UCI BIO 93 EXAM SCRIPT 2025/2026 QUESTIONS WITH
ANSWERS GRADED A+
✔✔What happens in prophase 1? - ✔✔The chromosomes condense, the nuclear
envelope breaks down, chromosomes cross over, and meiotic spindle forms.
✔✔What happens in metaphase 1? - ✔✔the pairs of homologous chromosomes are
now tightly condensed and coiled and become arranged on the metaphase plate.
✔✔What happens in anaphase 1? - ✔✔the pairs of chromosomes are pulled apart by
the spindle fibers (microtubules).
✔✔What happens in Telophase 1 and cytokinesis? - ✔✔The homologous chromosome
pairs complete their migration to the two poles as a result of the action of the spindle.
Now a haploid set of chromosomes is at each pole, with each chromosome still having
two chromatids. A nuclear envelope reforms around each chromosome set, the spindle
disappears, and cytokinesis follows.
✔✔What happens during meiosis 2? - ✔✔sister chromatids separate.
✔✔What happens in prophase 2 of meiosis? - ✔✔A new spindle forms around the
chromosomes.
✔✔What happens in metaphase 2 of meiosis? - ✔✔Metaphase 2 chromosomes line up
at the equator.
✔✔What happens in anaphase 2 of meiosis? - ✔✔Centromeres divide chromatids move
to opposite poles of the cells.
✔✔What happens during telophase 2 of meiosis? - ✔✔A nuclear envelope forms
around each set of chromosomes and the cytoplasm divides.
✔✔What makes meiosis a unique form of cell division - ✔✔Synapsis and crossing over
-- occurs in prophase 1, pairing up of homologous chromosomes, homologous
chromosomes cross over and exchange corresponding genetic information (the DNA
exchanged contain the same genes, but may have different alleles).
✔✔How does meiosis increase genetic variability? - ✔✔Independent assortment
(meiosis 1 -- homologous chromosomes separate independently), crossing over
(genetic recombination, prophase 1), and random fertilization (any egg can join with any
sperm -- most effective way to obtain genetic variability).
✔✔What is the law of segregation? - ✔✔Alleles coding for the same trait separate
independently during gamete formation.
,✔✔What is non-disjunction? - ✔✔When homologous chromosomes or sister chromatids
do not separate properly.
✔✔What is a character? - ✔✔An observable heritable feature that may vary among
individuals. Ex: flower color.
✔✔What is a trait? - ✔✔One of two or more detectable variants in a genetic character.
Ex: purple flower color/white flower color.
✔✔What does the blending theory state? Is this true? - ✔✔The offspring is a blend of
both parents (ex: a tall mom giraffe + a short dad giraffe = a medium height giraffe).
This is not true because if so, every single offspring would look the same.
✔✔What does particulate inheritance state? Is this true? - ✔✔Different traits are
inherited in separate distinct units (genes) (ex: F1 and F2 generations). This is always
true because of not every offspring looks the exact same (has the exact same genetics).
✔✔What is an allele? - ✔✔An alternate form of a gene (ex: the gene that determines
hair color).
✔✔What does the Law of Segregation state? - ✔✔The Law of Segregation states that
two alleles in a pair segregate into different gametes. (this deals with separation of
homologous pairs in Meiosis 1 producing haploid daughter cells after Meiosis 1).
✔✔What does Independent Assortment state? - ✔✔Each pair of alleles
assort/segregate separately from each other during gamete formation. AKA no gene
linkage.
✔✔What did Mendelian Genetics assume? - ✔✔Gregor Mendel, through his work on
pea plants, discovered the fundamental laws of inheritance. He deduced that genes
come in pairs and are inherited as distinct units, one from each parent. Mendel tracked
the segregation of parental genes and their appearance in the offspring as dominant or
recessive traits.
✔✔What is a dominant allele? - ✔✔An allele that is fully expressed in the phenotype of
the heterozygote.
✔✔What is a recessive allele? - ✔✔An allele whose phenotypic effect is not observed in
the heterozygote.
✔✔What is a test cross? - ✔✔A method of determining the genotype of an individual
with a dominant phenotype. We cannot know the genotype of an organism if they
express the dominant trait because they can be either homozygous dominant or
, heterozygous. Process: cross the individual with an unknown genotype to a
homozygous recessive individual and observe the phenotype of the progeny.
✔✔What is incomplete dominance? - ✔✔When one trait is not completely dominant
over the other. Ex: crossing red and white flowers leads to pink flowers when
heterozygous instead of the red allele completely dominating over the white allele.
✔✔What is co-dominance? - ✔✔When two alleles affect the phenotype in
distinguishable ways. Ex: blood type -- Ia and Ib are both dominant over i. Therefore, Ia
and Ib are co-dominant to i.
✔✔What is pleiotropy? - ✔✔When one gene affects more than one phenotype. Ex:
sickle cell anemia produces multiple symptoms (symptoms would be equivalent to
phenotypes).
✔✔What is epistasis? - ✔✔When a gene at one locus alters the expression of a gene at
another locus. Ex: gene 1 determines black or brown coat color and gene 2 determines
if pigment is deposited.
✔✔What is polygenic inheritance? - ✔✔When multiple genes affect a phenotype and
phenotypes are in a range or spectrum. This range is called a normal distribution. Most
likely phenotype = immediate phenotype and the least likely phenotype = the extreme
phenotype. Shaped like a bell curve -- immediate in middle with high peak and extreme
on both ends.
✔✔What can impact the phenotype of an organism? - ✔✔Environment (ex: hydrangeas
-- the acidity of the soil determines their color no matter their alleles), diet, epigenetics,
etc.
✔✔Is albinism dominant or recessive? - ✔✔recessive.
✔✔Is Achondroplasia (dwarfism) dominant or recessive? - ✔✔dominant.
✔✔Is Huntington's disease dominant or recessive? - ✔✔dominant.
✔✔What did Thomas Hunt Morgan study/discover? - ✔✔Morgan studied drosophila
(fruit flies) and their eye color. He discovered that certain genes such as fly eye color
are on specific chromosomes (ex: the X chromosome). This proved that genes are
located on specific chromosomes.
✔✔What is a wild type? - ✔✔A normal, unaffected phenotype.
✔✔What is a parental phenotype? - ✔✔Phenotype of parent generation.
ANSWERS GRADED A+
✔✔What happens in prophase 1? - ✔✔The chromosomes condense, the nuclear
envelope breaks down, chromosomes cross over, and meiotic spindle forms.
✔✔What happens in metaphase 1? - ✔✔the pairs of homologous chromosomes are
now tightly condensed and coiled and become arranged on the metaphase plate.
✔✔What happens in anaphase 1? - ✔✔the pairs of chromosomes are pulled apart by
the spindle fibers (microtubules).
✔✔What happens in Telophase 1 and cytokinesis? - ✔✔The homologous chromosome
pairs complete their migration to the two poles as a result of the action of the spindle.
Now a haploid set of chromosomes is at each pole, with each chromosome still having
two chromatids. A nuclear envelope reforms around each chromosome set, the spindle
disappears, and cytokinesis follows.
✔✔What happens during meiosis 2? - ✔✔sister chromatids separate.
✔✔What happens in prophase 2 of meiosis? - ✔✔A new spindle forms around the
chromosomes.
✔✔What happens in metaphase 2 of meiosis? - ✔✔Metaphase 2 chromosomes line up
at the equator.
✔✔What happens in anaphase 2 of meiosis? - ✔✔Centromeres divide chromatids move
to opposite poles of the cells.
✔✔What happens during telophase 2 of meiosis? - ✔✔A nuclear envelope forms
around each set of chromosomes and the cytoplasm divides.
✔✔What makes meiosis a unique form of cell division - ✔✔Synapsis and crossing over
-- occurs in prophase 1, pairing up of homologous chromosomes, homologous
chromosomes cross over and exchange corresponding genetic information (the DNA
exchanged contain the same genes, but may have different alleles).
✔✔How does meiosis increase genetic variability? - ✔✔Independent assortment
(meiosis 1 -- homologous chromosomes separate independently), crossing over
(genetic recombination, prophase 1), and random fertilization (any egg can join with any
sperm -- most effective way to obtain genetic variability).
✔✔What is the law of segregation? - ✔✔Alleles coding for the same trait separate
independently during gamete formation.
,✔✔What is non-disjunction? - ✔✔When homologous chromosomes or sister chromatids
do not separate properly.
✔✔What is a character? - ✔✔An observable heritable feature that may vary among
individuals. Ex: flower color.
✔✔What is a trait? - ✔✔One of two or more detectable variants in a genetic character.
Ex: purple flower color/white flower color.
✔✔What does the blending theory state? Is this true? - ✔✔The offspring is a blend of
both parents (ex: a tall mom giraffe + a short dad giraffe = a medium height giraffe).
This is not true because if so, every single offspring would look the same.
✔✔What does particulate inheritance state? Is this true? - ✔✔Different traits are
inherited in separate distinct units (genes) (ex: F1 and F2 generations). This is always
true because of not every offspring looks the exact same (has the exact same genetics).
✔✔What is an allele? - ✔✔An alternate form of a gene (ex: the gene that determines
hair color).
✔✔What does the Law of Segregation state? - ✔✔The Law of Segregation states that
two alleles in a pair segregate into different gametes. (this deals with separation of
homologous pairs in Meiosis 1 producing haploid daughter cells after Meiosis 1).
✔✔What does Independent Assortment state? - ✔✔Each pair of alleles
assort/segregate separately from each other during gamete formation. AKA no gene
linkage.
✔✔What did Mendelian Genetics assume? - ✔✔Gregor Mendel, through his work on
pea plants, discovered the fundamental laws of inheritance. He deduced that genes
come in pairs and are inherited as distinct units, one from each parent. Mendel tracked
the segregation of parental genes and their appearance in the offspring as dominant or
recessive traits.
✔✔What is a dominant allele? - ✔✔An allele that is fully expressed in the phenotype of
the heterozygote.
✔✔What is a recessive allele? - ✔✔An allele whose phenotypic effect is not observed in
the heterozygote.
✔✔What is a test cross? - ✔✔A method of determining the genotype of an individual
with a dominant phenotype. We cannot know the genotype of an organism if they
express the dominant trait because they can be either homozygous dominant or
, heterozygous. Process: cross the individual with an unknown genotype to a
homozygous recessive individual and observe the phenotype of the progeny.
✔✔What is incomplete dominance? - ✔✔When one trait is not completely dominant
over the other. Ex: crossing red and white flowers leads to pink flowers when
heterozygous instead of the red allele completely dominating over the white allele.
✔✔What is co-dominance? - ✔✔When two alleles affect the phenotype in
distinguishable ways. Ex: blood type -- Ia and Ib are both dominant over i. Therefore, Ia
and Ib are co-dominant to i.
✔✔What is pleiotropy? - ✔✔When one gene affects more than one phenotype. Ex:
sickle cell anemia produces multiple symptoms (symptoms would be equivalent to
phenotypes).
✔✔What is epistasis? - ✔✔When a gene at one locus alters the expression of a gene at
another locus. Ex: gene 1 determines black or brown coat color and gene 2 determines
if pigment is deposited.
✔✔What is polygenic inheritance? - ✔✔When multiple genes affect a phenotype and
phenotypes are in a range or spectrum. This range is called a normal distribution. Most
likely phenotype = immediate phenotype and the least likely phenotype = the extreme
phenotype. Shaped like a bell curve -- immediate in middle with high peak and extreme
on both ends.
✔✔What can impact the phenotype of an organism? - ✔✔Environment (ex: hydrangeas
-- the acidity of the soil determines their color no matter their alleles), diet, epigenetics,
etc.
✔✔Is albinism dominant or recessive? - ✔✔recessive.
✔✔Is Achondroplasia (dwarfism) dominant or recessive? - ✔✔dominant.
✔✔Is Huntington's disease dominant or recessive? - ✔✔dominant.
✔✔What did Thomas Hunt Morgan study/discover? - ✔✔Morgan studied drosophila
(fruit flies) and their eye color. He discovered that certain genes such as fly eye color
are on specific chromosomes (ex: the X chromosome). This proved that genes are
located on specific chromosomes.
✔✔What is a wild type? - ✔✔A normal, unaffected phenotype.
✔✔What is a parental phenotype? - ✔✔Phenotype of parent generation.
