Genetics of Quantitative Traits

The combined effect of multiple genes, where the contributions of each gene add up without any interactions.

A trait whose phenotype is determined by the combined effects of multiple genes (polygenic) and/or environmental factors (multifactorial).

Several genes influencing a single trait. Variation is based soleley on heredity.

A characteristic that is influenced by both genetic and environmental factors.

A heterozygous genotype results in an intermediate phenotype, unlike either homozygous.

The proportion of phenotypic variation in a population or family that is due to genetic variation. It is calculated as Vg/Vp, where Vg is genetic variance and Vp is phenotypic variance.

The proportion of phenotypic variation due to additive genetic variance (Va). Calculated as Va/Vp.

Specific regions on chromosomes that influence a quantitative trait.

Method to determine the location of genes on a chromosome.

A set of inbred lines derived from an initial cross of two different inbred parental lines

A type of mutation where one nucleotide base is replaced by another.

A mutation where one or more nucleotides are removed from a DNA sequence.

A mutation where one or more nucleotides are added to a DNA sequence.

A type of mutation that affects a single nucleotide pair in a DNA sequence.

A type of point mutation that does not change the amino acid sequence of the protein produced.

A mutation that changes one amino acid to another in the protein sequence.

A mutation that creates a premature stop codon, shortening the protein.

A mutation that shifts the reading frame of the genetic code, altering all subsequent codons and thus the amino acid sequence.

A mutation that occurs without external factors.

A mutation that's caused by exposure to external factors.

Gene therapy aims to treat diseases by modifying genes. However, there are several challenges to overcome. Getting the desired DNA into the correct cells, ensuring it's expressed properly, and minimizing immune responses are crucial.

Specialized viruses used to deliver therapeutic genes into cells. They offer efficiency and speed but require extensive modifications to ensure safety.

A method where cells are removed from the body, modified with the therapeutic gene outside the body, and then reintroduced. This allows precise targeting of cells.

DNA sequences that strongly activate gene expression, ensuring the therapeutic gene produces enough of the desired protein to have an effect.

DNA sequences that activate gene expression only in specific tissues, ensuring the therapeutic gene works only where it's needed.

The body's immune system can react against the viral vector or the therapeutic gene product, leading to reduced therapeutic effects or even serious health problems.

A genetic disorder where the body can't break down ammonia properly. Gene therapy trials using adenovirus to deliver the correct gene have faced challenges due to the widespread immunity to adenovirus.

Immune responses to gene therapy can lead to reduced therapeutic gene expression, as the immune system attacks the modified cells, and in severe cases, even death.

A gene primarily expressed in retinal pigment epithelium, responsible for producing an isomerase crucial for vision.

An enzyme that converts a molecule into its isomer. In RPE65's case, it transforms all-trans retinal to 11-cis retinal.

The process of converting all-trans retinal back to 11-cis retinal, essential for vision.

A rare inherited eye disorder affecting retinal function, often caused by mutations in genes like RPE65.

A treatment approach where a functional copy of the RPE65 gene is delivered to the eye using a virus, aiming to restore vision.

Gene therapy can trigger a massive immune response, potentially leading to death. This can occur when a patient's immune system is sensitized to the vector used in treatment.

There's a risk that the transgene (therapeutic gene) can insert into a functional gene, disrupting its function and potentially leading to problems like cancer.

Gene therapy successfully treated boys with SCID-X1, a genetic disorder impairing the immune system. However, some patients later developed leukemia.

The leukemia observed in some SCID-X1 patients was caused by the transgene inserting near a gene called LMO2, increasing its expression, leading to uncontrolled cell growth.

LCA is a genetic disorder leading to blindness, caused by mutations in genes vital for vision. There is no cure, with blindness progressing over time.

LCA is caused by mutations in specific genes crucial for vision. For a person to develop LCA, both copies of the gene must be mutated.

Gene therapy is being investigated as a potential treatment for LCA, targeting specific genes involved in the disease. However, it's still in the experimental phase.

Researchers use the candidate gene approach to study LCA. This involves focusing on genes suspected to be involved in the disease, based on their functions and potential role in vision.

X inactivation, the process of silencing one X chromosome in females, doesn't happen until the 100-cell stage in embryonic development. This means that both X chromosomes are active in the beginning of development.

A condition where a person has three copies of a particular chromosome instead of the usual two.

Trisomy 21, a genetic disorder caused by an extra copy of chromosome 21.

A genetic disorder in males caused by an extra X chromosome (XXY).

A technique using microarrays to detect duplications or deletions in DNA.

Tests conducted during pregnancy to assess fetal health and identify potential abnormalities.

An ultrasound measurement of the fluid-filled space at the back of the fetal neck, used as part of prenatal screening.

A prenatal diagnostic test where a small sample of placental tissue is taken for genetic analysis.

A prenatal diagnostic test where amniotic fluid is collected for genetic analysis.

Genetic screening of embryos before implantation in IVF, allowing for selection of healthy embryos.

Giant chromosomes found in some fly species, with multiple copies of DNA that are visible under a microscope.

A type of chromosomal mutation where a portion of a chromosome is missing.

The loop formed when a deleted segment of a chromosome pairs with its homologous chromosome during meiosis.

The expression of a recessive allele due to the deletion of the dominant allele on the homologous chromosome.

A type of chromosomal mutation where a segment of a chromosome is duplicated.