D3.2  Inheritance

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• What patterns of inheritance exist in plants and animals?
• What is the molecular basis of inheritance patterns?​

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​Linking Questions:  
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• What are the principles of effective sampling in biological research?
• What biological processes involve doubling and halving? 

D3.2.1-- Production of haploid gametes in parents and their fusion to form a diploid zygote as the means of inheritance.

• Define gamete and zygote.
• Define diploid and haploid.
• Explain why diploid cells have two copies of each autosomal gene.​

D3.2.2— Methods for conducting genetic crosses in flowering plants.

• Define P, F1 and F2.
• Outline the process of experimentally performing a genetic cross in flowering plants using cross pollination and self-fertilization. 
• State an application of performing genetic crosses in plants. 
• Determine possible alleles present in gametes given parent genotypes.
• Construct Punnett grids for single gene crosses to predict the offspring genotype and phenotype ratios.

D3.2.3-- Genotype as the combination of alleles inherited by an organism.

• Distinguish between gene and allele. 
• Compare and contrast different alleles of the same gene.
• Define homozygous and heterozygous.

D3.2.4-- Phenotype as the observable traits of an organism resulting from genotype and environmental factors.

• Distinguish between genotype and phenotype.
• State a phenotype in humans that is due to genotype only.
• State a phenotype in humans that is due to the environment only.
• State a phenotype in humans that is due to the interaction of genotype and the environment. ​

D3.2.5— Effects of dominant and recessive alleles on phenotype.

• Define dominant allele and recessive allele.
• Explain the usual cause of one allele being dominant over another. ​

D3.2.6- Phenotypic plasticity as the capacity to develop traits suited to the environment experienced by an organism, by varying patterns of gene expression.

• ​Define phenotypic plasticity.
• Outline an example of phenotypic plasticity.

 ​​​​D3.2.7- Phenylketonuria as an example of a human disease due to a recessive allele.

• Define “carrier” as related to genetic diseases.
• Explain why genetic diseases usually appear unexpectedly in a population.
• Outline the genetic cause of phenylketonuria.
• List consequences of phenylketonuria if untreated.
• State how phenylketonuria is treated.

D3.2.8- Single-nucleotide polymorphisms and multiple alleles in gene pools.

• State that new alleles of a gene are the result of mutation.
• Define single-nucleotide polymorphism.
• Define gene pool.
  
• Explain why any number of alleles of a gene can exist in the gene pool but an individual only inherits two alleles.
• Outline how the multiple alleles of the S-gene in the apple gene pool are a mechanism for preventing self-pollination.

D3.2.9- ABO blood groups as an example of multiple alleles.

• Describe ABO blood groups as an example of complete dominance and codominance.
• Outline the differences in glycoproteins present in people with different blood types.

D3.2.10- Incomplete dominance and codominance.

• Define codominant and incomplete dominant alleles.
• Using the correct notation, outline AB blood type as an example of codominant alleles.
• Using the correct notation, outline an example of incompletely dominant alleles in a flowering plant.​

D3.2.11- Sex determination in humans and inheritance of genes on sex chromosomes.

• Outline the structure and function of the two human sex chromosomes.
• Outline sex determination by sex chromosomes.
• Describe the mechanism by which the SRY gene  regulates embryonic gonad development.​

D3.2.12- Hemophilia as an example of a sex-linked genetic disorder.

• Define sex linkage.
• Using the correct notation, outline an example of the inheritance of hemophilia. 
• Describe the pattern of inheritance for sex linked genes.
• Describe the cause and effect of hemophilia.​

​​​​​​D3.2.13- Pedigree charts to deduce patterns of inheritance of genetic disorders.

• Outline the conventions for constructing pedigree charts.
• Deduce inheritance patterns given a pedigree chart.​

D3.2.14- Continuous variation due to polygenic inheritance and/or environmental factors.

• Compare continuous to discrete variation.
• State that a normal distribution of variation is often the result of polygenic inheritance.
• Explain polygenic inheritance using an example of a two gene cross with codominant alleles.
• State example human characteristics that are associated with polygenic inheritance.
• Outline two example environmental factors that can influence phenotypes.​

D3.2.15- Box-and-whisker plots to represent data for a continuous variable such as student height.

• Compare quantitative and qualitative data.
• Compare discrete and continuous data. 
• Determine if a data set contains an outlier. 
• Quantify variation using descriptive statistics.
• Create visualizations of biological variation using graphs. ​​​

AHL ​​​​​​D3.2.16- Segregation and independent assortment of unlinked genes in meiosis.

• State the outcome of allele segregation during meiosis.
• Describe random orientation of chromosomes and the resulting independent assortment of unlinked genes during meiosis I.
• Distinguish between independent assortment of genes and segregation of alleles.​
• Determine possible allele combinations in gametes that result from independent assortment of two unlinked genes.
  

AHL ​​​​​​D3.2.17-  Punnett grids for predicting genotypic and phenotypic ratios in dihybrid crosses involving pairs of unlinked autosomal genes.

• Use correct notation to depict a dihybrid cross between two unlinked genes.
• Construct a Punnett square to determine the predicted genotype and phenotype ratios of F1 and F2 offspring of dihybrid crosses. ​

AHL ​​​​​​D3.2.18- Loci of human genes and their polypeptide products.

• Define gene locus.​
  

AHL ​​​​​​D3.2.19- Autosomal gene linkage.

• Describe what makes genes “linked.”
• Outline why linked genes fail to assort independently during meiosis. 
• Using correct notation, construct a Punnett square to show the possible genotype and phenotype outcomes in a dihybrid cross involving linked genes. ​

AHL ​​​​​​D3.2.20- Recombinants in crosses involving two linked or unlinked genes.

• Define recombinant.
• Explain how independent assortment of unlinked genes can lead to genetic recombinants.
• Explain how crossing over between linked genes can lead to genetic recombinants.
• Construct a Punnett grid to identify the recombinants of a dihybrid cross involving unlinked genes. 
• Construct a Punnett grid to identify the recombinants of a dihybrid cross involving linked genes. ​

AHL ​​​​​​D3.2.21- Use of a chi-squared test on data from dihybrid crosses.

• Calculate a chi-square value to compare observed and expected results of a dihybrid genetic cross.
• With reference to a p value and the null/alternative hypothesis, determine if there is a significant difference between observed and expected results of a dihybrid cross. ​