Ch.+13-+Chromosomes,+Mapping,+and+the+Meiosis-Inheritance+Connection+(1)

Chromosomal Theory of Inheritance

The theory that genes are located on chromosomes, which segregate and assort independently during meiosis.

Sex-linked inheritance

A type of inheritance where a gene is located on a sex chromosome, leading to different patterns of inheritance for males and females.

Drosophila melanogaster

Fruit fly species commonly used in genetic experiments, notably by Thomas Hunt Morgan.

Test cross

A genetic cross between a homozygous recessive individual and a suspected heterozygous individual to determine the genotype of the latter.

X chromosome

One of the two sex chromosomes in mammals which contains many genes, including those involved in sex-linked traits.

Y chromosome

The male sex chromosome that, when present, typically determines male characteristics and contains few functional genes.

Dosage compensation

The process by which organisms equalize the expression of genes between individuals with different chromosome dosages, such as X chromosome inactivation in females.

Genetic mapping

The process of determining the distance between genes based on the frequency of recombination during meiosis.

Recombination frequency

The percentage of recombinant offspring arising from a genetic cross which indicates the distance between the loci on a chromosome.

Aneuploidy

An abnormal number of chromosomes in a cell, often resulting from nondisjunction events during meiosis.

X-inactivation

The process by which one of the X chromosomes in female mammals is randomly inactivated to ensure equal expression of X-linked genes.

Maternal inheritance

A type of genetic inheritance in which traits or genes are passed down from the mother, such as mitochondrial DNA.

Single nucleotide polymorphisms (SNPs)

Variations in a single nucleotide that occur at a specific position in the genome, useful as genetic markers.

Epigenetics

The study of heritable changes in gene expression that do not involve changes to the underlying DNA sequence.

Genomic imprinting

A process where only one allele of a gene is expressed depending on which parent it was inherited from.

Calico cat

A cat with a coat that has large patches of two colors due to X chromosome inactivation and is almost exclusively female.

Klinefelter syndrome

A genetic condition in males caused by an extra X chromosome, leading to physical and developmental differences.

Turner syndrome

A condition caused by the presence of only one X chromosome in females, resulting in physical and reproductive abnormalities.

Hemophilia

A genetic disorder caused by a mutation in one of the genes related to blood clotting, more common in males due to its location on the X chromosome.

Sickle cell anemia

A hereditary blood disorder caused by a mutation affecting hemoglobin, resulting in misshaped red blood cells.

Down syndrome

A genetic disorder caused by trisomy of chromosome 21, characterized by developmental delays and physical features.

Chorionic villi sampling (CVS)

A prenatal diagnostic procedure that involves taking a sample of tissue from the placenta to test for genetic defects.

Amniocentesis

A prenatal procedure to obtain amniotic fluid for genetic testing of the fetus.

Recombination frequency formula

Recombination frequency (RF) is calculated as RF = (Number of recombinant offspring / Total number of offspring) x 100%.

Centimorgan (cM)

A unit of measure for genetic linkage representing a 1% chance of recombination occurring between two genes.

Recombinant DNA

DNA that has been formed artificially by combining constituents from different organisms, often used in genetic engineering.

Chiasmata

The physical locations on chromosomes where crossing over occurs during meiosis, resulting in genetic recombination.

Double crossovers

Events where two separate crossover events occur between the same two chromosomes, affecting recombination frequency.