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

1. Introduction to Genetics

Fundamentals of Genetics

Genetics

1. Introduction to Genetics

Fundamentals of Genetics

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1:03 minutes

Problem 24a

Textbook Question

Suppose a genotype for a protein-producing gene can have any combination of three alleles, A₁, A₂, and A₃.
List all the possible genotypes involving these three alleles.

Verified step by step guidance

Understand that the problem involves three alleles (A₁, A₂, A₃) and that genotypes are combinations of two alleles because diploid organisms have two copies of each gene.

Recognize that the combinations can include both homozygous genotypes (where the two alleles are the same, e.g., A₁A₁) and heterozygous genotypes (where the two alleles are different, e.g., A₁A₂).

List all possible homozygous genotypes: A₁A₁, A₂A₂, and A₃A₃.

List all possible heterozygous genotypes by pairing each allele with the others without repetition: A₁A₂, A₁A₃, and A₂A₃. Note that the order of alleles does not matter (e.g., A₁A₂ is the same as A₂A₁).

Combine the homozygous and heterozygous genotypes into a complete list: A₁A₁, A₂A₂, A₃A₃, A₁A₂, A₁A₃, and A₂A₃.

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Key Concepts

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

Alleles

Alleles are different versions of a gene that can exist at a specific locus on a chromosome. In this case, the alleles A₁, A₂, and A₃ represent variations of a gene responsible for producing a particular protein. Each individual inherits two alleles for each gene, one from each parent, which can be the same (homozygous) or different (heterozygous).

Genotype

A genotype refers to the specific genetic makeup of an individual concerning a particular gene or set of genes. It is represented by the combination of alleles present, such as A₁A₁, A₁A₂, or A₂A₃. Understanding genotypes is crucial for predicting phenotypic traits and inheritance patterns in offspring.

Combinatorial Genetics

Combinatorial genetics involves calculating all possible combinations of alleles to determine potential genotypes. With three alleles (A₁, A₂, A₃), the possible genotypes can include homozygous combinations (e.g., A₁A₁) and heterozygous combinations (e.g., A₁A₂, A₁A₃, A₂A₃). This concept is essential for understanding genetic variation and inheritance.

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Suppose a genotype for a protein-producing gene can have any combination of three alleles, A₁, A₂, and A₃.

Each allele produces a protein with a distinct electrophoretic mobility. Allele A₁ has the highest electrophoretic mobility, A₃ has the lowest electrophoretic mobility, and the electrophoretic mobility of A₂ is intermediate between them. Draw the appearance of gel electrophoresis protein bands for each of the possible genotypes. Be sure to label each lane of the gel with the corresponding genotype.

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Textbook Question

Shorter fragments of DNA (those with fewer base pairs) have a higher electrophoretic mobility than larger fragments. Thinking about electrophoresis gels as creating a matrix through which fragments must migrate, briefly explain why the size of a DNA fragment affects its electrophoretic mobility.

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Textbook Question

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Consider the following segment of DNA: