Unit 5: Heredity

20 questions to review your knowledge of Chi Square and Heredity

Heredity is the concept of passing genes on from generation to generation. This starts with the creation of gametes, or sex cells, through cellular division called meiosis.

In this session, Caroline goes through a basic review of genetics. She then goes through specific examples related to Mendelian and Non-Mendelian genetics. Lastly, she introduces Chi-Square analysis and goes through an example.

Browse slides from the stream 'Mendelian and Non-Mendelian Genetics and Chi Square.'

Browse slides from the stream 'Mendelian and Non-Mendelian Genetics and Chi Square.'

Test your knowledge on genetics!

A detailed overview of meiosis and its contributions to genetic diversity and an intro into heredity.

Browse slides from the stream 'Meiosis and an Intro to Heredity.'

Browse slides from the stream 'Non-Mendelian Genetics & Pedigrees,' where we cover topics including DNA & Genetics, Cellular Processes, and Reproduction.

In this session, we discuss 4 types of Non-Mendelian Genetics and 5 pedigrees. We begin by showing the purpose for learning about these inheritance patterns, and discussing the 4 types. With codominance (co: together), we use a feather and cattle exam and show that it depends on the heterozygote. With Incomplete dominance, we use a flower color example. With multiple alleles (which we warn are a little more confusing), we remind students to write the allele like a superscript and complete 5 practice problems. We use blood types, reminding students that blood type is both codominant and dominant recessive. We discuss sex linked traits (diseases carried on the X or Y chromosome and they are more frequently occuring in males). Examples of sex linked traits are color blindness and hemophilia. We discuss 4 types of pedigrees (autosomal dominant, autosomal recessive, X-linked interactive / Y-linked interactive, and mitochondrial). The exam typically doesn’t state which pedigree is discussed in a problem, so we included characteristics for each pedigree that will help students identify which one it is on the exam.

This is a difficult concept, so in this session, we spend a lot of time working on practice problems. Chi Square Analysis lets us know if variation in data is due to chance or due to a variable of some other influencer (this analysis lets us know if the data is legitimate). We discuss equations that will be given to you on the day of the exam and important vocabulary to know (Chi-Squared test, null, hypothesis, degrees of freedom, critical values and purpose). We emphasize the purpose of Chi-Squared analysis and what we need to remember for the exam: if the value is greater than the critical value, then the null is rejected, meaning the results were not due to chance.

Browse slides from the stream 'Chi Square Analysis,' where we cover topics including Experimental Design.

Browse slides from the stream 'Mendelian Genetics,' where we cover topics including DNA & Genetics, Plants, and Reproduction.

In this presentation, we begin with a background on Gregor Mendel’s groundbreaking work. His work is the foundation for the progress of genetics. Mendel’s work with plants was critical to genetic study (he discovers that genetic material is passed down, generation to generation). We discuss the 7 characteristics of plants that Mendel discovers (flower color, seed color, seed shapes, pod shape, pod color, flower generation, and stem length) that lead to useful data. After Mendel, we know that DNA is our genetic material and can build on the basis of genetics (phenotype/genotype). We use a parent cross, to help us figure out what offspring might look like (Punnett Squares are just predictive). We end with practice problems.

Meiosis is the process that all organisms go through in order to produce gametes, or sex cells. The process differs from mitosis, the process of somatic cell division, in a number of key ways. Meiosis involves one round of DNA replication and two rounds of cellular division. The resulting cells are all genetically unique from one another and from the parent cell. The resulting cells are also haploid, meaning that they have half of the genetic content of a typical somatic cell, or diploid cell.

There are a few key concepts within meiosis that contribute to genetic diversity. Remember that diversity is the key to life. When all else fails, focus on diversity in your answers for the AP exam. Some key contributors to genetic diversity in meiosis are the concepts of crossing over, independent assortment, and random fertilization.

Gregor Mendel, the father of modern genetics, came up with some really important laws, including the law of independent assortment, that allows for scientists to determine how genes are inherited from generation to generation.

Most traits actually do not follow Mendel’s laws of dominant and recessive inheritance. The inheritance of these traits is referred to as Non-Mendelian genetics. A few important Non-Mendelian inheritance patterns are multiple alleles, sex-linked traits, incomplete dominance, and codominance. 

Environmental conditions may play a role in which phenotypes are prevalent in a certain environment. This goes back to the concept of natural selection, in which environmental conditions can determine which individuals survive and reproduce more than others.

As described before, chromosomes are inherited from both parents following the rules of genetics. There is an equal chance that either version of a gene may be inherited in offspring due to the law of Independent Assortment. Random fertilization allows for even more variation in that it is simply by chance that a certain egg and a certain sperm combine to form a zygote.