origin of life, organisms evolve on purpose, evolution is controversial among scientists, other theories should be taught
Who is Gregor Mendel?
father of genetics; studied pea plants; published his work "Experiments in Plant Hybridization"
What are the four evidences of evolution?
fossils, anatomy and embryology, biogeography, and molecular biology
What is the law of independent assortment?
genes do not influence each other with regard to the sorting of alleles into gametes, and every possible combination of alleles for every gene is equally likely to occur; ex.: a dihybrid cross (a cross between two true-breeding parents that express different traits for two characteristics
What is the central dogma?
genes specify the sequences of mRNAs (messenger RNA), which in turn specify the sequences of proteins; DNA --> RNA --> protein
What was James Hutton's proposal?
geological change occurred gradually by the accumulation of small changes from processes (over long periods of time) just like those happening today
What is the law of dominance?
in a heterozygote, one trait (dominant) will conceal the presence of another trait (recessive) for the same characteristic; ex.: the hybridization of violet and white flower's offspring all were violet, but the next generation had a mix of white and violet flowers
What was Jean-Baptist Lamarck's proposal?
inheritance of acquired characteristics; modifications in an individual caused by its environment, or the use or disuse of a structure during its environment, or the use or disuse of a structure during its lifetime, could be inherited by its offspring and, thus, bring about change in a species
What is sexual selection?
it affects an individual's ability to mate and thus produce offspring, and it leads to the evolution of dramatic traits that often appear maladaptive in terms of survival but persist because they give their owners greater reproductive success; it occurs in two ways: 1. male v. male competition 2. female selection of mates
*How is RNA processed before it leaves the nucleus?*
mRNA transcript is coated in RNA-stabilizing proteins to prevent it from degrading while it is processed and exported out of the nucleus, once elongation is complete, an enzyme then adds a string of approximately 200 adinine residues to the 3 end (all of these modifications help protect the pre-mRNA from degradation and signals to cellular factors that the transcript needs to be exported to the cytoplasm)
What are the 3 outcomes mutation can have on an organisms' phenotype?
may affect the phenotype of the organism in a way that gives it reduced fitness (lower likelihood of survival, resulting in fewer offspring; may produce a phenotype with a beneficial effect on fitness; many mutations, called neutral mutations, will have no effect on fitness
How does microevolution compare to macroevolution?
microevolution is the gradual change of a population over time while macroevolution is the process that gave rise to new species and higher taxonomic groups with widely divergent characters
How can DNA be repaired?
most mistakes are corrected during replication, although when this doesn't happen, the mismatch repair enzymes recognize the wrongly incorporated base and excise it from the DNA, replacing it with the correct base; nucleotide excision repair the DNA double strand is unwound and separated, the incorrect bases are removed along with a few bases on the 5 (prime) and 3 (prime) end, and these are replaced by copying the template with the help of DNA polymerase; if a mistake isn't corrected, it may result in a mutation
Where does genetic diversity in a population come from?
mutation and sexual reproduction
What was Darwin's arguments for evolution?
natural selection which is based off of 3 principles: 1. the characteristics of organisms are inherited, or passed from parent to offspring; 2. more offspring are produced than are able to survive; 3. offspring vary among each other in regard to their characteristics and those variations are inherited
What are the 4 most important evolutionary forces, which will disrupt the equilibrium?
natural selection, mutation, genetic drift, and migration
What are the building blocks of nucleic acid?
nucleotides: nitrogenous base, 5-carbon sugar (deoxyribose for DNA and ribose for RNA), and a phosphate group
What is the law of segregation?
paired unit factors (genes) must segregate equally into gametes such that offspring have an equal likelihood of inheriting either factor; ex.: for the F2 generation there were 3 possible combinations of genotypes: homozygous dominant, heterozygous, or homozygous recessive
What is the difference between the phenotype and genotype?
phenotype - observable traits expressed by an organism; genotype - an organism's underlying genetic makeup, consisting of both the physically visible and the non-expressed alleles
*How is DNA packaged in the cell?*
prokaryotes - contains a single, circular chromosome that is found in an area in the cytoplasm called the nucleoid and the DNA is twisted beyond the double helix in what is known as supercoiling; eukaryotes: chromosomes each consist of a linear DNA molecule, the DNA is wrapped around the histone to form structures called nucleosomes which is linked to the next one by a short strand of DNA that is free of histones (aka: beads on a string) the nucleosomes stack compactly onto each other to form a 30 nm wide fiber
What is the difference between bottleneck effect and founder effect?
the bottleneck effect is when there is a natural or human-caused disaster that randomly kills a large portion of the population causing a large portion of the genome suddenly being wiped out while the founder effect is when some portion of the population leaves to start a new population in a new location, or if a population gets divided by a physical barrier of some kind and in this situation, those individuals are unlikely to be representative of the entire population resulting in this effect which occurs when the genetic structure matches that of the new population's founding fathers and mothers
What are vestigial structures?
unused structures without function