Exercise 8 & 9 Question Sheet

Exercise 8, Human Genetics

Activity 1, Understanding genetics through chromosome analysis, #1-4

1. Figure 8-1 shows an example of a female karyotype.

Are there 46 total chromosomes? _____

How many pairs of autosomes are in the karyotype? _____

How many pairs of sex chromosomes? _____

2. Examine the homologous pair of sex chromosomes (Figure 8-1). Is there a visible difference between the maternal and paternal chromosomes? ______. Explain.

3. Figure 8-2 shows an example of a male karyotype.

Are there 46 total chromosomes? _____

How many pairs of autosomes are in the karyotype? _____

How many pairs of sex chromosomes? _____

4. Is there a visible difference between the X and Y chromosomes? _____ Explain.

Activity 2, Abnormal karyotypes, #1 and 3

1. In your report, include the following information:

Gender of patient: _________________

Description of any chromosomal abnormalities present in the karyotype: __________________

Name of abnormality (if present): ___________________

3. Would it be possible for the person who provided the karyotype in figure 8-5 to have a daughter with Down Syndrome if he or she had a spouse with a normal karyotype? Explain.

Activity 3, Relationship of chromosomes, genes, and alleles, #1-5

1. Which of the above genotypes represents an individual who is homozygous for the melanin trait? ______

2. Which of the genotypes listed in question one contains one maternal allele and one paternal allele? Explain.

3. Which genotype(s) listed in question one represent(s) an individual that is heterozygous? _____

4. Would there be a phenotypic difference between AA and Aa when the genes are expressed? Explain.

5. Which genotype listed in question one represents a person who is an albino? Explain.

Activity 4, Determining inheritance by combining alleles, #1-7

1. Based on your knowledge of dominant and recessive alleles, fill in the phenotypes for each allele combination.

Genotypes	Phenotypes
AA
Aa
aa

2. Combine the appropriate alleles to complete the other three boxes in the Punnett Square.

	A	a
A	AA
a

What is the probability that this couple could have an albino child?

3. If this couple does have an albino child, what is the probability they could have a second albino child? Explain.

4. If this couple has a child with normal skin color, is there any possibility that this normal child could have an albino baby? Explain.

5. Is he correct in his assumption? Explain.

6. What are the genotypes of all the individuals mentioned in the problem?

Genotypes: Steve _____ Steve’s Mom _____ Steve’s Dad _____ Marilyn _____

7. What is the probability that Steve and Marilyn could have an albino child?

Probability of an albino child: _____

Probability of a child with normal skin color: _____

Exercise 9, Molecular Genetics

Activity 1, Building a DNA model, #1-8

1. Table 9-1, DNA Color Codes

Gummy Bear Color	DNA base

5. Your DNA model contains a total of _____ bases.

6. How many triplets are present along the left side of the DNA molecule you made? ______

7. What is the last triplet on the right side of the DNA model? _____

8. If you were comparing your DNA to a classmate’s DNA, would you use the same bases to construct the DNA molecule? Explain.

Activity 2, Transcription, #1-5

1. Complete Table 9-2 by entering the appropriate bases.

DNA base	mRNA base
A
C
T
G

2. Looking at Figure 9-2 (next page), you can see that column one contains the DNA sequence found along one side of a double helix. Fill in the appropriate mRNA sequence in the second column.

Figure 9-2

1	2	3
DNA	mRNA	Amino Acids
A
T
G
T
A
T
G
T
T
T
T
G
A
C
G
G
G
A
G
A
C
C
C
C

3. The mRNA code is composed of a sequence of three bases along the mRNA molecule. The three bases are referred to as a codon.

ATG is the first triplet on the DNA sequence. What is the corresponding codon? _____

4. How many codons does your mRNA strand contain? _____

5. What is the base sequence of the fourth codon of your mRNA? _____

Activity 3, Translation and protein synthesis, #1-5

1. Fill in column three of Figure 9-2 with the correct amino acids.

2. How many amino acids does your protein contain? _____

3. What is the sixth amino acid in the polypeptide chain? _____

4. If the sixth triplet read GAA instead of GGA, would the sequence of amino acids change? Explain.

5. If the sixth triplet read GGC instead of GGA, would the sequence of amino acids change? Explain.