How are the predicted ratios different in linked genes?

This phenomenon is called genetic linkage. When genes are linked, genetic crosses involving those genes will lead to ratios of gametes (egg and sperm) and offspring types that are not what we'd predict from Mendel's law of independent assortment. Let's take a closer look at why this is the case depends upon the gene pair under consideration. Linked genes have a recombination frequency of less than 50%. The example we use above indicates tight linkage (the genes are close together), whereas other gene pairs give different percentages. A RF of 1% indicates tight linkage, whereas a RF closer to 50% would indicate that the genes lie.

Genetic linkage & mapping (article) Khan Academ

Key Difference - Linked vs Unlinked Genes Genes are the specific DNA sequences in chromosomes.There are 46 chromosomes in the human genome. Among them, 22 homologous pairs are called autosomes and one pair is known as sex chromosome.Thousands of genes are located on each chromosome Wild type (gray normal) Black vestigial Gray Black normal vestigial bg Sperm bb vg vg bb vgvg b*b vg yg bb vt vg of testcross offspring i and par 1 0 Predicted ratios if genes are located on different chromosomes: Sifcenes are located on the same chromosome 1 and parental alleles are always inherited together Data from Morgan's experiment: 0. Recall the phenotypic inheritance pattern for Mendel's dihybrid cross, which considered two non-interacting genes—9:3:3:1. Similarly, we would expect interacting gene pairs to also exhibit ratios expressed as 16 parts. Note that we are assuming the interacting genes are not linked; they are still assorting independently into gametes

Difference Between Linked and Unlinked Genes Compare the

Other variations on Mendel's rules involve interactions between pairs (or, potentially, larger numbers) of genes. Many characteristics are controlled by more than one gene, and when two genes affect the same process, they can interact with each other in a variety of different ways. For example: Complementary genes X-Linked Genes: the white gene in Drosophila melanogaster. A well-studied sex-linked gene is the white gene on the X chromosome of Drosophila melanogaster.Normally flies have red eyes but flies with a mutant allele of this gene called white-(w-) have white eyes because the red pigments are absent.Because this mutation is recessive to the wild type w + allele females that are heterozygous have.

In this figure, how do the results of a testcross Chegg

(homozygous recessive) fruit flies. The F dihybrid females were then used in a test cross. If the genes are always linked and no crossing over occurs, what would be the predicted ratio in the F generation? A. 9 : 3 : 3 : 1 B. 1 : 1 : 1 : 1 C. 3 : 1 D. 1 : Construct Punnett grids for sex linked crosses to predict the offspring genotype and phenotype ratios. Understanding: The pattern of inheritance is different with sex-linked genes due to to their location on sex chromosomes. 1. Create a key to the alleles using correct notation (XY with superscript alleles on the X ÐDeviations from 1:1:1:1 ratios can represent chance events OR linkage ÐRatios alone will never allow you to determine if observed data are significantly different from predicted values. ÐThe larger your sample, the closer your observed values are Linked genes lead to a larger number of parental class tha Define the chromosome theory of inheritance as genes are located on chromosomes Use phenotypic ratios to determine if genes are sex-linked; Predict possible offspring types and phenotypic ratios in the case of sex linkage; Apply pedigree analysis to distinguish between dominant, recessive, and sex-linked trait

•Linkage is different from sex linkage •Linked genes tend to be inherited together because they are located near each other on the same chromosome. Results from genes being closely linked on the same chromosome •Linked genes in genetic experiments deviate from the results expected from Mendel's law of independent assortment The gene-by-gene inheritance pattern can also be called epistasis. The take home-message on gene-by-gene interactions is that this phenomenon alters the expected phenotypic ratios of a Mendelian dihybrid cross (9:3:3:1) to a different pattern. This video gives an overview of a gene-by-gene interaction that controls coat color in mice 2. Single Gene Inheritance 4. Sex-linked Inheritance 1. Genetic Concepts 1. Basic Genetic Concepts The Nature of Inheritance (Genetics) Genetics is the study of how genes are inherited AND how they influence the physical characteristics of each individual. 1) the distribution of genes into haploid gametes 2) how the interaction of gene pairs in. A monohybrid cross involves the crossing of individuals and the examination of a single character (flower color or seed color or pod shape, etc.) in their offspring. The Punnett square is a useful tool for predicting the genotypes and phenotypes of offspring in a genetic cross involving Mendelian traits. Constructing a Punnett square is quite easy, as demonstrated by the Web sites below

MAKING A GENE MAP The recombination frequency is constant for any pair of linked loci and represents the genetic distance between them. Each 1 m.u. is the distance that will generate 1% recombination. It is possible to develop a gene map, showing the order of the loci and the distanc X-Linked Inheritance. Chromosome * s that both males and females possess in matched sets are called autosome * s. The X and Y-chromosomes that determine the sex of an individual in mammals follow a different pattern and are called allosome * s. The genes present on the X and Y-chromosomes are called sex-linked genes Sex-linked trait: Genes located on the sex-chromosomes called sex-linked genes. Usually found on the X chromosome. X-linked alleles are always expressed in males because males have only one X chromosome. Multiple Alleles: There are more than two-choices for the allele. Example is human blood group genes

The primary statistic that is used in genetics is the Chi-square test for goodness of fit.On order to carry out the c 2 test one calculates an expected distribution of phenotypes based on a model or null hypothesis.In genetics, the model is based on Mendelian laws. For example, in the F 2 of a cross between a homozygous gray, bicorn dust rhino and a homozygous white, unicorn dust rhino, with. Phenotypic ratio is a term that describes probability of finding the patterns and frequency of genetic trait outcomes in the offspring of organisms. A phenotype is an observable or measurable characteristic and is the result of expressed genes. For example, by noting the traits in a long-haired, pink-nosed and a short-haired, black-nosed guinea. We derive the conditional probabilities for estimating the sex ratio in families ascertained through affected males for the study of X-linked recessive diseases. These conditional probabilities correct for the fact that the probability that a family will be ascertained increases with the number of m Genes on the same chromosome should be linked. In other words, genes on the same chromosome should be dependently assorted (originally rejected by Mendel's dihybrid crosses), whereas genes on separate chromosomes should be independently assorted (as predicted by Mendel). Linked genes violate independent assortment

When RF values are close to 50 percent, the χ 2 test can be used as a critical test for linkage.Assume that we have crossed pure-breeding parents of genotypes A/A · B/B and a/a · b/b, and obtained a dihybrid A/a · B/b, which we have testcrossed to a/a · b/b.A total of 500 progeny are classified as follows (written as gametes from the dihybrid) When two genes are close together on the same chromosome, they do not assort independently and are said to be linked. Whereas genes located on different chromosomes assort independently and have a recombination frequency of 50%, linked genes have a recombination frequency that is less than 50% Mendel was able to explain this ratio if the factors (genes) that control the two characteristics are inherited independently; in other words one gene does not affect the other. This is summarised in Mendel's second law (or the law of independent assortment), what states that alleles of different genes are inherited independently Fill out the Punnett Square to determine the genotype and phenotype for the offspring of a dihybrid cross when the traits are tightly linked. Note that 3/4 of the offspring are predicted to have both dominant traits, and 1/4 are predicted to have both recessive traits. With unlinked traits, only 1/16 are predicted to have both recessive traits The 3:1 ratio predicted for Mendel's monohybrid cross and the 9:3:3:1 phenotypic ratio predicted for a dihybrid cross are hypothetical expected ratios. one copy of each chromosome. This law applies to, and is explained by, the separation of unlinked genes because these genes are located on different chromosomes. As a result, during meiosis.

12.3: Laws of Inheritance - Biology LibreText

experiment, including the expected ratios (in the final generation) of infertile to fertile males for two competing models: 1) two mutations in the same gene and 2) mutations in two different genes on different chromosomes To determine how close together on a gene two alleles are using reproductive data alone - that is, to solve gene mapping problems - scientists look at the difference between the predicted phenotypic ratios in a population of offspring and the actual ratios Functionally linked genes in bacterial and archaeal genomes are often organized into operons. However, the composition and architecture of operons are highly variable and frequently differ even. Use a Punnett square and state the predicted genotype ratio and phenotype ratio of. The cross-over percentages between 4 linked genes in Drosophila melanogaster are: A and B is 40%, between B and C is 20%, between C and D is 10%, between A and C is What might account for this difference? (2 marks) 16. In mice, coat colour is determined. Inheritance of X-Linked Recessive Genes. The X-linked recessive genes show criss-cross pattern of inheritance. In criss-cross inheritance, an X-linked recessive gene is transmitted from P1 male parent (father) to F2 male progeny (grandsons) through its F1 heterozygous females (daughters), which are called carriers) and different F1 and F2 results (ratios) in the reciprocal crosses

The height of a child cannot be predicted using the Punnett square method - there are too many variables and genes affecting this trait. Traits are inherited through genes, the memory banks of the cell. Every gene has two versions, called alleles. We use capital letters for dominant alleles (A), and lowercase for recessive alleles (a). Dominant. and be able to predict the outcome of crosses involving sex-linked traits. 36 Objective 23 Other traits, besides sex, are controlled by genes on the sex chromosomes. These are called sex-linked traits. Traits controlled by the X are X-linked. Traits controlled by the Y are Y-linked. Since most sex-linked traits ar

Assume the genes are located on different chromosomes and the gene for flower color is on chromosome 1. (b) Predict the possible phenotypes and their ratios in the offspring of a testcross between an Fl individual and a ggdd individual. (c) If the two genes were genetically linked, describe how the proportions of phenotypes of the resultin That some X-linked genes should escape inactivation was first predicted for pseudoautosomal genes on the X and Y chromosomes that show equivalent dosage, with two active copies in both males and. Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.Two genetic markers that are physically near to each other are unlikely to be separated onto different chromatids during chromosomal crossover, and are therefore said to be more linked than markers that are far apart If genes are unlinked and therefore assort independently, the phenotypic ratio of offspring from an F 1 testcross is expected to be 1:1:1:1. If the two genes are linked, however, the observed phenotypic ratio of the offspring will not match the expected ratio

Dihybrid crosses use Punnett squares to distribute parental alleles from two genes into gametes (eggs and sperm or pollen and ovum) as would be predicted by meiosis. In garden peas, the gene for Purple flowers (P) is dominant to the allele for white flowers (p). The gene for axial flowers (A) is dominant to the allele for terminal flowers (a) The phenotype ratio predicted for dihybrid cross is 9:3:3:1. The Principle of Independent Assortment: Segregation of the members of any pair of alleles is independent of the segregation of other pairs in the formation of reproductive cells. Or. Members of one gene pair segregate independently from other gene pairs during gamete formatio Black eyes are dominant to orange eyes, and green skin is dominant to white skin. Sam, a MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. Carole is MendAlien with orange eyes and white skin. If Sam and Carole were to mate, the predicted ratio of their offspring would be 3.4 X-Linked Dominant Inheritance. As in autosomal dominant inheritance, only one copy of a disease allele on the X chromosome is required for an individual to be susceptible to an X-linked dominant disease.. Both males and females can be affected, although males may be more severely affected because they only carry one copy of genes found on the X chromosome A Punnett Square (so named after it's creator, Reginald C. Punnett) is a chart drawn to determine the probable results of a genetic cross. It will show you every possible combination of offspring that result from a cross. Therefore, a Punnett square is a prediction that estimates what we should see in nature

Video: Variations on Mendel's laws (overview) (article) Khan

3.5: Sex-Linkage- An Exception to Mendel's First Law ..

IB Biology Chap 10 questions Flashcards Quizle

Reconstructing genome-wide regulatory network of E

orange. The gene is located on the X chromosome, making it a sex-linked trait. Refer to card #31. Explain why there could never be any male calico cats. 32 There can never be a calico male cat because two alleles are required. Since the alleles are X-linked, two X chromosomes are needed. Hemophilia is an sex linked disorder in which bloo (d) If the wing pattern and leg feather genes were linked, the phenotype ratios would be 3:1 with: • 12 bar wings and leg feathers • 4 barless wings and no leg feathers. Discuss why the phenotype ratio from the F2 cross in part (c), is different to the 3:1 ratio of the linked genes generation was 3.23:1, which shows no statistical difference to our expected ratio of 3:1, indicating that the gene for wing presence is on an autosome. We also accepted the X-linked inheritance hypothesis because the ratio observed in the F 2 generation was1.01:1, which showed no statistical difference to our expected ratio of 1:1, indicating. B. Allele pairs for different genes separate independently during gamete formation. C. Unlinked alleles are assorted with a 9 : 3 : 3 : 1 ratio in a dihybrid cross. D. Allele pairs for the same gene are assorted independently during gamete formation. Markscheme

3.4: Inheritance Flashcards Quizle

AP Biology FlyLab Assignments . To begin an experiment, you must first design the phenotypes for the flies that will be mated. In addition to wild-type flies, 29 different mutations of the common fruit fly, Drosophila melanogaster, are included in FlyLab.The 29 mutations are actual known mutations in Drosophila.These mutations create phenotypic changes in bristle shape, body color, antennae. Linkage and gene mapping studies have progressed to being a critical tool in cloning genes and providing more description of their roles in the organism. These approaches include: • Using map locations to distinguish different genes with similar sequences, mutant phenotypes, or functions

Chromosome theory of inheritance Biological Principle

  1. ology for Exa
  2. For several genes, their TSGE was highly predictable (PCC ≥ 0.7) in multiple tissues. We investigated whether TSGE prediction model is tissue specific by assessing whether the same or different WBT gene features were used in different tissues to predict the gene's expression
  3. 3.4.8 The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes. 36. 3.4.8 The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes. 37. 3.4.12 Red-green color-blindness and hemophilia as examples of sex-linked inheritance 38
  4. The closer two genes are located on a chromosome, the greater the chance that the genes will be inherited together 3. The pattern of inheritance (monohybrid, dihybrid, sex-linked, and genes linked on the same homologous chromosome) can be predicted from data that gives the parent genotype/phenotype and/or the offspring phenotypes/genotypes
  5. SVM outputs a posterior probability for each predicted gene to reflect its reliability. With the posterior probability >0.5, 2475 genes were predicted as hypertension genes (Table S3). The top 20 predicted genes are listed in Table 4. When set the posterior probability to 0.8 and 0.9, 695 and 177 genes were predicted as hypertension genes.
  6. A linkage group is a group of genes whose loci are on the same chromosome and hence don't independently assort. Linked genes will tend to be inherited together and hence don't follow normal Mendelian inheritance for a dihybrid cross. Instead the phenotypic ratio will be more closely aligned to a monohybrid cross as the two genes are.

Patterns of inheritance Biological Principle

Bateson reported a different phenotypic ratio in sweet pea than could be explained by simple Mendelian inheritance. This ratio is 9:7 instead of the 9:3:3:1 one would expect of a dihybrid cross between heterozygotes. Of the two genes (C and P), when either is homozygous recessive (cc or pp) that gene is epistatic to (or hides) the other 1. Introduction: Linked genes are on the same chromosome. In the last tutorial, we looked at dihybrid crosses and independent assortment.We saw how you can use the FOIL algorithm (First, Outside, Inside, Last) to determine how a dihybrid parent with genotype like BbEe can produce, through independent assortment, four possible combinations of alleles in its gametes: BE, Be, bE, and be The genes located on the inactivated X ho-molog are predicted to be influenced by the same underlying re-pression mechanism. To test the uniformity of cis-acting gene repression, 32 genetically identical F1 female mice were analyzed for differential expression of homologous alleles at three X-linked genes— Otc, Atp7a (4Mottled), and Hprt Change to 1b. Do not calculate a c2 value. Just calculate the expected phenotypic ratios if the genes for brown-ness and disease-resistance are actually the same gene (or completely linked). Then, say whether complete linkage is possible given the observed data. Don't forget about my office hours (MWF 9-11) and the Thursday night Q&A sessions Galtonian Patterns of Inheritance. Mendel's studies focused on dichotomous traits in plants, such as the color of peas (green or yellow) and plant size (tall or dwarf), but many traits have continuous distributions, such as height, weight, and intelligence. Galton was a contemporary of Mendel's who studied the inheritance of continuous.

Predicting Phenotypes and Genotypes - Biology 110 Master

There are three possible alleles for this gene. IA, IB, and i. IA and IB are co-dominant. There are four possible phenotypes: A, B, AB, and O. Genotypic ratios: The ratio of different genotype in the offspring from a genetic cross. E.g 1:2:1 Phenotypic ratios: The ratio of different phenotypes in the offspring from a genetic cross. E.g 3: You have upwards of 2,000 different genes on Chromosome 1 alone, for example. That's a lot of genes! And because they're all on the same chromosome, they're inherited pretty much as a package deal. Many experiments have been done on gene linkage in fruit flies (hopefully the scientists didn't have too much rotten fruit in their offices!) Predict the offspring from this cross. a. What is the genotype of the parents? _Rr x rr____ b. Set up a Punnett square with possible gametes. c. Fill in the Punnett square for the resultant offspring. d. What is the predicted genotypic ratio for the offspring? ___1 Rr : 1 rr__ e

X-Linked Inheritance Science Prime

Punnett Squares - SC TRITON Scienc

  1. then asked to predict the phenotype ratios from a testcross with the F. 1. individual and to describe how the proportions of phenotypes would likely differ if the two genes in question were genetically linked. Sample: 7A . Score: 3 . The response earned 1 point in part (a) for constructing a diagram that included two labelled unduplicate
  2. In particular, if genome structure and selection parameters in Rumex are comparable to humans, we would predict the most gene-rich regions of recombining chromosomes to experience an ∼60% reduction in diversity (McVicker et al. 2009), implying that our ratio of Y-linked to autosomal diversity in unconstrained regions may be as low as 0.011.
  3. The genotypic ratio for this cross is written 1:2:1. In animals and plants, each gene has 2 alleles or variations, one from each parent. When male and female gametes come together (cross) all the phenotype variations for the offspring are predicted using the Punnett square grid. The pairs of alleles for male and female are plotted individually.
  4. ant alleles But, also found odd ratios Example, yellow body and white eye
  5. g the interacting genes are not linked but still assorting independently into gametes

General Chi- Square = S - Rutgers Universit

  1. ance, co-do
  2. Answer: Whenever you know that you have a totally heterozygous individual, and you get this type of lopsided percentage during the testcross, you have discovered that the A and B genes are linked (i.e. they occur on the same chromosome). Thus, they are NOT assorting independently as Mendel states in his second law. If they were, you would get the 1:1:1:1 ratios
  3. ant. (d) The gene for deranged is X-linked and recessive. (e) Deranged is deter
  4. ant.
  5. Because genes are like beads on the string of DNA, some genes are near to each other, while others are far apart, even on different chromosomes from each other. Those genes on the same chromosome can be so close together that they are physically linked, violating Mendel's law of independent assortment
  6. Furthermore, the average expression ratio of the Y/X-linked genes was not significantly different from that (0.98) of the allelic pairs for the PAR genes or from that (0.98) of the sex-chromosomal allelic pairs . Thus, there was no obvious evidence for the deterioration of Y-linked genes

Phenotypic Ratio - The Definitive Guide Biology Dictionar

DIHYBRID CROSSES (UNLINKED GENES)Command term = CALCULATE and PREDICT. Linked genes: Genes that occur on the . same chromosome. Likely to be inherited together. Unlinked Genes: Genes that occur on . separate chromosomes. Follow . Mendel's Law of Independent Assortment - inheritance of alleles is . random. 10.2. 1. Calculate and predict the genotypic and phenotypic ratios of offspring of dihybrid crosses involving unlinked autosomal genes. 2. Distinguish between: autosome = non-sex chromosomes; in humans, chromosomes 1 through 22. sex chromosomes = those chromosomes which help determine the sex of an individual; in humans, the X and Y chromosomes. 3 6. In cats, there is a coat color gene located on the X chromosome. This gene is a different gene from the black/Siamese gene discussed in earlier problems. This gene has two alleles—orange and black. A heterozygous cat has tortoiseshell color (a splotchy mixture of orange and black). Predict the genotypi Recall the phenotypic inheritance pattern for Mendel's dihybrid cross, which considered two non-interacting genes—9:3:3:1. Similarly, we would expect interacting gene pairs to also exhibit ratios expressed as 16 parts. Note that we are assuming the interacting genes are not linked; they are still assorting independently into gametes

The equal segregation of alleles is the reason we can apply the Punnett square to accurately predict the offspring of parents with known genotypes. The physical basis of Mendel's law of segregation is the first division of meiosis, in which the homologous chromosomes with their different versions of each gene are segregated into daughter nuclei Genes located close together on the same chromosome are said to be linked genes. When genes are located in close proximity on the same chromosome, their alleles tend to be inherited together unless recombination occurs. This results in offspring ratios that violate Mendel's law of independent assortment Genetics - study of how traits are passed from parent to offspring. Traits are determined by the genes on the chromosomes. A gene is a segment of DNA that determines a trait. Chromosomes come in homologous pairs, thus genes come in pairs. Homologous pairs - matching genes - one from female parent and one from male parent quantitative analysis, where observed phenotypic ratios statistically differ from the predicted ratios - a. Genes that are adjacent and close to one another on the same chromosome may appear to be genetically linked; the probability that genetically linked genes will segregate as a unit can be used to calculate the map distance between them Given the principles revealed in a monohybrid cross, Mendel hypothesized that the result of two characters segregating simultaneously (a dihybrid cross) would be the product of their independent occurrence. Consider two characters, seed color and seed shape. As previously shown, Y dominates y to determine seed color, and R factor for round dominates the r factor for wrinkled to determine.

Estimating sex ratio biases in X-linked disorders: is

For genes to be considered essential for optimal growth, we required the corresponding ratios to be below 0.2 and to be reproducible in both M. tuberculosis and M. bovis BCG libraries (each library was analysed twice, and mutants were considered to be reproducibly attenuated if the average of the resulting ratios was significantly different. 10.2.S2 Identification of recombinants in crosses involving to linked genes 10.2.S3 Use of a chi-squared test on data from dihybrid crosses Read the dihybrid question shown below and then carry out the steps necessary in a chi-squared test (see 10.2.U5 to review the steps) The original parents may have had different genotypes, such as PpSS or PPSs. These genotypes when crossed together will not produce a 9:3:3:1 ratio typical of a true dihybrid cross. Another reason for an incorrect hypothesis might be due to linkage (autosomal linkage), where more than one gene is linked to the same chromosome Autism spectrum disorder (ASD) is phenotypically and genetically heterogeneous, and the relevance of de novo missense variants to neurodevelopmental outcomes remains unclear. A new study by Koire et al. suggests genes and pathways that could be involved in ASD. These authors assessed bias toward a predicted fitness impact among rare de novo missense variants in functionally related genes

Beyond Mendel — The Biology Prime

  1. 01 May 2020. Rare but powerful gene variants help scientists understand how disease develops, but they are hard to find. By pooling data on people with different early onset dementias to get cohorts of a workable size, researchers pulled out an association between mutations in the DNA demethylase ten-eleven translocation 2 (TET2) and elevated risk for Alzheimer's disease, frontotemporal.
  2. Having a higher genetic likelihood for greater body mass index (BMI), a measure of body fat, increases the risk for rheumatoid arthritis (RA), according to an analysis of data of more than 700,000 people.. The study, Obesity‐related traits and the development of rheumatoid arthritis — evidence from genetic data, was published in the journal Arthritis & Rheumatology
  3. 4.) Genes assort independently (are NOT on the same chromosome and NOT linked) if they follow the 9:3:3:1 rule (on the 16 square Punnett square) resulting from a dihybrid cross. In this dihybrid cross: Observed 556 184 193 61 Expected 559 186 186 62 The total observed is 994, so I found the expected values as so: 9/16= x/994 x= 55
  4. ation and differentiation process in shrimp, we performed sex-specific transcriptome sequencing of the Zoea I larvae in Litopenaeus vannamei (L. vannamei) using a DNA/RNA co-extraction method. The sex-specific genes and the sex-linked SNPs were identified. De novo assembly of all the clean reads generated 41,270 unigenes with an average length of 1026 bp and.

Chi-square test for linkage - An Introduction to Genetic

We previously reported a protein-specific or gene-specific approach to variant pathogenicity prediction in the X linked CACNA1F gene.6 To assess the generalisability of this approach, we again selected X linked disease-causing genes as our test case. From a total of 482 X linked genes from HGMD, no missense variants were reported for 329 genes Non-Mendelian inheritance is any pattern of inheritance in which traits do not segregate in accordance with Mendel's laws.These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus. In Mendelian inheritance, each parent contributes one of two possible alleles for a trait. If the genotypes of both parents in a genetic cross are known, Mendel's laws can be. Chapter 3 Learning Objectives. Know the terms Gene: an inherited factor that determines a characteristic Allele: two or more alternative forms of a gene Locus: specific place on a chromosome occupied by an allele Genotype: set of alleles possessed by an individual Phenotype: the appearance of a characteristic Heterozygous: an individual organism possessing 2 different alleles at the same locus. A dihybrid cross is a breeding experiment between P generation (parental generation) organisms that differ in two traits. The individuals in this type of cross are homozygous for a specific trait or they share one trait. Traits are characteristics that are determined by segments of DNA called genes. Diploid organisms inherit two alleles for each gene. An allele is an alternative version of.