WEEK 8 - Mendelian inheritance Flashcards
What is a point mutation?
A single-base substitution in the DNA sequence.
Examples include changes in the sequence such as TGCATTCG to TGCATTCG.
What is an insertion mutation?
A sequence of DNA (any length) inserted into existing DNA.
Example: TGCATTCG to TGCATTTAGGC.
What is a deletion mutation?
A sequence of DNA (any length) removed from existing DNA.
Example: TGCATTCG to TGCATTCCG.
What occurs during gene duplication?
Any number of genes can be duplicated, potentially even entire genomes.
Define inversion in genetics.
A segment of DNA is flipped around and re-inserted.
What is chromosome fusion?
When two chromosomes become joined together as one.
What do mutations generate?
Genetic diversity.
What is a genotype?
The genetic composition of an organism.
What is a phenotype?
The physical manifestation of the genotype.
True or False: Mendel’s experiments showed that inheritance is blending.
False.
Mendel’s work suggested that inheritance is particulate, not blending.
What is the ratio of gametes produced by two heterozygous parents for a single gene?
1:2:1.
What is a polygenic trait?
A trait influenced by many genetic loci.
Define quantitive genetics.
The study of the genetic mechanisms of continuous phenotypic traits.
What is broad sense heritability?
Proportion of phenotypic variance explained by genetic differences among individuals.
Fill in the blank: The equation for heritability is h2 = _____ / VP.
VG.
What are the components of phenotypic variation?
VP = VG + VE.
What happens when two individuals with two different genes mate?
There are 16 different combinations of gametes produced.
What is epistasis?
Interaction between alleles.
Fill in the blank: The average phenotype amongst parents can be calculated using the formula (Frequency of PP x 0) + (Frequency of Pp x 1) + (Frequency of pp x 2) = _____ .
Average phenotype.
What is phenotypic plasticity?
Interaction with the environment affecting traits.
True or False: Continuous traits have a simple genetic basis.
False.
Continuous traits have a complex genetic basis.
What does the slope represent in estimating heritability?
Heritability.
What is the significance of Mendel’s choice of phenotypes in his experiments?
He chose phenotypes influenced by a single gene.
What type of inheritance is shown by traits with recessivity and dominance?
Discrete inheritance.
What does a heritability value of 0.642 indicate?
Perfect correspondence between parent phenotype and offspring phenotype
A heritability value of 0.642 suggests a moderate to high genetic contribution to a trait.
What is the formula for the average offspring phenotype based on parent phenotype?
Y = b0 + b1X with b0 = 0 and b1 = 1
This indicates a direct linear relationship between parent and offspring phenotypes.
How has the heritability of PKU changed over time?
Heritability has declined due to environmental factors
Availability of screening and low phenylalanine diets have reduced the impact of genetics on PKU.
What was historically true about PKU?
PKU was genetically determined with high heritability
PKU is caused by inheriting two recessive alleles, leading to the disease phenotype.
What factors now influence whether an infant displays the PKU phenotype?
Largely a function of the environment
Environmental interventions can prevent the manifestation of PKU despite genetic predisposition.
Fill in the blank: The heritability of a trait is calculated as h2 = _____ / 0.
VG
VG represents the genetic variance contributing to the trait.
What does the notation ‘PP’, ‘Pp’, and ‘pp’ represent?
Genotypes of individuals regarding a trait
‘PP’ indicates homozygous dominant, ‘Pp’ indicates heterozygous, and ‘pp’ indicates homozygous recessive.
True or False: The slope (b1) in the average offspring phenotype formula can be less than 1.
False
In this context, the slope is equal to 1, indicating a one-to-one relationship.
What does VP = 0 indicate in the context of PKU?
Indicates no phenotypic variance under certain conditions
This suggests that environmental factors can eliminate the expression of the phenotype.
