Class Notes (906,590)
CA (538,616)
UTSC (32,642)
BIOA01H3 (714)
Lecture

lecture 11 for BGYA01

12 Pages
163 Views

Department
Biological Sciences
Course Code
BIOA01H3
Professor
Clare Hasenkampf

This preview shows pages 1-3. Sign up to view the full 12 pages of the document.
1
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
www.notesolution.com
2
is 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.
www.notesolution.com
3
In a monohybrid cross the geneticists try to ignore all the other 1000’s of genes]
Parental generation P is the term we use to designate the starting parents in the original
mating.
Mendel crossed a true breeding line of peas that had smooth seeds with a true breeding
line of plants that had dented seeds. Figure 10.4, page 212.
Smooth is the name of the gene determining seed coat texture.
Homozygous is a term we use for the situation when an organism has functionally
identical versions of the gene pair, of the alleles. Homozygotes breed true.
The P generation individuals in Figure 10.4, page 212 are homozygotes.
The smooth seeded individual was homozygous for the S allele. Its genotype is
symbolized S S.
The dented seeded individual was homozygous for the s allele. Its genotype is
symbolized s s .
We can symbolized the genotypes of the parental generation of the cross
S S x ss.
The first filial generation F1 is the term we use to designate the offspring of the parental
cross. What would be the genotype of the F1 offspring for Mendels monohybrid cross?
Parent 1, the one with smooth seeds could only donate an S version of the gene, since it
was homozygous for S, and the dented parent could only donate the s version of the allele
since it was homozygous for the s allele.
Thus after fertilization, all of the F1 offspring have the genotype symbolized by S s.
We say the F1 offspring are heterozygous.
Heterozygous is a term we use for the situation when an organism has functionally
different versions of the gene pair. It has different alleles at the genetic locus.
We also call the F1 individuals monohybrids meaning they are heterozygous for one
genetic locus.
The F1 is heterozygous, with the genotype S s but it looks like the smooth seeded
parent. The S s plant is smooth seeded because the S allele is the dominant allele.
A dominant allele completely determines the phenotype when it is present.
An allele that can be seen in heterozygotes is typically indicated with an uppercase letter.
www.notesolution.com

Loved by over 2.2 million students

Over 90% improved by at least one letter grade.

Leah — University of Toronto

OneClass has been such a huge help in my studies at UofT especially since I am a transfer student. OneClass is the study buddy I never had before and definitely gives me the extra push to get from a B to an A!

Leah — University of Toronto
Saarim — University of Michigan

Balancing social life With academics can be difficult, that is why I'm so glad that OneClass is out there where I can find the top notes for all of my classes. Now I can be the all-star student I want to be.

Saarim — University of Michigan
Jenna — University of Wisconsin

As a college student living on a college budget, I love how easy it is to earn gift cards just by submitting my notes.

Jenna — University of Wisconsin
Anne — University of California

OneClass has allowed me to catch up with my most difficult course! #lifesaver

Anne — University of California
Description
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
Unlock Document


Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

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


OR

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.


Submit