BIOLOGY 1107: MENDEL AND
INHERITANCE (CHAPTER 11 & 12)
How are Genes passed along? - Correct Answers -- The "blending" hypothesis is the
idea that genetic material from the two parents blends together (the way blue and yellow
paint blend to make green)
- The "particulate" hypothesis is the idea that parents pass on discrete heritable units
(genes)
Mendel documented a particulate mechanism
NOTE:
- Parents are going to pass specific
"Blending" Hypothesis - Correct Answers -The idea that genetic material contributed by
the two parents mixes, just as blue and yellow paints blend to make green.
NOTE:
- It predicted that over many generations a freely mating population will give rise to a
uniform population of individuals—something we don't see.
- The blending hypothesis also fails to explain how traits can reappear after skipping a
generation.
- Both the male and female genes blended together
- Think: Think of blending two colors of paint together
"Particulate" Hypothesis - Correct Answers -Parents pass on discrete heritable units—
genes—that retain their separate identities in offspring.
NOTE:
- An organism's collection of genes is like a deck of cards.
- Like cards, genes can be shuffled and passed along, generation after generation, in
undiluted form.
- Mendel documented a particulate mechanism through his experiments with garden
peas
,- It passes along the discrete heritable gene
Mendel's Experiment - Correct Answers -- Mendel - scientific approach to identify 2 laws
of inheritance:
- Discovered basic principles of heredity by breeding garden peas in planned
experiments
- Peas have a specific variety of traits or characters ➝ selected two specific traits
- He could strictly control mating between plants
- Used varieties that were true-breeding ➝ mated these in process called hybridization
• True-breeding parents = P generation
• Hybrid offspring of P generation = F1 generation
• F1 individuals self-pollinate or cross-pollinate with F1 hybrids = F2 generation
NOTE:
- Mendel chose to work with peas because there are available in many varieties with
distinct heritable features, or characters (such as flower color); character variants (such
as purple or white flowers) are called traits
- He also chose to track only those characters that occurred in two distinct, alternative
forms
Character - Correct Answers -A heritable feature that varies among individuals
NOTE:
- Example: Flower color
Trait - Correct Answers -Each variant for a character
NOTE:
- Example: Purple or white color for flower
Two Laws of Inheritance - Correct Answers -1. Law of Segregation
2. Law of Independent Assortment
Law of Segregation - Correct Answers -Mendel's first law, stating that the two alleles in
a pair segregate (separate from each other) into different gametes during gamete
formation.
,Law of Independent Assortment - Correct Answers -Mendel's second law, stating that
each pair of alleles segregates, or assorts, independently of each other pair during
gamete formation; applies when genes for two characters are located on different pairs
of homologous chromosomes or when they are far enough apart on the same
chromosome to behave as though they are on different chromosomes.
True breeding - Correct Answers -Referring to organisms that produce offspring of the
same variety over many generations of self-pollination.
NOTE:
- Example: Over many generations of self-pollination, these plants had reproduced only
the same variety as the parent plant
- Example: A plant with purple flowers is true-breeding if the seeds produced by self-
pollination in successive generations all give rise to plants that also have purple flowers.
- Example: The pea plant is the true parents. You get a hybrid offspring
- P generation - grandparents
- F1 generation - Parents
- F2 generation - You!
Hybridization - Correct Answers -In genetics, the mating, or crossing, of two true-
breeding varieties.
P generation (parental generation) - Correct Answers -True-breeding parents
NOTE:
- The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are
derived in studies of inheritance.
- (P stands for parental.)
F1 generation (first filial "son" generation) - Correct Answers -The first filial, hybrid
(heterozygous) offspring arising from a parental (P generation) cross.
F2 generation (second filial generation) - Correct Answers -The offspring resulting from
interbreeding (or self-pollination) of the hybrid F1 generation.
NOTE:
-
Law of Segregation - Correct Answers -- Mendel observed the same pattern of
inheritance in six other pea plant characters, each represented by two traits
, - What Mendel called a "heritable factor" is what we now call a gene
- When Mendel crossed contrasting, true-breeding white- and purple-flowered pea
plants, all of the F1 hybrids were purple
• Crossed the F1 hybrids, many of the F2 plants had purple flowers, but some had
white
• Mendel discovered a ratio of about three to one, purple to white flowers, in the F2
generation
- Felt the heritable factor for white flowers was hidden or masked in presence of purple-
flower factor
• Purple flower color a dominant trait and white flower color a recessive trait
- Developed a model to explain 3:1 inheritance pattern observed in F2 offspring
NOTE:
- Example: All the F1 plants were purple. When they were self or crossed breed they
showed three purple flowers and one white flower.
- Purple flowers are the dominate trait.
- White flowers are the recessive trait
-
Dominant trait - Correct Answers -A genetic trait is considered dominant if it is
expressed in a person who has only one copy of the gene associated with the trait.
NOTE:
- A genetic factor that blocks another genetic factor
Recessive trait - Correct Answers -A trait that reappears in the second generation after
disappearing in the first generation when parents with different traits are bred.
The F2 generation always produced a - Correct Answers -3:1 ratio
NOTE:
- The dominant trait is present three times as often as the recessive trait.
- Mendel coined two terms to describe the relationship of the two phenotypes based on
the F1 and F2 phenotypes.
- The hereditary determinants are of a particulate nature.
INHERITANCE (CHAPTER 11 & 12)
How are Genes passed along? - Correct Answers -- The "blending" hypothesis is the
idea that genetic material from the two parents blends together (the way blue and yellow
paint blend to make green)
- The "particulate" hypothesis is the idea that parents pass on discrete heritable units
(genes)
Mendel documented a particulate mechanism
NOTE:
- Parents are going to pass specific
"Blending" Hypothesis - Correct Answers -The idea that genetic material contributed by
the two parents mixes, just as blue and yellow paints blend to make green.
NOTE:
- It predicted that over many generations a freely mating population will give rise to a
uniform population of individuals—something we don't see.
- The blending hypothesis also fails to explain how traits can reappear after skipping a
generation.
- Both the male and female genes blended together
- Think: Think of blending two colors of paint together
"Particulate" Hypothesis - Correct Answers -Parents pass on discrete heritable units—
genes—that retain their separate identities in offspring.
NOTE:
- An organism's collection of genes is like a deck of cards.
- Like cards, genes can be shuffled and passed along, generation after generation, in
undiluted form.
- Mendel documented a particulate mechanism through his experiments with garden
peas
,- It passes along the discrete heritable gene
Mendel's Experiment - Correct Answers -- Mendel - scientific approach to identify 2 laws
of inheritance:
- Discovered basic principles of heredity by breeding garden peas in planned
experiments
- Peas have a specific variety of traits or characters ➝ selected two specific traits
- He could strictly control mating between plants
- Used varieties that were true-breeding ➝ mated these in process called hybridization
• True-breeding parents = P generation
• Hybrid offspring of P generation = F1 generation
• F1 individuals self-pollinate or cross-pollinate with F1 hybrids = F2 generation
NOTE:
- Mendel chose to work with peas because there are available in many varieties with
distinct heritable features, or characters (such as flower color); character variants (such
as purple or white flowers) are called traits
- He also chose to track only those characters that occurred in two distinct, alternative
forms
Character - Correct Answers -A heritable feature that varies among individuals
NOTE:
- Example: Flower color
Trait - Correct Answers -Each variant for a character
NOTE:
- Example: Purple or white color for flower
Two Laws of Inheritance - Correct Answers -1. Law of Segregation
2. Law of Independent Assortment
Law of Segregation - Correct Answers -Mendel's first law, stating that the two alleles in
a pair segregate (separate from each other) into different gametes during gamete
formation.
,Law of Independent Assortment - Correct Answers -Mendel's second law, stating that
each pair of alleles segregates, or assorts, independently of each other pair during
gamete formation; applies when genes for two characters are located on different pairs
of homologous chromosomes or when they are far enough apart on the same
chromosome to behave as though they are on different chromosomes.
True breeding - Correct Answers -Referring to organisms that produce offspring of the
same variety over many generations of self-pollination.
NOTE:
- Example: Over many generations of self-pollination, these plants had reproduced only
the same variety as the parent plant
- Example: A plant with purple flowers is true-breeding if the seeds produced by self-
pollination in successive generations all give rise to plants that also have purple flowers.
- Example: The pea plant is the true parents. You get a hybrid offspring
- P generation - grandparents
- F1 generation - Parents
- F2 generation - You!
Hybridization - Correct Answers -In genetics, the mating, or crossing, of two true-
breeding varieties.
P generation (parental generation) - Correct Answers -True-breeding parents
NOTE:
- The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are
derived in studies of inheritance.
- (P stands for parental.)
F1 generation (first filial "son" generation) - Correct Answers -The first filial, hybrid
(heterozygous) offspring arising from a parental (P generation) cross.
F2 generation (second filial generation) - Correct Answers -The offspring resulting from
interbreeding (or self-pollination) of the hybrid F1 generation.
NOTE:
-
Law of Segregation - Correct Answers -- Mendel observed the same pattern of
inheritance in six other pea plant characters, each represented by two traits
, - What Mendel called a "heritable factor" is what we now call a gene
- When Mendel crossed contrasting, true-breeding white- and purple-flowered pea
plants, all of the F1 hybrids were purple
• Crossed the F1 hybrids, many of the F2 plants had purple flowers, but some had
white
• Mendel discovered a ratio of about three to one, purple to white flowers, in the F2
generation
- Felt the heritable factor for white flowers was hidden or masked in presence of purple-
flower factor
• Purple flower color a dominant trait and white flower color a recessive trait
- Developed a model to explain 3:1 inheritance pattern observed in F2 offspring
NOTE:
- Example: All the F1 plants were purple. When they were self or crossed breed they
showed three purple flowers and one white flower.
- Purple flowers are the dominate trait.
- White flowers are the recessive trait
-
Dominant trait - Correct Answers -A genetic trait is considered dominant if it is
expressed in a person who has only one copy of the gene associated with the trait.
NOTE:
- A genetic factor that blocks another genetic factor
Recessive trait - Correct Answers -A trait that reappears in the second generation after
disappearing in the first generation when parents with different traits are bred.
The F2 generation always produced a - Correct Answers -3:1 ratio
NOTE:
- The dominant trait is present three times as often as the recessive trait.
- Mendel coined two terms to describe the relationship of the two phenotypes based on
the F1 and F2 phenotypes.
- The hereditary determinants are of a particulate nature.
