Chapter 6 & 7 Practice Questions

Chapter 11 Practice Questions – Genetics Part I

Part I. Fill in the blank. Complete each sentence below with the word(s) that best fit.

Heredity Allele Probability Genetics Dominant Recessive

Segregation True Breeding Genotype Dihybrid Genes Alleles

Homozygous Heterozygous Phenotype Independent Assortment Tall

1. ______is the study of heredity.

2. ______is the likelihood of an event occurring.

3. ______is the passing of traits from parents to offspring.

4. Mendel stated the law of ______, which stated that the 2 alleles of a gene will separate when the sex cells are made during meiosis.

5. The ______is the form of a genetic trait that appears, or is visible in an organism. An example would be brown eyes.

6. Mendel stated the law of ______, which said that genes that segregate independently do not influence each other’s inheritance, so hair color and eye color are not linked.

7. The genetic composition of an organism is its ______. An example is Bb.

8. Mendel started his pea plant experiments with plants that were pure for a particular trait. These plants were called the ______generation.

9. In Mendel’s pea plant experiment, he crossed pure tall (TT) with pure short (tt). The offspring were ______in appearance.

10. The different forms of a trait are called ______, such as a straight thumb vs. a hitchhiker’s thumb.

11. The form of a trait that is expressed any time it is present is the ______form. It cancels out the ______form of the trait, which is only expressed when an individual inherits it from both parents.

12. Mendel used a ______cross to prove his Law of Independent Assortment.

13. Mendel thought a pair of “factors” controlled each trait. Today we know that traits are controlled by our ______.

14. Both alleles of a pair are alike ______. Example is ee or EE.

15. Two alleles of a pair are different ______. Example is Ee. 16. If an organism has a recessive trait, what can be inferred about its genotype? Is it homozygous or heterozygous?

17. If an organism is a hybrid (mixed) for a certain trait, what can be inferred about its genotype? Is it homozygous or heterozygous?

18. Look at the figure below for tallness in pea plants. Which trait is dominant, short or tall? Secondly, cross two pea plants from the second generation (Tt x Tt) using a punnett square. In your own words explain why a short plant reappeared.

19. If the genotype of an organism is Aa, how would you describe its genotype in words?

Aa is ______. 20. Situations in which one allele for a gene is not completely dominant over another allele for that gene is a particular type of genetic inheritance. An example is when a cross of a red flower and a white flower give a pink flower. What is this type of inheritance called? ______

RR = red

RW = pink

WW = white

Solve this cross RW (pink) crossed with RW (pink), gives what percentage of flower colors?

21. What would be the genotype of this cow (it is red and white spotted)? Use R = red, W = white? Genotype = ______.

22. Situations in which one allele “shares” dominance with another allele for that gene is a particular type of genetic inheritance. An example is when a cross of a red cow and a white cow give a red and white spotted cow (called roan – shown in the picture above). What is this type of inheritance called? ______

RR = red hairs RW = roan (red and white hairs)

WW = white hairs

Solve this cross, RW (roan) cow crossed with RR (red), gives what percentage of offspring that could be red, white or roan?

23. Variation in skin color, eye color, hair color, and how tall you are examples of ______traits because they are influenced by more than one set of genes.

24. In simple Mendelian genetics, how many genes influenced each trait? In other words, how many letters are used to represent the genotype of an individual? ______

25. Which blood type is the universal donor? Remember, it will be the blood cell that does not have any surface proteins on its surface. Universal donor = ______. What would physically happen to the blood if type B blood was given to a type A blood person?

26. How many phenotypes of blood type are there in ABO blood typing? Use the table above to help you.

Part II. Practice problems.

27. Mom is heterozygous for a straight thumb, and Dad is homozygous recessive with no straight thumb. Having a straight thumb is a dominant trait. What percent of their kids are likely to have a straight thumb? (use T = straight thumb, and t = no straight thumb) 28. Using the information from question 25, what is the probability that they will have five kids in a row with a straight thumb?

29. Mom and dad are heterozygous for a widow’s peak. A widow’s peak is a dominant trait. What is the probability that they will have a child who has a widow’s peak? Also, write the genotype and phenotype ratios for mom and dad’s potential offspring

30. Roan cattle show codominance for the color of their hair. There are alleles for red hair and white hair. What would you expect a heterozygous roan bull to look like if the trait showed incomplete dominance instead?

31. Hint: this is a dihybrid cross: In pigs, curly tails (C) are dominant over straight tails (c). Pink color (P) is dominate over gray (p). You are to cross a male pig that is heterozygous for curly tail and homozygous dominant for body color with a female pig that is homozygous recessive for type of tail and heterozygous for body color. What percentage of the offspring from this cross will be curly tailed, pink pigs?

30.A breed of chicken shows codominance for feather color. One allele codes for black feathers, another codes for white feathers. The feathers of heterozygous chickens of this breed will be what color(s)? 31.Show how it is possible to get a red four o’clock plant and a white four o’clock plant from two pink parents, when color is inherited using incomplete dominance.

32. Mom has type B blood. Dad has type O blood. They have a child with type O blood. Make a punnett square to show what Mom’s genotype must be to have a child with type O blood.