Gene Interaction Flashcards
When discrete phenotypic categories are produced that vary from one another in a qualitative way
Discontinuous variation
Phenotypic categories vary in a quantitative way
Continuous variation
is a form of gene interaction in which one gene masks the phenotypic expression of another gene at a different locus
Epistasis
*alleles that are masking the effect
epistatic alleles
*alleles whose effect is being masked
hypostatic alleles
Fur color in Labrador Retrievers is controlled by two separate genes.
Fur color is a __________ trait!
Gene 1: Represented by B
: Controls color
Gene 2: Represented by E
: Controls expression of B
polygenic
Recessive at one either locus masks the expression of the dominant phenotype at the other locus.
Duplicate Recessive (9:7)
Recessive Trait at one locus masks the effect of the second locus.
Single Recessive (9:3:4)
- The dominant trait at either locus will expression one phenotype, the other phenotype is homozygous at both loci.
Duplicate Dominant (15:1)
Dominant trait at one locus masks the expression of the second locus.
Single Dominant (12:3:1)
Duplicate effects from the two loci.
The phenotypes are:
* Two dominant
* One dominant
* None dominant.
Dominant ´ Recessive (9:6:1)
Pattern of inheritance:
* Involve genes in the nucleus
Maternal effect and epigenetic inheritance
Inheritance pattern:
* Involves genes in organelles other than the nucleus
- Mitochondria
- Chloroplasts
Extranuclear inheritance
refers to an inheritance pattern for certain nuclear genes in which the genotype of the mother directly determines the phenotype of her offspring
* Surprisingly, the genotypes of the father and offspring themselves do not affect the phenotype of the offspring
Maternal effect
Genetic phenomenon?
Phenotype determined by genes located on the sex chromosome
Sex-linked characteristic
Genetic phenomenon?
Phenotype determined by genes on autosomal chromosomes that are more readily expressed in one sex
Sex-influenced characteristic
Genetic phenomenon?
Phenotype determined by autosomal genes whose expression is limited to one sex
Sex-limited characteristic
Genetic phenomenon?
Phenotype determined by nuclear genotype of the maternal parent
Genetic maternal effect
Genetic phenomenon?
Phenotype determined by cytoplasmic genes, which are usually inherited entirely from only one parent
Cytoplasmic inheritance
Genetic phenomenon?
Phenotype determined by genes whose expression is affected by the sex of the transmitting parent
Genomic imprinting
- percentage of individuals that show at least some degree of expression of a mutant genotype
- Ex. If 15 percent of flies with a given mutant genotype show the wild-type appearance, the mutant gene is said to have a ___________ of 85 percent.
penetrance
- reflects the range of expression of the mutant genotype.
- Ex. Flies homozygous for the recessive mutant gene eyeless exhibit phenotypes that range from the presence of normal eyes to a partial reduction in size to the complete absence of one or both eyes
Expressivity
Type of penetrance:
identical known genotypes yield <100% of expected phenotype
Incomplete penetrance
Type of penetrance:
identical known genotypes yield 100% expected phenotype
Complete penetrance
Type of expressivity:
Identical known genotypes with an expressivity effect yield a range of phenotypes
Variable expressivity
Type of expressivity:
Identical known genotypes with no expressivity effect yield 100% expected phenotype
Constant expressivity
Identical known genotypes produce a broad range of phenotypes, due to varying degrees of gene activation and expression
Incomplete penetrance with variable expressivity
Measure the degree to which an allele is expressed at the phenotypic level
Expressivity
- the physical location of a gene in relation to other genetic material may influence its expression
- Ex. if a region of a chromosome is relocated or rearranged (called a translocation or inversion event), normal expression of genes in that chromosomal region may be modified
POSITION EFFECT
- Provides an organisms with its genetic potential- a possible phenotype.
Genotype
- Act on organism as it grows to produce an individual with a unique phenotype.
ENVIRONMENTAL FACTORS
ENVIRONMENTAL FACTORS INCLUDE SUCH VARIABLES AS:
WIND EXPOSURE
WATER AVAILABILITY
ACIDITY
TEMPERATURE
SOIL TYPE
LIGHT
PREDATION
Sources of genetic variation:
Dominant alleles
Recessive alleles
Mutations
Crossing over
Independent assortment
Gene interactions
Sources of environmentally induced variation
Wind
Water availability
Acidity
Temperature
Soil type
Light
Predation
Evening primrose produces red flowers when grown at 23°C and white flowers when grown at 18°C
reason behind*
chemical activity depends on the kinetic energy of the reacting substances (depends on the surrounding temperature)
Some breeds of cat and rabbit have distinctive darker fur on the extremities (called __________)
EXAMPLE: Siamese cats, Himalayan rabbits
pointing
The environmental influence of a genotype on the phenotype
phenocopy
The sex of some animals is determined by the temperature at which they were incubated during embryonic development
EXAMPLE: crocodiles, American alligators, and turtles
In some species:
* - high incubation temperature produce males
* - low incubation temperatures produce females
* - in some species the opposite is true
Plants of the same species produce a smaller or stunted phenotype with higher altitude. Such patterns are observable in vegetation growing on mountainsides.
This may be due to the combined effects of:
- Wind exposure
- Cooler temperatures
- Water availability
- Rarified atmosphere (low oxygen)
The presence of other members of the same species may control the determination of sex in other individuals of the group.
EXAMPLE: ________________
* 1. These fish live in groups comprising females and juveniles with a single male.
* 2. In the presence of the male, all juvenile fish of this species grow into females.
* 3. When the male dies, the dominant female will change her sex to become a male for the group.
Sandagers wrasse (parrotfish)
In microorganisms, mutations that prevent synthesis of nutrient molecules are quite common, such as when an enzyme essential to a biosynthetic pathway becomes inactive
What do you call these organisms?
Auxotroph
EXAMPLE: _______________
* If can no longer synthesize the amino acid leucine, proteins cannot be synthesized
* If leucine is present in the growth medium, the detrimental effect is overcome.
bread mold Neurospora
Cannot metabolize the amino acid phenylalanine
Phenylketonuria
Cannot metabolize galactose
Galactosemia
Cannot metabolize lactose
Lactose intolerance
The color of some flowers is determined by the pH of the soil they grow in.
EXAMPLE: Flower color in _______
* Acid soil – _________
* Alkaline soil – ________
hydrangeas
pink flowers
blue flowers
The sedative drug caused improper development of the fetus leading to abnormally stunted limbs
thalidomide
What is the gene interaction if the ratio is 9:3:3:1
Additive
What is the gene interaction if the ratio is 9:7
Complementary
What is the gene interaction if the ratio is 9:3:4
Recessive epistasis
What is the gene interaction if the ratio is 12:3:1
Dominant epistasis
What is the gene interaction if the ratio is 15:1
Duplicate genes
