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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
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17. Viruses37m
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26. Prokaryotes4h 59m
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28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
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30. Overview of Animals34m
- Overview of Animals
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31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
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  1h 2m
35. Soil37m
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  20m
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  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
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- Digestion
  1h 3m
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- Endocrine System
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- Animal Reproduction
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  1h 8m
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  46m
46. Sensory Systems46m
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47. Muscle Systems23m
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48. Ecology3h 11m
49. Animal Behavior28m
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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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1:32 minutes

Problem 7

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

Verified step by step guidance

Understand that independent assortment means each gene pair segregates independently during gamete formation. This is based on Mendel's law of independent assortment.

For each gene pair, calculate the probability of inheriting a specific allele combination. For example, the probability of inheriting 'aa' from 'Aa' is 1/4, since each parent can contribute either 'A' or 'a'.

Apply the probability rule for independent events: multiply the probabilities of each independent event to find the overall probability of a genotype. For example, the probability of 'aabbccdd' is the product of the probabilities of 'aa', 'bb', 'cc', and 'dd'.

Repeat the calculation for each requested genotype. For instance, for 'AaBbCcDd', calculate the probability of inheriting 'Aa' (1/2), 'Bb' (1/2), 'Cc' (1/2), and 'Dd' (1/2), then multiply these probabilities.

Consider the dominance and recessiveness of alleles if needed, but in this case, focus on the probability of allele combinations rather than phenotypic expression.

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Key Concepts

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

Independent Assortment

Independent assortment is a principle of Mendelian genetics stating that alleles of different genes segregate independently during gamete formation. This means the inheritance of one trait generally does not affect the inheritance of another, allowing for various combinations of alleles in offspring. In a tetrahybrid cross, each gene pair segregates independently, leading to diverse genotypic possibilities.

Probability in Genetics

Probability in genetics involves calculating the likelihood of specific genotypes or phenotypes appearing in offspring. This is done using the principles of Mendelian inheritance, where the probability of inheriting a particular allele from each parent is considered. For a tetrahybrid cross, probabilities are calculated by multiplying the chances of inheriting each allele independently.

Punnett Square

A Punnett square is a diagram used to predict the genotypes of offspring from a particular genetic cross. It helps visualize how alleles from each parent combine, showing all possible genetic outcomes. In a tetrahybrid cross, a Punnett square can be complex, but it systematically illustrates the independent assortment and combination of alleles for multiple genes.

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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

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c. Heterozygous for all three characters

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Textbook Question

What is the probability that each of the following pairs of parents will produce the indicated offspring? (Assume independent assortment of all gene pairs.)

a. AABBCC×aabbcc→AaBbCc

b. AABbCc×AaBbCc→AAbbCC

c. AaBbCc×AaBbCc→AaBbCc

d. aaBbCC×AABbcc→AaBbCc

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Textbook Question

In rabbits, black hair depends on a dominant allele, B, and brown hair on a recessive allele, b. Short hair is due to a dominant allele, S, and long hair to a recessive allele, s. If a true-breeding black short-haired male is mated with a brown long-haired female, describe their offspring. What will be the genotypes of the offspring? If two of these F1 rabbits are mated, what phenotypes would you expect among their offspring? In what proportions?

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In fruit flies, the genes for wing shape and body stripes are linked. In a fly whose genotype is WwSs, W is linked to S, and w is linked to s. Show how this fly can produce gametes containing four different combinations of alleles.

Which are parental-type gametes?

Which are recombinant gametes? How are the recombinants produced?

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