FCB Spring 2026 Study Guide Module 2
Class 1 -
1. Sexual reproduction has benefits over asexual reproduction.
● Asexual reproduction produces offspring that are genetically identical to the
parent and to each other.
● Sexual reproduction mixes up the genes of the parents to produce genetically
variable offspring.
● Increased variability in genotype and phenotype in a population increases the
probability that some of the individuals will be better adapted to survive if the
environmental conditions change.
● Evolution by natural selection acts on the variation in a population. More
variability means faster evolution.
2. Sexual reproduction involves the combination of two haploid cells (gametes) into one
diploid cell (zygote).
● Haploid cells have one copy of each chromosome.
● Diploid cells have two copies of each chromosome, one from each parent.
● Gametes include eggs and sperm.
3. 2 homologous chromosomes have the same genes, however the exact sequences may
be different due to the different environmental histories and genetic origins of the
parents. Genetic variability arises from which homologous chromosome a parent passes
on to its offspring via the haploid gamete.
● Corresponding genes on homologous chromosomes are called alleles.
4. Meiosis is the process of producing haploid gametes from diploid cells.
● Meiosis occurs only in germline cells, not somatic cells.
● In meiosis, the genome is duplicated once, then divided two times.
● Meiosis produces non-identical haploid cells.
● Process
1. DNA is duplicated. All chromosomes go from 1-strand to 2-strands.
2. Homologous chromosomes pair up.
3. Crossing over occurs between sister chromatids of homologous
chromosomes.
4. Homologous chromosomes are pulled apart. Cells divide.
5. Each daughter cell now has only one set of chromosomes, but they are
still 2-strands. Chromosomes line up.
6. Sister chromatids are pulled apart. Cells divide.
5. Genetic abnormalities arise when meiosis is not completed correctly
, ● Nondisjunction: Homologous chromosomes do not separate before the
first cell division.
● Aneuploidy: Abnormal number of chromosomes (more or less than usual)
in a cell.
6. Gregor Mendel made important discoveries about sexual reproduction by using pea
plants as a model organism
● Pea plants reproduce sexually. Pollen carries the male gametes. The female
gametes are inside the flower. Each pea bean/seed is a new juvenile individual
pea plant.
● Pea plants can fertilize themselves, or cross pollinate another individual.
● Mendel conducted this experiment by breeding/crossing specific pea plants and
observing the traits of the resulting offspring. He then compared the traits of the
parents to the traits of the offspring.
● A key component of Mendel’s experiments was crossing plants from different
generations.
○ F1: The offspring resulting from the first cross of parent plants.
○ F2: The offspring resulting from the crossing of a plants from the F1
generation with itself.
7. Genotype is the set of alleles present in the genome of an individual. Phenotype is the
set of observed traits in an individual.
● One cannot always determine the genotype of an individual based on the
phenotype.
● Heterozygotes have mixed genotypes, but may only express one phenotype.
8. Gregor Mendel’s experiments with pea plants showed dominant and recessive alleles
existed
9. Mendel’s Law of Segregation:
○ Each (diploid) parent has in its genome 2 alleles for every gene.
○ During (sexual) reproduction, each parent gives only 1 of those alleles to its
offspring.
○ The probability of giving one allele to the offspring is equal to the probability of
giving the other allele to the offspring.
○ This occurs because homologous chromosomes line up at random during
meiosis and there is no requirement for which homologous chromosome gets
pulled to which of the first two daughter cells during the first division.
10. A Punnet square is a chart used to determine all possible combinations of alleles that
may be present in the offspring during a single event of sexual reproduction between two
parent organisms.
○ Based on the equal-probability principle of Mendel’s Law of Segregation, each
parent is equally likely to provide either of its two alleles to the offspring.
, ○ The Punnet square allows us to organize all possible allele combinations in the
offspring.
11. Mendel’s Law of Independent Assortment:
○ How the alleles for one trait get assigned to gametes does not affect how the
alleles for other traits get assigned.
○ Example: Alleles for seed color and seed shape assort independently. Just
because the offspring received the allele for seed color from its maternal parent
does not mean it has to receive the allele for seed shape from its maternal
parent.
○ This occurs because alleles are easily swapped between sister chromatids of
homologous chromosomes during meiosis.
○ Punnett squares can still be used to model “dihybrid crosses”, though the
complexity increases.
12. Mendel’s laws are not entirely true for all sexually reproducing organisms all of the time.
○ Sometimes, nondisjunction occurs during meiosis, breaking Mendel’s Law of
Segregation.
○ Sometimes alleles are too close together on the same chromosome to be easily
separated during crossing-over events. This leads to “linked traits” and breaks
Mendel’s Law of Independent Assortment.
○ Sometimes heterozygotes do not display dominant/recessive phenotypes. Hybrid
offspring may express both traits at the same time, or a blend of both traits.
Class 2-
1. Scientists use forward and reverse genetic approaches to study the function of genes in
model organisms.
● Goal: Determine the function of a gene in an organism.
● Forward genetics approach:
1. Gather (or create) mutant individuals that display the phenotype of
interest (positive for disease, lack of color, missing organ, etc).
2. Screen the genomes of the mutant individuals and look for a gene
mutation that all of the individuals share.
3. If all of the individuals with the phenotype of interest have a mutation in
the same gene, this gene is likely responsible for the phenotype.
● Reverse genetics approach:
1. Select a gene to investigate in a model organism.
2. Mutate that specific gene of interest using chemicals or molecular biology
techniques. Usually this gene is inactivated (“knocked-out”).
3. Observe the phenotype of the individuals with the mutated gene of
interest.
Class 1 -
1. Sexual reproduction has benefits over asexual reproduction.
● Asexual reproduction produces offspring that are genetically identical to the
parent and to each other.
● Sexual reproduction mixes up the genes of the parents to produce genetically
variable offspring.
● Increased variability in genotype and phenotype in a population increases the
probability that some of the individuals will be better adapted to survive if the
environmental conditions change.
● Evolution by natural selection acts on the variation in a population. More
variability means faster evolution.
2. Sexual reproduction involves the combination of two haploid cells (gametes) into one
diploid cell (zygote).
● Haploid cells have one copy of each chromosome.
● Diploid cells have two copies of each chromosome, one from each parent.
● Gametes include eggs and sperm.
3. 2 homologous chromosomes have the same genes, however the exact sequences may
be different due to the different environmental histories and genetic origins of the
parents. Genetic variability arises from which homologous chromosome a parent passes
on to its offspring via the haploid gamete.
● Corresponding genes on homologous chromosomes are called alleles.
4. Meiosis is the process of producing haploid gametes from diploid cells.
● Meiosis occurs only in germline cells, not somatic cells.
● In meiosis, the genome is duplicated once, then divided two times.
● Meiosis produces non-identical haploid cells.
● Process
1. DNA is duplicated. All chromosomes go from 1-strand to 2-strands.
2. Homologous chromosomes pair up.
3. Crossing over occurs between sister chromatids of homologous
chromosomes.
4. Homologous chromosomes are pulled apart. Cells divide.
5. Each daughter cell now has only one set of chromosomes, but they are
still 2-strands. Chromosomes line up.
6. Sister chromatids are pulled apart. Cells divide.
5. Genetic abnormalities arise when meiosis is not completed correctly
, ● Nondisjunction: Homologous chromosomes do not separate before the
first cell division.
● Aneuploidy: Abnormal number of chromosomes (more or less than usual)
in a cell.
6. Gregor Mendel made important discoveries about sexual reproduction by using pea
plants as a model organism
● Pea plants reproduce sexually. Pollen carries the male gametes. The female
gametes are inside the flower. Each pea bean/seed is a new juvenile individual
pea plant.
● Pea plants can fertilize themselves, or cross pollinate another individual.
● Mendel conducted this experiment by breeding/crossing specific pea plants and
observing the traits of the resulting offspring. He then compared the traits of the
parents to the traits of the offspring.
● A key component of Mendel’s experiments was crossing plants from different
generations.
○ F1: The offspring resulting from the first cross of parent plants.
○ F2: The offspring resulting from the crossing of a plants from the F1
generation with itself.
7. Genotype is the set of alleles present in the genome of an individual. Phenotype is the
set of observed traits in an individual.
● One cannot always determine the genotype of an individual based on the
phenotype.
● Heterozygotes have mixed genotypes, but may only express one phenotype.
8. Gregor Mendel’s experiments with pea plants showed dominant and recessive alleles
existed
9. Mendel’s Law of Segregation:
○ Each (diploid) parent has in its genome 2 alleles for every gene.
○ During (sexual) reproduction, each parent gives only 1 of those alleles to its
offspring.
○ The probability of giving one allele to the offspring is equal to the probability of
giving the other allele to the offspring.
○ This occurs because homologous chromosomes line up at random during
meiosis and there is no requirement for which homologous chromosome gets
pulled to which of the first two daughter cells during the first division.
10. A Punnet square is a chart used to determine all possible combinations of alleles that
may be present in the offspring during a single event of sexual reproduction between two
parent organisms.
○ Based on the equal-probability principle of Mendel’s Law of Segregation, each
parent is equally likely to provide either of its two alleles to the offspring.
, ○ The Punnet square allows us to organize all possible allele combinations in the
offspring.
11. Mendel’s Law of Independent Assortment:
○ How the alleles for one trait get assigned to gametes does not affect how the
alleles for other traits get assigned.
○ Example: Alleles for seed color and seed shape assort independently. Just
because the offspring received the allele for seed color from its maternal parent
does not mean it has to receive the allele for seed shape from its maternal
parent.
○ This occurs because alleles are easily swapped between sister chromatids of
homologous chromosomes during meiosis.
○ Punnett squares can still be used to model “dihybrid crosses”, though the
complexity increases.
12. Mendel’s laws are not entirely true for all sexually reproducing organisms all of the time.
○ Sometimes, nondisjunction occurs during meiosis, breaking Mendel’s Law of
Segregation.
○ Sometimes alleles are too close together on the same chromosome to be easily
separated during crossing-over events. This leads to “linked traits” and breaks
Mendel’s Law of Independent Assortment.
○ Sometimes heterozygotes do not display dominant/recessive phenotypes. Hybrid
offspring may express both traits at the same time, or a blend of both traits.
Class 2-
1. Scientists use forward and reverse genetic approaches to study the function of genes in
model organisms.
● Goal: Determine the function of a gene in an organism.
● Forward genetics approach:
1. Gather (or create) mutant individuals that display the phenotype of
interest (positive for disease, lack of color, missing organ, etc).
2. Screen the genomes of the mutant individuals and look for a gene
mutation that all of the individuals share.
3. If all of the individuals with the phenotype of interest have a mutation in
the same gene, this gene is likely responsible for the phenotype.
● Reverse genetics approach:
1. Select a gene to investigate in a model organism.
2. Mutate that specific gene of interest using chemicals or molecular biology
techniques. Usually this gene is inactivated (“knocked-out”).
3. Observe the phenotype of the individuals with the mutated gene of
interest.
