bio final ch 21-25

• true regarding homeotic genes


  homeotic genes are important in controlling the pattern formation of body parts

  
  

  also called Hox genes

  highly conserved amongst organisms

  associated with development
• true regarding genetic variation


  for a population to evolve by natural selection, genetic variation must already be present
• sexual reproduction creates:


  genetic variation
• occur in populations evolving

  -the population has variation of heritable genetic information

  -the environment cannot support all of the offspring produced

  -specific heritable traits increase the fitness of offspring
• Jean-Baptiste de Lamarck's hypothesis


  species evolved through use and disuse of body parts and the inheritance of acquired characteristics
• from Darwin's book "the origin of species," he explained what 3 broad observations?


  -unity of life

  -diversity of life

  -the way organisms are suited to live in their environments
• retrotransposons


  moves via an RNA intermediate
• transposons


  -move via DNA intermediate

  -"cut and paste" or "copy and paste"
• most of the human genome is made up of

  repetitive DNA sections related to transposable elements
• smallest portion of the human genome

  exons
• in a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.3. what is the frequency of individuals that are heterozygous at this locus?


  .42

  
  

  q = 3

  p + q = 1

  p = 1 - q

  p = .7

  heterozygous = 2pq

  = .42
• correctly describes one characteristic of a multigene family


  a multigene family includes genes whose sequences are very similar and that probably arose by duplication
• for the Hardy-Weinberg equation, why is the "2" needed for 2pq?

  heterozygotes can come about in two ways
• an organism's fitness is measured by


  contribution to the gene pool of the next generation
• harmful mutations occur in both diploid and haploid organisms. would we expect to find more harmful mutations in diploid or halpoid organisms? explain why


  more harmful mutations in populations of diploid than haploids, because the mutations are protected from selection in diploid heterozygotes
• under the influence of natural selection, what is the correct order of events?


  -a change occurs in the environment

  -poorly adapted individuals have decreased survivorship

  -well-adapted individuals leave more offspring than do poorly adapted individuals

  -genetic frequencies within the population change

  
  

  -natural selection is acting on individuals that were already present!!!
• ways transposable elements contribute to genome evolution


  -facilitate recombination, or crossing over, between different chromosomes

  -insertion in regulatory sequences can increase or decrease gene expression

  -one of the genes present in multiple copies can diverge by accumulating mutations
• not a way transposable elements contribute to genome evolution


  false pairing during metaphase I can lead to nondisjunction events
• after exposing a population of bacteria to penicillin (an antibiotic), within six months the bacteria are resistant to penicillin. explain how the bacteria evolved


  -some drug-resistant bacteria were present at the start of treatment, and natural selection increased their frequency

  
  

  -natural selection does NOT create individuals with favorable traits; rather, it favors individuals that were ALREADY present
• the Hardy-Weinberg equation is useful in that it allows scientists to


  provide evidence that an evolutionary force is acting on a population

  
  

  Hardy-Weinberg describes a population that is NOT evolving
• 4 steps of the whole-genome shotgun approach to sequencing


  -cut the DNA into overlapping fragments short enough for sequencing

  -clone the fragments in plasmid or other vectors

  -sequence each fragment

  -order the sequences into one overall sequence with computer sequencing
• even though they have become adapted for different functions, the forelimbs of humans, cats, whales, and bats are all constructred from the same basic features

  homologous structures

  
  

  structures in different species from a common ancestor
• gene density is correctly represented by


  Z. mays have 14 genes per million base pairs

  
  

  gene density is the number of genes in a given length of DNA
• explain Darwin's theory of evolution by natural selection


  Darwin's theory emphasized populations that vary and allele frequencies change over time

  
  

  survival of the fittest; heritable traits that are advantageous
• during meiosis, an error occurs resulting in an extra copy of a chromosome. how can an extra copy facilitate evolution?


  over time, mutations can accumulate in the extra sets of genes and allow evolution of novel functions

  
  

  evolution of genes with novel functions

  -as long as one copy of genes retain their original function
• not a condition for Hardy-Weinberg equilibrium

  assortative mating
• conditions for Hardy-Weinberg equilibrium


  no mutations

  random mating

  no natural selection

  extremely large population size

  no gene flow
• humans have 23 pairs of chromosomes, chimps have 24 pairs. what is the most likely explanation for these differences?


  during human evolution, two ancestor chromosomes fused end to end
• a species of crocodiles migrated to neverland where there are many ecological niches unoccupied. the species evolved into many different species to fill the diverse array of niches. this is an example of:


  adaptive radiation

  
  

  diversification of a group of organisms into forms filling different ecological niches (ex. Finches)
• can be duplicated in a genome


  DNA sequences

  chromosomes

  entire sets of chromosomes
• proteomics is different from genomics in the fact that proteomics can reveal:


  the set of proteins present within a cell or tissue type
• genomics


  the study of whole sets of genes and their interactions
• proteomics


  the study of large sets of proteins and their properties
• strains of cultivated rice have accumulated different mutant recessive alleles. hybrids between them are vigorous and fertile, but plants in the next generation carry too many of these recessive alleles and are small and sterile. this is an example of


  hybrid breakdown

  
  

  first gen of hybrids are viable and fertile, but when they mate, offspring are feeble and sterile
• most likely represents the sequence, from earliest to most recent, in the origin of cell organelles and cellular organization


  photosynthetic prokaryotes, mitochondria, chloroplasts, multicellular eukaryotes
• comparisons of Galapagos Finch DNA and South American bird DNA shows high base similarity. which process could generate these results?


  gene flow
• four populations of birds look very similar, but the males from each population sing different songs to attract females. the different songs are an example of


  behavioral isolating barrier
• habitat isolation


  two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers
• temporal isolation


  species that breed at different times of the day, or different seasons
• two different species of lemurs mate and successfully produce a zygote. however, the embryo dies shortly after fertilization occurs. which reproductive barrier keeps the species separated?

  reduced hybrid viability