Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

22. Evolutionary Genetics

Phylogenetic Trees

Genetics

22. Evolutionary Genetics

Phylogenetic Trees

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0:45 minutes

Problem 27

Textbook Question

What is meant by the term homology? How is that different from the meaning of homoplasmy?

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Homology refers to the similarity in DNA, RNA, or protein sequences between different organisms due to shared ancestry. For example, homologous genes in humans and mice may have similar sequences because they were inherited from a common ancestor.

Homology can be further categorized into orthologs (genes in different species that evolved from a common ancestral gene) and paralogs (genes related by duplication within a genome).

Homoplasmy, on the other hand, is a term used in mitochondrial genetics and refers to the presence of a single type of mitochondrial DNA (mtDNA) within a cell or organism. This means all copies of the mtDNA are identical.

The key difference is that homology is about evolutionary relationships and sequence similarity, while homoplasmy is about uniformity in mitochondrial DNA within a cell or organism.

Understanding these terms is important because homology helps in studying evolutionary biology, while homoplasmy is significant in understanding mitochondrial inheritance and diseases.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Homology

Homology refers to the similarity in structure or sequence between biological molecules, such as genes or proteins, due to shared ancestry. In genetics, homologous chromosomes are pairs of chromosomes that have the same genes at the same loci, but may have different alleles. This concept is crucial for understanding evolutionary relationships and genetic inheritance.

Homoplasmy

Homoplasmy describes a condition where all copies of a particular mitochondrial DNA (mtDNA) are identical within a cell or organism. This contrasts with heteroplasmy, where there is a mixture of different mtDNA sequences. Homoplasmy is significant in studies of mitochondrial inheritance and can influence traits and diseases linked to mitochondrial function.

Genetic Variation

Genetic variation refers to the differences in DNA sequences among individuals within a population. This variation is essential for evolution, as it provides the raw material for natural selection. Understanding genetic variation helps clarify the distinctions between homologous traits, which arise from common ancestry, and homoplasmic traits, which may arise independently through convergent evolution.

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Examine the following figure and answer the following questions.

What characteristics are shared by the mammalian clade and the primate clade? What characteristic distinguishes the primates from other members of the mammalian clade?

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Textbook Question

Examine the following figure and answer the following questions.

What characteristic is shared by all clades in the figure?

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Examine the following figure and answer the following questions.

How many clades are shown in the figure?

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Textbook Question

Considering the phylogenetic assignment of Plasmodium falciparum, the malarial parasite, to the phylum Apicomplexa, what might you speculate as to whether the parasite is susceptible to aminoglycoside antibiotics?

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Textbook Question

If one is constructing a phylogeny of reptiles using DNA sequence data, which taxon (birds, mammals, amphibians, or fish) might be suitable to use as an outgroup?

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Textbook Question

Recent reconstructions of evolutionary history are often dependent on assigning divergence in terms of changes in amino acid or nucleotide sequences. For example, a comparison of cytochrome c shows 10 amino acid differences between humans and dogs, 24 differences between humans and moths, and 38 differences between humans and yeast. Such data provide no information as to the absolute times of divergence for humans, dogs, moths, and yeast. How might one calibrate the molecular clock to an absolute time clock? What problems might one encounter in such a calibration?

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Multiple Choice

Which of the following structures on a phylogenetic tree represents the evolutionary connections between organisms?

Which principle is NOT used to construct a phylogenetic tree?

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