Module 3 Unit 2: Variations in Gene Expression Flashcards
The Traits that we have learned from the previous units are considered?
qualitative traits
These traits are controlled by genes with a cumulative effect such that the phenotypes show small, gradual differences.
quantitative traits
Is an interplay between genetic makeup and environmental factors.
phenotypic variations
They are influenced by the type, number, and inheritance pattern of the gene/s.
phenotypic variations
Refers to the proportion of a population that will exhibit a particular trait if the allele is found in their genotype.
Penetrance or Quantitative Concept
100% of all individuals with the same allele in their genotype expresses the trait
Complete Penetrance
Not all individuals with the same allele in their genotype expresses the trait.
This is the type of penetrance exhibited by incomplete dominance, codominance, gene interaction, and epistasis.
Incomplete / Reduced Penetrance
Refers to the degree of expression of a penetrant gene
Expressivity / Qualitative Concept
Expressivity is dependent on?
penetrance
A trait must be __________ for expressivity to be assessed.
penetrant
Is a trait that is non- genetic
Phenocopy
Is due to an environmental factor but mimics a phenotype.
Phenocopy
These two terms refer to the expression of traits by members of monozygotic twins
Concordance and Discordance
If both monozygotic twins exhibit a trait, the trait is called?
concordant
It means that the trait has a genetic basis
Concordance
True or False:
Since monozygotic twins have exactly the same genetic composition, a genetic trait present in one member is also present in the other.
True
If a trait is exhibited by one member of a monozygotic twin but is not exhibited by the other member, the trait is?
discordant
If both members of a monozygotic twin were born deaf, then the trait most likely has a genetic basis, thus?
concordant
If only one member of the monozygotic twin is deaf, the condition cannot be genetic, thus considered?
discordant
Quantitative traits are governed by multiple genes thus referred to as?
polygenic traits
Each allele of each gene interacts ______ and contribute to the expression of that particular trait
Additively
Regions of the DNA that contribute to a quantitative trait are collectively referred to as ________ and located in different chromosomes
quantitative trait loci (QTL)
Most regions are protein-coding regions called ______, while some are __________ (thus not called genes) but still contribute to the trait
- genes
- regulatory regions
Quantitative traits are affected by both the DNA and the environment, thus called?
multifactorial
Is considerably variable because of the small continuous differences
polygenic trait
Is determined by the genes of an individual and the environment
Phenotypic Variance
Phenotypic Variance Formula
VP = VG + VE
Is determined by incomplete dominance, complete dominance, and gene interactions and epistasis
Genotypic variance
Genotypic variance Formula
VG = VA + VD + VI
Differences in the phenotype observed in a population
phenotypic variance
Differences observed in a population that is due ONLY to the genotype
genotypic variance
Differences observed in a population that is due ONLY to environmental factors
environmental variance
Refers to the variance due to the total quantitative effects of each allele in a polygene
Additive Variance
It is also known as the breeding value because it represents the worth of the genes to the next generation; how much would the genes contribute to the phenotype of the offspring
Additive Variance
Refers to some genes that act on the same characteristic exhibit complete dominance
dominance variance
Some genes that act on the same characteristic exhibit gene interactions
interaction variance
Refers to the variance due to the interaction between genes at different loci.
interaction variance
Refers to the percentage of phenotypic variation that is due to genotypic variations
Heritability
The proportion of the phenotypic variation due to ALL the genetic factors
Broad Sense Heritability (H2)
Broad Sense Heritability (H2) Formula
H^2= Vg/Vp x 100
Proportion of the phenotypic variation based on the additive genetic variance
Narrow Sense Heritability (h2)
It is a measure of how likely an offspring will resemble its parents
Narrow Sense Heritability (h2)
It is important in determining how a trait will respond to selection
Narrow Sense Heritability (h2)
Extremely important for breeding because it deals with traits that are of value for the next generation
Narrow Sense Heritability (h2)
Narrow Sense Heritability (h2) Formula:
h2 = Va/Vp x 100
If H2 = 0?
The phenotypic variance is due to environmental factors only
If H2 = 100%?
The phenotypic variance is due to the genotype only
If H2> 0?
the phenotypic variance is partly due to genotype
If h2 = 0?
the phenotypic variance is due to environmental factors only
If h2 =100%
the phenotypic variance is due to the additive genetic variance
If h2> 0
the phenotypic variance is partly due to genotype
Comes from the word “epi” which means outside and “genetics” referring to the genes
Epigenetics
Refers to the study of factors that alter gene expression without changing the DNA nucleotide sequence.
Epigenetics
Refers to the study of factors that alter gene expression without changing the DNA nucleotide sequence.
Epigenetics
Molecules that alter gene expression either promote or prevent the transcription of genes. All these “gene expression-altering” molecules taken together make up the entire ______.
Epigenome
T or F:
Most epigenetic changes are irreversible.
True
All ________ daughter cells inherit the change,
thus remain throughout the lifetime of the organism.
mitotic
Can occur if the epigenetic change is retained during gametogenesis, that is, the gametes still have the epigenetic change
Transgenerational epigenetic inheritance
Functions to turn off gene expression
DNA methylation
It prevents gene transcription, thus involved in gene silencing
DNA methylation
T or F:
Histone proteins have tails that stick out of the nucleosome.
Histone modification
Histone proteins have tails that are easily accessible for epigenetic modifications that alter the packaging of the DNA, to either promote or prevent transcription. This process is called?
Histone modification
Non-coding RNAs (ncRNAs) are transcribed by the DNA but not translated to
proteins
Gene Silencing by ncRNA
Aside from differentiation, epigenetic processes may also occur due to environmental factors that could trigger DNA methylation, histone modifications, and miRNA post-translational modification
Epigenetic Factors
One allele (paramutagenic) will prevent the expression of another allele (paramutable). This is called?
Paramutation
What is the rule in paramutation?
As long as the paramutagenic a is present in the genotype, the paramutable A is not expressed, thus the color of the corn kernel becomes light.
One allele is marked via DNA methylation for silencing, while the other allele is expressed.
Genomic Imprinting
Balances the expression of the X-linked genes in males and females
Dosage Compensation
