Chapter 14 Mendel and the Gene Idea Flashcards
What are the two laws of inheritance Mendel discovered?
The law of segregation
The law of independent assortment
The pea plants he studied had many varieties with distinct features called _____________ (such as flower color)
Variants of these (such as purple or white flowers) are called ________
Characters
Traits
What is true breeding?
Plants that produce offspring of the same variety when they self-pollinate
*every generation is the same
In a typical experiment mental would mate two contrasting, true breeding varieties, this process is called…..
When only a single factor is crossed and allows for variation in one character it is called….
Hybridization
Monohybrid
True breeding parents is the _____ generation
P
What did Mendel see when he crossed contesting true breeding pea plants?
What did he see when he crossed those F1 plants?
All the F1 hybrids were the dominate trait (purple)
3 to 1 ratio
What Mendel called a “___________” we now call a gene
Heritable factor
What is the first concept of Mendel’s model?
Alternative versions of genes account for variations in inherited characters
This called an allele
What is the second concept of Mendel’s model?
For each character, an organism inherits two alleles, one from each parent
*He made this deduction without knowing about chromosomes
What is the third concept of Mendel’s model?
If the two alleles at a locus differ, then one, the dominate allele, determines the appearance and the other has no noticeable effect on appearance
What is the forth concept of Mendel’s model?
What’s it also known as?
AKA the law of segregation
Two alleles for a heritable character separate during gamete formation and end up in different gametes
Mendel’s ______________ model accounts for the 3:1 ratio he observed in the F2 generation
Segregation
Only ____________ are true breeding
Homozygotes
Phenotype vs. genotype?
Physical appearance
Genetic makeup
How can we tell the genotype of an individual with a dominant phenotype?
Carry out a cross test
How is a cross test done?
Breed the mystery individual with a homozygous resssive individual
If any are recessive phenotype, then the mystery parent must be heterozygous
How did Mendel identify this second law of inheritance (independent assortment)?
By following two characters at the same time
These are called dihybrids
A cross between F1 dihybrids, can determine weather two characters are transmitted to offspring as a package or independently
What is this cross called?
Dihybrid cross
What ratio do you get when you cross two heterozygous traits?
9:3:3:1
Using a dihybrid cross Mendel declines the law of…….
Independent assortment
This law states that each pair of alleles segregates independently of each other pair of alleles during gamete formation
This is only when they are on different chromosomes***
Law of segregation
The law of segregation only applies to….
Genes on different, non homologous chromosomes or those far apart on the same chromosome
Genes located near each other on the same chromosome tend to be …..
Inherited together
When they are different chromosomes they sort independently
Mendel’s laws of segregation and independent assortment reflect the rules of……
Probability
What rule states that The probability that two or more independent events will occur together is the product of their individual probabilities
Multiplication rule
What law states that the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities
Addition rule
What are the three types of dominance?
Complete- when the phenotypes of the Heterozygote and dominant homozygous or identical
Incomplete dominance-when the phenotype of F1 is somewhere in between the phenotypes of the two parental varieties
Codominance- two dominate alleles affect the phenotype in separate, distinguishable ways
When a hetrozygote has intermediate phenotype
Ex. Half the amount of protein for flowers is not enough to make the flower red, it’s pink instead
Incomplete dominance
If you do not see a 3:1:1 ratio it could be
Incomplete dominance
Ex: could be a cross with a 1:2:1 ratio
Most genes have multiple phenotypic effects, a property called….
Pleiotropy
When a mistake in one gene causes multiple problems, when it effects more than one phenotype.
Pleiotropy
Examples of pleiotropy
Cystic fibrosis
Sickle cell
A gene at one locus alters the phenotypic expression of a gene at a second locus
Epistasis
Ex: lab dogs
Quantitive characters are those that Vary in a population along a continuum
Usually indicated polygenic inheritance, an additive effect of two or more genes on a single phenotype
Ex: height, skin color
Ploygenic Inheritance
An additive effect of two or more genes on a single phenotype
Polygenic inheritance
A ratio of 9:3:4 means what?
Epistasis is taking place
The phenotypic range of a genotype influenced by the environment
Norm of reaction
Norms of reaction are generally broadest for…:
Polygenic characters
Search characters are called ______________ because genetic and environmental factors collectively influence phenotype
Multifactorial
If a child had a trait but parents did not, it is…..
Recessive
One of the parents must show the trait to be…….
Dominate
Albinism, sickle cell and cystic fibrosis are….
Recessive
Most common lethal genetic disease in the US
Results in defective or absent chloride transport channels in plasma membrane’s leading to a build up of chloride ions outside the cell
Mucus buildup
Cystic fibrosis
Dwarfism and Huntington’s disease are….
Dominate
Degenerative disease of the nervous system
Huntington’s disease
