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13. Mendelian Genetics

Monohybrid Crosses

13. Mendelian Genetics

Monohybrid Crosses

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1

concept

Monohybrid Crosses

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in this video, we're going to begin our lesson on mono hybrid crosses. And so a mono hybrid cross is really just a cross fertilization event between two mono hybrid organisms. And so recall from our previous lesson videos that mono hybrids are really just organisms that are hetero zegas for just one specific gene. And that's because the root mono is a route that means want. And so, if we take a look at our example image down below, we're showing you the pun, it square of a mono hybrid cross. And again, the motto Hybrid crosses across of two mono hybrid organism. And so at the top, What we have is a mono hybrid organism. Ah, parent, that is hetero Xigaze for one gene the color gene, if you will, where it has one dominant alil or one capital Y, and one lower case of Leo or one lower case wide and it's game. It's air across the top here, and parent number two is exactly the same. Another mono hybrid and it's game meats are across the side. And when you fill out the pundits square for this mano hybrid cross, which you end up getting our ah ho Mosaic is dominant possibility in the top left a hetero zegas possibility and the top right, Another hetero zegas possibility And the bottom left and a homo zegas recess if possibility and the bottom Right. And so again, this is a mono hybrid cross a cross fertilization between two mono hybrid organisms or two organisms. That airhead arose, I guess, for one gene. And so this here concludes our brief introduction to mono hybrid crosses. And in our next video, we'll get to talk a little bit more about them, so I'll see you all there.

2

concept

Genotypic vs. Phenotypic Ratio

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in this video, we're going to distinguish between the Gina Tip IQ and FINA tip IQ ratios. And so the Gina typical ratio, as its name implies, is going to be the ratio of different Gina types observed amongst the offspring. And so the characteristic Gina typical ratio from a mono hybrid cross is 1 to 2 toe one, where there is one home, a zegas dominant individual for every two hetero zegas individuals for every one Homo zegas recess of individual. Now the FINA typical ratio, as its name implies, is going to be the ratio of different fino types of observed amongst the offspring. And so the characteristic FINA typical ratio from a mono hybrid cross is three toe one, where there are three individuals that display the dominant phenotype and one individual that displays the recess of phenotype. And so, of course, previously we had done a mono hybrid cross here. And of course, the results of the mono hybrid cross are in this pawn it square, and what you can see is that once again, the Gino typical ratio shows the ratios of the Gina types. So there is again one Homo zegas, dominant individual to hetero Zegas individuals or possibilities. And one ho Mose, I guess recess it possibility, and so that 1 to 2 to one is coming straight from that one. Homo zegas dominant to hetero Zegas and one Hamas, I guess. Recessive. Now again, the Gina typical ratio is different than the FINA typical ratio. The FINA typical ratio looks at the FINA types, and the FINA types are the colors of the peas. And so amongst the offspring, there are three possibilities for the offspring to be yellow and one possibility for the offspring to be green. And so the ratio is three toe one. And those are the characteristic Gina Typical and FINA typical ratios of mono hybrid crosses, and that's important to keep in mind. So this here concludes our introduction to Gina Tipping and FINA typical ratios, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video

3

example

Monohybrid Crosses Example 1

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So here we have an example problem that says capital T is the dominant alil for plant height resulting in tall plants. Whereas lower case T is the recess of Alil for plant height resulting in short plants a mono hybrid cross of two hetero zegas parents or one capital T one lower case t results in offspring having a tall plant to short plant ratio of which one of these four potential answer options down below. And so to solve this example problem. Of course, we're going to need to perform the mono hybrid cross that they're asking us about. And so, of course, in order to perform a mono hybrid cross, we first need to create our pun it square, which is right here. And then we're going to be crossing to hetero zegas parents. And so that means that we're gonna have a capital T and a lower case D for each of the gambling's of the parents. And so when we fill this pundit square out, what we get is to capital teas here, a capital T and a lower case t here, another capital T in a lower case t here, and to lower case tease here. And so again, this problem is asking us about the tall plant toe short plant ratio. And, of course, tall plants and short plants are the FINA type, not the Gina type. So it's asking us about the Fino tip IQ ratio. And so here what we should write is fino tip pick, because these are the FINA types and we're looking for the FINA typical ratio. And, of course, it's tall plant to short plants. So we want the first number to be the tall plant and the second number to represent short plants. And so when we take a look at the individuals and uh, the individual possibilities in this Planet Square, notice that three of these possibilities would result in tall plants because they have at least one dominant alil, at least one Capital T. And so that means that there will be three tall plants, and this is going to be three tall plants for every one short plant. And so, really, this is the ratio that we are looking for. Three tall plants for everyone. Short plant a 3 to 1 ratio, and the answer option that matches three toe One is of course gonna be answer option B 321 So we can go ahead and indicate that be here is the correct answer. And all of these other ones are incorrect. And so that concludes this example problem. And we'll be able to get some more practice applying these as we move forward. So I'll see you all in our next video.

4

Problem

Problem

Which of the following is the genotypic ratio of offspring created from a cross of two heterozygous parents for a single gene?
a) 2:2
b) 3:1
c) 1:2:1
d) 1:3

A

2:2

B

3:1

C

1:2:1

D

1:3

5

Problem

Problem

In a single gene cross between a homozygous dominant parent and a homozygous recessive parent, which generation is always completely heterozygous?
a) F1 generation.
b) F2 generation.
c) F3 generation.
d) P generation.

A

F1 generation.

B

F2 generation.

C

F3 generation.

D

P generation.

6

Problem

Problem

Which of the following single gene crosses would always result in all offspring with the dominant phenotype?
a) tt x tt.
b) Tt x Tt.
c) TT x tt.
d) Tt x tt.

A

tt x tt.

B

Tt x Tt.

C

TT x tt.

D

Tt x tt.

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Additional resources for Monohybrid Crosses

PRACTICE PROBLEMS AND ACTIVITIES (3)