Test 2 Flashcards
Prevalent alleles in a population are termed..
Wild-type alleles
___ ___ can produce more than one wild-type in large populations.
Genetic polymorphism
Alleles that have been altered by mutation are termed..
Mutant alleles
Gain-of-function
Protein encoded by the mutant gene is changed so it gains a new or abnormal function
Dominant-negative
Protein encoded by the mutant gene acts antagonistically to the normal protein
Haploinsufficiency
Loss of function
Heterozygote does not make enough product to give the wild type phenotype
Incomplete penetrance
In some instances, a dominant allele does not influence the outcome of a trait in a heterozygote individual
Expressivity
The degree to which a trait is expressed
Incomplete dominance
The heterozygote exhibits a phenotype that is intermediate between the corresponding homozygotes
Overdominance
Heterozygote is more vigorous than both of the corresponding homozygotes
Heterozygote advantage
At the molecular level, overdominance is due to..
Two alleles that produce slightly different proteins
Three possible explanations for overdominance at the molecular level
- Disease resistance
- Homodimer formation
- Variation in functional activity
Type O blood people can only accept what type of blood?
Type O
Who can type O blood donate to?
Anyone
Universal donor
Sex-linked genes
Found on one of the two types of sex chromosomes, but not both
Pseudoautosomal inheritance
Very few genes found on both X and Y chromosomes
Sex-influenced traits
Involve an allele that is dominant in one sex but recessive in the opposite sex
Lethal allele
One that has the potential to cause of death of an organism
Essential genes
Those that are absolutely required for survival
Nonessential genes
Those not absolutely required for survival
Conditional lethal alleles
May kill an organism only when certain environmental conditions prevail
Semilethal alleles
Kill some individuals in a population, not all of them
Pleiotrophy
Multiple effects of a single gene on the phenotype of an organism
Gene interactions
Occur when two or more different genes influence the outcome of a single trait
Epistasis
When the alleles of one gene mask the phenotypic effects of the alleles of another
Gene knockout
Geneticists have developed techniques to directly generate loss-of-function alleles
Maternal effect
An inheritance pattern for certain nuclear genes in which the genotype of the mother directly determines the phenotype of her offspring
Maternal effect and epigenetic inheritance involves..
Genes in the nucleus
Extranuclear inheritance involves..
Genes in organelles other than the nucleus
The non-Mendelian inheritance pattern of maternal effect genes can be explained by the process of ___ in female animals.
Oogenesis
Epigenetic inheritance
A pattern in which a modification occurs to a nuclear gene or chromosome that alters gene expression
Lyon hypothesis
Mechanism of X inactivation
The process of X inactivation can be divided into 3 stages:
Initiation
Spreading
Maintenance
Initiation
One of the X chromosomes is targeted for inactivation
Spreading
The chosen X chromosome is inactivated
Maintenance
The inactivated X chromosome is maintained as such during future cell divisions
Genomic imprinting
A phenomenon in which a segment of DNA is marked and the effect is maintained throughout the life of the organism inheriting the marked DNA
Monoallelic expression
Depending on how the genes are marked, the offspring expressed either the maternally-inherited or the paternally-inherited allele
Three stages of imprinting
- Establishment of the imprint during gametogenisis
- Maintenance of the imprint during embryogenesis and in the adult somatic cells
- Erasure and reestablishment of the imprint in the germ cells
Genomic imprinting must involve a ___ ___.
Marking process
Genomic imprinting is permanent in the somatic cells of an ___ animal.
Individual
Extranuclear inheritance
Inheritance patterns involving genetic material outside the nucleus
The genetic material of mitochondria and chloroplasts is located in a region called the ___.
Nucleoid
The genome is composed of a single chromosome containing..
Double-stranded DNA
The two most important examples are due to genetic material with what two organelles?
Mitochondria and chloroplasts
The main function of choroplasts is ___
Photosynthesis
Species with maternal inheritance may, on occasion, exhibit ___ ___.
Paternal leakage
Paternal leakage
The paternal parent occasionally provides mitochondria through the sperm
Heteroplasmy
Important factor in mitochondrial disease
Endosymbiosis theory
Describes the evolutionary origin of mitochondria and chloroplasts
Bacteria reproduce ___
Asexually
Genetic transfer
A segment of bacterial DNA is transferred from one bacterium to another
Bacteriophages
Viruses that infect bacteria
Transfer of genetic material from one bacterium to another can occur in 3 ways:
Conjugation
Transduction
Transformation
Conjugation
Involves direct physical contact
Transduction
Involves viruses
Transformation
Involves uptake of genes from the environment
Auxotrophs
Cannot synthesize a needed nutrient
Prototrophs
Make all their nutrients from basic components
Genetic transfer in bacteria was discovered by who?
Lederberg and Tatum
U-tube
Large enough to allow the passage of the genetic material but small enough to prevent the passage of bacterial cells
Fertility plasmids
Allow conjugation
Resistance plasmids
Contain genes conferring resistance to antibiotics
Degradative plasmids
Carry genes allowing digestion of unusual substances
Col-plasmids
Contain genes for colicins, proteins that kill other bacteria
Virulence plasmids
Carry genes that turn bacterium into pathogenic strains
The ___ of ___ of the integrated F factor determines the starting point and direction of the transfer process.
Origin of transfer
thr+
Able to synthesize the essential amino acid threonine
leu+
Able to synthesize the essential amino acid leucine
azi^s
Sensitive to killing by azide
ton^s
Sensitive to infection by T1
lac+
Able to metabolize lactose and use it for growth
gal+
Able to metabolize galactose and use it for growth
str^s
Sensitive to killing by streptomycin
Cotransduction
The packaging and transfer of two closely-linked genes
Cotransduction frequency
(1-d/L)^3
Natural transformation
DNA uptake occurs without outside help
Artificial transformation
DNA uptake occurs with the help of special techniques
Competent cells
Bacterial cells able to take up DNA
“Illegitimate” recombination
The DNA that enters the cell is not homologous to any genes on the host chromosome
