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

21. Population Genetics

Allelic Frequency Changes

Genetics

21. Population Genetics

Allelic Frequency Changes

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1:18 minutes

Problem 1e

Textbook Question

How do we know the age of the last common ancestor shared by two species?

Verified step by step guidance

Understand that the age of the last common ancestor shared by two species is estimated using molecular clock techniques, which rely on the accumulation of genetic mutations over time.

Identify homologous DNA or protein sequences from the two species to compare their genetic differences; these sequences should be orthologous (derived from a common ancestor).

Calculate the number of genetic differences (mutations) between the sequences, often measured as the number of nucleotide substitutions per site.

Use a known mutation rate (substitutions per site per year) for the gene or genomic region studied to convert the genetic distance into an estimate of divergence time.

Apply the formula

T = \frac{D}{r}

, where

T

is the time since the last common ancestor,

D

is the genetic distance, and

r

is the mutation rate, to estimate the age of the last common ancestor.

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Key Concepts

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

Molecular Clock Hypothesis

The molecular clock hypothesis posits that genetic mutations accumulate at a relatively constant rate over time. By comparing genetic differences between two species, scientists can estimate the time since their last common ancestor by calibrating mutation rates with known fossil records or geological events.

Phylogenetic Analysis

Phylogenetic analysis involves constructing evolutionary trees based on genetic or morphological data to infer relationships among species. By examining shared and divergent traits, researchers can identify common ancestors and estimate divergence times between species.

Genetic Variation and Mutation Rates

Genetic variation arises from mutations, which occur at measurable rates. Understanding these mutation rates is essential for estimating evolutionary timelines, as they provide the basis for calculating how long ago two species diverged from a common ancestor.