lecture 11 for BGYA01

12 Pages
Unlock Document

University of Toronto Scarborough
Biological Sciences
Clare Hasenkampf

BGYA01 Lecture 11 October 18, 2007 Last class we talked about chromosome behavior during mitosis and meiosis. Now I want to talk about biological inheritance. Clicker question Which stage of an M phase division has one kinetochore per chromosome a) Prophase of mitosis b) Prophase I of meiosis c) Anaphase of mitosis d) Anaphase I of meiosis e) All of the above except NOT a) ******* Inheritance considers the pattern by which traits are passed from one generation to the next. The behavior of chromosomes during meiosis accounts for many of the laws of inheritance. Why? The reason is 1) DNA is the hereditary material AND the DNA packaged with proteins is the what the chromosome is made of. 2) The units of heredity are called genes; each gene is a distinct segments of much larger DNA molecules. 3) Genes are used as templates to make RNAs and mRNAs provide the code for making proteins. 4) Proteins control many important cellular processes that affect the traits we observe in individuals. A gene occurs at a specific location on a specific DNA molecules, therefore genes occur on a specific region of a specific chromosome. The exact location of the gene is called a genetic locus. You can think of a locus as a genes address. Because diploids have two versions of each chromosome, they have two versions of each gene. We call the two versions of the same gene- alleles. Alleles can have identical DNA sequences, or alleles can have somewhat different DNA sequences due to a change of the original DNA sequence. Lets, for a minute, think about how the different versions (alleles) arise. They do this by the process of mutation. A mutation is an inheritable change in the DNA. It is through the process of mutation that we have different versions of genes. That is, it 1 www.notesolution.comis through the process of mutation that there exists more than one version of a particular gene. Once we have different version of the same gene (alleles) we can begin to follow these alleles through generations to detect the patterns of inheritance. Gregor Mendel is considered to be the Father of Genetics and he formulated the first two laws of inheritance. These two laws are often referred to as Mendels laws. In Mendels first law arose from his theory Mendel said something along the lines of I think sexually reproducing organisms are diploid (have two versions of each gene), but they only give one version to their offspring. His experiment strongly supported this theory and it became known (many years later) as Mendels First Law: Segregation of Alleles. In Mendels time scientists did not yet have microscopes powerful enough to allow us to see chromosomes, and back then it was not even know that DNA is the hereditary material. Mendel came up with his Laws by doing genetic experiments with garden peas. Lets look at his experiments. Well need some more terms. Genotype is a term that refers to the specific alleles of a particular gene that are present in an individual. Phenotype is a term we use to refer to an observable trait or character of an organism. The phenotype is determined by the genotype (but is also influenced by the environment). Why? It is because: Genes are specific regions of the DNA that encode the information to make proteins. Usually one gene encodes one protein. Proteins are essential to the individual cells of the organism and are essential to the organism. The proteins determine the appearance and functions of the organism. Genes encode the proteins and the proteins determine the specific characteristics of the organism. Before he began his experiments, Mendel created sets of true breeding lines. This was very important. If two true breeding individuals, with the same phenotype are mated, their offspring will have the same phenotype (for the trait being studied) as the parents; i.e. they breed true to their form. Mendel first did a monohybrid cross. A Monohybrid cross is one in which the inheritance for one genetic locus is being studied, and the starting parents have different genotypes for the one locus being studied. 2 www.notesolution.com
More Less

Related notes for BIOA01H3

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.