GENERAL BIOLOGY I
TEST IV
REVIEW
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TERMS TO KNOW
• Cell Cycle
• Interphase (G0, G1, S, G2) and mitosis
• An ordered sequence of events in the life of a cell, from its origin in the division of a parent cell
until its own division into two. The eukaryotic cell cycle is composed of interphase (including G1,
S, and G2 subphases) and M phase (including mitosis and cytokinesis).
• Prophase
• Chromatin condenses into chromosomes, nuclear membrane dissolves.
• The first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible
with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears but the
nucleus remains intact.
• Metaphase
• Chromosomes line up along the center of the cell
• The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to
microtubules at their kinetochores, are all aligned at the metaphase plate.
• Anaphase
• Chromatids begin pulling apart
• The fourth stage of mitosis, in which the chromatids of each chromosome have separated and
the daughter chromosomes are moving to the poles of the cell.
• Telophase
• Chromosomes move to opposite ends of the cell, nuclear membranes reform
• The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has
typically begun.
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TERMS TO KNOW
• Cytokinesis
• Cleavage of the cell, involves cleavage furrow in animal cells and cell plate
formation in plant cells
• The division of the cytoplasm to form two separate daughter cells immediately
after mitosis, meiosis I, or meiosis II.
• Chromosome
• Tightly bundled DNA
• A cellular structure carrying genetic material, found in the nucleus of
eukaryotic cells. Each chromosome consists of one very long DNA molecule
and associated proteins. (A bacterial chromosome usually consists of a single
circular DNA molecule and associated proteins. It is found in the nucleoid
region, which is not membrane bounded.)
• Chromatid
• One of a pair of duplicated chromosomes
• One of the longitudinal subunits of a replicated chromosome.
• Chromatin
• Loose DNA
• The complex of DNA and proteins that makes up eukaryotic chromosomes.
When the cell is not dividing, chromatin exists in its dispersed form, as a mass of
very long, thin fibers that are not visible with a light microscope.
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TERMS TO KNOW
• Karyotype
• The number and appearance of chromosomes in the nucleus of a
eukaryotic cell.
• A display of the chromosome pairs of a cell arranged by size and
shape.
• Karogram - A graph depicting all 23 pairs of chromosomes lined up in
order from largest to smallest
• Haploid
• One complete set of chromosomes, i.e. 23 chromosomes in haploid
human gametes
• Diploid
• Two complete sets of chromosomes, i.e. 23 pairs of chromosomes in
somatic human cells
• Gamete
• Haploid reproductive cells
• A haploid reproductive cell, such as an egg or sperm. Gametes unite
during sexual reproduction to produce a diploid zygote.
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TERMS TO KNOW
• Centromere
• Center of a chromosome
• In a duplicated chromosome, the region on each sister chromatid where they are
most closely attached to each other by proteins that bind to specific DNA
sequences; this close attachment causes a constriction in the condensed
chromosome. (An uncondensed, unduplicated chromosome has a single
centromere, identified by its DNA sequence.)
• Kinetochore
• Protein in the center of a chromosome where spindle fibers attach
• A structure of proteins attached to the centromere that links each sister chromatid
to the mitotic spindle.
• Homologous Chromosomes
• A pair of the same chromosomes, one from each parent, may have different
versions of the same alleles
• A pair of chromosomes of the same length, centromere position, and staining
pattern that possess genes for the same characters at corresponding loci. One
homologous chromosome is inherited from the organism’s father, the other from the
mother. Also called homologs, or a homologous pair.
• Fission of Bacteria
• The method by which bacteria reproduce, doubling of chromosomes and splitting
of one cell into two with no mitosis occurring. This takes place with out the formation
of spindles.
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TERMS TO KNOW
• Autosomes
• autosome - A chromosome that is not directly involved in determining
sex; not a sex chromosome.
• Sex Chromosomes
• sex chromosome - A chromosome responsible for determining the sex
of an individual.
• Gametophyte
• Haploid organism that makes gametes via mitosis
• In organisms (plants and some algae) that have alternation of
generations, the multicellular haploid form that produces haploid
gametes by mitosis. The haploid gametes unite and develop into
sporophytes.
• Sporophyte
• Diploid organism that makes spores via meiosis
• In organisms (plants and some algae) that have alternation of
generations, the multicellular diploid form that results from the union of
gametes. The sporophyte produces haploid spores by meiosis that
develop into gametophytes.
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TERMS TO KNOW
• Recombination
• Increases genetic variation during meiosis I. Two types of recombination.
• Crossing over – exchange of DNA between homologous chromosomes.
• Random separation – (assortment/segregation) of homologous chromosomes.
• Independent assortment – orientation of homologous pairs to poles is random.
• All possible combinations of gametes should be formed in equal frequency
• Formula for number of combinations is 2n
• Gregor Mendel
• Proposed the existence of particulate unit factors (genes) are passed from
generation to generation
• Proposed three postulates of inheritance
• Unit factors (alleles of genes) exist in pairs (in diploid)
• If an organism has two different alleles (heterozygous) then one is dominant and the
other is recessive. One expresses phenotype in heterozygote, and the other is hidden
in heterozygote
• The paired unit factors segregate independently during gamete formation (meiosis).
• Proposed that traits assort independently during gamete formation.
• Used true breeding strains of peas with seven characteristics, each
characteristic had two contrasting traits.
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TERMS TO KNOW
• Allele
•
•
•
•
Alternative forms of the same gene
A single type of a gene, i.e. brown eye vs blue eye genes
A variation of a gene or alternate form of a gene
Any of the alternative versions of a gene that may produce
distinguishable phenotypic effects.
• Genotype
• The genetic makeup of an individual. The combination of alleles of an
organism. (Alleles of a gene; example AA, Aa, or aa.).
• The genetic makeup, or set of alleles, of an organism.
• Phenotype
• Composite of an organism’s observable characteristics
• The observed characteristics.
• The observable physical and physiological traits of an organism, which
are determined by its genetic makeup.
• Genotype + Environment  Phenotype
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Genotype vs Phenotype
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TERMS TO KNOW
• Homozygous
• Having two of the same alleles for a specific trait
(true breeding)
• When the alleles for a trait in an individual are the same. Example AA or aa
• Heterozygous
• Having two different alleles for a specific trait
• When the alleles for a trait in an individual are different. Example Aa
• Parental Generation
• The first set of parents crossed in which their genotype is the basis for predicting
the genotype of their offspring, which in turn may be crossed.
• P generation - The true-breeding (homozygous) parent individuals from which
F1 hybrid offspring are derived in studies of inheritance; P stands for “parental.”
• F1 Generation
• F1 is the first cross of the parental generation,
• F1 generation - The first filial, hybrid (heterozygous) offspring arising from a
parental (P generation) cross.
• F2 Generations
• F2 is a cross of the F1 generation
• F2 generation -The offspring resulting from interbreeding (or self-pollination) of
the hybrid F1 generation.
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TERMS TO KNOW
• Dominant
• Allele that is always expressed if present
• dominant allele - An allele that is fully expressed in the phenotype of a
heterozygote.
• Recessive
• Allele that is only expressed if homozygous for that allele
• recessive allele - An allele whose phenotypic effect is not observed in
a heterozygote.
• Test Cross
• Dominant phenotype of unknown genotype being crossed with
recessive phenotype to determine genotype
• Breeding an organism of unknown genotype with a homozygous
recessive individual to determine the unknown genotype. The ratio of
phenotypes in the offspring reveals the unknown genotype.
• Haploid
• Having a single set of chromosomes (n)
• Diploid
• Having two sets of chromosomes (2n)
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TERMS TO KNOW
• Complete dominance
• One allele is completely dominant over the other, and is always expressed if
present
• The situation in which the phenotypes of the heterozygote and dominant
homozygote are indistinguishable.
• Co-dominance
• Both alleles are completely expressed, i.e. AB blood type
• The situation in which the phenotypes of both alleles are exhibited in the
heterozygote because both alleles affect the phenotype in separate,
distinguishable ways.
• Incomplete dominance
• Both alleles are expressed, i.e. pink flowers being a cross of red and white
• The situation in which the phenotype of heterozygotes is intermediate between
the phenotypes of individuals homozygous for either allele.
• Multiple alleles
• More than one allele exists, i.e. ABO blood types
• In a population of organisms, the presence of three or more alleles of the same
gene.
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TERMS TO KNOW
• Monohybrid cross
• Monohybrid cross: Crossing of alleles for one trait
• A cross between two organisms that are heterozygous for the character being
followed (or the self-pollination of a heterozygous plant).
• Dihybrid cross
• A cross between two organisms that are each heterozygous for both of the
characters being followed (or the self-pollination of a plant that is heterozygous
for both characters).
• Dihybrid cross: Crossing of alleles for two traits
• Dependent assortment (like linked genes) vs. independent assortment
• Dependent assortment: Theory that alleles on the same chromosome are
crossed together
• Independent assortment: Theory that alleles on the same chromosome are
crossed separately
• Pleiotropy
• The ability of a single gene to have multiple effects.
• Polygenic
• Phenotype is determined by multiple genes
• polygenic inheritance - The transmission of a phenotypic trait whose expression
depends on the additive effect of a number of genes.
The Academic Support Center @ Daytona State College (Science 65, Page 13 of 31)
CONCEPT QUESTIONS
• MITOSIS: Be able to identify pictorial/symbolic representations of
mitosis.
Pro
• Chromosomes condense during ___________
phase; chromosomes are
located in the equator during ___________
phase, chromatids separate
Meta
Ana
Telo
during ___________ phase, chromosomes relax during ___________
phase?
Pro
• Centrioles move to the poles during _________
phase of mitosis?
Pro
• The nuclear membrane disassembles during _________
phase, and
Telo
reassembles during ________ phase and is absent in-between phases.
• How do spindle fibers move chromosomes during anaphase?
• In anaphase, spindle fibers pull sister chromatids toward the spindle poles. Spindle
fibers not connected to chromatids lengthen and elongate the cell.
Forming a cell plate
• Cytokinesis in plants is by _____________________
and cytokinesis in animals is
Forming
a
cleavage
furrow
by ________________________. Centrioles are found in
Animals
higher level Plants
_______________________
but not __________________________?
• If a cell had 10 chromatids in metaphase of mitosis, how many
chromosomes are in each resulting nucleus?
• 5
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CONCEPT QUESTIONS
• What is the life cycle of animals?
• Diploid with an extremely reduced haploid stage
• What is the life cycle (alternation of generation) of plants?
• Alternating haploid and diploid generations, sporophyte and
gametophyte
• What are the differences between meiosis and mitosis?
• Meiosis forms haploid cells, Mitosis forms diploid cells
• Meiosis involves crossing over and shuffling of genes, mitosis makes
two exact replicas
• Meiosis is a two stage process Meiosis 1 and Meiosis 2.
• What are the similarities between meiosis and mitosis?
• Both Meiosis and Mitosis go through the four phases; prophase,
metaphase, anaphase, and telophase.
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LIFE CYCLE OF A FERN EXAMPLE OF
ALTERNATION OF GENERATIONS
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LIFE CYCLE OF A MOSS EXAMPLE OF
ALTERNATION OF GENERATIONS
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LIFE CYCLE OF AN ANIMAL
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CONCEPT QUESTIONS
• If there are 100 chromosomes before meiosis, how many
are there after meiosis?
• 50
• If there are 100 chromosomes before mitosis, how many
are there after mitosis?
• 100
• If a cell has two pair of homologous chromosomes before
mitosis (after S phase), then how many chromatids does it
have?
• 8
• If a cell has two pair of homologous chromosomes before
meiosis (after S phase), then how many chromatids does it
have?
• 8
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PUNNETT SQUARES
P
p
P
p
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PUNNETT SQUARES
P
p
P
PP
Pp
p
Pp
pp
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PUNNETT SQUARES
IA
IB
i
i
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PUNNETT SQUARES
IA
IB
i
IAi
IBi
i
IAi
IBi
The Academic Support Center @ Daytona State College (Science 65, Page 23 of 31)
Dihybrid Cross:
a cross that shows the possible offspring for
two traits
Fur Color:
B: Black
b: White
Coat Texture:
R: Rough
r: Smooth
In this example, we will cross a
heterozygous individual with another
heterozygous individual. Their
genotypes will be:
BbRr x BbRr
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Dihybrid Cross
BbRr x BbRr
First, you must find ALL possible gametes
that can be made from each parent.
Remember, each gamete must have one B
and one R.
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Dihybrid Cross
BbRr x BbRr
Possible gametes:
Next, arrange all possible
BR
gametes for one parent along the
Br
top of your Punnett Square, and
all possible gametes for the other
bR
parent down the side of your
Punnett Square…
br
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Dihybrid Crosses:
a cross that shows the possible offspring for two traits
BbRr x BbRr
BR
Fur Color:
B: Black
b: White
BR
Coat Texture:
R: Rough
r: Smooth
Br
Then, find
the possible
genotypes
of the
offspring
Br
bR
br
bR
br
The Academic Support Center @ Daytona State College (Science 65, Page 27 of 31)
Dihybrid Crosses:
a cross that shows the possible offspring for two traits
BR
Br
bR
br
BR
BBRR
BBRr
BbRR
BbRr
Br
BBRr
BBrr
BbRr
Bbrr
bR
BbRR
BbRr
bbRR
bbRr
br
BbRr
Bbrr
bbRr
bbrr
BbRr x BbRr
Fur Color:
B: Black
b: White
Coat Texture:
R: Rough
r: Smooth
The Academic Support Center @ Daytona State College (Science 65, Page 28 of 31)
How many of the
offspring would have a
black, rough coat?
How many of the
offspring would have a
black, smooth coat?
How many of the
offspring would have a
white, rough coat?
How many of the
offspring would have a
white, smooth coat?
BR
Br
bR
br
BR BBRR
BBRr
BbRR
BbRr
Br
BBRr
BBrr
BbRr
Bbrr
bR
BbRR
BbRr
bbRR
bbRr
br
BbRr
Bbrr
bbRr
bbrr
Fur Color:
Coat Texture:
B: Black
R: Rough
b: White
r: Smooth
The Academic Support Center @ Daytona State College (Science 65, Page 29 of 31)
How many of the
offspring would have
black, rough coat?
BR
How many of the
offspring would have a
black, smooth coat?
How many of the
offspring would have a
white, rough coat?
How many of the
offspring would have a
white, smooth coat?
Phenotypic Ratio
9:3:3:1
Br
bR
br
BR BBRR
BBRr
BbRR
BbRr
Br
BBRr
BBrr
BbRr
Bbrr
bR
BbRR
BbRr
bbRR
bbRr
br
BbRr
Bbrr
bbRr
bbrr
Fur Color:
Coat Texture:
B: Black
R: Rough
b: White
r: Smooth
The Academic Support Center @ Daytona State College (Science 65, Page 30 of 31)
Questions
Prepared by
K. Martin (Peer Tutor) & D. Leonard (Learning Specialist)
The Academic Support Center @ Daytona State College
http://www.daytonastate.edu/asc/ascsciencehandouts.html
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