Chapter 14/15 - Patterns of Inheritance Flashcards
The passing of traits from parents to offspring through asexual or sexual reproduction
Heredity
Heredity by means of genes assumed
traits were from ‘fluid’ like blood
The first investigator to achieve and document successful experimental hybridizations, or the mating of unlike parents
Josef Klreuter
Who in 1760 cross-fertilized (or crossed, for short) different strains of tobacco and obtained fertile offspring?
Josef Klreuter
By cross-fertilizing (or crossed, for short) different strains of tobacco Josef Klreuter produced __________
hybrids
Who observed variations different from parent
plants
Josef Klreuter
Josef Klreuter:
Hybrid offspring crosses resulted in ___________________________________
even more differences compared to the grandparents and parent plants
Who crossed garden pea plants that had either yellow or green seeds (true-breeding)?
What did this result in?
T.A. Knight (1823)
Hybrids produced yellow or green seeds (segregating)
Offspring produced from self-fertilization, remaining uniform from one generation to the next.
true breeding
Some offspring exhibit one form of a trait (yellow seeds), and other offspring from the same mating exhibit a different form (green seeds).
segregating
Was a scientist, friar and abbot
Grew up on a farm
Math and physics background allowed him to approach genetics from a mathematical standpoint
Gregor (Johann) Mendel
Mendel studied __________________________
hybrid crosses in pea plants
What characteristics did Mendel find easily distinguishable in pea plants?
shape of seeds
color of seeds
color of pods
shape of pods
plant height
position of flowers
flower color
Mendel studied hybrid crosses in pea plants due to ___________________________________
Due to true-breeding, pure varieties of each trait were available
Mendel studied hybrid crosses in pea plants because pea plants are _______________________
small and grow fast
While studying pea plants Mendel discovered that male and female parts on the same flower of the plant, allow for ____________________________
self-fertilization (retention of trait)
Mendel usually conducted his experiments in three stages: Which were?
- Mendel allowed plants of a given variety to self-cross for multiple generations to assure himself that the traits he was studying were indeed true-breeding—that is, transmitted unchanged from generation to generation
- performed crosses between true-breeding varieties exhibiting alternative forms of traits. He also performed reciprocal crosses: using pollen from a whiteflowered plant to fertilize a purple-flowered plant, then using pollen from a purple-flowered plant to fertilize a white-flowered plant.
3.Finally, Mendel permitted the hybrid offspring produced by these crosses to self-fertilize for several generations, allowing him to observe the inheritance of alternative forms of a trait. Most important, he counted the numbers of offspring exhibiting each trait in each succeeding generation.
.
concepts of inheritance in which traits of parents were carried by fluid and “blended” in offspring.
blending inheritance,
A cross that follows only two variations on a single trait, such as white- and purple-colored flowers. This deceptively simple kind of cross can lead to important conclusions about the nature of inheritance.
monohybrid cross
One trait, two variations
monohybrid cross
exhibits only one of two traits with no blending
F1 generation
When Mendel crossed white-flowered and purple-flowered plants, the hybrid offspring he observed did not have flowers of intermediate color, as the hypothesis of blending inheritance would predict. Instead, in every case the flower color of the offspring resembled that of one of their parents. These offspring are customarily referred to as the ______________________
first filial generation, or F1
No blending of traits
Always inherit same trait as one parent
first filial generation, or F1
In a cross of white-flowered and purple-flowered plants, the F1 offspring all had _________ flowers.
Mendel called these flowers the ___________ trait.
purple
purple; dominant
In Mendels experiment, what color flowers were referred to as the recessive trait
white
Mendel referred to the form of each trait expressed in the F1 plants as ________________ and to the alternative form that was not expressed in the F1 plants as _________________
dominant
recessive
exhibits a 3:1 ratio of both traits
F2 generation
After allowing individual F1 plants to mature and self-fertilize, Mendel collected and planted the seeds from each plant to see what the offspring in the ________________ generation would look like.
second filial generation, or F2,
What generation are offspring?
second filial generation, or F2,
What did Mendel find in the second filial generation, or F2?
Predominantly purple flower(75%) with reappearance of recessive white flowers (25%) , whom was hidden in F1 generation.
the dominant-to-recessive ratio among the F2 plants was always close to _________
3:1; or 1:2:1
1 true-breeding dominant: 2 not-true-breeding dominant: and 1 true-breeding recessive.
ratio of F2 plants
ratio of F2 plants
1 true-breeding dominant: 2 not-true-breeding dominant: and 1 true-breeding recessive.
Mendel performed crosses (Parents, then F1)
for all 7 traits in pea plants
– Found similar results. Describe his results___________________________
75% possessed dominant trait
25% possessed recessive trait
Further experiments by Mendel revealed that the
recessive trait was always
_____________________, F3, F4, F5 generations
always had __________flowers
true-breeding
white
⅓ of the dominant, purple-flowered F2 individuals were ________________, ____ were not.
true breeding
⅔
Mendel’s Principle of Segregation explains ___________________
monohybrid observations
Mendels Conclusions:
- plants he crossed did not produce progeny of intermediate appearance
- For each pair of alternative forms of a trait, one alternative was not expressed in the F1 hybrids, although it reappeared in some F2 individuals. The trait that “disappeared” must therefore be latent (present but not expressed) in the F1 individuals.
- The pairs of alternative traits examined were segregated among the progeny of a particular cross, some individuals exhibiting one trait and some the other.
- These alternative traits were expressed in the F2 generation in the ratio of ¾ dominant to ¼ recessive. This characteristic 3:1 segregation is referred to as the Mendelian ratio for a monohybrid cross.
Principle of Segregation
plants crossed did not produce progeny of intermediate appearance
These alternative traits were expressed in the F2 generation in the ratio of ¾ dominant to ¼ recessive. This characteristic 3:1 segregation is referred to as the _______________ for a monohybrid cross.
Mendelian ratio
Modern day description of Mendel’s findings:
Parents pass their physiological traits to their offspring via ____________ , individual receives _____copy of each _______ from each parent
genes
one
gene
Modern day description of Mendel’s findings:
Not all copies of a gene are___________
The alternative forms of a gene are called_________
When two haploid gametes containing the same allele fuse during fertilization, the resulting offspring is said to be _____________
When the two haploid gametes contain different alleles, the resulting offspring is said to be __________
identical
alleles
homozygous
heterozygous
Modern day description of Mendel’s findings:
The two alleles remain discrete—they neither _____ with nor _____ each other. Therefore, when the individual matures and produces its own gametes, the alleles ________________________
blend; alter
segregate randomly into these gametes (offspring)
Modern day description of Mendel’s findings:
In all individuals, only ____ allele is expressed
dominant) and the other is unexpressed (recessive
one
Modern day description of Mendel’s findings:
The total set of alleles that an individual contains is called ______________
The physical appearance or other observable characteristics of that individual, which result from an allele’s expression, is termed _______________
the _________ is the blueprint, and the _________ is the visible outcome in an individual.
genotype
phenotype
genotype
phenotype
What process is this?
Alternative alleles for a character segregate from each other during gamete formation and remain distinct
Principle of Segregation
