biology 121 lab

Mendelian   Genetics  –  Dragon  Genes     In  chapter  one,  we  covered  the  Cell  Theory  and  Evolution  and  established  these  as  two  of  the  basic  foundations   of  biology.   A  third  mainstay  of  modern  biology  is  the  Chromosome  Theory  of  inheritance.  The  modern  science  of   genetics  traces  its   roots  to  Gregor  Johann  Mendel,  a  German-­‐-­‐-­‐Czech  Augustinian  monk  and  scientist  who  studied   the  nature  of  inheritance  in   plants.  Mendel  first  noted  that  certain  traits  were  passed  from  parent  to  offspring  in   a  predictable  manner.  Although  this   pattern  of  inheritance  could  only  be  observed  for  a  few  traits,  Mendel's   work  suggested  that  heredity  was  particulate,  not   acquired,  and  that  the  inheritance  patterns  of  many  traits   could  be  explained  through  simple  rules  and  ratios.     The  experiments  that  led  to  his  well-­‐known  theory  began  with  the  testing  of  thirty-­‐four  varieties  of  the  edible  pea   (Pisum),  followed  by  eight  years  of  hybridization  (crossing;  1856–1863).  Considering  seven  traits,  he  followed  the   hereditary  transmission  of  each.  The  scale  of  the  research  was  unprecedented,  the  size  of  his  progeny  populations   being  such  that  clear  statistical  regularities  emerged.  It  was  not  simply  that  he  noted  the  separate  behavior  of  the   seven  traits  he  studied,  or  that  there  was  a  marked  difference  between  the  population  sizes  of  those  carrying  two   contrasting  characters,  but  that  they  approximated  to  the  ratio  3:1.  Thus,  for  the  trait  seed  color,  Mendel  harvested   6,022  green  seeds  and  2,001  yellow  from  his  hybrid  progeny,  offering  the  most  striking  example  among  his  seven   traits  of  a  predictable  3:1  ratio.  Further  research  revealed  that  two-­‐thirds  of  the  larger  class  did  not  breed  true,  while   the  other  third  bred  true.  Hence,  the  3:1  ratio  was  really  constituted  of  three  classes  in  a  1:2:1  ratio.  His  experiments   led  him  to  make  two  generalizations:    the  Law  of  Segregation  and  the  Law  of  Independent  Assortment,  which  later   came  to  be  known  as  Mendel's  Laws  of  Inheritance.     We  will  use  dragons  as  a  model  to  illustrate  Mendel’s  model  and  the  exceptions  to  his  predictions.  

  Introduction  -­‐  Dragon   Genes   Getting  started  –  In  the  download  folder  locate  the  modern  genetics  folder   Double  click  on  the  link.    Follow  each  modules  instructions  and  answer  the     questions  in  the  program  AND  the  questions  on  your  handout.     Complete  all  four  modules:   Intro  &  rules   Meiosis   Pedigree  and  Genes   The  Plates  Problem    

Intro  &  rules     What  do  dragons  look  like  and  why?  Goals   • learn  to  use  the  software.   • make  connections  between  the  physical  traits  of  each  dragon,  the  genetic  make-­‐-­‐-­‐up  of  each  dragon,  and     also  identify   particular   chromosomes,   genes,   and   alleles.   • identify  male  and  female  sex  chromosomes.   • learn  that  specific  combinations  of  alleles  produce  specific  traits,  learn  that  some  combinations  of  alleles     are  deadly   Follow  this  segment  in  order  to  learn  BioLogica’s  Chromosome  Model  and  its  representations  of     chromosomes,  genes  and   alleles.  It  stresses  the  connection  between  genotype  and  phenotype.  

Step  One:  Introduction  to  the  BioLogica  dragons  and  characteristics.   Step  Two:  Become  acquainted  with  dragon  characteristics  and  answer  questions  pertaining  to  on  screen   activities.   Step  Three:  Become  acquainted  with  the  Chromosome  model.  Note  the  differences  between  male  &  female   chromosomes.   Step  Four:  Manipulate  the  dragon  chromosomes  in  order  to  change  the  alleles  and  traits  of  dragons  (remember;   genotype  determines   phenotype).  Note  which  traits  are  dominant  and  which  are  recessive.    

Meiosis   Why  don't  members  of  a  family  look  more  alike?     Meiosis  introduces  gamete  formation  by  modeling  the  random  distribution  of  chromosomes.  Inspect,  in  an  enlarged   window,  the  alleles  in  each  gamete  and  choose  particular  gametes  for  fertilization  to  produce  a  dragon  with  a  specific   trait.     Goals   •   develop  an  understanding  of  the  process  of  meiosis.  Understand  meiosis  as  a  process  of  reduction  and  

division.   •   manipulate  the  gametes  in  the  model.   •   Know  the  stages  of  meiosis.   •   Be  able  to  describe  the  main  results  of  meiosis.     Part  One:  Introduction  to  Meiosis  focuses  on  learning  to  use  the  Meiosis  Model,  understanding  how  chromosomes   and  alleles  participate  in  meiosis,  and  linking  the  Meiosis  Model’s  representations  of  gametes  and  chromosomes  with   the  Chromosome  Model  introduced  previously.  The  Meiosis  Model  simulates  the  process  of  meiosis  comparable  to   the  diagrams  of  the  phases  of  meiosis  found  in  textbooks.   Part  Two:  Designer  Dragons  challenges  you  to  create  specific  offspring  by  examining  the  chromosomes  in  the   gametes  of  each  parent  and  selecting  those  that  will  produce  the  desired  phenotype  in  the  offspring.     Pedigree  and  Genes   Now  that  you  know  how  to  breed  dragons,  let's  try  some  selective  breeding.  This  is  the  pedigree  view.     Use  the  cross  tool  to  breed  a  new  generation  of  dragons.  Then  breed  two  of  the  dragons  from  this  new  (F1)   generation  together.  Repeat  this  as  far  as  you  wish.  What  do  you  notice  about  the  dragons  as  you  continue  to  breed   more  generations  this  way?     Use  the  chromosome  tool  to  examine  the  genes  of  the  dragons  more  closely.    If  you  had  trouble  answering  the  sex-­‐ linked  question  above,  now  you  can  observe  and  compare  the  X  and  Y  chromosomes.  Can  you  find  any  genes  that  are   different  among  the  members  of  your  F8  generation?  How  many  generations  do  you  have  to  breed  until  all  the   dragons  are  exactly  the  same?     You  are  creating  an  inbred  strain  of  dragons  in  the  last  generations  of  this  process.  Write  a  note  describing  your   strain,  and  explain  what  is  special  about  all  individuals  in  an  inbred  strain  of  organisms.       Goals   • develop  an  understanding  of  how  genes  and  chromosomes  separate  (principal  of  segregation)   • develop  an  understanding  of  how  these  relate  to  one  another  during  meiosis  (principal  of  independent  

assortment)   • be  able  to  predict  the  phenotype  based  on  the  genes  you  see  as  you  develop  your  pedigree.   • Be  able  to  determine  the  results  of  different  generations  and  the  loss  of  fixing  of  certain  traits.    

The  Plates  Problem   Try  breeding  some  offspring  to  see  what  crosses  between  these  strains  produce.  Does  the  inheritance  of   the  plates  tell  you  anything  useful?     Goals   • Develop  an  understanding  of  how  genes  relate  to  one  another   • Gain  a  better  understanding  of  linked  genes  and  how  this  relates  to  the  phenotype.