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Genetics Study Guide

Monohybrid Crosses = crosses of _______ trait(s) at a time. 1. Match the following genotypes to their type --- MM, Mm, mm.

_____ Homozygous recessive _____ Hybrid

_____ Pure dominant _____ Pure recessive

_____ Heterozygous _____ Homozygous dominant

2. In Mendel’s Pea plants, tall stems (T) are completely dominant to short stems (t). He

crossed a pure dominant plant with a pure recessive plant. What are the expected

genotypes, phenotypes, genotypic ratios, and phenotypic ratios? (Be sure to show how you

got your answer --- Punnett Square!)

trait: _______________________

alleles: ________ and __________

cross: __________ X __________

genotypes _____________________

phenotypes ____________________

genotype Probabilities: ___________________________________________

phenotype Probabilities: __________________________________________

What TYPE of cross is this --- P, F1, or F2? _______________

3. Mendel then crossed the F1 offspring from the P-generation cross above – he crossed two

hybrid plants. What are the expected genotypes, phenotypes, genotypic ratios, and

phenotypic ratios trait:

cross: __________ X __________

genotypes ________ ________ ________

phenotypes _______ ________ ________

genotype Probabilities: ___________________________________________

phenotype Probabilities: __________________________________________

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4. In horses, the Chestnut/brown (B) coat color is Incompletely Dominant over

Cremello/whitish (b) coat color. The intermediate coat color is known as Palomino/tan. Cross

a homozygous Chestnut horse with a homozygous Cremello horse and calculate offspring

probabilities.

trait:_______________________

alleles:________ and ___________

cross: __________ X __________

genotypes _____________________

phenotypes ____________________

genotype Probabilities: ___________________________________________

phenotype Probabilities: __________________________________________

What TYPE of cross is this --- P1, F1, or F2? _______________

5. Show the results of an F1 cross for horse coat color from question #4.

cross: __________ X __________

genotypes _____________________

phenotypes ____________________

genotype Probabilities: ___________________________________________

phenotype Probabilities: __________________________________________

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6. In humans, blood type is a Codominant trait. Multiple Alleles determine 4 different blood

types. Alleles A and B are both Codominant with each other and they are both Completely

Dominant over O. Therefore, O is Recessive. Fill in all the possible genotypes that can code

for the blood types listed below:

Blood Type A: _______ ________

Blood Type B: _______ ________

Blood Type AB: ________

Blood Type O: _________

Make a cross between a heterozygous A type and a heterozygous B type: ______ X ______

genotypes _______ _______ _______ _______

Probabilities for each Blood type:

A = __________

B = __________

AB = _________

O = __________

7. Make a cross between an AB type and an O type: ______ X ______

genotypes _______ _______

Probabilities for each Blood type:

A = __________

B = __________

AB = _________

O = __________

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8. A type A woman has an AB-type baby what are the possible genotypes for her and her B

type husband? Show your answers in punnett squares:

Possible Genotypes:

Mom’s Genotype: ______

Dad’s Genotype: ______

Mom’s Genotype: ______

Dad’s Genotype: ______

Mom’s Genotype: ______

Dad’s Genotype: ______

Mom’s Genotype: ______

Dad’s Genotype: ______

9. Nondisjunction occurs when ______________ fail to separate during ____________ resulting in

one gamete receiving _________ copies and the other gamete receiving ______ copies.

10. Reproduction using gametes produced under the conditions of nondisjunction results in an

offspring that is either ____________________ (having one copy of a particular chromosome) or

_________________ (having three copies of a particular chromosome).

11. Three significant genetic disorders caused by nondisjunction include:

_______________________ - caused by a trisomy of chromosome #21

_______________________ - caused by monosomy of the X chromosome

_______________________ - caused by a trisomy (or polysomy) of the X chromosome

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12. The father of genetics is ___________________ ____________________

13. He studied ___________ plants and looked at how many traits? ____________

14. He observed that when pure bred plants (AKA Homozygous or Heterozygous) are crossed for

opposing alleles (e.g., tall X short plant) that the offspring all display the Dominant or Recessive trait,

which led him to the Principle of Dominance that states that the Dominant or Recessive allele will

always mask or hide the Dominant or Recessive allele.

15. He called the first generation of purebred plants that he crossed that P or F1 or F2 generation.

16. The offspring from this cross were called the P or F1 or F2 generation.

17. He then crossed these offspring to generate the P or F1 or F2 generation and observed that in

this 3rd generation, the ___________ trait shows up ______% of the time.

18. He drew the conclusion that the Law of Segregation states that _____________ separate

during meiosis resulting in gametes from the same parent having different alleles.

19. He also determined the Law of Independent Assortment that state alleles separate together or independently from each other during Meiosis.

20. Humans have a total of _______ chromosomes that exist in how many Homologous pairs? _____

21. All but one pair of chromosomes in humans are collectively known as ____________________.

22. The last pair, the X and Y chromosomes are known as the ________ chromosomes.

23. What two Sex Chromosomes do Males inherit? _______; Females? _______.

24. Genes that are located on the X or Y chromosome are called ______-________.

25. Defective genes located on the X chromosome cause more disorders in Males or Females because

males receive One or Two copies of the X chromosome. Females receive One or Two copies of the X

chromosome so they have a better chance of receiving at least one good gene.

26. List two examples of sex-linked disorders: ________________ & __________________

27. A chart used by geneticists which allows them to determine gender and see certain genetic

disorders caused by _____________ or __________ chromosomes is called a _______________.

28. These charts are made by taking photographs of chromosomes during _____________ and then

are cut out and placed together in pairs based on ___________ and _____________.

29. A chart used by geneticists to look at inheritance patterns within family lines is known as a

_________________. This chart shows which family members exhibited a certain trait, which

didn’t, and which were heterozygous, known as _______________.

30. Explain what happens in sickle cell disease: _______________________________________

____________________________________________________________________________

31. Sickle cell disease is caused by a Dominant or Recessive allele.

32. Traits that are produced by more than two genes (like skin color, human height, and intelligence)

are called _______________.

33. Explain the difference between Homozygous and Heterozygous: ________________________

____________________________________________________________________________

34. A chart used by geneticists to predict the possible outcome of offspring from any two known

parents’ genotypes is called a ___________________ ______________.

35. A cross between two parents to evaluate the probabilities for a single trait is known as a

________________ cross.

36. A cross between two parents to evaluate the probabilities for two traits is known as a

________________ cross.

37. Know the difference between Genotype and Phenotype: _______________________________

____________________________________________________________________________