Chapter 11 Mendel And The Gene Idea Flashcards
The blending hypothesis
Is the idea that genetic material from two parents blends together
The particulate hypothesis
Is the idea that parents pass on discrete heritable units called genes
Mendel discovered the basic principles of heredity by breeding
Garden peas
Mendel chose peas because
There are many varieties with distinct features or characters
Character variants are called traits
He could control mating
Mendel chose to track only characters that occurred in
Two distinct alternative forms
True breeding
Plants that produce offspring of the same variety when they self pollinate
Hybridization
Mating two contrasting true breed varieties
The true breeding plants are called the_______ and the hybrid offspring of the P Generation are called _________
P Generation, F1 Generation
When F1 individuals self pollinate or cross pollinate with each other the _________generation is produced
F2
Mendel reasoned that in the _______plants, the heritable factor for white flowers was masked in the presence of the purple flower factor
F1
Mendel model to explain the 3:1 pattern
Alternative versions of genes account for variations in inherited characters l. These are called alleles
For each character an organism inherits two alleles, one from each parent
If two alleles differ then the dominant allele determines appearance
Law of segregation-the two alleles for a heritable character separate during gamete formation
An organism with two identical alleles for a character is said to be
Homozygous
An organism that has two different alleles for a gene is said to be
Heterozygous
Phenotype va genotype
Phenotype is physical appearance
Genotype is genetic makeup
How can we tell the genotype of an individual with a dominant phenotype?
Test cross by breeding the mystery individual with a homozygous recessive individual and if any offspring display the recessive phenotype the mystery parent must be heterozygous
Mono hybrids
Individuals that are heterozygous for one character
A cross between monohybrids is called
Monohybrid cross
Crossing two true breeding parents differing in two characters produces
Dihybrids
A dihybrid cross between F1 dihybrids can determine whether two characters are transmitted to offspring as a package or independently
Law of independent Assortment
Each pair of alleles segregates independently of any other pair during gamete formation
Inheritance may deviate from simple Mendelian patterns in the following situations
Alleles are not completely dominant or recessive
When a gene has more than two alleles
When a single gene produces multiple phenotypes
Three degrees of dominance
Complete dominance-when phenotypes of the heterozygote and dominant homozygote are identical
Incomplete Dominance- the phenotype F1 hybrids is somewhere in between the phenotypes of the two parental varieties
Codominance-two dominant alleles affect the phenotypes in separate distinguishable ways
Alleles are simply variations in
A genes nucleotide sequence
Tay-Sachs
A dysfunctional enzyme causes an accumulation of lipids in the brain
Dominant alleles are not necessarily more common than
Recessive alleles
Pleiotropy
Genes have multiple phenotypic effects
Epistasis
A gene at one locus alters the phenotypic expression of a gene at a second locus
Example is a Labrador coat color depends on two genes
Quantitative Characters
Are those that vary in the population along a continuum
Polygenic Inheritance
An additive effect of two or more genes on a single phenotype
Example is skin color in humans
Multifactorial
Genetic and environmental factors collectively influence phenotype
Pedigree
A family tree that describes the interrelationships of parents and children across generations
Carriers
Are heterozygous individuals who carry the recessive allele but are phenotypically normal
Cystic fibrosis
The most common lethal genetic disease in the United States
Allele results in defective chloride transport channels in plasma membranes leading to a buildup of chloride ions outside the cell
Huntington’s Disease
A degenerative disease of the nervous system
