14 Mendel and the Gene Flashcards
What is genetics?
The branch of biology that focuses on inheritance
Who worked out the rules of inheritance through a series of brilliant experiments on garden peas?
Gregor Mendel
What is heredity?
Is the transmission of traits from parents to their offspring
What is a trait?
Is any characteristic of an individual?
What basic questions was Mendel trying to address?
- why offspring resemble their parents?
- how does transmission of traits occurs?
What two hypothesis had been formulated to try to answer these two question?
1) blending inheritance
- parental traits blend
- such that their offsprings have intermediate traits
2) inheritance of acquired characteristics
- parental traits are modified
- then passed on to their offspring
Why did Mendel choose the common garden pea?
- it is easy to grow
- its reproductive cycle is short
- it produces large number of seeds
- its matings are easy to control
- its traits are easily recognizable
How did Mendel arrange mating?
- peas normally pollinate themselves through self-fertilization
- Mendel could prevent self-pollination by removing stamen containing pollen from each flower
- he then used this pollen to fertilize the female reproductive organ on different plants
- thus performing cross-pollination
What traits did Mendel study?
- seed shape
- seed color
- pod shape
- flower color
- flower position
- pod position
- stem length
What is phenotype?
And individuals observable features
-Mendel pea population had two distinct phenotype for each of the seven traits
What does F indicate in F generation?
F indicates first filial
How did Mendels first experiment contradict blending hypothesis?
Mendel crossed plants with only one differing trait: round seeds and plants with wrinkled seed
- all F1 generation had round seeds
- contradicted blending inheritance because genetic determinant for wrinkled seeds seemed to have disappeared
- Mendel allowed F1 to self pollinate and wrinkled seeds reappeared in F2 generation
What are the principles of segregation?
- two members of each gene pair must segregate
- they separate into different gamete cells
- during the formation of eggs and sperm in parents
What is the principle of independent assortment?
Alleles of different genes are transmitted independently of each other.
Chromosome theory of inheritance
Arose out of Sutton and Boveri’s careful observations of meiosis
States:
- chromosomes compose of Mendel’s hereditary determinants (what are now called genes)
- separation of alleles during anaphase of meiosis 1 is responsible for Mendel’s principle of segregation
What is the wild type?
The most common phenotype for each trait
Mutations
- phenotypes that differed from the wild type
- resulted from a change in a gene
Mutants
Individuals with traits attributable to mutation
Sex-linked inheritance
The various inheritance patterns that can occur when genes are carried on the sex chromosomes
Non-sex chromosomes are called
Autosomes
Autosomal inheritance
Genes on autosomes
Linked genes
- are genes predicted to always be transmitted together during gamete formation
- should violate the principle of independent assortment
- are inherited together unless crossing over occurs
Recombinant
-the combination of alleles in offsprings is different from the combination of alleles in parents
Recombinant genotypes occur
During the crossing over of prophase in meiosis I
