Category: Ecology

Chapter 26 Early Earth & the Origin of Life

 

Chapter 26    Early Earth & the Origin of Life
Objectives
The Origin of Life
1. Describe the four stages of the hypothesis for the origin of life on Earth by chemical evolution.
2. Describe the contributions that A. I. Oparin, J.B.S. Haldane, and Stanley Miller made toward developing a model for the abiotic synthesis of organic molecules. Describe the conditions and locations where most of these chemical reactions probably occurred on Earth.
3. Describe the evidence that suggests that RNA was the first genetic material. Explain the significance of the discovery of ribozymes.
4. Describe how natural selection may have worked in an early RNA world.
5. Describe how natural selection may have favored the proliferation of stable protobionts with self-replicating, catalytic RNA.
Introduction to the History of Life
6. Explain how the histories of Earth and life are inseparable.
7. Explain how index fossils can be used to determine the relative age of fossil-bearing rock strata. Explain how radiometric dating can be used to determine the absolute age of rock strata. Explain how magnetism can be used to date rock strata.
8. Describe the major events in Earth’s history from its origin until 2 billion years ago. In particular, note when Earth first formed, when life first evolved, and what forms of life existed in each eon.
9. Describe the mass extinctions of the Permian and Cretaceous periods. Discuss a hypothesis that accounts for each of these mass extinctions.
The Major Lineages of Life
10. Describe how chemiosmotic ATP production may have arisen.
11. Describe the timing and significance of the evolution of oxygenic photosynthesis.
12. Explain the endosymbiotic theory for the evolution of the eukaryotic cell. Describe the evidence that supports this theory.
13. Explain how genetic annealing may have led to modern eukaryotic genomes.
14. Describe the timing of key events in the evolution of the first eukaryotes and later multicellular eukaryotes.
15. Explain how the snowball-Earth hypothesis explains why multicellular eukaryotes were so limited in size, diversity, and distribution until the late Proterozoic.
16. Describe the key evolutionary adaptations that arose as life colonized land.
17. Explain how continental drift explains Australia’s unique flora and fauna.
18. Explain why R. H. Whittaker’s five-kingdom system has been replaced by a new system with three domains.
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Chapter 14 – Mendel Objectives

 

 

Chapter 14   Mendel & the Gene Idea
Objectives
Gregor Mendel’s Discoveries
1. Explain how Mendel’s particulate mechanism differed from the blending theory of inheritance.
2. Define the following terms: true-breeding, hybridization, monohybrid cross, P generation, F1 generation, and F2 generation.
3. List and explain the four components of Mendel’s hypothesis that led him to deduce the law of segregation.
4. Use a Punnett square to predict the results of a monohybrid cross, stating the phenotypic and genotypic ratios of the F2 generation.
5. Distinguish between the following pairs of terms: dominant and recessive; heterozygous and homozygous; genotype and phenotype.
6. Explain how a testcross can be used to determine if an individual with the dominant phenotype is homozygous or heterozygous.
7. Use a Punnett square to predict the results of a dihybrid cross and state the phenotypic and genotypic ratios of the F2 generation.
8. State Mendel’s law of independent assortment and describe how this law can be explained by the behavior of chromosomes during meiosis.
9. Use the rule of multiplication to calculate the probability that a particular F2 individual will be homozygous recessive or dominant.
10. Given a Mendelian cross, use the rule of addition to calculate the probability that a particular F2 individual will be heterozygous.
11. Use the laws of probability to predict, from a trihybrid cross between two individuals that are heterozygous for all three traits, what expected proportion of the offspring would be:
a. homozygous dominant for the three traits
b. heterozygous for all three traits
c. homozygous recessive for two specific traits and heterozygous for the third
12. Explain why it is important that Mendel used large sample sizes in his studies.
Extending Mendelian Genetics
13. Give an example of incomplete dominance and explain why it does not support the blending theory of inheritance.
14. Explain how phenotypic expression of the heterozygote differs with complete dominance, incomplete dominance, and codominance.
15. Explain why Tay-Sachs disease is considered recessive at the organismal level but codominant at the molecular level.
16. Explain why genetic dominance does not mean that a dominant allele subdues a recessive allele. Illustrate your explanation with the use of round versus wrinkled pea seed shape.
17. Explain why dominant alleles are not necessarily more common in a population. Illustrate your explanation with an example.
18. Describe the inheritance of the ABO blood system and explain why the IA and IB alleles are said to be codominant.
19. Define and give examples of pleiotropy and epistasis.
20. Describe a simple model for polygenic inheritance and explain why most polygenic characters are described in quantitative terms.
21. Describe how environmental conditions can influence the phenotypic expression of a character. Explain what is meant by “a norm of reaction.”
22. Distinguish between the specific and broad interpretations of the terms phenotype and genotype.
Mendelian Inheritance in Humans
23. Explain why studies of human inheritance are not as easily conducted as Mendel’s work with his peas.
24. Given a simple family pedigree, deduce the genotypes for some of the family members.
25. Explain how a lethal recessive allele can be maintained in a population.
26. Describe the inheritance and expression of cystic fibrosis, Tay-Sachs disease, and sickle-cell disease.
27. Explain why lethal dominant genes are much rarer than lethal recessive genes.
28. Give an example of a late-acting lethal dominant gene in humans and explain how it can escape elimination by natural selection.
29. Define and give examples of multifactorial disorders in humans.
30. Explain how carrier recognition, fetal testing, and newborn screening can be used in genetic screening and counseling.

 
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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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Campbell Problem 7

Molecular Genetics Problem 7
7. Using the information from problem 6, a further testcross was done using a heterozygote for height and nose morphology. The offspring were tall-upturned nose, 40; dwarf-upturned nose, 9; dwarf-downturned nose, 42; tall-downturned nose, 9. Calculate the recombination frequency from these data; then use your answer from problem 6 to determine the correct sequence of the three linked genes.

Experiment 3. (Frequency/Distance between T and S)

Determine the recombination frequency for the genes controlling Tallness and Snout:

40 tall-upturned snout = 40% expected
42 dwarf-downturned snout = 42% expected
9 dwarf-upturned snout = 9% recombinant
9 tall-downturned snout = 9% recombinant

Total = 100%

Therefore this recombination frequency between genes T and S is 18%

One can determine the relative frequency between genes using the percent frequencies as distances.

The Recombinant relationships from experiments 1-3 are:

Exp. 1 T-A = 12 map units Exp. 2 A-S = 5 map units Exp. 3 T-S = 18 map units

An arrangement that fits the data would be:

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Campbell Problem 10

Molecular Genetics Problem 10
10. An aneuploid person is obviously female, but her cells have two Barr bodies. What is the probable complement of sex chromosomes in this individual?

This individual probably is XXX.

The individual is a female. Nondisjunction of sex chromosomes produces a variety of aneuploid conditions in humans. Most of these conditions appear to upset genetic balance less than aneuploid conditions involving autosomes. Extra copies of the X chromosome are deactivated as Barr bodies in the somatic cells. Females with trisomy of the X chromosome (XXX), which occurs about once in approximately 1000 live births, are healthy and cannot be distinguished from XX females except by karyotype.

An Example of nondisjunction:

Klinefelter’s syndrome

49 ,XXXXY

This karyotype shows a variant of Klinefelter’s syndrome.

Individuals with this syndrome are male, typically with the karyotype 47,XXY.

Individuals with Klinefelter’s syndrome exhibit a characteristic phenotype including tall stature, infertility, gynecomastia and hypogonadism.

Aneuploidy above one extra chromosome is usually fatal but because of X-inactivation, which “turns off” all but one X chromosome per cell, the effects of 3 extra chromosomes are reduced.

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