Gregor Mendel
the father of Modern Genetics
Austrian monk who studied the inheritance patterns in pea plants
P Generation
the starting generation of purebred plants that Mendel used in his experiments
Fore instance, a purebred purple flowering pea plant
F1 generation
1st filial
Cross between the members of the P generation
For example, Mendel crossed the Purple Flower Purebred with the White Flower Purebred pea plants
All the offspring were purple
F2 Generation
2nd filial generation
Mendel allowed the members of the F1 generation to self-pollinate
The offspring had a 3:1 ratio of purple to white flowers
Self pollinate
Mendel was able to combine the male and female gametes from the same plant
Cross pollinate
when the gametes from two different plants are combined
Can be done by hand, wind, insects, etc.
allele
the different forms of a trait
For instance an allele for yellow seeds or an allele for green seeds
dominant trait
the trait that is expressed if present
this allele is represented by a capital letter (P=purple)
recessive trait
in order to be expressed the individual must inherit 2 copies of this allele
this allele is represented by a lower case letter (p=white)
homozygous
the individual has two of the same alleles (RR or rr)
heterozygous
the individual has two different alleles (Rr)
genotype
the type of alleles present for a gene (TT)
phenotype
the physical appearance or expression of the genotype
for example TT= tall plant
Punnett Square
tool used to predict the probability of having offspring with certain traits
male alleles go on the top of the square, female alleles on the left side
incomplete dominance
inheritance pattern where there is a blend of the two different alleles for a trait.
The phenotype of a heterozygote show an intermediate between the 2 alleles
For instance RW for a four o'clock flower represents the incomplete dominant trait of pink flowers
codominant
two alleles are both dominant and both expressed in the phenotype
polygenic
trait that is controlled by more than one gene
For example, skin color
sex-influenced traits
traits that are turned on or off by the presence of male or female hormones
sex-linked trait
traits that are carried on the X or Y chromosome
autosome
a typical body chromosome (numbered in humans from 1-22)
sex chromosomes
X or Y
XX
female
XY
male
Multiple alleles
when a trait can have more than 2 alleles and a heirarchy exists in the dominance
Example: Blood Type, hair color
Karyotype
a picture of the chromosomes in a cell
helps to identify chromosome number and structure as well as sex of the individual
pedigree
a genetic family tree that traces inheritance patterns
circle in pedigree
female
square in pedigree
male
horizontal line between circle and square in pedigree
marriage
vertical line and bracket in pedigree
children of the two individuals they are connected to
roman numerals in pedigrees
the generation number
digits (numbers) in pedigrees
represents the individuals in the family
germ cell mutation
a mutation that occurs in an egg or sperm
will be passed down to the offspring
somatic cell mutation
a mutation that happens in a typical body cell like in the skin
Will only be experienced by the individual who has the mutation
is not passed down to next generation
lethal mutation
mutation where there are so many errors, the cell self-destructs
Mendel's Law of Segregation
members of each pair of alleles are separated when gametes form
Mendel's Law of Independent Assortment
the inheritance of one trait does not influence the inheritance of another trait.
frameshift mutation
a mutation in the DNA that results the entire code of the DNA to be chaged from that point on.
point mutation
a mutation that affects only one nucleotide
translocation
when a piece of one chromosome breaks off and joins a different non-homologous chromosome.
diploid
contains two copies of each chromosome (human diploid number 46)
haploid
cells that contain half the genetic info (human haploid number is 23)
non-disjunction
a chromosome mutation when homologous pairs fail to separate in humans