Exploring Mendelian Genetics 11- GENES are more complicated than Mendel thought Some traits have MORE than 2 allele choices = MULTIPLE ALLELE TRAIT http://www.eslkidstuff.com/images/tallshort.gif EX: blood type Allele choices A B O http://sps.k12.ar.us/massengale/genetics%20tutorial.htm GENES are more complicated than MENDEL thought Some traits are determined by MORE THAN ONE GENE = POLYGENIC TRAIT EX: human height. intelligence, skin & eye color http://www.bcps.org/offices/lis/models/life/images/grow.jpg GENES are more complicated than MENDEL thought Traits determined by MORE than ONE gene have many in-between phenotypes There aren t just SMART people and DUMB people. there is a whole range of intelligences in-between http://www.newtonswindow.com/problem-solving.htm GENES are more complicated than MENDEL thought KINDS OF DOMINANCE COMPLETE DOMINANCE INCOMPLETE DOMINANCE CO-DOMINANCE COMPLETE DOMINANCE Dominant allele masks the recessive one PATTERN? Recessive allele returns in a ratio :1 in the generation F 2 http://www.emc.maricopa.edu/faculty/farabee/biobk/biobooktoc.html 1
INCOMPLETE DOMINANCE DON T SEE expected :1 ratio in F 2 generation Heterozygous organisms with one dominant and one recessive allele show a BLENDED in-between trait Image modified from: http://www.emc.maricopa.edu/faculty/farabee/biobk/biobooktoc.html CO-DOMINANCE BOTH traits are expressed at SAME TIME ( ) NO BLENDING in heterozygote A HORSE ROAN has BOTH RED hair and WHITE hair side by side CO-DOMINANCE Both traits are expressed together (NO BLENDING) in heterozygote Persons with an A allele AND a B allele have blood type AB REMEMBER Membrane proteins with sugars attached that help cells recognize self = GLYCOPROTEINS http://www.mannanw.com/super-sugars.htm BLOOD TYPES have more than 2 allele choices = MULTIPLE ALLELE TRAIT The pattern of sugars that is attached is determined by genes Allele choices are: A B O BLOOD TYPES An A allele tells the cell to put A glycoproteins on its surface 2
BLOOD TYPES A B allele tells the cell to put a different B glycoprotein on its surface BLOOD TYPES An O allele tells the cell NOT to put anything on the surface A and B are CO-DOMINANT A cell with BOTH an A and a B allele has BOTH A and B glycoproteins on its surface So what does that mean about O type allele? It s recessive BLOOD TYPES & ALLELES GENOTYPE AA AO BB BO OO AB PHENOTYPE (BLOOD TYPE) A A B B O AB DONOR BLOOD DONOR BLOOD A and AB see A as like me Body images modified from: B and O see A as Different! IMMUNE SYSTEM ATTACKS! B and AB see B as like me Body images modified from: A and O see B as Different! IMMUNE SYSTEM ATTACKS!
DONOR BLOOD DONOR BLOOD O can donate to EVE BLOOD TYPE = UNIVERSAL DONOR YOU DON T HAVE ANYTHING I DON T HAVE! Body images modified from: Nothing on surface to recognize as NOT SELF Only AB sees AB as like me Body images modified from: A, B, and O see AB as Different! IMMUNE SYSTEM ATTACKS! Body image modified from: AB can only GIVE to AB BUT... AB can RECEIVE FROM EVE BLOOD TYPE = UNIVERSAL RECIPIENT BLOOD TYPE FREQUENCY IN USA A 40% B 10% AB 4% O 46% http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/newton/bldtyping.html ABO SYSTEM is NOT THE ONLY ONE OTHER BLOOD TYPES NO PROBLEMS IF: Rh + Rh - MOM is & BABY is Image modified from: http://www.wsd1.org/lessonplans/images/body.gif Rh + MOM is Rh + Rh + & BABY is Rh - 4
Can be a PROBLEM IF: Mom is Rh - Baby is Rh+ 1 st baby OK but few baby cells entering mom s bloodstream put mom s immune system on alert for + cells. DIHYBRID CROSSES (2 traits) Next + baby, mom s immune system can attack baby as it is growing Image modified from: http://www.wsd1.org/lessonplans/images/body.gif Mom given shot after 1 st birth prevents this http://mac122.icu.ac.jp/biobk/biobookgenintro.html Mendel also asked the question? Does the gene that determines if a seed is round or wrinkled have anything to do with the gene for seed shape? Must a seed that is yellow also be round? MAKING A CROSS with = TWO gene traits DIHYBRID CROSS A Punnett square for a DIHYBRID CROSS looks like this: Section 11- Go to Section: Figure 11-10 Independent Assortment in Peas LET S MAKE A DIHYBRID CROSS HOMOZYGOUS YELLOW ROUND RY HOMOZYGOUS GREEN WRINKLED rryy 1. Figure out what parent alleles are 2. Choose correct Punnett square size. Put in possible parent gametes 4. Fill in boxes with offspring combinations 5. Determine of & probabilities phenotypes genotypes 5
LAW OF INDEPENDENT ASSORTMENT the factors are distributed to gametes independently of other factors PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE? HOMOZYGOUS ROUND YELLOW R R Y Y Each gamete should get one of each kind of gene R Y R Y R Y R Y Image modified from: http://anthro.palomar.edu/mendel/mendel_1.htm PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE? HOMOZYGOUS WRINKLED GREEN r r y y Each gamete should get one of each kind of gene r y r y r y r y PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE? HETEROZYGOUS ROUND YELLOW R r Y y Each gamete should get one of each kind of gene R Y r y r Y R y ry ry ry ry RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy MAKE ANOTHER CROSS HETEROZYGOUS ROUND YELLOW X HETEROZYGOUS ROUND YELLOW RrYy RrYy RrYy RrYy R r Y y R r Y y 100% of offspring = RrYy genotype ROUND YELLOW phenotype 6
POSSIBLE PARENT GAMETES? ry ry Ry Ry ry ry Ry ry ry RY Ry RrYY RrYy Ry RRyy RrYy Rryy RrYY RrYy rryy rryy RrYy Rryy rryy rryy Round & Yellow Round & green Wrinkled & yellow 1 wrinkled & green Sign of a heterozygous dihybrid cross is a 9:::1 ratio in offspring. 9 9 dominant TRAIT 1 ; dominant TRAIT 2 dominant TRAIT 1; recessive TRAIT 2 recessive TRAIT 1; dominant TRAIT 2 1 recessive TRAIT 1; recessive TRAIT 2 PRACTICE MAKING GAMETES for DIHYBRID CROSSES ratio 9:::1 is a clue that it s a cross HETEROZYGOUS TWO gene http://www.emc.maricopa.edu/faculty/farabee/biobk/biobooktoc.html What are the possible gametes? What are the possible gametes? pure round & pure tall = R R T T R T R T R T R T What gametes can it produce? Heterozygous Tall = T t R R & pure round T R t R t R T R What gametes can it produce? 7
What are the possible gametes? What are the possible gametes? Hybrid tall & pure wrinkled = T t r r Heterozygous tall & hybrid round = T t R r T r t r t r T r What gametes can it produce? T R t r t R T r What gametes can it produce? SOUTH DAKOTA CORE SCIENCE STANDARDS LIFE SCIENCE: Indicator 1: Understand the fundamental structures, functions, classifications, and mechanisms found in living things 9-12.L.1.1. Students are able to relate cellular functions and processes to specialized structures within cells. Storage and transfer of genetic information Core High School Life Science Performance Descriptors High school students performing at the ADVANCED level: High school students performing at the PROFICIENT level: High school students performing at the BASIC level predict how traits are transmitted from parents to offspring explain how traits are transmitted from parents to offspring; identify that genetic traits can be transmitted from parents to offspring; SOUTH DAKOTA ADVANCED SCIENCE STANDARDS LIFE SCIENCE: Indicator 2: Analyze various patterns and products of natural and induced biological change. 9-12.L.2.1A. Students are able to predict the results of complex inheritance patterns involving multiple alleles and genes. (SYNTHESIS) Examples: human skin color, polygenic inheritance 8