Ch.14: Mendel & the Gene Flashcards
is considered the father of Genetics
Discovered the basic principles of heredity by breeding garden peas in carefully planned experiments
Described basic principals of heredity with no knowledge of DNA or the process of Meiosis
Gregor mendel
Advantages of pea plants for genetic study:
There are many heritable features, or characters (such as flower color);
And character variants (such as purple or white flowers) called traits
Mating of plants can be controlled
Controlled breeding can be achieved by dusting one plant with pollen from another
plants that produce offspring of the same variety when they self-pollinate
true breeding
Mendel mated two contrasting, true-breeding varieties, a process called
hybridization
Mendel discovered a ratio of about ____ ____ ____, purple to white flowers, in the F2 generation
three to one
purple flower is _______ _____ while the white flower is the ____ _____
dominant trait
recessive trait
What Mendel called a “heritable factor” is what we now call a _____
gene
Mendel’s four concept
- The first concept is that differing versions of genes account for variations in inherited characters
- The second concept is that for each character an organism inherits two alleles
one from each parent transferred via the gametes - if the two alleles differ, then one (the dominant allele) determines the organism’s appearance
- law of segregation
These alternative versions of a gene are now called
alleles
two alleles for a heritable character separate during gamete formation and end up in different gametes
law of segregation
Letters are used to represent characters
A capital letter represents the dominant allele, and a lowercase letter represents the recessive allele
A parent can be Homozygous for either allele
or
Heterozygous, having different alleles
punnet square
physical appearance
phenotype
genetic makeup
genotype
The F1 offspring produced in this cross were _________, individuals that are heterozygous for one character
monohybrids
A cross between such heterozygotes is called a
monohybrid cross
Crossing two true-breeding parents differing in two characters produces _______ in the F1 generation, heterozygous for both characters
A XXXXXx cross can determine whether two characters are transmitted to offspring as a package or independently
dihybrids
Using a dihybrid cross, Mendel developed the ______ ______ _____ _____ ___.
Each pair of alleles segregates independently of other alleles during gamete formation
“Strictly speaking, this law applies only to genes on different chromosomes”
Genes located near each other on the same chromosome usually are inherited together
law of independent assortment
Deviations from simple Mendelian patterns occurs in the following situations:
When alleles are not completely dominant or recessive
When a gene has more than two alleles
Human Blood types
When a gene produces multiple phenotypes
Pleiotrophy
When a character is determined by more than one gene.
Epistasis
occurs when phenotypes of the heterozygote and dominant homozygote are identical
complete dominance
the phenotype of heterozygotes is somewhere between the phenotypes of the two homozygotes
incomplete dominance
two dominant alleles affect the phenotype in separate, distinguishable ways
codominance
Most genes have multiple phenotypic effects Called ________. responsible for the multiple symptoms of certain hereditary diseases, such as cystic fibrosis and sickle-cell disease
pleiotropy
a gene at one locus alters the phenotypic expression of a second gene
Two genes for one trait
epistasis
Another departure from Mendelian genetics arises when the phenotype for a character depends on ________ as well as genotype
environment
why are Humans are not good subjects for genetic research
Generation time is too long
– Parents produce relatively few offspring
– Breeding experiments are unethical
a family tree that describes the interrelationships of parents and children across generations
Inheritance patterns of particular traits can be traced and described using XXXXX
XXXXX are also very useful to animal and plant breeders that are seeking certain, desirable traits
pedigrees
Recessively inherited disorders show up only in individuals
homozygous for the allele
are heterozygous individuals who carry the recessive allele but are phenotypically normal (i.e., pigmented)
carriers
the liquid that bathes the fetus is removed and tested
amniocentesis
a sample of the placenta is removed and tested
chorionic villus sampling
