Category: Ecology

Chapter 15 – Chromosomal Basis of Heredity Objectives

 

Chapter 15     Chromosomal Basis of Heredity
Objectives
Relating Mendelian Inheritance to the Behavior of Chromosomes

1.  Explain how the observations of cytologists and geneticists provided the basis for the chromosome theory of inheritance.

2.  Explain why Drosophila melanogaster is a good experimental organism for genetic studies.

3.  Explain why linked genes do not assort independently.

4.  Distinguish between parental and recombinant phenotypes.

5.  Explain how crossing over can unlink genes.

6.  Explain how Sturtevant created linkage maps.

7.  Define a map unit.

8.  Explain why Mendel did not find linkage between seed color and flower color, despite the fact that these genes are on the same chromosome.

9.  Explain how genetic maps are constructed for genes located far apart on a chromosome.

10. Explain the effect of multiple crossovers between loci.

11. Explain what additional information cytogenetic maps provide.

Sex Chromosomes

12. Describe how sex is genetically determined in humans and explain the significance of the SRY gene.

13. Distinguish between linked genes and sex-linked genes.

14. Explain why sex-linked diseases are more common in human males.

15. Describe the inheritance patterns and symptoms of color blindness, Duchenne muscular dystrophy, and hemophilia.

16. Describe the process of X inactivation in female mammals. Explain how this phenomenon produces the tortoiseshell coloration in cats.

Errors and Exceptions in Chromosomal Inheritance

17. Explain how nondisjunction can lead to aneuploidy.

18. Define trisomy, triploidy, and polyploidy. Explain how these major chromosomal changes occur and describe possible consequences.

19. Distinguish among deletions, duplications, inversions, and translocations.

20. Describe the type of chromosomal alterations responsible for the following human disorders: Down syndrome, Klinefelter syndrome, extra Y, triple-X syndrome, Turner syndrome, cri du chat syndrome, and chronic myelogenous leukemia.

21. Define genomic imprinting. Describe the evidence that suggests that the Igf2 gene is maternally imprinted.

22. Explain why extranuclear genes are not inherited in a Mendelian fashion.
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Chapter 16 – Molecular Basis of Inheritance

 

Chapter 16   Molecular Basis of Inheritance
Objectives
DNA as the Genetic Material
1. Explain why researchers originally thought protein was the genetic material.
2. Summarize the experiments performed by the following scientists that provided evidence that DNA is the genetic material:
a. Frederick Griffith
b. Oswald Avery, Maclyn McCarty, and Colin MacLeod
c. Alfred Hershey and Martha Chase
d. Erwin Chargaff
3. Explain how Watson and Crick deduced the structure of DNA and describe the evidence they used. Explain the significance of the research of Rosalind Franklin.
4. Describe the structure of DNA. Explain the base-pairing rule and describe its significance.
DNA Replication and Repair
5. Describe the semiconservative model of replication and the significance of the experiments of Matthew Meselson and Franklin Stahl.
6. Describe the process of DNA replication, including the role of the origins of replication and replication forks.
7. Explain the role of DNA polymerases in replication.
8. Explain what energy source drives the polymerization of DNA.
9. Define antiparallel and explain why continuous synthesis of both DNA strands is not possible.
10. Distinguish between the leading strand and the lagging strand.
11. Explain how the lagging strand is synthesized even though DNA polymerase can add nucleotides only to the 39 end. Describe the significance of Okazaki fragments.
12. Explain the roles of DNA ligase, primer, primase, helicase, topoisomerase, and single-strand binding proteins.
13. Explain why an analogy can be made comparing DNA replication to a locomotive made of DNA polymerase moving along a railroad track of DNA.
14. Explain the roles of DNA polymerase, mismatch repair enzymes, and nuclease in DNA proofreading and repair.
15. Describe the structure and function of telomeres.
16. Explain the possible significance of telomerase in germ cells and cancerous cell.

 
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Chapter 17 AP Objectives

 

Chapter 17    From Gene to Protein
Objectives
The Connection Between Genes and Proteins
1. Explain why dwarf peas have shorter stems than tall varieties.
2. Explain the reasoning that led Archibald Garrod to first suggest that genes dictate phenotypes through enzymes.
3. Describe Beadle and Tatum’s experiments with Neurospora and explain the contribution they made to our understanding of how genes control metabolism.
4. Distinguish between the “one geneÐone enzyme” hypothesis and the “one geneÐone polypeptide” hypothesis and explain why the original hypothesis was changed.
5. Explain how RNA differs from DNA.
6. Briefly explain how information flows from gene to protein.
7. Distinguish between transcription and translation.
8. Compare where transcription and translation occur in prokaryotes and in eukaryotes.
9. Define codon and explain the relationship between the linear sequence of codons on mRNA and the linear sequence of amino acids in a polypeptide.
10. Explain the early techniques used to identify what amino acids are specified by the triplets UUU, AAA, GGG, and CCC.
11. Explain why polypeptides begin with methionine when they are synthesized.
12. Explain what it means to say that the genetic code is redundant and unambiguous.
13. Explain the significance of the reading frame during translation.
14. Explain the evolutionary significance of a nearly universal genetic code.
The Synthesis and Processing of RNA
15. Explain how RNA polymerase recognizes where transcription should begin. Describe the promoter, the terminator, and the transcription unit.
16. Explain the general process of transcription, including the three major steps of initiation, elongation, and termination.
17. Explain how RNA is modified after transcription in eukaryotic cells.
18. Define and explain the role of ribozyme.
19. Describe the functional and evolutionary significance of introns.
The Synthesis of Protein
20. Describe the structure and functions of tRNA.
21. Explain the significance of wobble.
22. Explain how tRNA is joined to the appropriate amino acid.
23. Describe the structure and functions of ribosomes.
24. Describe the process of translation (including initiation, elongation, and termination) and explain which enzymes, protein factors, and energy sources are needed for each stage.
25. Describe the significance of polyribosomes.
26. Explain what determines the primary structure of a protein and describe how a polypeptide must be modified before it becomes fully functional.
27. Describe what determines whether a ribosome will be free in the cytosol or attached to the rough endoplasmic reticulum.
28. Describe two properties of RNA that allow it to perform so many different functions.
29. Compare protein synthesis in prokaryotes and in eukaryotes.
30. Define point mutations. Distinguish between base-pair substitutions and base-pair insertions. Give examples of each and note the significance of such changes.
31. Describe several examples of mutagens and explain how they cause mutations.
32. Describe the historical evolution of the concept of a gene.

 
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Campbell Problem 14

Molecular Genetics Problem 14
14. In Drosophila, the gene for white eyes and the gene that produces “hairy” wings have both been mapped to the same chromosome and have a crossover frequency of 1.5%. A geneticist doing some crosses involving these two mutant characteristics noticed that in a particular stock of flies, these two genes assorted independently; that is they behaved as though they were on different chromosomes. What explanation can you offer for this observation?

One possibility is that a translocation has occurred where a segment of chromosome containing only one of the 2 genes has moved to a different chromosome.

 

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Campbell Problem 5

Molecular Genetics Problem 5
5. In another cross, a wild-type fruit fly (heterozygous for gray body color and red eyes) was mated with a black fruit fly with purple eyes. The offspring were as follows: wild-type, 721; black-purple, 751; gray-purple, 49; black-red, 45. (a) What is the recombination frequency between these genes for body color and eye color? (b) Following up on this problem and problem 4, what fruit flies (genotypes and phenotypes) would you mate to determine the sequence of the body color, wing shape, and eye color genes on the chromosomes?

 

To help see the process write out the genotypes. The genes can be symbolized as follows:

b+ = gray body b = black body pr+= red eyes pr = purple eyes

Genotype of the heterozygous wild type (gray body and red eyes) using Morgan’s method:

 

The genotype of the homozygous recessive individual (used in a testcross) would be:

 

Determine the recombination frequency:

721 wild-type (gray-red) 721/1566 = 46% expected
751 black-purple 751/1566 = 48% expected
49 gray-purple 49/1566 = 3% recombinant
45 black-red 45/1566 = 3% recombinant

Total flies = 1566

 

(a) The percent recombination is therefore 6%

 

(b) Example: cross a wild type fly heterozygous for body color and wing shape with a fly homozygous recessive for the same traits (black body/curly wings)

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