Chapter 14: Mendelian Inheritance Flashcards
Self-fertilization
- the male organ and female organ are on the same plant
- male organ provides female organ with sperm cells needed to provide its own fertilization; not needed from another plant
- will end up with identical offspring, no varying traits
Cross-fertilization
- process where anther is cut off of a plant, and pollen from a different plant is transferred to them
- collect pollen from one individual and transfer it to the female organ of a flower on another plant, whose male organs have been removed
hybrids
- result from crosses in fertilization between true-breeding parents
Homozygous
Two dominant or two recessive alleles
Heterozygous
One dominant and one recessive allele
Dominant
more prevalent phenotype
In studies ALWAYS seen in F1 generation
3 to 1 in F2(3 dominant, 1 recessive expression)
recessive
less prevalent phenotype
Describe Mendel’s general experiment: What were the results?
- Takes true breeding varieties(parental generation)
If self-fertilized, the same characteristics will always appear
So Mendel Performs crosses between true-breeding parents to make hybrids(first filial generation – F1); then Mendel has Self-fertilized hybrids(second filial generation-F2)
This resulted in an F1 generation having all round seeds, and the F2 generations having round and wrinkled seeds in a 3:1 ratio
What traits were studied in the Mendel Experiment?
shape, color, shape of pod, pod color, flower color, flower and pod position, and stem length
How did Mendel’s experiment counteract previous conceptions of inheritance?
Mendel helped discover genes are not a blending inheritance of the two different parents of the offspring; they either show the trait or do not show the trait
Exceptions later on
Describe Mendel’s general experiment: What were the results?
- Makes true breeding varieties(parental generation)
If self-fertilized, the same characteristics will always appear
So Mendel Performs crosses between true-breeding parents to make hybrids(first filial generation – F1); then Mendel has Self-fertilized hybrids(second filial generation-F2)
This resulted in an F1 generation having all round seeds, and the F2 generations having round and wrinkled seeds in a 3:1 ratio
ALL OF THE CROSSES IN HIS STUDIES YIELDED A 3:1 ratio (3 dominant traits shown to the 1 recessive trait shown)
Particulate Inheritance
discrete units are inherited, not blended
Genes
sequence of nucleotides in DNA(later used to transcribe RNA of sorts)
Alleles
different versions of a gene
A singular allele would be presented as one letter
alleles are different versions of a gene (e.g. blue eyes vs brown eyes) that can be present at a gene locus (a gene’s location on a chromosome)
Example: Rr would have two alleles, an R allele and an r allele
Genotype
genetic makeup; made up of two parents producing the offspring; total sum of alleles
Phenotype
expressed characteristics that can be observed
Genotype vs Phenotype
phenotype is seen, genotype is part of type of formula/set letters
Punnet squares
Used (in Mendel experiments) to explain and predict genotypic and phenotypic ratios
Explain setup of Mendel’s seed example through genotype and phenotype
R = dominant allele(Round)
r = recessive allele(wrinkled)
Genotypes possible
RR = homozygous dominant
Rr = heterozygous (dominant) - hybrid!!
rr = homozygous recessive
IMPORTANT TO LOOK BACK AT MEIOSIS HERE! Forming a zygote means it holds a copy of each gene
Explain the interpretation of Mendel’s epxeriment in genotypic and phenotypic seed example
RR x rr: gives all Rr offspring(F1 generation)
* One trait disappears
* Genotype: heterozygous
* Phenotype: round seeds
F1 generation
* Rr x Rr
* Offspring genotype:
1 RR(homozygous dominant)
2 Rr(heterozygous)
1 rr (homozygous recessive)
Offspring phenotype: 3 round seeds, 1 wrinkled seed; Phenotype vs genotype ratios differ; Multiple traits for F2 generation produced; Trait reappears
DRAW Punnett square!!
Mendel’s Law
Law of segregation: two different alleles segregate from each other during meiosis
(Ex: RR and rr separated into R & R, r & r)
during gamete formation, the segregation of one gene does not influence the segregation of another gene for a different trait
Note Separation of homologous chromosomes pairs in meiosis I!!
What did Mendel’s studies lead to?
Chromosome Theory of Inheritance(found by someone else): Genes are located on chromosomes, each at a particular gene locus
This explains Mendel’s Principle of Segregation: the physical basis for the segregation of Mendel’s traits is the separation of alleles when homologous chromosomes pairs are separated in Meiosis I
REMEMBER EVEN IF THESE LAWS ARE CONNECTED TO MEIOSIS, THEY HAVE EXCEPTIONS TODAY
Mendel’s Second Law
Independent Assortment:
Because two genes are usually located on separate chromosomes, they sort independently of each other during meiosis
Example: seed color and seed shape do not predict the other
Linked genes are just referring to genes on same chromosome
REMEMBER EVEN IF THESE LAWS ARE CONNECTED TO MEIOSIS, they HAVE EXCEPTIONS TODAY!
Testcross
breeding the plants/organisms tests to determine unknown genotypes
HAS TO BE DONE an individual of dominant phenotype but unknown genotype (homozygous dominant or heterozygous) and with an individual of known recessive genotype AND phenotype
Creates 1:1 phenotypic and genotypic ratio!!
