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Unit III
Chapter 13
1. - Meiosis (A two stage type of cell division in sexually reproducing organisms that results in
gametes with half the chromosome number of the original cell.) figure 13.6 (campbell book)
a) Prophase I (The chromosomes begin to condense, two chromatids come together as
pairs.)
b) Metaphase I (Spindle fibers from one pole of the cell attach to one chromosome of each
pair, while spindle fibers from the opposite pole attach to the homologue.)
c) Anaphase I (The spindle apparatus moves the chromosomes toward the poles. However,
sister chromatids remain attached at their centromeres and move as a single unit toward
the same pole.)
d) Telophase I and Cytokinesis (The spindle apparatus continues to separate the
homologous chromosome pairs until the chromosomes reach the poles of the cell. Each
pole now has a haploid chromosome set, but each chromosome still has two chromatids.
Usually Cytokinesis (division of the cytoplasm) occurs simultaneously with Telophase I,
forming two daughter cells.)
e) Prophase II (A spindle apparatus forms, and the chromosomes progress toward the
metaphase II plate.
f) Metaphase II (The chromosomes align on the metaphase plate in mitosis like fashion, with
the kinetochores of sister chromatids of each chromatids of sister chromatids of each
chromosome pointing toward opposite poles.
g) Anaphase II (The centromeres of sister chromatids finally separate, and the sister
chromatids of each pair, now individual chromosome, moves toward opposite poles of the
cell.
h) TelophaseII (Nuclei begin to form at opposite poles of the cell, and Cytokinesis occurs.
There are now four daughter cells, each with the haploid number of chromosomes.
2. -Differences between mitosis and meiosis Figure 13.7 (campbell book)
1. Meiosis
a) Reduction division
(1) 2n to 1n
(2) Diploid to haploid
b) Creates genetic variation
(1) Gametes carry half of chromosomes
(2) When egg & sperm fuse, new genetic combination produced
c) Two divisions
d) Synapsis occurs; tetrads produced
e) Homologous pairs (tetrads) align on metaphase plate
f) Metaphase I
(1) Separates homologous chromosomes
(2) Sister chromatids pulled toward same pole
g) Metaphase II – separates sister chromatids
2. Mitosis
a) Maintains chromosome number
(1) 2n to 2n
(2) Diploid to diploid
b) Daughter cells clones of mother cells
c) One division
d) No synapsis; no tetrads
e) Individual chromosomes align on metaphase plate
a) Metaphase separates sister chromatids.
Chapter 14
1. - Mendel and the gene idea outline Figure 14.1 (campbell book)
a) Mendel brought an experimental and quantitative approach to the genetics
1) Mendel formulated a particulate theory of inheritance based on experiments with
garden peas, carried out in the 1860s.
2) He showed that parent’s pass on to their offspring discrete genes that retain their
identity through the generations.
2. - By the law of segregation, the alleles for a character are packed into separate gametes
Figure 14.1 and 14.2 (campbell book)
a) Mendel arrived at this law by making hybrid offspring and letting them self- pollinate.
b) The Hybrids (F1) exhibited the dominant trait.
c) The (F2) generation, 75% of offspring had the dominant trait and 25% had the recessive
trait, for a 3:1 Ratio.
d) Mender’s explanation was that genes have alternative forms (Now called alleles) and that
each organism inhibits one alleles for each gene from each parent.
e) These separate (segregate) during gamete formation, so that a sper or an egg carries only
one allele.
3. – By the law of independent assortment, each pair of alleles segregates into gametes
independently. Figure 14.5 (campbell book)
a) Mendel proposed this law based on dihybrid crosses between plants contrasting in two or
more characters. ( E.G., Flower color and seed shape)
b) Alleles for each character segregate into gametes independently of alleles for other
characters
c) The F2 generation of a dihybrid cross has four possible phenotypes in a 9:3:3:1 ratio.
4. - Mendelian inheritance reflects rules of probability. Figure 14.9 (campbell book)
a) The rule of multiplication states that the probability of a compound events equal to the
product of the separate probabilities of the independent single events.
b) The rule of addition states that the probability of an even that can occur in two or more
independent ways is the sum of the separate probabilities.
5. - Mendelian Inheritance in humans Figure 14.14 (capbell book)
a) Pedigree analysis reveals Mendelian patterns in human inheritance
1. - Family pedigrees can be used to deduce the possible genotypes of individuals and
make prediction about future offspring.
2. - Any predictions are usually statistical abilities rather than certainties.
b) Many humans disorders fallow Mendelian patterns of inheritance. Figure 14.15
1. - Certain genetic disorders are inherited as a simple recessive trait from
phenotypically normal heterozygous carries.
2. - Some Human disorders are due to dominant alleles.
3. - Medical researchers are beginning to sort out the genetic and eviromental
components of multifactorial disorders, such as heart disease and cancer.
C) Technology is providing new tools for genetic testing and caunseling. Figure
14.16
1. - Using family histories, genetic counselors help couples determine the odds
that their children will have genetic disorders.
2. - For certain disease, test that identy carries define the odds more
accurately.
3. - Once a child is conceived amniocentesis and chorionic villus sampling can
help determine whether a suspected genetic disorder is present.
Chapter 15
1. - The Chromosomal basis of inheritance. Figure 15.1
a) Mendelian inheritance has its physical basis in the behavior of chromosomes
during sexual life cycles.
b) In the early 1900s, geneticists showed that chromosomal movement in
meiosis account for Mender’s laws.
2. - Linked genes tend to be inherited together because they are located on the same
chromosomes. Figure 15.3
a) Each chromosome has hundreds or thousands of genes.
b) Linked genes do not assort independently
3. - Sex Chromosomes. Figure 15.8
a) The Chromosomal basis of sex varies with the organism
1. - Sex an inherited phenotypic character usually determined by the presence or
absence of special chromosomes: the exact mechanism varies among deferent
species.
2. - Humans and other mammals, like fruit flies, have a x-y system.
A xy male gives ether an X-chromosomes or a Y chromosome to the sperm, which
combines with an ovum containing an X chromosome from an XX female.
3. - The offspring’s sex is determine at conception by whether the sperm carries X
or Y.
b) Sex- linked genes have unique patterns of inheritance. Figure 15.9
1. - The sex chromosomes carry certain gene traits that are unrelated to meleness
or femaleness.
2. - The sex chromosomes carry certain gene traits that are unrelated to maleness
or femaleness.
3. - In mammalian females, one of the two x chromosomes in each is randomly
inactivated during early embryonic development.
4. – Errors and exception to chromosomal inheritance.
a) Alterations of chromosome number or structure cause some genetic
disorders. Figure 15.12
1. - Errors (meiosis can change the number of chromosomes per cell or the
structure of individual chromosomes.
2. - Such alterations can affect phenotype.
Aneuploidy, an abnormal chromosome number, arise when a normal gamete
unites with one containing two or no copies of a particular chromosome as a result
of nosdisjuction during meiosis.
3. – Polyploidy, in which there are more than complete sets of chromosomes, can result
from complete nondisjuction during gamete formation.