Genetics test 3

Parental Progeny

Progeny with the same combination of markers as the parent.

Null Hypothesis

A statement saying your observed data fits a model.

P-value below .05

Indicates to reject the null hypothesis.

P-value above .05

Indicates to accept the null hypothesis.

Chi-squared (X^2)

Amount of deviation from your expected model.

Linking

Genes (alleles) on the same chromosome are likely to be inherited together.

Linkage Group

A set of linked genes.

Genetic Map

Shows the order of linked genes and distances between the genes on a chromosome.

Genetic Marker

DNA sequence such as a SNP or repeat.

Physical Marker

Phenotype associated with a gene locus.

Recombinant Progeny

Progeny with a different combination of markers than the parent.

Double Crossover

Occurs when two chiasmata form, with a double exchange between two nonsister chromatids.

Genetic Balance

The ratio of sex chromosomes to autosomes controlling the amount of sex-determining gene products.

Chromosome Determination

Presence or absence of specific gene product(s) encoded in a sex chromosome.

Mating-type determination

Expression of gene variants called idiomorphs controls mating type.

Environmental sex determination

Determination of sex based on environmental signals such as day length, temperature, and social cues.

Barr Bodies

Inactivated X chromosomes; in XX mammals, an X is deactivated during the blastocyst stage.

XIST Gene Copy

The expressed copy that silences the X chromosome, creating a barr body.

Mosaicism

Mixed phenotype resulting from different genotypes or gene expression levels in the cells of a multicellular organism.

Mosaic

Cells within an individual have different genotypes.

Female

An individual having 2 X chromosomes.

Male

An individual with the presence of a Y chromosome.

SRY

Encodes transcription factor activator that triggers testes formation and ovarian suppression.

Hemizygous

Presence of only one allele for a characteristic; having one member of a pair of homologous chromosomes instead of two.

Codominance

Equal expression of gene products from both alleles; heterozygotes express both dominant and recessive traits.

Complete recessive alleles

A null allele that does not encode a final gene product.

Complete dominant alleles

A gain-of-function mutation that causes increased activity of a gene product.

Incomplete dominance

One allele is not completely dominant over the other, resulting in a blended phenotype.

Pleiotropy

One gene is responsible for multiple traits.

Haploinsufficiency

An individual has one dose of a gene product due to having only one functional allele.

Threshold effect

When having one dose of a gene product due to one functional allele affects phenotype.

Recessive lethal allele

Needs two copies of the lethal allele to exhibit a lethal phenotype.

Dominant lethal allele

Both homozygotes and heterozygotes for a dominant allele display the lethal phenotype.

Genetic anticipation

Early onset and/or increased severity/expression of a trait in successive generations.

Epistasis

One gene (epistatic) masks the phenotype caused by a second gene (hypostatic).

Recessive epistasis

Phenotypic ratio of 9:4:3 in specific genetic crosses.

Dominant Epistasis

Dominant allele at locus A blocks the phenotypic expression at locus B.

Heterogeneous traits

A phenotype resulting from a mutation in one of several genes.

Polygenic

Many genes contribute to a singular trait.

Incomplete penetrance

Not all individuals with the genotype display the expected phenotype.

Variable expressivity

Individuals with an associated genotype have differing phenotypes.

Phenotypic plasticity

The environment can affect phenotypic expression.

Organelle Heredity

Transmission of traits through mitochondrial DNA (mtDNA) and plastid DNA (cpDNA).

Maternal affect

Offspring phenotype is influenced by nuclear gene products from the mother’s egg.

Extranuclear inheritance

Transmission of genetic information through components in the cytoplasm.

Heteroplasmy

Presence of mitochondria or chloroplasts from different sources with varying genotypes.