Honors Biology
Mendelian Genetics
Module 8
December 5, 2013
Notebook Check Today
Through Module 7
1.
2.
3.
4.
On Your Own questions
Study Guide questions
Module tests
Lab book completed
Class Challenge
Quiz: Figure 7.6
• Draw and label:
Meiosis Stage I and Stage 2
Mendelian Genetics
During 8 years of scientific work, Mendel studied breeding
of pea plants. He noticed that pea plants had certain
definable characteristics that seemed to change from
plant to plant.
• Some pea plants were tall (6 feet high)
• Some were small (1 ½ feet high)
• Some flowers grew along the sides of the plants. (Axial
flowers)
• While others grew on the top of the plant. (Terminal flowers)
• Some pea pods were green
• Some pea pods were yellow
• Some peas were wrinkled
• Some peas were smooth
True Breeding
Figure 8.1
Mendel noticed that some plants bred so as to produce
offspring with the same characteristic.
• Some tall plants would always give rise to other tall
plants.
• When this happens, the tall plant has bred true.
If an organism has a certain characteristic that is always
passed on to its offspring, we say that this organism
bred true with respect to that characteristic.
Figure 8.1 and Figure 8.2
Mendel developed the four principles of genetics that
are still the foundation of science today.
1.
2.
3.
4.
The traits of an organism are determined by packets of
information called “factors.”
Each organism has not one, but two factors that
determine its traits.
In sexual reproduction, each parent contributes ONLY
ONE of its factors to offspring.
In each definable trait, there is a dominate factor. If it
exists in an organism, the trait determined by that
dominant factor will be expressed.
As you study Figure 8.3 and 8.4
There are traits that a dominate trait (they
are represented by a Capital letter)
There are traits that are recessive ( they are
represented by a lower-case letter)
Dr Wile’s CD
• Figure 8.2
• Figure 8.3
Terms to Know
Scientists do not use the term “factor” any more.
We know that the packets of information are
genes.
We know that animals have homologous pairs of
chromosomes, we know that genes come in
pairs, with one gene on each homologous
chromosome. Each gene that makes up one of
these pairs is called an allele.
Allele is one of a pair of genes that occupies the
same position on homologous chromosomes.
Mendel’s “factors” are called Alleles
• Each definable trait has two alleles that
help determine it, and they can each be
represented by a letter.
• When we put two alleles together
(for example Tt or tt), we are describing a
genotype.
TT and Tt
TT and Tt (genotype) will result in a tall
plant.
The allele T (tall) is dominant.
The expression of an organism’s genotype is
called a phenotype. It is what it looks
like. (A tall plant)
There are two phenotypes possible
Tall (TT, Tt) or Short (tt)
When the genotype is composed of identical
alleles (TT) or (tt) we say that the
genotype is homozygous.
When the genotype has mixed alleles (Tt)
we say that it is heterozygous.
Dr Wile
Example 8.1
Example 8.2
Dominant or Recessive
Dominant allele: An allele that will
determine phenotype if just one is present
in the genotype.
Recessive allele: An allele that will not
determine the phenotype unless the
genotype is homozygous in that allele.
A Restatement of Mendel’s
Principles
1. The traits of an organism are determined by its
genes.
2. Each organism has two alleles that make up
the genotype for a given trait.
3. In sexual reproduction, each parent contributes
ONLY ONE of its alleles to its offspring.
4. In each genotype, there is a dominant allele. If
it exists in an organism, the phenotype is
determined by that trait.
1. The reason that animals have two alleles for each
genetic trait is because they have diploid cells.
2. They have homologous pairs of chromosomes.
3. In sexual reproduction, each parent contributes only
one allele to the offspring.
4. This is why meiosis takes diploid cells and makes
them haploid. The process of meiosis separates the
homologous pairs, separating the alleles from each
other. Each gamete (sperm and egg) when fused
will result with a zygote that has two alleles: one
from the father and one from the mother.
Mendelian Genetics
http://youtu.be/NWqgZUnJdAY
Get your lab books out for questions found
at 7:21 minute marker
A Beginner's Guide to Punnett
Squares
http://youtu.be/Y1PCwxUDTl8
Dr Wile
• Example 8.3
Identifying Traits in our class
Hair color
Eye color
Ear lobes
Tongue curls
Hitchhikers thumb
Experiment 8.1
Object : To interpret your own pedigree with
respect to earlobe attachment.
Procedure:
Homework
1. Read Module 8: MENDELIAN GENETICS
(p. 247-257)
2. Answer OYO question 8.1 – 8.7
3. Answer Study Guide questions: a-j and
questions 2 – 9
4. Complete Experiment 8.1 Making your own
Earlobe Pedigree. It will be graded on Dec 12.
5. Quiz: Mendel’s scientific contribution to the
study of genetics.
6. Class challenge: