Genetics-Q Courtney Chaplin Bridget Jackson Edward Turk Joshua Guicherit

Punnett Squares  The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a punnett square.  F1 and F2 crosses

Dihybrid Crosses  A version of a punnett square used to find the probability of the offspring’s traits when crossing two independent alleles.  Alleles are independently assorted. Ex: Seed shape doesn’t determine a seed’s color.

Dominant Traits  Dominant Traits are represented by a capital letter in a punnett square.  They will always overrule the recessive trait when they are present in a cross.

Recessive Traits  Recessive traits are represented by a lowercase letter in a punnett square.  They will only be present if you have a homozygous recessive genotype.

Homozygous Traits  Homozygous traits are present when you have two dominant traits or two recessive traits. Ex: RR or rr

Heterozygous Traits  Heterozygous traits are present when there is one dominant trait and one recessive trait. Ex: Rr  In a heterozygous trait the dominant allele always overrules the recessive trait.

Genotype  The genetic makeup of an organism.  It determines your phenotype.

Phenotype  The physical characteristics of an organism.  Determined by your genotype.  You can’t tell the difference between a homozygous dominant or a heterozygous genotype in a phenotype.

Codominance  Both alleles contribute to the phenotype.  In chickens, the allele for black feathers is codominant with the alleles for white feathers meaning that heterozygous chickens are speckled with black and white feathers.  White chicken+black chicken=

Incomplete Dominance  When a heterozygous phenotype is somewhere in between the homozygous phenotypes.  If a red flower mixes with a white flower they will produce pink colored offspring.

Multiple Choice

1.An uppercase letter on a Punnett square indicates: a. Dominant Allele a. Dominant Allele b. Codominance b. Codominance c. Recessive Allele c. Recessive Allele 2. Which is homozygous? a. AT a. AT b. TA b. TA c. TT c. TT d. AA d. AA e. Both c and d e. Both c and d 3. T = tall t = short, a plant is Tt, is it tall or short? a. tall a. tall b. short b. short

 4. If a white and red plant cross and they are in incomplete dominance what color will the offspring be?  a. Red and White spots  b. Pink  c. White  d. Red  5. If a white and a red plant cross and the alleles are codominant what color will the offspring be?  a. Red and White Spots  b. Pink  c. Red  d. White  6. The F1 generation is what?  a. The first children  b. The parents  c. The grandchildren

 7. What are multiple alleles?  a. A gene that has more than 2 alleles  b. A gene that has 1 allele  c. A gene with exactly 4 alleles  d. Doesn’t exist  8. What are polygenic traits?  a. Multiple Alleles  b. Recessive  c. Traits controlled by 2 or more alleles  d. Traits controlled by exactly 4 alleles  9. Are traits affected by the environment?  a. Yes, the environment gives organisms characteristics  b. No, only by genes  c. By both the environment and genes

 10. What is genetics?  a. A scientific study of Mendel  b. A scientific study of probability  c. A scientific study of plants  d. A scientific study of heredity  11. What happens during fertilization?  a. Male and female cells break apart  b. C and D  c. Male and female reproductive cells join  d. A embryo is produced  12. What happens due to true-breeding?  a. Identical offspring  b. Different offspring  c. Small offspring

 13. What is a trait?  a. specific characteristic that varies in between organisms  b. specific characteristic that does not vary in between organisms  c. the different forms of a gene  d. a characteristic  14. What are alleles?  a. All the same genes  b. characteristics of the plant  c. A and C  d. the different forms of a gene  15. What is gametes?  a. Identical offspring  b. Different offspring  c. Sex cells

 16. What is probability?  a. specific characteristic that varies in between organisms  b. the likelihood that a particular event will occur  c. the amount of money you get on payday  d. a characteristic  17. Probability can predict what?  a. the outcome of genetic crosses  b. characteristics of the plant  c. A and B  18. What is the difference between heterozygous and homozygous?  a. one has Identical offspring  b. one has Different offspring  c. one has different alleles and one has the same alleles

 19. What is phenotype?  a. specific characteristic that varies in between organisms  b. the likelihood that a particular event will occur  c. a physical characteristic  d. a genetic characteristic  20. What is genotype?  a. a physical characteristic  b. a genetic characteristic  c. A and B

Answer Key! 1.A 2.E 3.A 4.B 5.A 6.A 7.A 8.C 9.C 10.D 11. B 12. A 13. A 14. D 15. C 16. B 17. C 18. C 19. C 20. D

Websites and other Resources  gy/mendelian-genetics/punnett-squares gy/mendelian-genetics/punnett-squares gy/mendelian-genetics/punnett-squares   California Prentice Hall Biology Book  probability.html probability.html probability.html

Good Luck! Good Luck!