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

2. Mendel's Laws of Inheritance

Probability and Genetics

Genetics

2. Mendel's Laws of Inheritance

Probability and Genetics

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1:56 minutes

Problem 5

Textbook Question

Two parents plan to have three children. What is the probability that the children will be two girls and one boy?

Verified step by step guidance

Identify the total number of children and the desired gender combination: 3 children with exactly 2 girls and 1 boy.

Recognize that each child’s gender is an independent event with a probability of 1/2 for a girl and 1/2 for a boy.

Calculate the number of different ways to arrange 2 girls and 1 boy among 3 children using combinations:

C (3, 2) = 3

Determine the probability of one specific arrangement (e.g., girl, girl, boy) by multiplying the probabilities:

{\frac{1}{2}}^{2} \times \frac{1}{2}

Multiply the number of arrangements by the probability of one arrangement to get the total probability:

C (3, 2) \times {\frac{1}{2}}^{2} \times \frac{1}{2}

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Key Concepts

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

Basic Probability

Probability measures the likelihood of an event occurring, expressed as a number between 0 and 1. In genetics, it helps predict the chances of offspring having certain traits, such as gender, assuming each outcome is equally likely and independent.

Binomial Probability Distribution

This distribution calculates the probability of a specific number of successes (e.g., girls) in a fixed number of independent trials (e.g., children), each with the same probability of success. It uses combinations to account for different orders of outcomes.

Combinatorics (Permutations and Combinations)

Combinatorics involves counting the number of ways events can occur. For this problem, combinations determine how many ways two girls and one boy can be arranged among three children, which is essential for calculating the total probability.

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Multiple Choice

In a family of five children what is the probability that… Two are males and three are females

In a family of six children, where both parents are heterozygous for albinism, what is the probability that four are normal and two are albinos?

A man, J.B., has a sister with autosomal recessive galactosemia (OMIM 230400), and his partner, S.B., has a brother with galactosemia. Galactosemia is a serious condition caused by an enzyme deficiency that prevents the metabolism of the sugar galactose. Neither J.B. nor S.B. has galactosemia, but they are concerned about the risk that a future child of theirs will have the condition. What is the probability their first child will have galactosemia?

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Textbook Question

A woman, S.R., had a maternal grandfather with hemophilia A (OMIM 306700), an X-linked recessive condition that reduces blood clotting. S.R.'s maternal grandmother and paternal grandparents are free of the condition, as are her partner, his parents, and his grandparents. S.R. has no siblings. She wants to know the chance that a son of hers will have the condition. What is that probability?

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Textbook Question

A 40-year-old woman whose father had Huntington disease currently shows no symptoms of the disease. She is newly pregnant with her first child and seeks your best estimate of the chance her child will inherit the disease. What is your estimate and how did you arrive at it? (Hint: See Figure 4.11)

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Textbook Question

Consider the cross AaBbCC × AABbCc.

Use the forked-line method to predict the expected ratio of offspring phenotypes.

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Textbook Question

Consider the cross AaBbCC × AABbCc.

Use a Punnett square to predict the expected ratio of offspring phenotypes.

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