BIOL 113 Questions and Answers A+
Graded (2025) PASSED
What .is .Mendel's .Law .of .Segregation? .- .CORRECT .ANSWER-The .two .forms .of
.a .gene .(alleles) .present .in .each .parent .segregate .independently.
What .experimental .results .led .to .the .formulation .of .Mendel's .Law .of
.Segregation? .- .CORRECT .ANSWER-Results .from .monohybrid .crosses .between
.true-breeding .individuals .differing .in .one .character, .where .all .F1 .progeny
.resembled .one .parent, .and .both .parental .traits .appeared .in .the .F2 .generation
.in .a .3:1 .ratio.
What .is .the .significance .of .dominant .and .recessive .traits .in .Mendelian
.inheritance? .- .CORRECT .ANSWER-One .trait .is .dominant .and .masks .the
.recessive .trait, .which .is .not .lost .in .the .F1 .generation.
What .is .Mendel's .Law .of .Independent .Assortment? .- .CORRECT .ANSWER-Each
.pair .of .alleles .assorts .independently .of .each .other .during .gamete .formation.
How .was .Mendel's .Law .of .Independent .Assortment .formulated? .- .CORRECT
.ANSWER-It .was .formulated .by .studying .the .inheritance .of .two .characters
.simultaneously .through .dihybrid .crosses, .resulting .in .a .9:3:3:1 .phenotypic
.ratio.
What .would .happen .if .independent .assortment .did .not .occur? .- .CORRECT
.ANSWER-The .alleles .for .two .traits .would .be .inherited .together, .resulting .in
.only .two .types .of .gametes .and .no .recombinants .in .the .F2 .generation.
How .does .segregation .of .alleles .account .for .the .outcome .of .a .monohybrid
.cross? .- .CORRECT .ANSWER-Each .organism .has .two .alleles .that .segregate
.during .gamete .formation, .leading .to .four .different .combinations .in .the
.offspring, .three .of .which .contain .the .dominant .allele.
What .is .a .testcross .and .how .is .it .used? .- .CORRECT .ANSWER-A .testcross
.determines .the .genotype .of .an .individual .with .a .dominant .phenotype .by
.crossing .it .with .a .homozygous .recessive .individual.
,What .are .the .expected .outcomes .of .a .testcross .if .the .dominant .phenotype
.individual .is .heterozygous? .- .CORRECT .ANSWER-The .F1 .progeny .would .show
.a .50-50 .outcome .of .two .phenotypes.
What .are .the .expected .outcomes .of .a .testcross .if .the .dominant .phenotype
.individual .is .homozygous? .- .CORRECT .ANSWER-The .F1 .progeny .would .be
.100% .the .dominant .phenotype.
How .do .you .combine .probabilities .to .solve .complex .genetic .problems? .-
.CORRECT .ANSWER-Multiply .the .individual .probabilities .for .each .trait.
What .are .the .key .events .of .interphase .in .meiosis? .- .CORRECT .ANSWER-
Chromosomes .replicate .into .homologous .pairs .to .form .a .diploid .cell.
What .happens .during .Meiosis .I? .- .CORRECT .ANSWER-Homologous
.chromosomes .separate .to .form .two .haploid .cells .with .replicated .chromosomes.
What .happens .during .Meiosis .II? .- .CORRECT .ANSWER-Sister .chromatids
.separate .into .haploid .cells .with .unreplicated .chromosomes.
What .are .the .main .differences .between .meiosis .and .mitosis? .- .CORRECT
.ANSWER-Mitosis .occurs .in .somatic .cells .with .one .division, .producing .two
.identical .diploid .cells; .meiosis .occurs .in .germ .line .cells .with .two .divisions,
.producing .four .non-identical .haploid .gametes.
What .is .unique .to .meiosis .that .is .not .found .in .mitosis? .- .CORRECT .ANSWER-
Synapsis, .the .pairing .of .homologous .chromosomes.
What .is .the .chromosomal .theory .of .inheritance? .- .CORRECT .ANSWER-Mendel's
.heritable .factors .(genes) .are .located .at .specific .positions .(loci) .on
.chromosomes, .which .undergo .segregation .and .independent .assortment.
How .do .Mendel's .Laws .relate .to .the .behavior .of .chromosomes .during .meiosis?
.- .CORRECT .ANSWER-Sutton .linked .chromosome .behavior .during .meiosis .to
.Mendel's .laws, .observing .that .chromosome .pairs .segregate .equally .into
.gametes .and .assort .independently.
What .explains .Mendel's .Law .of .Segregation .in .terms .of .chromosome .behavior?
.- .CORRECT .ANSWER-Each .allele .is .on .a .different .member .of .a .homologous
.pair .of .chromosomes .and .moves .to .opposite .poles .during .anaphase .I.
What .explains .Mendel's .Law .of .Independent .Assortment .in .terms .of
.chromosome .behavior? .- .CORRECT .ANSWER-Homologous .pairs .line .up
.randomly .on .the .metaphase .plate .during .meiosis .I, .leading .to .equal
.probabilities .of .genotype .combinations .in .gametes.
What .are .the .main .sources .of .genetic .variability .in .sexually .reproducing
.organisms? .- .CORRECT .ANSWER-Mutation, .independent .assortment, .crossing-
over, .random .fertilization.
, What .is .crossing .over .and .when .does .it .occur .during .meiosis? .- .CORRECT
.ANSWER-Crossing .over .is .the .process .of .genetic .recombination .that .occurs
.during .the .pachytene .phase .of .prophase .I, .where .homologous .chromosomes
.exchange .genetic .information .at .the .chiasma.
How .does .linkage .interfere .with .independent .assortment? .- .CORRECT
.ANSWER-Linked .genes .are .located .on .the .same .chromosome .and .tend .to .be
.inherited .together, .violating .the .principle .of .independent .assortment .during
.gamete .formation.
What .are .some .reasons .for .deviations .from .Mendelian .ratios? .- .CORRECT
.ANSWER-Sex-linkage, .incomplete .dominance, .co-dominance, .pleiotropy,
.polygenic .inheritance, .and .epistasis.
What .is .the .difference .between .incomplete .dominance .and .co-dominance? .-
.CORRECT .ANSWER-Incomplete .dominance .occurs .when .a .dominant .allele
.does .not .completely .mask .a .recessive .allele, .resulting .in .an .intermediate
.phenotype .(e.g., .snapdragon .flower .color). .Co-dominance .occurs .when .both
.alleles .are .expressed .distinctly .in .the .phenotype .(e.g., .ABO .blood .group
.system).
What .is .pleiotropy? .- .CORRECT .ANSWER-Pleiotropy .is .when .a .single .gene .has
.multiple .effects .on .the .phenotype, .such .as .a .pea .gene .affecting .both .flower
.and .seed .color.
What .is .polygenic .inheritance? .- .CORRECT .ANSWER-Polygenic .inheritance .is
.when .a .single .trait .is .determined .by .multiple .genes, .resulting .in .continuous
.variation .in .the .population.
Give .examples .of .polygenic .inheritance .in .humans. .- .CORRECT .ANSWER-
Height, .weight, .skin .pigmentation, .hair .color, .eye .color.
What .is .epistasis .and .how .does .it .affect .Mendelian .ratios .in .a .dihybrid .cross? .-
.CORRECT .ANSWER-Epistasis .occurs .when .one .gene .masks .or .modifies .the
.expression .of .another .gene, .leading .to .modified .ratios, .such .as .a .9:3:4 .ratio .in
.mice .coat .color.
Why .is .a .recessive .sex-linked .gene .always .expressed .in .male .Drosophila .or
.humans? .- .CORRECT .ANSWER-Males .have .only .one .X .chromosome, .so .a
.recessive .allele .on .the .X .is .expressed, .while .females .need .two .copies .of .the
.allele .for .expression.
What .are .the .steps .to .make .a .karyotype? .- .CORRECT .ANSWER-1. .Draw .blood
.and .culture .in .growth .medium. .2. .Add .phytohemagglutinin .to .stimulate .mitosis.
.3. .Treat .with .colcemid .to .stop .mitosis. .4. .Centrifuge .and .lyse .cells. .5. .Stain .and
.examine .chromosomes .under .a .microscope.
Graded (2025) PASSED
What .is .Mendel's .Law .of .Segregation? .- .CORRECT .ANSWER-The .two .forms .of
.a .gene .(alleles) .present .in .each .parent .segregate .independently.
What .experimental .results .led .to .the .formulation .of .Mendel's .Law .of
.Segregation? .- .CORRECT .ANSWER-Results .from .monohybrid .crosses .between
.true-breeding .individuals .differing .in .one .character, .where .all .F1 .progeny
.resembled .one .parent, .and .both .parental .traits .appeared .in .the .F2 .generation
.in .a .3:1 .ratio.
What .is .the .significance .of .dominant .and .recessive .traits .in .Mendelian
.inheritance? .- .CORRECT .ANSWER-One .trait .is .dominant .and .masks .the
.recessive .trait, .which .is .not .lost .in .the .F1 .generation.
What .is .Mendel's .Law .of .Independent .Assortment? .- .CORRECT .ANSWER-Each
.pair .of .alleles .assorts .independently .of .each .other .during .gamete .formation.
How .was .Mendel's .Law .of .Independent .Assortment .formulated? .- .CORRECT
.ANSWER-It .was .formulated .by .studying .the .inheritance .of .two .characters
.simultaneously .through .dihybrid .crosses, .resulting .in .a .9:3:3:1 .phenotypic
.ratio.
What .would .happen .if .independent .assortment .did .not .occur? .- .CORRECT
.ANSWER-The .alleles .for .two .traits .would .be .inherited .together, .resulting .in
.only .two .types .of .gametes .and .no .recombinants .in .the .F2 .generation.
How .does .segregation .of .alleles .account .for .the .outcome .of .a .monohybrid
.cross? .- .CORRECT .ANSWER-Each .organism .has .two .alleles .that .segregate
.during .gamete .formation, .leading .to .four .different .combinations .in .the
.offspring, .three .of .which .contain .the .dominant .allele.
What .is .a .testcross .and .how .is .it .used? .- .CORRECT .ANSWER-A .testcross
.determines .the .genotype .of .an .individual .with .a .dominant .phenotype .by
.crossing .it .with .a .homozygous .recessive .individual.
,What .are .the .expected .outcomes .of .a .testcross .if .the .dominant .phenotype
.individual .is .heterozygous? .- .CORRECT .ANSWER-The .F1 .progeny .would .show
.a .50-50 .outcome .of .two .phenotypes.
What .are .the .expected .outcomes .of .a .testcross .if .the .dominant .phenotype
.individual .is .homozygous? .- .CORRECT .ANSWER-The .F1 .progeny .would .be
.100% .the .dominant .phenotype.
How .do .you .combine .probabilities .to .solve .complex .genetic .problems? .-
.CORRECT .ANSWER-Multiply .the .individual .probabilities .for .each .trait.
What .are .the .key .events .of .interphase .in .meiosis? .- .CORRECT .ANSWER-
Chromosomes .replicate .into .homologous .pairs .to .form .a .diploid .cell.
What .happens .during .Meiosis .I? .- .CORRECT .ANSWER-Homologous
.chromosomes .separate .to .form .two .haploid .cells .with .replicated .chromosomes.
What .happens .during .Meiosis .II? .- .CORRECT .ANSWER-Sister .chromatids
.separate .into .haploid .cells .with .unreplicated .chromosomes.
What .are .the .main .differences .between .meiosis .and .mitosis? .- .CORRECT
.ANSWER-Mitosis .occurs .in .somatic .cells .with .one .division, .producing .two
.identical .diploid .cells; .meiosis .occurs .in .germ .line .cells .with .two .divisions,
.producing .four .non-identical .haploid .gametes.
What .is .unique .to .meiosis .that .is .not .found .in .mitosis? .- .CORRECT .ANSWER-
Synapsis, .the .pairing .of .homologous .chromosomes.
What .is .the .chromosomal .theory .of .inheritance? .- .CORRECT .ANSWER-Mendel's
.heritable .factors .(genes) .are .located .at .specific .positions .(loci) .on
.chromosomes, .which .undergo .segregation .and .independent .assortment.
How .do .Mendel's .Laws .relate .to .the .behavior .of .chromosomes .during .meiosis?
.- .CORRECT .ANSWER-Sutton .linked .chromosome .behavior .during .meiosis .to
.Mendel's .laws, .observing .that .chromosome .pairs .segregate .equally .into
.gametes .and .assort .independently.
What .explains .Mendel's .Law .of .Segregation .in .terms .of .chromosome .behavior?
.- .CORRECT .ANSWER-Each .allele .is .on .a .different .member .of .a .homologous
.pair .of .chromosomes .and .moves .to .opposite .poles .during .anaphase .I.
What .explains .Mendel's .Law .of .Independent .Assortment .in .terms .of
.chromosome .behavior? .- .CORRECT .ANSWER-Homologous .pairs .line .up
.randomly .on .the .metaphase .plate .during .meiosis .I, .leading .to .equal
.probabilities .of .genotype .combinations .in .gametes.
What .are .the .main .sources .of .genetic .variability .in .sexually .reproducing
.organisms? .- .CORRECT .ANSWER-Mutation, .independent .assortment, .crossing-
over, .random .fertilization.
, What .is .crossing .over .and .when .does .it .occur .during .meiosis? .- .CORRECT
.ANSWER-Crossing .over .is .the .process .of .genetic .recombination .that .occurs
.during .the .pachytene .phase .of .prophase .I, .where .homologous .chromosomes
.exchange .genetic .information .at .the .chiasma.
How .does .linkage .interfere .with .independent .assortment? .- .CORRECT
.ANSWER-Linked .genes .are .located .on .the .same .chromosome .and .tend .to .be
.inherited .together, .violating .the .principle .of .independent .assortment .during
.gamete .formation.
What .are .some .reasons .for .deviations .from .Mendelian .ratios? .- .CORRECT
.ANSWER-Sex-linkage, .incomplete .dominance, .co-dominance, .pleiotropy,
.polygenic .inheritance, .and .epistasis.
What .is .the .difference .between .incomplete .dominance .and .co-dominance? .-
.CORRECT .ANSWER-Incomplete .dominance .occurs .when .a .dominant .allele
.does .not .completely .mask .a .recessive .allele, .resulting .in .an .intermediate
.phenotype .(e.g., .snapdragon .flower .color). .Co-dominance .occurs .when .both
.alleles .are .expressed .distinctly .in .the .phenotype .(e.g., .ABO .blood .group
.system).
What .is .pleiotropy? .- .CORRECT .ANSWER-Pleiotropy .is .when .a .single .gene .has
.multiple .effects .on .the .phenotype, .such .as .a .pea .gene .affecting .both .flower
.and .seed .color.
What .is .polygenic .inheritance? .- .CORRECT .ANSWER-Polygenic .inheritance .is
.when .a .single .trait .is .determined .by .multiple .genes, .resulting .in .continuous
.variation .in .the .population.
Give .examples .of .polygenic .inheritance .in .humans. .- .CORRECT .ANSWER-
Height, .weight, .skin .pigmentation, .hair .color, .eye .color.
What .is .epistasis .and .how .does .it .affect .Mendelian .ratios .in .a .dihybrid .cross? .-
.CORRECT .ANSWER-Epistasis .occurs .when .one .gene .masks .or .modifies .the
.expression .of .another .gene, .leading .to .modified .ratios, .such .as .a .9:3:4 .ratio .in
.mice .coat .color.
Why .is .a .recessive .sex-linked .gene .always .expressed .in .male .Drosophila .or
.humans? .- .CORRECT .ANSWER-Males .have .only .one .X .chromosome, .so .a
.recessive .allele .on .the .X .is .expressed, .while .females .need .two .copies .of .the
.allele .for .expression.
What .are .the .steps .to .make .a .karyotype? .- .CORRECT .ANSWER-1. .Draw .blood
.and .culture .in .growth .medium. .2. .Add .phytohemagglutinin .to .stimulate .mitosis.
.3. .Treat .with .colcemid .to .stop .mitosis. .4. .Centrifuge .and .lyse .cells. .5. .Stain .and
.examine .chromosomes .under .a .microscope.
