A pea plant heterozygous for plant height, pod shape, and...

Name: Problem 28, Chapter 2: Genetics: From Genes to Genomes
Uploaded: 2023-03-16T03:56:06-08:00
Duration: 5 min 5 s
Channel: Bryan Valdivia
Description: A pea plant heterozygous for plant height, pod shape, and flower color was selfed. The progeny consisted of 272 tall, inflated pods, purple flowers; 92 tall, inflated, white flowers; 88 tall, flat pods, purple; 93 dwarf, inflated, purple; 35 tall, flat, white; 31 dwarf, inflated, white; 29 dwarf, flat, purple; 11 dwarf, flat, white. Which alleles are dominant in this cross?

A pea plant heterozygous for plant height, pod shape, and flower color was selfed. The progeny consisted of 272 tall, inflated pods, purple flowers; 92 tall, inflated, white flowers; 88 tall, flat pods, purple; 93 dwarf, inflated, purple; 35 tall, flat, white; 31 dwarf, inflated, white; 29 dwarf, flat, purple; 11 dwarf, flat, white. Which alleles are dominant in this cross?

Key Concepts

Alleles and Genes

Alleles are the different forms of a gene that arise by mutation and are found at the same place on a chromosome. Understanding alleles is fundamental to genetics as they determine the variations seen in traits such as plant height, pod shape, and flower color.

Dominance Relationships

Dominance refers to the phenomenon where one allele masks the expression of another allele at the same locus in a heterozygote. In genetic crosses, the allele that is expressed in the phenotype when present in a heterozygous condition is known as the dominant allele.

Heterozygosity

A heterozygous organism has two different alleles at a specific gene locus. This condition is important in genetic crosses because the manifestation of dominant and recessive traits can be observed, helping to determine which alleles are dominant.

Self-Fertilization

Self-fertilization (selfing) is a process where an organism's gametes combine to produce offspring. This method of reproduction is particularly useful in genetic experiments to analyze segregation of alleles and observe phenotypic ratios that result from homozygosity and heterozygosity.

Mendelian Inheritance

Mendelian inheritance involves the principles of segregation and independent assortment, which explain how alleles separate during gamete formation and how different genes independently separate from one another during the formation of gametes. This forms the foundation for predicting the distribution of traits in progeny.

Multifactorial (Trihybrid) Cross Analysis

A trihybrid cross examines the inheritance of three distinct traits simultaneously. It involves analyzing phenotypic ratios among progeny to determine the dominant and recessive relationships among the alleles controlling each trait.

Transcript

00:01 Not to answer this question, let's talk about inheritance.

00:03 It says a p plant heterocygot for plant, a height, pot shape, and flower color was self.

00:10 Okay, so practically in this case, this plant was heterocygot for the three traits.

00:15 And it says, and it was self.

00:18 It says, the project only consisted of 272, 272 tall, inflated, and purple.

00:31 You also have 92 tall, inflated and white.

00:43 Then 88 for tall, flat pots and purple.

00:54 93 for dwarf, inflated and purple.

01:08 Then you have 35 for tall, flat, white, and you have 31 for dwarf then you have 11 for dwarf and i'm sorry 35 then 31 then 29 and then 11 for dwarf flat and white okay so this is just the important genotype space here now what is the total of off print that you have in this case you have to add these values here so you have to add 272 plus 88 plus 93 plus 35 plus 31 plus 31 plus 29 and plus 11 and this is equal to 651 now let's find the frequencies okay remember that when you have a tri -hybridged cross the phenotypical atio is 27 -99999 -9 3 3 and 1 okay where this is this one is for the aggressive a, which is in v, aggressive c.

02:34 So if we find the frequency that is analogous to this one here, we want to find which phenotype is possessive and which one is dominant.

02:47 So in this case, first, 272 divided by 651.

02:53 So you have 272 divided by 651.

02:57 This is equal to approximately 0 .42.

03:00 In this case, 92 is equal divided by 651, this is equal to approximately 0 .14.

03:10 And we can make the same for all of them, but the most importance are this and this one here.

03:15 So you have 11 divided by 651, and this is going to be equal to 0 .017 approximately.

03:26 Okay...

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