A. Read pages 275-278. Due 30 April.
Terms & Concepts:
Understand that meiosis
is a specialized form of cell
division that produces daughter cells with half the number of usual
chromosomes (eg gametes).
That is the chromosome number is reduced from
diploid
(2N) to haploid
(1N0. Appreciate why this is necessary in
sexually reproducing organisms. Use the diagram on pages 276-277 to
learn the steps of meiosis, especially the first division cycle. As
with mitosis, be able to describe the major events that take place in
each stage of meiosis. Also be able to compare the events of meiosis to
the corresponding events in mitosis, especially prophase I through
telophase I
of meiosis. Understand what a tetrad
is and how they form
from the pairing of homologous
chromosomes. Appreciate that the
formation of tetrads leads to the "crossing
over" of chromosomes and
the rearrangement of genes on the chromosomes. This has important
implications for the rate of
evolution. Use the diagram on page 278 to
see the difference in gamete formation between males and
females.
Questions
pages
283-284: 7-9.
B. Read
pages 263-266.
Due 4 May.
Terms &
Concepts:
Appreciate that genetics
is the study not only of how inherited
traits
pass from one generation to the next, but also an important
element in understanding how evolution
has shaped the biodiversity
of
the biosphere. Be aware of the basic historical information concerning
Gregor Mendel's
life and work. Understand that much of his ground
breaking work was possible because he opted to study garden peas rather
than some other organism. Know what is means to be a true breeding
plant (or animal) and its significance to Mendel's experiments. Use the
diagrams on the bottom of pages 264-265 to follow the classic
experiments of Mendel that led to his conclusions regarding dominance.
Understand the concept of dominant
and recessive
traits refers to
different versions of the same gene
called alleles. Be
sure
you
the clearly distinguish between the terms gene and allele. Understand
the significance of the
independent segregation of alleles and how the
experiment on the bottom of page 265 led Mendel to this conclusion. You
have learned about meiosis
and the production of haploid
gametes. Be
sure you can relate Mendel's law of segregation to the events of
meiosis.
Questions
pages 283-284: 1, 2, 4.
C. Read
pages 267-269. Due 6 May .
Terms &
Concepts:
Review the basic rules of probability
from you math classes. Understand
that probability is a fundamental tool for the analysis of classical
Mendelian genetics. Be able to set up a Punnett
Square and use it to
predict the results of a genetic
cross or analyze the results
of
a genetic cross to determine the genotypes
of the parents and progeny.
It is especially important that you distinguish between the
genotype
and phenotype of
an individual. Know that the terms homozygous
and heterozygous
refer to genotypes not phenotypes. Most important,
understand that the results of a Punnett Square are predictions of the
results of a genetic cross, not the actual results. In other words, the
Punnett Square is a hypothesis
to be tested against the actual results
of the cross.
Questions
pages 283-284: 3, 5, 12, 24.
D. Read
pages 270-274. Due 8 May.
Terms &
Concepts: Realize that the results of Mendel's
two-factor crosses
with pea plants demonstrated that the genes for
different inherited traits are passed on to the next generation
independently of one another; ie independent
assortment. Be able to
set up and complete simple two-factors (or dihybrid)
crosses using the
Punnett Square technique. You will see later on that there are many
exceptions to this rule. Appreciate that there are a number of
situations that are more complicated than Mendel's experiments. Be
familiar with incomplete
dominance (common in the color of flowers).
Distinguish this from codominance
which is common in the hair color of
horses and rodents. Finally be familiar with multiple alleles and
polygenic traits.
These are actually much more common than the simple
examples that Mendel studied. Don't be mislead into thinking that genes
have total control over the phenotype;. The environment interacts with
the genotype in many important ways to produce the final phenotype.
Questions
pages 283-284: 6, 14-16, 25, 27.
E. Read
pages 279-280. Due 12 May.
Terms & Concepts: Compare the observation of Mendel that
different traits assort independently from one another and
those of Morgan
that showed some traits seem to be inherited together.
Be able to explain why this gene
linkage takes place despite the fact
that chromosomes do assort independently. Understand how the occurrence
of gene linkage changes the predictions of the Punnett Square. Also
appreciate that linked genes have been used as a tool by geneticists to
create gene linkage maps
that show the location of genes along the
length of a chromosome. See the diagram on page 280 for an examples of
a gene map for the fruit fly, Drosophila..
Questions
pages 283-284: 10, 21, 28.
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