Download Mitosis (Chapter 12)

Mitosis (Chapter 12)
What is Mitosis?
Mitosis- A process of nuclear division in eukaryotic cells conventionally divided into five
stages: prophase, prometaphase,metaphase,anaphase, and telophase. Mitosis
conserves chromosome number by distributing replicated chromosomes equally to each
of the daughter nuclei (Campbell Biology)
Step of Mitosis
Prophase: The first and longest stage, the chromosomes become visible and the
centrioles separate and move to the opposite poles of the cell.
Prometaphase: The second stage, the physical barrier that encloses the nucleus called
the nuclear envelope, breaks down.
Metaphase: The third stage, chromosomes line up across the center of the cell and
become connected to the spindle fiber at their centromere.
Anaphase: The fourth stage, the sister chromatids separate into individual
chromosomes and are pulled apart.
Telophase: The fifth stage, the chromosomes gather at opposite ends of the cell and
lose their distinct rod-like shapes. Two new nuclear membranes then form around each
of the two regions of DNA and the spindle fibers disappear.
Cytokinesis: This follows the last stage of mitosis, two complete copies of the DNA now
in two different regions of one cell, the cell membrane will pinch and divide the
cytoplasm in half. The result is two individual cells that are identical to the original cell.
Each of the two new cells have a complete copy of the DNA and contain all of the
organelles that the original cell had.
***INTERPHASE: A period of cell growth and normal activity. Cells that do not need to
replicate will spend their time in this stage. (If a cell does need to divide, it will copy all of
it's DNA while period. This way, the cell has two complete copies of its DNA before it
begins the process of mitosis.) (pg.232,233)
Lab Reference- The mitosis lab, where we looked through microscopes to identify the
different stages of mitosis. We also calculated the numbers of cells in each phase using
the Chi Square calculation.
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Meiosis (Chapter 13)
What is Meiosis?
- Meiosis- A type of cell division that forms gametes in sexually reproducing
organisms.
Meiosis I
-
Prophase I- Chromosomes become condensed and crossing over occurs which
is the genetic rearrangement between non-sister chromatids.
- Metaphase I- Homologous chromosomes are arranged at the metaphase plate.
- Anaphase I- Homologs move toward opposite poles guided by the spindle
apparatus.
- Telophase I and Cytokinesis- Each half of the cell has a complete haploid set of
duplicated chromosomes. Cytokinesis occurs simultaneously forming two haploid
daughter cells.
Meiosis II
- Prophase II- A spindle apparatus forms.
- Metaphase II- Chromosomes are positioned at metaphase plate. The sister
chromatids are not identical and the kinetochores are attached to microtubules.
- Anaphase II- The chromatids separate and move toward opposite poles.
- Telophase II and Cytokinesis- The nuclei is formed and the chromosomes begin
to decondensing. When cytokinesis occurs there will be four haploid daughter
cells.
Lab Reference- The meiosis lab, where we observed the evidence of crossing over by
studying asci.
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Patterns of Inheritance (Chapter 14)
Patterns of Inheritance:
- Gregor Mendel was the first person to systematically pursue the questions of
genetics.
- The theory of Natural Selection did not fit with the prevailing view of inheritance
blending.
- Blending would produce uniform populations, and such populations could not
evolve.
- Many observations did not fit blending due to the small amount of research that
had been able to prove that blending was a main factor in evolution.
Mendel’s Insight Into Inheritance Patterns:
1.) Gregor Mendel used experiments in plant breeding and a knowledge of
mathematics in order to form his hypothesis.
2.) Mendel used the Garden Pea while performing his experiments.
a.) This Plant was able to fertilize itself; true breeding varieties were available to
Mendel.
b.) Peas can also be cross-fertilized by human manipulation of the pollen.
3.) Mendel Cross-fertilized true-breeding garden pea plants, which both had clear
contrasting traits.
Terms Used in Genetics:
- Genes are units of information about specific traits.
- Each Gene has a locus on a chromosome
- Diploid cells have2 genes (a gene pair) for each trait each on a homologous
chromosome.
- Alleles are various molecular forms of a gene for the same trait
- True-breeding lineage occurs when offspring inherit identical alleles, generation
after generation; non-identical alleles produce hybrid offspring.
- When both alleles are the same, the condition is called the homozygous
condition; if the alleles differ; then it is the heterozygous condition.
- When heterozygous, one allele is dominant (A), and the other is recessive (a).
- Homozygous dominant = AA, homozygous recessive = aa,
and heterozygous =Aa
- Genotype is the sum of the genes, and phenotype is how the genes are
expressed (what you observe).
- P= Parental generation; F1= First generation offspring; F2= Second generation
offspring
Mendel’s Theory of Segregation:
1.) Mendel suspected that every plant inherits two “units” (genes) of information for a
trait, one from each parent.
2.) Mendel’s first experiments were monohybrid crosses. (Cross Involved with 1 trait.
Purple X White, or Tall X Short.)
a.) Mendel’s monohybrid crosses have 2 parents that are true-breeding for
contrasting forms of a trait.
b.) One form of the trait disappeared in the first generation offspring (F1), Only to
show up in the second generation (F2).
c.) We now know that all members of the first generation offspring are
heterozygous because one parent could produce only an “A” gamete and the
other could produce only an “a” gamete.
Test Cross
1.) To support his concept of segregation, Mendel crossed F1 plants with
homozygous recessive individuals.
2.) A 1:1 ratio of recessive and dominant phenotypes supported his hypothesis.
3.) Epistasis is when one gene can affect another corresponding gene.
TtPp X TtPp
(FOIL)
Ex:
TP
Tp
tP
tp
TP
TTPP
TTPp
Ttpp
TtPp
Tp
TTPp
TTpp
TtPp
TtPp
tP
TtPP
TtPp
ttPP
ttPp
tp
TtPp
Ttpp
ttPp
ttpp
Steps to Solving a Trihybrid Cross:
AaBbCc X AaBbCc
Aa= ½
bb= ¼
cc= ¼
½ x ¼ x ¼ = 1/32
Probability = 1/32
Steps to Solving a Dihybrid Cross:
Ex:
Bb
Cc
Bb
BBbb
BbCc
Cc
BbCc
CcCc
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Chromosomal Basis of Inheritance (Chapter 15)
Mendelian inheritance has physical relevance within chromosomes
The chromosome theory of inheritance states that
- genes are found on specific loci on chromosomes
- chromosomes segregate and indecently assort in meiosis
Sex-linked genes
Thomas Hunt Morgan studied sex-linked eye color in Drosophila melanogaster flies,
where red eyes was the dominant wild type to white eyes
Females have 2 X chromosomes, 1 maternal 1 paternal
Males have 1 X and 1 Y chromosome. Sperm carry only one type
Offspring’s sex is determined by the type of sperm that fertilizes the egg
Because males have 1 X chromosome, they can directly inherit a sex-linked disease
from their mother
By random selection, females have one of their X chromosomes methylated into a Barr
body, thus allowing for proper gene dosage
Linked genes are usually inherited together
Linked genes are found on same chromosome and they aren't separated by
independent assortment, but by possibility of crossing over
The further distance between 2 genes on a chromosome, the more likely crossing over
can occur
Genetic recombination from crossing over can yield parental type offspring or
recombinants
Chromosomal alteration in meiosis yields disorder
Nondisjunction- homologs or sister chromatids do not separate correctly
Aneuploidy- The faulty gamete has incorrect quantity of a chromosome after fertilization
Monosomy- Fertilized eggs with 1 copy of a chromosome
Trisomy- Fertilized eggs with 3 copies of a chromosome
Chromosomal mutations
Mutations such as deletions (lost fragment), duplications (repeated fragment),
inversions (backwards fragment), and translocations (fragment joins nonhomologous
chromosome) alter one’s chromosomes
Common disorders
Klinefelter syndrome- XXY sex chromosomes of a male, which leads to sterility
Turner syndrome- XO sex chromosome of a female, which leads to sterility
Down syndrome- Trisomy 21 chromosome
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Biology Big Ideas
Big Idea 1: The process of EVOLUTION drives the diversity and unity of life.
Project Reference: The process of mitosis has evolved from prokaryotes to eukaryotes. Proteins
involved in binary fission are related to eukaryotic proteins that function in mitosis. The process
of binary fission in bacteria somehow gave rise to mitosis
Big Idea 2: Biological systems utilize free ENERGY and molecular building blocks to grow, to
reproduce and to maintain dynamic homeostasis.
Project Reference: With the process of meiosis there is growth and reproduction because
gamete formation is happening by two parent cells giving off chromosomes to form a complete
daughter cell.
Big Idea 3: Living systems store, retrieve, transmit and respond to INFORMATION essential to
life processes.
Project Reference: ​Genetic information encoded by the genes in chromosomes is unique
in every organism. Through the molecular mechanisms of crossing over and individual
assortment in meiosis, genetic variation in offspring will result
Big Idea 4: Biological systems interact, and these systems and their INTERACTIONS possess
complex properties.
Project Reference: ​The way biological systems interact deals with complex properties that are
shown through this project. Genes are passed through genetics and different traits are
expressed, this is represented with a test cross. Gregor Mendel was the first person to really
study and observe genetics and traits between the garden pea plant. Because of his
observations, we now have a basic understanding of modern genetics.