NAME:

Genetics Study Guide (Due on Day of Test: Tuesday, 11/22)

FLIP / FLOP
1. In simple Mendelian Genetics, alleles are either dominant or recessive. In these types of word problems, you will see key words such as dominant, recessive, or heterozygous. Remember to set up the genotypes and phenotypes for these word problems BEFORE you attack the problem.
GG – Homozygous Dominant
Gg – Heterozygous
gg – Homozygous Recessive
The first generation produced from the parental generation is called the F1 generation. If two offspring from the F1 generation are crossed, the resulting generation is called the F2 generation. / 1. In watermelons, stripes are dominant to no stripes. Cross a homozygous, recessive non-striped watermelon with a heterozygous striped watermelon. What are the genotypes and phenotypes of the F1 generation?
2. Other types of inheritance patterns are not simple Mendelian inheritance patterns. The first example of this is Incomplete Dominance. In this type of inheritance, neither allele is dominant over the other so you end up with a blending of traits, which creates the appearance of a third phenotype.
Example of Symbols:
rr – red
rw – pink
ww – white
Think Incomplete = “In Between” / 2. When a blue flower is crossed with a red flower, all of the offspring created are purple. Cross a purple flower with a red flower. What is the phenotypic ratio of the offspring created?
3. The next type of non-Mendelian inheritance is Codominance. In codominance both alleles are equally dominant, so you use two different capital letters to represent the genotypes. You see both phenotypes distinctly in the offspring.
Example of Symbols:
BB – black
BY – black and yellow spotted
YY – yellow
Think Codominant = “Both Show” / 3. In horses, hair color is codominant. Cross an all brown horse with an all white horse. What would be the genotypes and phenotypes of the F1 generation? What if you crossed two offspring from the F1 generation, what would be the results in the F2 generation?

Instructions: Read the flip and answer the flop. Answer all questions!

FLIP / FLOP
4. Blood types are a specific example multiple alleles and of codominance. In blood typing, offspring can have different genotypes and phenotypes from their parents.
Symbols to use for blood types
Phenotype / Genotype
A
B
AB
O / IAIA or IAi
IBIB or IBi
IAIB
ii
Think Blood Type = “ABO” / 4. Jane Smith married a man with type B blood. They had a child with type O blood. Jane must have what genotype? Explain. Show a Punnett square to support your answer.
5. John Smith has been taken to court for a paternity dispute. He is accused of fathering a child out of wedlock. The child in the case has type AB blood. John has blood type B. Can John be the child’s father? Explain. Show a Punnett square to support your answer.
5. The last type of non-Mendelian inheritance pattern that we discussed are sex-linked recessive traits. When you see sex-linked, think “X linked” and automatically know that you need to use your X and Y chromosomes as part of the symbols. Also, remember that males are more likely to have a sex-linked trait because their Y allele does not carry any genes to mask the recessive allele that might be on the X chromosome. Therefore, males only need one recessive form of a trait to have the condition.
Example of Symbols
XNXN = normal female
XNXn = carrier female (normal phenotype)
XnXn = diseased female
XNY = normal male
XnY = diseased male / 6. Colorblindness is a recessive sex linked trait. Show the cross between a color-blind female and a normal vision male.


Vocabulary Review

_____ 1. Genetics A. A picture of an individual’s chromosomes; used to see disorders
_____ 2. Test Cross B. When both traits are expressed at the same time
_____ 3. Genotype C. The study of heredity (passing on traits)
_____ 4. Phenotype D. This procedure is used to create a karyotype of a fetus.
_____ 5. Gene E. A physical characteristic that is passed on by genes
_____ 6. Allele F. Different forms of a gene
_____ 7. Heterozygous G. The genetic combination that produces a phenotype (ex. Tt)
_____ 8. Homozygous H. Alleles that are always expressed if present (T)
_____ 9. Dominant I. When two alleles are different (Tt)
_____ 10. Recessive J. A person does not show a disorder, but has 1 copy of the allele
_____ 11. Incomplete dominance K. Alleles that are masked or hidden unless there are two (t)
_____ 12. Co-dominance L. The physical expression of a gene; what you see (ex. brown)
_____ 13. Multiple alleles M. More than 1 alleles controls the phenotype for 1 trait (blood type)
_____ 14. Sex-linked inheritance N. Inheritance when there is a 3rd blending phenotype
_____ 15. Pedigree O. A graphical family tree showing the inheritance of 1 trait
_____ 16. Karyotype P. When two alleles are the same (TT or tt)
_____ 17. Carrier Q A section of DNA that makes a specific protein and trait
_____ 18. Amniocentesis R. When you cross an organism with a homozygous recessive
_____ 19. Polygenic Traits S. More than 1 gene controls a trait (ex. height, skin color)

Pedigree (Greenhouse Biology, you do NOT have to do the pedigree!)

Karyotypes


You must show a Punnett square for every problem!

1.  A woman names her former boyfriend in a paternity suit. Her child has type O blood. The woman has type A blood. The accused man has type B blood. What must be the parents genotypes for this to be his child?

A. Mother: AA and Father: BB

B. Mother: AO and Father: BB

C. Mother: AA and Father: BO

D. Mother: AO and Father: BO

2.  Hemophilia is a sex-linked recessive trait. What would be the probability that a male with hemophilia and a normal female (not a carrier) would have a son with hemophilia?

A. 100%

B. 75%

C. 50%

D. 0%

3.  Colorblindness is a sex-linked recessive trait. A mother with normal color-vision and a colorblind father have a color-blind daughter. Which of the following statements is correct? (Show the cross and Punnett square to help)

A. All of their daughters will be colorblind

B. The mother is a carrier of the colorblindness gene

C. All of their sons will have normal color vision

D. All of their sons will be colorblind.

4.  The red flower gene is incompletely dominant over the white flower gene. When a pure red flower is crossed with a pure white flower, all of the offspring are pink. When a white flower is crossed with a pink flower, what are the expected genotypes? (show the cross and Punnett square to help you)

A. 100% RW

B. 50% RW and 50% WW

C. 25% RR, 50% RW and 25% WW

D. 100% WW

5.  A white horse is mated with a brown horse and all of their offspring are white and brown. This is known as codominance. What will be the resulting phenotypes when two of their offspring (two white & brown horses) are crossed? (Show cross and Punnett square)

A. 25% white, 50% white and brown, 25% brown

B. 100% white and brown

C. 50% white and 50% brown

D. 50% white and brown 50% brown

6.  Gregor Mendel, the Father of Genetics, worked with pea plants to study genetics. He saw that yellow seed color is dominant to green seed color. If Mendel crossed a heterozygous pea plant with a plant that is recessive for seed color, what is the probability (%) that the offspring will have green seeds?

A. 0%

B. 25%

C. 50%

D. 100%

7.  In certain rats, short hair (S) is dominant over long fur (s). A test cross can be used to determine the genotype of the short hair rat. Draw the Punnett square that represents a test cross that would produce an offspring including 15 short haired rats and no long haired rats. Go back to your notes to remember what you use for a test cross! What is the genotype of the parents?

A. SS x SS

B. Ss x SS

C. SS x ss

D. Ss x ss