Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

13. Mendelian Genetics

Punnett Square Probability

General Biology

13. Mendelian Genetics

Punnett Square Probability

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4:31 minutes

Problem 4

Textbook Question

Two pea plants heterozygous for the characters of pod color and pod shape are crossed. Draw a Punnett square to determine the phenotypic ratios of the offspring.

Verified step by step guidance

Identify the genotypes of the parent pea plants. Since they are heterozygous for both traits, their genotypes are RrYy, where 'R' and 'r' represent the alleles for pod color, and 'Y' and 'y' represent the alleles for pod shape.

Determine the possible gametes each parent can produce. Each parent can produce four types of gametes: RY, Ry, rY, and ry. This is because each allele for one trait can combine with each allele for the other trait.

Set up a 4x4 Punnett square. Label the rows with the gametes from one parent (RY, Ry, rY, ry) and the columns with the gametes from the other parent (RY, Ry, rY, ry).

Fill in the Punnett square by combining the alleles from the gametes at the top of each column with those at the beginning of each row. This will give you 16 possible genotypes for the offspring.

Determine the phenotypic ratios by analyzing the genotypes in the Punnett square. Count how many of each phenotype appear, considering that 'R' is dominant over 'r' and 'Y' is dominant over 'y'.

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Key Concepts

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

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through the actions of alleles, which are different forms of a gene. Gregor Mendel's principles, including the law of segregation and the law of independent assortment, explain how alleles separate and recombine during reproduction, leading to genetic variation in offspring.

Punnett Square

A Punnett square is a diagram used in genetics to predict the genotypes of offspring from a particular cross or breeding experiment. It allows visualization of how alleles from each parent combine, showing all possible genetic combinations and their associated probabilities, which helps in determining phenotypic ratios.

Phenotypic Ratio

The phenotypic ratio refers to the relative number of offspring manifesting different traits or phenotypes resulting from a genetic cross. In a dihybrid cross involving two heterozygous parents, the typical phenotypic ratio is 9:3:3:1, representing the distribution of dominant and recessive traits in the offspring.

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Related Practice

Multiple Choice

An AABbccDdEeFF individual is crossed with an individual with the genotype AaBBCCDdEeff. What is the probability that their offspring will have the genotype AaBBCcddEEFf?

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Multiple Choice

If each parent can produce 100 genetically distinct gametes, how many genetically distinct offspring can two parents produce?

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Multiple Choice

Michelle and Keith are apparently healthy, but their daughter was born with alkaptonuria, an inherited metabolic disorder. If alkaptonuria is like most other human hereditary disorders, the probability of their next child being born with alkaptonuria is __________.

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Textbook Question

A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits. Remember that extra digits is a dominant trait. What fraction of this couple's children would be expected to have extra digits?

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Textbook Question

Flower position, stem length, and seed shape are three characters that Mendel studied. Each is controlled by an independently assorting gene and has dominant and recessive expression as indicated in Table 14.1.

If a plant that is heterozygous for all three characters is allowed to self-fertilize, what proportion of the offspring would you expect to be each of the following? (Note: Use the rules of probability instead of a huge Punnett square.)

a. Homozygous for the three dominant traits

b. Homozygous for the three recessive traits

c. Heterozygous for all three characters

d. Homozygous for axial and tall, heterozygous for seed shape

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Textbook Question

Tim and Jan both have freckles but their son Mike does not. Show with a Punnett square how this is possible. If Tim and Jan have two more children, what is the probability that both will have freckles?

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Textbook Question

The genotype of F₁individuals in a tetrahybrid cross is AaBbCcDd. Assuming independent assortment of these four genes, what are the probabilities that F₂ offspring will have the following genotypes?

a. aabbccdd

b. AaBbCcDd

c. AABBCCDD

d. AaBBccDd

e. AaBBCCdd

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Textbook Question

Both Tim and Jan have a widow's peak (see Module 9.8), but Mike has a straight hairline.

What are their genotypes?

What is the probability that Tim and Jan's next child will have freckles and a straight hairline?

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