Mess up my notes please part 1 codominance: an inheritance pattern in which the alleles are neither recessive nor dominant, and both alleles are expressed in the offspring

incomplete dominance: an inheritance pattern in which neither allele is dominant, and the offspring demonstrate an intermediate form of the alleles from the parents

multiple alleles: three or more different forms of a gene for a single trait

polygenic: an inheritance pattern in which a trait is controlled by many genes

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Section 1

00:00:00TEACHER: Hi there. You notice this beautiful horse staring at you wondering, hey, life is so beautiful, right? Well, is there something else that you notice? Can see the difference in the coloring of this horse's head and its neck? Why is there a splattering of white fur on the horse's neck?

00:00:19We will answer these questions as we answer the lesson question, what are some different ways traits are inherited?

• Section 2

00:00:00TEACHER: To address your lesson question, we will explore the different ways traits are inherited. To do this, we will differentiate between codominance and incomplete dominance. And finally, we will examine multiple alleles and polygenic inheritance, and give examples of each. Next, let's look at some vocabulary words

00:00:22that you'll need to know for this lesson. The words are codominance, incomplete dominance, multiple alleles, and finally, polygenic. Don't forget to type these into your notes and check your glossary for the correct definitions. Now, let's review how a trait is affected by a single gene with two alleles, one dominates and one recessive. Recall, that a dominant allele mask

00:00:55the appearance of the recessive allele. It dominates or rules over the recessive allele. For a seed color, the allele for yellow seeds is obviously dominant, and it's represented by a big Y. A recessive allele is masked or hidden when the dominant allele is present. So green is the recessive allele for seed color, and it is represented by the small y as recessive.

00:01:32So now when you have two parent plants that are crossed, so as you can see, here you got the yellow parent, and the green parent. The alleles combine to form different genotypes, as you can see here. In this example, a plant with yellow seeds, so here's the yellow seeds, and then you got the green seeds, well, the genotypes will determine what those seeds will look like.

00:02:04So this appearance is called the phenotype. The offspring of this cross are all plants with yellow seeds, because the yellow seed allele dominates or hides the effect of the green seed allele as you can see in all the Punnett square.

Section 1

00:00:00TEACHER: In traits affected by a single gene with dominant and recessive alleles, dominant alleles hide the recessive alleles. But it is this always the case? Well, if you look at these two horses here you see the red one and then you see the white horse. They are the parents of the horse

00:00:19you saw earlier with red hair on its face and white hair mixed into the red on its neck. Well, why does the offspring not have all red hair or all white hair? Next, we can explain the horse's color by looking at some special inheritance patterns, incomplete dominance, and co-dominance.

Section 2

00:00:00TEACHER: Let's examine incomplete dominance by looking closer at the horse example. Incomplete dominance is an inheritance pattern in which neither allele is dominant, and the offspring demonstrates an intermediate form of the alleles from the parents. Now, intermediate here means that the color

00:00:22of the hair of the offspring is a blending of the two colors of the hair of the parents. If you look at those pictures here, notice that the cross between a chestnut horse here on the left, galloping, and a cremello horse here in the middle, the beautiful white horse, results in a palomino horse. The color of the palomino horse is somewhere

00:00:45between the dark chestnut and the milky-white cremello horse. It is a blend of the two hair colors. So, I will write the word blending. Therefore, when you think of incomplete dominance, well, think blending. Now, let's use a Punnett square to explore incomplete dominance further.

00:01:10This flower that you see here, it's called a snapdragon. Suppose a red snapdragon is crossed with a white snapdragon. We'll use a big R for the allele that produces red snapdragons and a small r for the allele that produces white snapdragons. So, a red snapdragon then would have the genotype big R, big R here, as you can see on the top of the Punnett square.