ch 14 ; mendel and the gene idea

Define character in genetics.

A heritable feature that varies among individuals.

What is a trait in genetics?

Each variant for a feature.

What are true-breeding plants?

Plants that over many generations of self-pollination, only produce the same variety as the parent plant (homozygous of the trait).

What is hybridization in genetics?

The mating/crossing of two true-breeding parents.

What is the P generation in genetics?

Parental generation of true breeding parents.

What is the F1 generation in genetics?

First filial generation (hybrid of true-breeding parents).

What is the F2 generation in genetics?

Second filial generation (hybrid of F1 generation).

What are alleles in genetics?

Alternative versions of a gene.

What is a dominant allele in genetics?

An allele that determines the organism's appearance.

What is a recessive allele in genetics?

An allele that has no noticeable effect.

What is the law of segregation in genetics?

States that the two alleles for a heritable character segregate during gamete formation and end up in different gametes.

What is a Punnett square in genetics?

A diagrammatic device for predicting the allele composition of offspring from a cross between individuals of known genetic makeup.

What is a homozygote in genetics?

An organism that has a pair of identical alleles for a gene.

What is a heterozygote in genetics?

An organism that has two different alleles for a gene.

What is phenotype in genetics?

An organism's appearance/observable traits & physiological traits.

What is genotype in genetics?

An organism's genetic makeup.

What is a testcross in genetics?

Breeding an organism of unknown genetic makeup with a recessive homozygote to reveal the genotype of the organism.

What are monohybrids in genetics?

The F1 generation of heterozygous offspring for one particular character followed in a cross (AA x aa = Aa).

What is a monohybrid cross in genetics?

A cross between monohybrids.

What are dihybrids in genetics?

The F1 offspring of two true-breeding parents of two particular characters (AABB x aabb = AaBb).

What is a dihybrid cross in genetics?

A cross between dihybrids.

What is the law of independent assortment in genetics?

States that each pair of allele segregates independently of any other pair of allele during gamete formation.

What is complete dominance in genetics?

Occurs when phenotypes of the heterozygote and dominant homozygote are identical.

What is incomplete dominance in genetics?

Occurs when the phenotype of F1 hybrids is in between the phenotypes of the two parental varieties.

What is codominance in genetics?

Occurs when two dominant alleles affect the phenotype in separate, distinguishable ways.

What is Tay-Sachs disease in genetics?

An inherited disorder in humans, where the brain cells of a child with Tay-Sachs disease cannot metabolize certain lipids because a crucial enzyme doesn't work properly. The lipids accumulate, causing seizures, blindness, and degeneration of motor and mental performance and death within a few years.

What is pleiotropy in genetics?

The property of most genes to have multiple phenotypic effects. A single gene can affect a number of characteristics. They're responsible for multiple symptoms of some hereditary diseases, like cystic fibrosis and sickle-cell disease.

What is epistasis in genetics?

When the phenotypic expression of a gene at one locus alters the phenotypic expression of a gene at a second locus.

What are quantitative characters in genetics?

Those that vary in the population along a continuum. Usually indicates polygenic inheritance.

What is polygenic inheritance in genetics?

An additive effect of two or more genes on a single phenotype.

What does multifactorial mean in genetics?

That many factors, both genetic and environmental, collectively influence phenotype.

What is a pedigree in genetics?

A family's history for a particular trait assembled into a family tree throughout generations.

What are carriers in genetics?

Heterozygotes that may transmit the recessive allele to their offspring.

What is cystic fibrosis in genetics?

The most common lethal genetic disease in Canada, affecting one out of every 2,500 people of European descent. It results from defective or absent chloride transport channels in plasma membranes leading to a buildup of chloride ions outside the cell. Symptoms from mucus buildup and abnormal absorption of nutrients in the small intestine.

What is sickle-cell disease in genetics?

Affects one out of 400 African-Americans. It's caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells. In homozygous individuals, all hemoglobin is abnormal (sickle-cell). Symptoms include physical weakness, pain, organ damage, and even paralysis. Heterozygotes are usually healthy but may suffer some symptoms. About 1 in 10 African Americans carries the sickle cell allele— heterozygotes are less susceptible to the malaria parasite, so there's an advantage to being hetero