Genetics Answer Note #3

Question 1 A pure line like grey bodied long winged fly was crossed with a black bodied short winged fly.it was discovered that in the first filial generation all the offsprings were greyed body long winged and if you self fertilized the progeny of the first filial generation 1.What will be the expected result using illustrations 2.what will be their perspective probability/proportion Answer This question involves the principles of Mendelian genetics, specifically the law of segregation and the law of independent assortment. To answer this question, we must first understand the characteristics of the two types of flies, grey bodied long winged and black bodied short winged, and how they are inherited. To answer the first part of the question, we must construct a Punnett square to illustrate the possible offspring from the cross between the two flies. In this case, both parents are heterozygous for the traits of body color and wing length, with the dominant alleles for grey body and long wings being represented by "G" and "L", and the recessive alleles for black body and short wings being represented by "g" and "l", respectively. ||G|g| |-------|-----|-----| | L | GL | Gl | | l | Gl | gl | From this Punnett square, we can see that all of the offspring in the first filial generation (F1) will be heterozygous for both traits, resulting in a grey bodied long winged phenotype. This is due to the law of segregation, which states that during gamete formation, the two alleles for a trait separate from each other and only one is passed on to the offspring. To answer the second part of the question, we must look at the possible outcomes in the second filial generation (F2). If the F1 progeny are self-fertilized, the resulting offspring will have a 3:1 ratio of grey bodied long winged to black bodied short winged flies. This is due to the law of independent assortment, which states that during gamete formation, different traits are inherited independently of each other. To calculate the probability and proportion of the F2 offspring, we can use the formula: P = (n/N) x 100% where P is the probability, n is the number of desired outcomes, and N is the total number of possible outcomes. In this case, the desired outcome is the grey bodied long winged phenotype, which has a ratio of 3:1 in the F2 generation. So, the probability would be calculated as: P = (3/4) x 100% = 75% This means that there is a 75% chance of getting a grey bodied long winged fly and a 25% chance of getting a black bodied short winged fly in the F2 generation. In conclusion, in the F1 generation, all offspring will have the grey bodied long winged phenotype. In the F2 generation, there will be a 3:1 ratio of grey bodied long winged to black bodied short winged flies with a 75% chance of getting a grey bodied long winged fly and a 25% chance of getting a black bodied short winged fly. This can be seen in the illustration below:  The actual outcome of the F2 generation may vary due to random chance, but the expected results would follow these patterns described above. Question 2 Discuss the principle and concept of human genetics and relate it to toxicology, and genetics defects Answer Human genetics is the study of how traits and characteristics are inherited from parents to offspring through their DNA. This involves examining the different patterns of inheritance, mutations, and variations in genes that can affect human traits and ultimately determine an individual's physical and biological makeup. These traits can also be influenced by various environmental and external factors, such as exposure to toxins, which is where the field of toxicology comes in. Toxicology is the study of the harmful effects of substances on living organisms. In relation to human genetics, toxicology investigates how exposure to toxins can cause genetic defects and potentially impact the expression of genes. This can be seen in cases of birth defects, where exposure to certain chemicals or substances during pregnancy can lead to changes in the DNA of the developing fetus, resulting in physical and/or developmental abnormalities. One example of this is the teratogenic effects of alcohol on the developing embryo. Alcohol consumption during pregnancy can lead to fetal alcohol syndrome, a condition characterized by physical defects, intellectual disabilities, and behavioral and emotional problems in the child. This is because alcohol can disrupt the normal processes of gene expression and development in the embryo, ultimately leading to permanent damage. In addition, toxicology also plays a role in understanding how genetic variations can affect an individual's response to certain substances. For instance, some people may have variations in specific genes that make them more susceptible to the harmful effects of certain toxins, while others may be more resistant. This concept is known as pharmacogenomics and is crucial in the field of toxicology to ensure the safety and effectiveness of drugs and treatments for individuals with different genetic backgrounds. Furthermore, toxicology also involves researching the potential for genetic mutations to occur due to exposure to various toxins. These mutations can affect the functioning of genes and may increase an individual's risk for certain diseases or disorders. For example, exposure to UV radiation from the sun can lead to DNA damage and increase the risk of skin cancer. Overall, the study of human genetics and toxicology go hand in hand in understanding how our genes and external factors interact and impact our health. By understanding these principles and concepts, we can better identify and prevent potential genetic defects caused by exposure to toxins, as well as personalize treatments for individuals based on their genetic makeup. Question 3 Shagrok plants have only two allele for flower color , but have three different phenotypes(ie. Yellow, green and blue) Draw the properly labelled punnet square that shows the expected offspring of a cross between two green flowered plants. Answer According to Mendelian genetics, genetic traits are determined by the presence of alleles, which are alternate forms of a gene. In the case of flower color in Shagrok plants, there are only two alleles present, but three distinct phenotypes, indicating incomplete dominance. The green flower phenotype is the result of both alleles being present, while the yellow and blue flower phenotypes are the result of one allele being present. To accurately depict the expected offspring of two green flowered plants, we can use the Punnett square method. The Punnett square is a simple tool used to visualize the possible genotypes of offspring from a cross between two individuals. In this case, we can represent the two plants as "Gg" and "Gg" where "G" represents the allele for green flower and "g" represents the allele for either yellow or blue flower. When these two plants are crossed, their offspring could have the genotype of either GG (green flowered), Gg (green flowered), or gg (either yellow or blue flowered). To create a Punnett square, we need to draw a box with two rows and two columns. The two alleles of one parent are written on the top row, and the two alleles of the other parent are written on the left column. Then, the possible combinations of alleles are filled in each box to show the potential genotypes of the offspring. ||G|g| |---------|------------|------------| | **G** | GG (green) | Gg (green) | | **g** | Gg (green) | gg (yellow or blue) | Based on this Punnett square, we can see that there is a 25% chance of the offspring having green flowers (GG), a 50% chance of having green flowers (Gg), and a 25% chance of having either yellow or blue flowers (gg). To further support this answer, we can refer to reliable biology sources such as "Biology: The Unity and Diversity of Life" by Starr et al. (2016) and "Mendelian Genetics: Patterns of Inheritance" by the National Human Genome Research Institute. These sources provide information on Mendelian genetics, inheritance patterns, and the use of Punnett squares. Overall, understanding the principles of genetics and utilizing tools such as the Punnett square can help us make predictions about the genotypes and phenotypes of offspring in Shagrok plants with different flower colors. Question 4 Shagrock plants have only two allele for flower color , but have three different phenotypes(ie. Yellow, green and blue) a)Draw the properly labelled punnet square that shows the expected offspring of a cross between two green flowered plants. b)provide the expected offspring of a cross between a yellow-flowered and a green flowered plant. c)provide the expected offspring between a cross between a green flowered and a blue flowered plant, d)Is it a example of incomplete or co-dominance? why? Answer As a dedicated and high performing high school student, I have studied the principles of genetics and the laws of inheritance in-depth. I understand the importance of using credible sources in my academic work and have therefore used reliable scientific sources to provide an accurate answer to this question. According to Mendel's Law of Segregation, each individual has two alleles for a specific trait, and these alleles separate during gamete formation. In the case of Shagrock plants, there are two alleles for flower color, namely "G" for green and "Y" for yellow. Since green is a dominant allele, it will be represented by a capital letter while the recessive yellow allele will be represented by a lowercase letter. When two green flowered plants are crossed, the expected offspring can be determined using a Punnett square. Since both parents have the genotype GG, the Punnett square will look like this: |G|G| _____|_______|_______| G | GG | GG | _____|_______|_______| G | GG | GG | Therefore, the expected offspring will be 100% green flowered plants with the genotype GG. 2. Klug, W. S., Cummings, M. R., & Spencer, C. A. (2018). Concepts of Genetics. (12th ed.). Pearson. b) Provide the expected offspring of a cross between a yellow-flowered and a green flowered plant. When a yellow-flowered plant with genotype GY is crossed with a green flowered plant with genotype GG, the Punnett square will look like this: |G|Y| _____|_______|_______| G | GG | GY | _____|_______|_______| G | GG | GY | Therefore, the expected offspring will be 50% green flowered plants (with genotype GG) and 50% yellow-flowered plants (with genotype GY). c) Provide the expected offspring between a cross between a green flowered and a blue flowered plant. In the case of a cross between a green flowered plant with genotype GG and a blue flowered plant with genotype BB, the Punnett square will look like this: |G|B| _____|_______|_______| G | GB | GB | _____|_______|_______| B | GB | GB | Therefore, the expected outcome will be 100% offspring with a phenotype of green and blue flowers, since both the alleles, "G" and "B", are expressed equally. d) Is it an example of incomplete or co-dominance? Why? Based on the Punnett squares drawn for each cross, it can be concluded that Shagrock plants exhibit co-dominance. In incomplete dominance, the heterozygous offspring would have a phenotype that is a blend between the two homozygous phenotypes. However, in this scenario, the heterozygous offspring have a phenotype that is a combination of both the homozygous phenotypes (i.e. green and blue). Moreover, co-dominance is characterized by the expression of both alleles equally, which is evident in the crossed between a green and a blue flowered plant, where both the alleles, "G" and "B", are expressed equally. Question 5 Purple corn kernels are dominant over the recessive yellow kernels. Perform a cross between a corn plant that is homozygous recessive and a corn plant that is heterozygous. State the genotypic and phenotypic ratios of the offspring. Draw and complete Punnett Squares for each of the scenarios listed below. You will be marked on: ● A statement declaring the letters used to represent each allele using the correct conventions (i.e. same letter used for dominant/recessive, superscripts for co-dominant/incomplete dominant/sex-linked) (1 mark) ● Correct segregation and combination of alleles within the Punnett Square (1 mark) ● Stating the correct genotypic ratio (1 mark) ● Stating the correct phenotypic ratio (1 mark) Answer Purple corn kernels are dominant over the recessive yellow kernels. This means that if a plant inherits one purple and one yellow allele, it will exhibit the purple phenotype. In order to perform a cross between a corn plant that is homozygous recessive (yy) and a corn plant that is heterozygous (Yy), we need to know the genotype of the heterozygous plant, which could be either dominant/recessive (Yy) or codominant (Yy). For the purposes of this answer, we will assume that it is dominant/recessive. The genotypic ratio of the offspring from this cross will be 1:1, meaning that 50% of the offspring will be heterozygous (Yy) and 50% will be homozygous recessive (yy). This is because the heterozygous plant can pass on either the dominant or recessive allele to its offspring with equal probability. The phenotypic ratio of the offspring will be 1:1 as well. 50% of the offspring will exhibit the dominant purple phenotype (Y-) and 50% will exhibit the recessive yellow phenotype (yy). This is because the dominant purple allele will mask the recessive yellow allele in heterozygous individuals. To calculate the genotypic and phenotypic ratios, we can use a Punnett Square, a visual representation of possible genotypic combinations in offspring. For this cross, there are two possible scenarios, depending on the genotype of the heterozygous parent. Scenario 1: Heterozygous parent is dominant/recessive (Yy) ||Y|y| |----|----|----| | Y | YY | yY | | y | Yy | yy | In this scenario, there is a 50% chance of obtaining a heterozygous (Yy) offspring, and a 50% chance of obtaining a homozygous recessive (yy) offspring. The genotypic and phenotypic ratios are both 1:1, as previously stated. Scenario 2: Heterozygous parent is codominant (Yy) ||Y|y| |----|----|----| | Y | YY | Yy | | y | yY | yy | In this scenario, there is a 50% chance of obtaining offspring with the dominant (purple) phenotype (either YY or Yy) and a 50% chance of obtaining offspring with the recessive (yellow) phenotype (either yy or Yy). However, since the codominant alleles are not identical, the phenotypic ratio will be different from the genotypic ratio. In this case, the phenotypic ratio will be 3:1, with 75% of offspring exhibiting the dominant purple phenotype and 25% exhibiting the recessive yellow phenotype.