prelim genetixs lesson 5 Flashcards
THE FATHER OF GENETICS
Gregor Johann Mendel
- Born in 1822
- Now remembered as a pioneer of
genetics
Gregor Johann Mendel
In 1856, began his historic
studies on pea plants.
Gregor Johann Mendel
For 8 years, he grew and crossed
thousands of pea plants in a small 23- by 115-foot garden.
Gregor Johann Mendel
He published his work, entitled
Experiments on Plant Hybrids, in 1866.
Gregor Johann Mendel
When two
distinct individuals with different
characteristics are bred to each other
Cross/hybridization
Offspring out of hybridization
Hybrid
The pollen and
eggs are derived from the SAME
plant.
Self-fertilization
Pollen from
one plant be placed on the stigma
of another plant. Crosses between
DIFFERENT plants.
Cross-fertilization
General characteristics of an organism
Characters
Describe the specific properties of character
Trait or Variant
A trait DOES NOT vary in appearance from generation to generation
Breeding true-
A variety that
continues to produce the same trait after several generations
of self-fertilization
True-breeding strain or true-breeding line
a cross in
which an experimenter observes
one character.
Single factor cross
a cross between
two parents with different
variants for a given character
produces single-character
hybrids
Monohybrids
True breeding parents that differ
in character.
Parental generations or P generation-
Crossing true-breeding parents to each other
P-cross-
Latin: Filus- Son, offspring of the P
generation. Shows the trait of one parent but not the other.
F1 generation (First filial generation)-
Offspring of the F1 generation
that was allowed to self-fertilize.
F2 generation (Second filial generation)-
one trait is prevalent than the other trait.
Dominant
masked by the presence of a dominant trait but reappears in
subsequent generations
Recessive
Mendel referred to the genetic determinants as unit factors, but we now call them
genes
in which the genetic determinants that govern traits are inherited as discrete units that remain unchanged as they are passed from parent to offspring.
Particulate theory of inheritance
from each other during the process that gives rise to gametes.
Genes segregate
unit heredity that may influence the outcome of an organism’s
traits.
Genes-
Latin: Alius- other, refers to an alternative form of a particular gene.
Allele-
- Homozygous- Home-like, Zygo- pair,
Heterozygous- Hetero-different-
- Homozygous- Home-like, Zygo- pair,
Heterozygous- Hetero-different-
is consistent with the law of segregation
Mendel’s 3:1 ratio
An easy way to predict the outcome of simple genetic crosses
and self-fertilization experiments
PUNNETT SQUARES
Predict the types of offspring
PUNNETT SQUARES
British geneticist
Reginald Punnett
step by step PUNNETT SQUARES
STEP 1
* Write down the genotypes of both parents
STEP 2
* Write down the possible gametes that each parent can make.
STEP 3
* Create an empty Punnett square.
STEP 4
* Fill in the possible genotypes of the offspring by
combining the alleles of the gametes
STEP 5
* Determine the relative proportions of
genotypes and phenotypes of the offspring.
are TT, Tt, and tt in a 1:2:1 ratio.
Genotypes
is 3:1, or 3 tall plants : 1 dwarf
plant.
Phenotypes
a mating experiment
between two organisms that are
identically hybrid for two trait
Dihybrid-
The
inheritance of two different
characters within the same groups
of individuals
Two-factor crosse
Two genes always stay associated with each other. The alleles of the same gene are not linked
Linked assortment
Two different genes randomly segregate into haploid cells
Independent assortment
combination of traits were not found in the true-breeding of
the parental generation. Contradicts the linkage model.
Non-parentals-
When an offspring receives a
combination of alleles that
differs from those in the
parental generation
Genetic recombination
between two individuals that
are heterozygous for three different
traits. Ratio 27:9:9:9:3:3:3:1
Trihybrid
we can simply use the product rule and multiply these three combinations together
Multiplication method-
the genetic proportions are determined by
multiplying together the probabilities of each phenotype
Forked-line method
charts representing family relationships.
Pedigrees
aimed at determining the type of
inheritance pattern that a gene follows.
Pedigree analysis
Each generation is given a roman numeral designation
PEDIGREES
Individuals within the same generation are numbered from left to right.
PEDIGREES
affected individuals are depicted by filled symbols that distinguish them
from unaffected individuals.
PEDIGREES
Vertical lines connect each succeeding generation.
PEDIGREES
