Questions to Ponder: Exam 2
Key: Purple = My initial thoughts Red = Vigna's answer
Inheritance questions, Pedigree questions and:
1. Who was Mendel and what were his contributions to Genetics?
Did experimental crosses with Peas – determined the idea that we have two of each gene – on homologous chromosomes. And that these homologous chromosomes separate during the production of egg and sperm (meiosis) to put only one of each homologous pair in each daughter cell. So, he figured out that we’re diploid, and that chromosomes do independent assortment.
2. A man denies fathering a child of blood type A. He is blood type B. Could this man be the child’s biological father? Does this test prove for certain that he is or isn’t?
Child is phenotype A, so is either AA or AO. Man is phenotype B, so is either BB or BO. The man could be the father, if his genotype is BO and the child’s genotype is AO. It doesn’t prove that he is for certain, because we don’t know their exact genotypes, and there are lots of men with B blood.
3. A man with blood type A and a woman with blood type B have three children: A daughter with type AB and two sons, one with type B and the other with type O blood. Remembering that blood type is expressed with codominant inheritance, determine the genotypes of the parents.
Woman is phenotype B, so could be BB or BO. The fact that one of their children is O, and therefore OO, means that the parents have to be AO and BO.
4. If the hair of the field mouse was controlled by genes that were expressed with Complete dominance, what color would the hair of a “Bb” individual be, where B is for Black and b is for the white trait. What if the genes were expressed with Incomplete Dominance? What if the genes were expressed with Co-dominance
a. Complete dominance: Bb = black
b. Incomplete dominance: Bb = gray
c. Codominance: Bb = white and black
5. What gametes (sex cells) could be produced during Meiosis in the following individual? AaBb
AB, Ab, aB, ab
6. What gametes could be produced during Meiosis in the following individual? AABb
AB, Ab
7. What does Independent Assortment have to do with the two questions above?
These different combinations occur because the chromosome pair that holds gene A is assorting independently from the chromosome that holds gene B. So, all combinations of these alleles are possible.
8. Coat color in Labrador retrievers is governed by two genes: Bb and Ee.
B=black pigment
b=brown pigment
E=allows pigment to be deposited
e=does not allow pigment to be deposited
The B allele is dominant to the b, and E is dominant to e. The ee genotype specifies a golden lab regardless of what B/b allele combination it carries. This is because the black or brown pigment cannot be deposited in a proper manner. If a heterozygous black lab is mated to a black lab, and they have some golden puppies:
What are the genotypes of the parents?
BbEe (BbEe or BBEe)
What is the chance that these parents will be able to generate black lab puppies (Hint: do a dihybrid punnet square)? Brown labs? Golden labs?
i. Black puppies – must have at least one dominant B and one dominant E – 9/16
ii. Brown puppies – must have two recessive b and at least one dominant E – 3/16
iii. Golden puppies – must have two recessive e – 4/16 or ¼
In a litter of 12 puppies, how many theoretically will be golden based on your answer in (b)?
3 puppies will theoretically be golden
9. If a gene is “X-linked”, why does the trait usually show up in men?
It really depends if it is X-linked recessive or X-linked dominate. It if is recessive then the trait is more prevalent in men because there only needs to be one recessive X chromosome in men because men have one X and one Y. If the one X has the trait then the male will have the phenotype as well. If the gene is an X-linked dominate trait then the trait will show up in women more often because women have two X's and thus two times the chances of receiving one dominate X allele.
Carrier mothers pass it to their sons (the son gets the Y from the father, and therefore always gets his X from mom). Dad’s pass their X to their daughters, but since females have another X that could carry a dominant allele, the X linked recessive trait is often “hidden” in the females. These females are carriers and pass it to their sons, who only have one X.
10. The following mRNA was transcribed from a gene.
Write the double-stranded DNA segment that served as the template for this message.
Indicate both the 5’ and the 3’ ends of both DNA strands.
Also, translate the protein that is encoded by this mRNA message.
Template: 3'- C G A T T T A C C G T C G T G T A A C T G A G C C C C A G T C T A G G C -5'
5’–G C U A A A U G G C A G C A C A U U G A C U C G G G G U C A G A U C C G–3’
MET-ALA-ALA-HIS
More Questions
What is the sequence of the other strand?
8. Why would a DNA structure in which each base type (A,T,G,C) could form hydrogen bonds with any of the other three bases not produce a molecule that could be easily replicated?
9. What were the key pieces of evidence that were critical in determining the structure of DNA? Who were the scientists that did the work in these areas?
10. Why must DNA be replicated using both Leading and Lagging strands?
Inheritance questions, Pedigree questions and:
1. Who was Mendel and what were his contributions to Genetics?
Did experimental crosses with Peas – determined the idea that we have two of each gene – on homologous chromosomes. And that these homologous chromosomes separate during the production of egg and sperm (meiosis) to put only one of each homologous pair in each daughter cell. So, he figured out that we’re diploid, and that chromosomes do independent assortment.
2. A man denies fathering a child of blood type A. He is blood type B. Could this man be the child’s biological father? Does this test prove for certain that he is or isn’t?
Child is phenotype A, so is either AA or AO. Man is phenotype B, so is either BB or BO. The man could be the father, if his genotype is BO and the child’s genotype is AO. It doesn’t prove that he is for certain, because we don’t know their exact genotypes, and there are lots of men with B blood.
3. A man with blood type A and a woman with blood type B have three children: A daughter with type AB and two sons, one with type B and the other with type O blood. Remembering that blood type is expressed with codominant inheritance, determine the genotypes of the parents.
Woman is phenotype B, so could be BB or BO. The fact that one of their children is O, and therefore OO, means that the parents have to be AO and BO.
4. If the hair of the field mouse was controlled by genes that were expressed with Complete dominance, what color would the hair of a “Bb” individual be, where B is for Black and b is for the white trait. What if the genes were expressed with Incomplete Dominance? What if the genes were expressed with Co-dominance
a. Complete dominance: Bb = black
b. Incomplete dominance: Bb = gray
c. Codominance: Bb = white and black
5. What gametes (sex cells) could be produced during Meiosis in the following individual? AaBb
AB, Ab, aB, ab
6. What gametes could be produced during Meiosis in the following individual? AABb
AB, Ab
7. What does Independent Assortment have to do with the two questions above?
These different combinations occur because the chromosome pair that holds gene A is assorting independently from the chromosome that holds gene B. So, all combinations of these alleles are possible.
8. Coat color in Labrador retrievers is governed by two genes: Bb and Ee.
B=black pigment
b=brown pigment
E=allows pigment to be deposited
e=does not allow pigment to be deposited
The B allele is dominant to the b, and E is dominant to e. The ee genotype specifies a golden lab regardless of what B/b allele combination it carries. This is because the black or brown pigment cannot be deposited in a proper manner. If a heterozygous black lab is mated to a black lab, and they have some golden puppies:
What are the genotypes of the parents?
BbEe (BbEe or BBEe)
What is the chance that these parents will be able to generate black lab puppies (Hint: do a dihybrid punnet square)? Brown labs? Golden labs?
i. Black puppies – must have at least one dominant B and one dominant E – 9/16
ii. Brown puppies – must have two recessive b and at least one dominant E – 3/16
iii. Golden puppies – must have two recessive e – 4/16 or ¼
In a litter of 12 puppies, how many theoretically will be golden based on your answer in (b)?
3 puppies will theoretically be golden
9. If a gene is “X-linked”, why does the trait usually show up in men?
It really depends if it is X-linked recessive or X-linked dominate. It if is recessive then the trait is more prevalent in men because there only needs to be one recessive X chromosome in men because men have one X and one Y. If the one X has the trait then the male will have the phenotype as well. If the gene is an X-linked dominate trait then the trait will show up in women more often because women have two X's and thus two times the chances of receiving one dominate X allele.
Carrier mothers pass it to their sons (the son gets the Y from the father, and therefore always gets his X from mom). Dad’s pass their X to their daughters, but since females have another X that could carry a dominant allele, the X linked recessive trait is often “hidden” in the females. These females are carriers and pass it to their sons, who only have one X.
10. The following mRNA was transcribed from a gene.
Write the double-stranded DNA segment that served as the template for this message.
Indicate both the 5’ and the 3’ ends of both DNA strands.
Also, translate the protein that is encoded by this mRNA message.
Template: 3'- C G A T T T A C C G T C G T G T A A C T G A G C C C C A G T C T A G G C -5'
5’–G C U A A A U G G C A G C A C A U U G A C U C G G G G U C A G A U C C G–3’
MET-ALA-ALA-HIS
More Questions
- A man denies fathering a child of blood type O. He is blood type AB, while the mother is blood type O. Could he have fathered this child? Why or why not?
- A man denies fathering a child of blood type A. He is blood type B. Could this man be the child’s biological father? Does this test prove for certain that he is or isn’t?
- If a gene is “X-linked”, why does the trait usually show up in men?
- Long stems are dominant to short stems, purple flowers are dominant to white, and round seeds are dominant to wrinkled. Each trait is determined by a single, different gene. A plant that is heterozygous at all three genes is self-crossed, and 2048 progeny are examined. How many of these plants would you expect to be long stemmed with purple flowers, producing wrinkled seeds?
- When and why does DNA need to replicate? How might the structure of DNA allow replication to occur with accuracy and efficiency?
- Why shouldn’t we inbreed?
- If one strand of a double-stranded DNA chromosome has the sequence:
What is the sequence of the other strand?
8. Why would a DNA structure in which each base type (A,T,G,C) could form hydrogen bonds with any of the other three bases not produce a molecule that could be easily replicated?
9. What were the key pieces of evidence that were critical in determining the structure of DNA? Who were the scientists that did the work in these areas?
10. Why must DNA be replicated using both Leading and Lagging strands?