What percentage of offspring becomes heterozygous dominant and homozygous dominant?
Inheritance patternsSickle-cell disease is an inherited condition that causes pain and damage to organs and muscles. Instead of having flattened, round red blood cells, people with the disease have stiff, sickle-shaped cells. The long, pointy blood cells get caught in capillaries, where they block blood flow. Muscle and organ cells don’t get enough oxygen and nutrients, and they begin to die. Show The disease has a recessive pattern of inheritance: only individuals with two copies of the sickle-cell allele have the disease. People with just one copy are healthy. In addition to causing disease, the sickle-cell allele makes people who carry it resistant to malaria, a serious illness carried by mosquitos. Malaria resistance has a dominant inheritance pattern: just one copy of the sickle cell allele is enough to protect against infection. This is the very same allele that, in a recessive inheritance pattern, causes sickle-cell disease! Now let’s look again at the shape of the blood cells. People with two copies of the sickle-cell allele have many sickled red blood cells. People with two copies of the “normal” allele have disc-shaped red blood cells. People with one sickle-cell allele and one normal allele have a small number of sickled cells, and their cells sickle more easily under certain conditions. So we could say that red blood cell shape has a co-dominant inheritance pattern. That is, individuals with one copy of each allele have an in-between phenotype. So is the sickle cell allele dominant, recessive, or co-dominant? It depends on how you look at it. Protein functionIf we look at the proteins the two alleles code for, the picture becomes a little more clear. The affected protein is hemoglobin, the oxygen-carrying molecule that fills red blood cells. The sickle-cell allele codes for a slightly modified version of the hemoglobin protein. The modified hemoglobin protein still carries oxygen, but under low-oxygen conditions the proteins stick together. When a person has two sickle cell alleles, all of their hemoglobin is the sticky form, and the proteins form very long, stiff fibers that distort red blood cells. When someone has one sickle-cell allele and one normal allele, only some of the hemoglobin is sticky. Non-sticky hemoglobin is made from the normal allele, and sticky hemoglobin is made from the sickle-cell allele (every cell has a copy of both alleles). The sticking-together effect is diluted, and in most cells, the proteins don’t form fibers. The protist that causes malaria grows and reproduces in red blood cells. Just exactly how the sickle-cell allele leads to malaria resistance is complex and not completely understood. However, it appears that the parasite reproduces more slowly in blood cells that have some modified hemoglobin. And infected cells, because they easily become misshapen, are more quickly removed from circulation and destroyed. To see more examples of how variations in genes influence traits, visit The Outcome of Mutation. Know how to use a Punnett Square to predict inheritance for a monohybrid cross. Vocab:
A is a grid formed by 4 squares to form a larger square. Scientists use this as a way to predict a trait or genotype that comes from two different people or organisms. Before talking about how to use a Punnett square, the next important topic is alleles and the different types of alleles. Each human cell has 23 pairs of chromosomes and each consists of hundreds of thousands of different genes. are used to pass traits from parent to offspring. An is a pair of genes on a chromosome that determine a hereditary trait. With alleles, there are two main types of alleles that are essential. A is one that will be more overpowering than another allele and a is an allele that can be overpowered by a dominant allele. Dominant alleles are represented by capital letters and recessive alleles are represented by lowercase letters. For example, blue eyes are a recessive trait and brown eyes are a dominant trait. Therefore, if a female has blue eyes they can be represented by “bb” and if a male has brown eyes this can be represented as “BB” or “Bb”. The reason why brown eyes can be represented as “Bb” is that the capital “B” is dominant over the lowercase “b”. For the example, assume that the male has the “Bb”. A is a cross between two organisms with different variations of one trait. A Punnet square is a monohybrid cross and is going to be used to compare the traits of the example given earlier. For traits that have either two capital letters or two lowercase letters are known as a trait and for traits that have alternating letters are known as traits. In heterozygous alleles, the capital letter will always come first. To begin, write the two letters of the blue-eyed female on top and the two letters of the brown brown-eyed male on the side. Next, we’re just going to match the letters down each square and look at the possible outcomes if they had offspring.  As you can see there is a 50% chance that the homozygous recessive trait of blue eyes will be shown on their next kid, a 50% chance that the heterozygous dominant trait of brown eyes is given on the next offspring, and a 0% chance of a homozygous dominant trait given to the offspring. In some cases, there are two dominant alleles that are present and causes no blending. For example, if a flower had the dominant allele of Red and the dominant allele of White the flower petals will show spots of red and white. This is called co-dominance. In the case of incomplete dominance, the flower would blend the two colors to form a pink petals. Another example where we can use a punnett square is with blood types. Let’s say a female has a blood type of AB and a male has the blood type of O. Both A and B are considered co-dominant meaning that both the A and the B are present on the females blood cells. The O blood type is a recessive allele and for the punnett square it will be written as “oo”. Here is a list of genotypes for each blood type.
Let’s try to draw a punnett square with the AB female and the O male. First we always begin by drawing the punnett square and writing the genotypes on the top and side. For our example, I will write the female on top and the male on the side. Next, we will match the letters for each box on the punnett square. As you can see from the punnett square, the offspring of these two people would have a 50% chance of the blood type A and a 50% chance of the blood type B. In this case, both of these blood types would be heterozygous because the genotypes consist of the o allele. Figure 1 Image Credit: “Figure 1” by Libertas Academica is licensed under CC BY 2.0 What percentage of the offspring will be heterozygous dominant?The Punnett square below makes it clear that at each birth, there will be a 25% chance of you having a normal homozygous (AA) child, a 50% chance of a healthy heterozygous (Aa) carrier child like you and your mate, and a 25% chance of a homozygous recessive (aa) child who probably will eventually die from this ...
What percentage of the offspring are homozygous dominant?Homozygous dominant: 25% or 0.25. Heterozygous: 50% or 0.50. 11. If two heterozygotes are crossed, the probability that an offspring will show the dominant trait is 75% or 0.75.
What is the chance in percentage (%) that the child would have dimples?Because dimples is an autosomal dominant trait, heterozygosity will express dimples, leading to a 50% chance that the child will have dimples.
What is the percentage of two heterozygous offspring?If we cross two heterozygous individuals (Aa), then the percentage of offsprings with recessive phenotype will be: Aa x Aa = AA Aa Aa aa, so recessive phenotypes would be 1/4 = 25%. Thus, the correct answer is option D.
|
