MENDELIAN GENETICS Flashcards
PART 1 AND 2
- Gregor Johann Mendel
- 1866
- major postulates of transmission genetics
- garden pea (Pisum sativum)
- discrete units of inheritance exist and predicted their behavior during the formation of gametes (elementen)
- Mendel’s postulates were accepted as the basis for the study of what is known as transmission genetics.
MENDELIAN GENETICS
- easy to grow and hybridize
artificially - self-fertilizing in nature
- seven visible features (unit characters), each represented by two contrasting forms, or traits
- Character: stem height: traits: tall and dwarf
- He selected six other visibly contrasting pairs of traits involving seed shape and color, pod shape and color, and pod and flower arrangement.
GARDEN PEA
Mendel’s simplest crosses involved only one pair of contrasting traits from two parent strains, each exhibiting one of the two contrasting forms of the character under study
MONOHYBRID CROSS
Offspring of self-fertilizing individuals
SELFING
MENDELIANS’ FIRST THREE POSTULATES:
Genetic characters are controlled by unit factors that exist in pairs in individual organisms.
UNIT FACTORS IN PAIRS
MENDELIANS’ FIRST THREE POSTULATES:
When two unlike unit factors responsible for a single character are present in a single individual, one unit factor is dominant to the other, which is said to be recessive.
DOMINANCE/RECESSIVENESS
MENDELIANS’ FIRST THREE POSTULATES:
During the formation of gametes, the paired unit factors separate or segregate randomly so that each gamete receives one or the other with equal likelihood.
SEGREGATION
MODERN GENETIC TERMINOLOGY:
The physical appearance of a trait is the ____ of the individual.
PHENOTYPE
MODERN GENETIC TERMINOLOGY:
Mendel’s unit factors represent units of inheritance called ___ by modern geneticists.
GENES
MODERN GENETIC TERMINOLOGY:
The phenotype is determined by alternative forms of a single gene called
ALLELES
MODERN GENETIC TERMINOLOGY:
When alleles are written in pairs to represent the two unit factors (DD, Dd, or dd), these symbols are called the ____.
GENOTYPE
MODERN GENETIC TERMINOLOGY:
When both alleles are the same (DD or dd), the individual is _____ or a ______.
HOMOZYGOUS OR A HOMOZYGOTE
MODERN GENETIC TERMINOLOGY:
When the alleles are different (Dd), we use the term ____ or a ____.
HETEROZYGOUS OR A HETEROZYGOTE
TERMINOLOGIES:
The genetic constitution of a individual (PP, Pp, pp)
GENOTYPE
TERMINOLOGIES:
The outward appearance of an individual (purple, white)
PHENOTYPE
TERMINOLOGIES:
The phenotype seen when two alternative alleles are present together (Pp: purple)
DOMINANT PHENOTYPE
TERMINOLOGIES:
The form of the gene that is expressed when two alternative alleles are present together (P>p)
DOMINANT ALLELE
TERMINOLOGIES:
The form of the gene that is not expressed when two alternative alleles are present together.
RECESSIVE ALLELE
TERMINOLOGIES:
The phenotype that is only seen when two identical alleles are found together (pp: white)
RECESSIVE PHENOTYPE
TERMINOLOGIES:
having two identical alleles (PP or pp)
HOMOZYGOUS
TERMINOLOGIES:
having two different alleles (Pp)
HETEROZYGOUS
Punnett square was named after
Reginald C. Punnett
PUNNETT SQUARES:
The vertical column represents those of the ___ parent
FEMALE
PUNNETT SQUARES:
The horizontal row represents those of the ___ parent.
MALE
PUNNETT SQUARES:
The process thus lists all possible
RANDOM FERTILIZATION EVENTS
PUNNETT SQUARES:
The genotypes and phenotypes of all potential offspring are
ASCERTAINED
THE TESTCROSS: ONE CHARACTER
A test cross resulting in all dominant offspring indicates that the parent is ____
HOMOZYGOUS DOMINANT
THE TESTCROSS: ONE CHARACTER:
A test cross resulting in a 1:1 ratio of yellow to green offspring indicates that the parent is _____
HETEROZYGOUS
To distinguish the genotype, Mendel devised the _____.
The organism expressing
the dominant phenotype,
but of unknown genotype, is crossed to a known homozygous
recessive individual.
TESTCROSS METHOD
Such a cross, involving two pairs of contrasting traits, is a
DIHYBRID CROSS OR TWO-FACTOR CROSS
On the basis of similar results in numerous dihybrid crosses, Mendel proposed a fourth postulate called
This postulate stipulates that segregation of any pair of unit factors occurs independently of all others. As a result of random segregation, each gamete receives one member of every pair of unit factors.
All possible combinations of gametes are formed in equal frequency
INDEPENDENT ASSORTMENT
Three pairs of contrasting traits, in what is called a
When F1 individuals serve as parents, each produces eight different gametes in equal frequencies
At this point, we could construct a Punnett square with 64 separate boxes and read out the phenotypes
TRIHYBRID CROSS OR THREE-FACTOR CROSS
Such a family tree is called a
Forked-Line Method or Branch Diagram
PEDIGREE
Fraternal twins or also known as
DIZYGOTIC TWINS (sex may be the same or different)
Identical twins or also known as
MONOZYGOTIC TWINS (sex may be the same)
