BIO 3200 Exam #2

Codominance

Joint expression of both alleles in a heterozygote (showing both traits
Example: MN blood group

incomplete dominance

A cross between parents with contrasting traits may sometimes generate offspring with an intermediate phenotype (mixture of both parents phenotypes)
Example: Red and White snapdragons can create pink snapdragons

gain of function

The mutation of a gene may be affecting the regulation of the transcription of the gene under consideration
Example: Genetic conversion of proto-oncogenes, which regulates the cell cycle, to oncogenes, where regulation is overridden by excess genes product

multiple alleles

When two or more alleles of the same gene are present in a population the resulting mode of inheritance may be unique
Example: ABO Blood Types

Loss of function or null

If a gene is responsible for the synthesis of a specific enzyme, a mutation in that gene may ultimately change the conformation of this enzyme and reduce or eliminate its affinity for the substrate

Bombay Phenotype

One parent has AB blood but can have children with O type, hh genotype means O blood no matter the blood genotype

Lethal alleles

Has potential to cause death of an organism, alleles are the result of mutations in essential genes, typically inherited recessively
Example: Huntington’s Disease (dominant)

types of gene interaction

Dominant- recessive
Codominance
Incomplete Dominance
Lethal Alleles

epistasis

Expression of one gene masks/modifies effect of another gene pair, gene masks phenotypic effects of another gene

recessive epistasis

bb genotype masks expression of A allele (Color of mice black, agouti, albino)

dominant epistasis

dominant allele at one loci masks an allele at second loci (summer squash color)

continuous variation of phenotypic expression

The pattern of genetic transmission typical of quantitative inheritance

polygenes

The varying phenotypes that result from the input of genes at more than one, and often many, loci

multifactorial traits

Quantitative (polygenic) traits whose phenotypes result from the gene action and environmental influences

1:4:6:4:1

Dihybrid ratio with independent assortment of polygenes

continuous traits

Measured on a continuous numerical scale (ex. Weight and height)

meristic traits

Where the phenotypes are described as whole numbers (ex. Number of peas in a pod)

threshold traits

Polygenic (frequently multifactorial) but they are distinguished from continuous and meristic traits by having a small number of discrete phenotypic classes (ex. Type II diabetes)

Nilsson-Ehle study of wheat grain color

Shows that there are additive alleles which contribute to the red grain color and nonadditive alleles that don’t contribute to the red color in the grain

calculation of number of polygenes

1/4^n – determines number of gene pairs involved
(2n+1) – number of categories available in F2

mean

The arithmetic average of a set of measurements

variance

The average squared distance of all measurements from the mean of a sample

standard deviation

the square root of the variance; A quantitative measure of the amount of variation present in a sample

error

Measures the accuracy of the sample mean

heritability

Used to describe what proportion of the total phenotypic variation in a population is due to genetic factors

concordant trait

Both either express a given trait of neither express it

discordant trait

If one twin expresses a trait and the other hasn’t

advantages of twin studies

they help scientists quantify genetic and modifiable environmental factors that increase the risk of certain diseases

disadvantages of twin studies

By the time they are born, MZ twins do not necessarily have identical genomes, Gene-expression patterns in MZ twins change with age; this leads to phenotypic differences

forms of extranuclear inheritance

Organelle heredity, infectious heredity, and maternal effect

mitochondria and chloroplasts

Organelles involved in the organelle heredity

heteroplasmy

the presence of more than one type of organellar genome within a cell or individual

mitochondrial swapping

The exchange of defective mitochondria in an egg with normal mitochondria to correct a mitochondrial disorder. This is accomplished by transferring the nucleus from an egg with defective mitochondria into a non-defective egg that has had its nucleus removed. The reconstructed egg is fertilized via in vitro fertilization and implanted for development

maternal inheritance

An offspring’s phenotype for a particular trait is under the control of nuclear gene products present in the egg

is maternal inheritance

inheritance of shell coiling in Lymnaea peregra

petite mutations in yeast

Mutations named petite due to small size of colonies
Deficiency in cellular respiration
Mitochondria performs abnormal electron transport

endosymbiotic theory

Theory that states that mitochondria and chloroplasts arose independently from free living protobacteria (primitive bacteria)

criteria for mitochondria mutations in human disorders

1. Inheritance must exhibit a maternal rather than a Mendelian pattern
2. The disorder must reflect a deficiency in the bioenergetic function of the organelle
3. There must be a mutation in one or more of the mitochondrial genes

Inheritance of the green and white patches phenotype in Mirabilis jalapa (four o'clocks)

The mode of inheritance is organelle heredity this is because the white patches are caused by the lack of chlorophyll that is produced by the chloroplasts