Mendel and the Gene Idea Flashcards
What genetic principles account for the transmission of traits from parents to offspring?
- “Blending” Hypothesis
- “Particulate” Hypothesis of inheritance: the gene idea
the idea that genetic material contributed by two parents mixes in a manner analogous to the way blue and yellow paints blend to make green
Blending hypothesis
Hypothesis which states that parents pass on discrete heritable units, genes
Particulate Hypothesis of Inheritance: The Gene Idea
documented a particulate mechanism of inheritance through his experiments with garden peas
Gregor Mendel
What approach did Mendel use to identify the two laws of inheritance?
scientific approach
How did Mendel discover the basic principles of heredity?
By breeding garden peas in carefully planned experiments
Why did Mendel choose to work with peas?
- Available in many varieties
- Could strictly control which plants mated which
By crossing (mating) two true-breeding varieties of an organism, scientists can study __ __ __
patterns of inheritance
Results: When pollen from white flower fertilizes eggs of purple flower, the first generation hybrids all have ___ flowers
Purple
a heritable feature
character
example of a character
flower color
a variant of a character
trait
example of a trait
purple or white flowers
What characters did Mendel chose to only track?
characters that varied in an “either-or” manner
What did Mendel make sure when starting the experiments?
His varieties were true-breeding
What do you call the process where Mendel mated two contrasting, true-breeding varieties?
Hybridization
The true-breeding parents are called?
P generation
The hybrid offspring of the P generation are called?
F1 generation
What do you call the offspring when F1 individuals self-pollinate?
F2 generation
Law states that hybrid offspring will only inherit the dominant characteristics in the phenotype. The alleles that suppress a trait are recessive traits, whereas the alleles that define a trait are known as dominant traits.
Law of Dominance
The two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes
Law of Segregation
What is the first law of inheritance?
Law of Dominance
What is the second law of inheritance?
Law of Segregation
When Mendel crossed the F1 plants, he discovered a ratio of about __ to __, __ to __ flowers, in the F2 generation
3:1, purple:white
Mendel reasoned that in F1 plants, purple flower color was __, and white flower color was __
purple = dominant
white = recessive
Four (4) concepts that make up the Mendel’s model
- Alternative versions of genes
- An organism inherits two alleles, one from each parent, and a genetic locus is represented twice
- If the two alleles at a locus differ, the dominant allele determines the organism’s appearance
- Law of segregation
An organism that is homozygous for a particular gene has a pair of ___ alleles for that gene and exhibits ____
Identical alleles
Exhibits True-breeding
An organism that is heterozygous for a particular gene has a pair of alleles that are ___ for that gene
Different
its physical appearance
phenotype
its genetic makeup
genotype
allows us to determine the genotype of an organism with the dominant phenotype
testcross
How do you testcross?
cross an individual with the dominant phenotype with an individual that is homozygous recessive for a trait
The F1 offspring produced in the testcross were __, __ for one character
monohybrid, heterozygous
How did Mendel derive the law of segregation?
by following a single trait
How did Mendel derive his second law of inheritance?
by following two characters at the same time
Crossing two, true-breeding parents differing in two characters produces __ in the __ generation, __ for both characters
dihybrids; F1; heterozygous