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