Question 18 A mating of two organisms produces a 1:2:1 ratio...

Question 18 A mating of two organisms produces a 1:2:1 ratio of phenotypes in the progeny. The parental genotypes, and the mode of inheritance are most likely: Selected answer will be automatically saved. For keyboard navigation, press up/down arrow keys to select an answer. a Aa x aa, A is dominant to a b Aa x Aa, incomplete dominance or codominance c AA x aa, incomplete dominance or codominance d Aa x Aa, X-linked, A is dominant to a e Aa x Aa, A is dominant to a

Transcript

00:02 Hi there.

00:03 In this question, we actually have three questions that are related to genetics.

00:07 So let's go ahead and get started.

00:09 In the first question, we are crossing two dihybrids.

00:15 So that would look something like this.

00:20 And in a dihybrid cross, we always get, assuming these are on different chromosomes and are not linked, we always get a nine to three to three to one phenotypic ratio.

00:41 Where 9 .16th of the offspring demonstrate both dominant traits.

00:50 3 .16th of the offspring represent one of the dominant traits and one of the recessive traits, while another three represent the recessive trait and the dominant trait, and then 1 .16th express both recessive traits.

01:06 All right.

01:07 So that would be our correct answer here, a 9 to 3 to 3 to 1 phenotypic ratio.

01:13 What they look like, not their genotypes.

01:16 So correct answer here is letter b, a 9 to 3 to 3 to 1 phenotypic ratio.

01:31 Let's get question two.

01:33 Abo blood type inheritance.

01:35 Let's talk about this for a minute.

01:37 It's actually the result of three alleles.

01:41 We have the one that codes for type a.

01:45 We have the allele that codes for type b, and both of these are dominant.

01:52 And then we have the recessive allele that does not code for any antigens, and is how we get o -type blood.

01:59 So from our different types, we can get type a, we can get type b, we can get type o, or we can also get type a -b.

02:09 And the way we get type a -b is by the individual having both of the dominant alleles.

02:20 And they are both expressed.

02:22 So the individual has both antigens to type a and antigens to type b...

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