World Biology Championship

Classical Genetics19 September 2011

Rules of the GameYou have been assigned to a team of 5-6 people and will be asked to sit in a row.

A question will flash on the board and you will have 45 seconds to work the problem on your individual whiteboard.

At the end of the time, the teacher will call a number between 1 and 5/6. The person in each group with the number called will raise his/her board.

Each group with the correct answer will receive one point for their group.

The Spoils of Winning

The victorious group will receive:

Bonus points on the Classical Genetics Unit Exam

A group photograph on the World Bio Championship wall of winners

Bragging rights until the next installment of the W.B.C.

A mystery prize

Ready...Set...Go!

Question # 1

Explain in one complete sentence the difference between being homozygous and being heterozygous.

Question # 2Mrs. Stefano has freckles (r) but her husband, George does not (RR). Which of these is the predicted ratio of children with no freckles to the children with freckles?

a. 1 : 3

b. 2 : 2

c. 3 : 1

d. 4 : 0

Question # 3A cross was created between a black guinea pig and a brown guinea pig. All the offspring ended up black. Which of the following is the reason for this?

a. Black is recessive so it showed up.

b. Brown is heterozygous so it showed up.

c. Black is dominant so it hid the brown trait.

d. Brown is heterozygous so it was hidden.

Question # 4

How many individuals in the pedigree to the right have the trait in question?

How many of the affected individuals are female? Male?

Question # 5

Hemophilia is caused by a sex-linked recessive trait. What is the genotype of a male who has hemophilia?

Question # 6In horses, the allele for straight hair (B) is dominant to the allele for curly hair (b). Which of the sets of parents can produce offspring with curly hair?

heterozygous female with straight hair and a homozygous male with straight hair

homozygous female with curly hair and homozygous male with straight hair

heterozygous female with straight hair and a heterozygous male with straight hair

homozygous female with straight hair and heterozygous male with straight hair

Question # 7

An allele that can be present in a person’s genes without being expressed is called __________.

Question # 8If individual III-4 marries a man heterozygous for the trait, what is the probability of having a child that has the trait?

0 %

25 %

50 %

75 %

Question # 9

Explain in one complete sentence the difference between a genotype and a phenotype.

Question # 10

In humans colorblindness (b) is an example of a sex-linked recessive trait. In this problem, a male with colorblindness marries a female who is not colorblind but carries the (b) allele. Using a Punnett square, determine the genotypic and phenotypic probabilities for their potential offspring.

Question # 11

In the pedigree to the right, is the trait shown dominant or recessive? How do you know?

Question # 12

In dogs, there is hereditary type of deafness caused by a recessive gene. Two dogs who carry the gene for deafness but have normal hearing are mated. What are the possible genotypes and phenotypes of their offspring and the percent chance for each?

Question # 13

In beagles, the allele for brown fur (F) is codominant to the allele for white fur (f). If a heterozygous beagle is crossed with a white furred beagle, what will be the genotypic and phenotypic ratios of their offspring?

Question # 14

How is it possible for two parents to have a child that has a disease even when neither parent has the disease?

Question # 15

Explain in one complete sentence the concept of a sex-linked trait.

Question # 16

If individuals II-1 and II-2 had another child together, what is the probability that it would have the trait in question?

Question # 17

In guinea pigs, short hair is dominant over long hair. If a short haired SS guinea pig is crossed with a long haired ss guinea pig, what are the possible genotypes and phenotypes of their offspring and the percent chance of each?

Question # 18

Explain in one complete sentence what a pedigree is and how it can be used.

Question # 19

In rabbits, the allele for black fur (B) is incompletely dominant with the allele for white fur (b). If a black rabbit and a white rabbit are crossed, what will be the genotypic and phenotypic ratios of their offspring?

Question # 20

Explain in one complete sentence the difference between codominance and incomplete dominance.

That’s all folks!