Biology now Chapter 7 - Patterns of inheritence

Complex trait

Known as quantitative traits, they are traits that do not behave according to simple Mendelian inheritance laws. Such traits show a continuous range of variation and are influenced by both environmental and genetic factors

Law of Segregation

Mendel's first law. States that the two alleles of a gene are separated during meiosis and end up in different gametes. One of the two alleles is found on one of the chromosomes in a homologous pair, and the other allele is found on the other chromosome in a pair. It can be used to predict how a single trait will be inherited.

Law of independent assortment

Mendel's second law. States when gametes form, the two alleles of any given gene segregate during meiosis independently of any two alleles of other genes

P generation

Parental generation, the first two individuals that mate in a genetic cross

Codominance

Situation in which both alleles of a gene contribute to the phenotype of the organism

Physical traits

The body's physical attributes

Self-fertilization

The fertilization of plants and some invertebrate animals by their own pollen or sperm rather than that of another individual.

Genetic cross

Used frequently in transmission genetics, involves the breeding of two selected individuals and the subsequent analysis of their offspring to try to understand how traits are passed from parents to offspring.

Genome

the complete instructions for making an organism, consisting of all the genes in that organism's chromosomes

Incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits

Gene

A segment of DNA on a chromosome that codes for a specific trait

Pleiotropy

A single gene having multiple effects on an individuals phenotype

Epistasis

A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited

Behavioral traits

Affect the ways that an organism responds to its environment (some genetic basis)

Recessive

An allele that is masked when a dominant allele is present. Doesn't appear in the phenotype. Represented by a lower-case letter.

Genotype

An organism's genetic makeup, or allele combination

Phenotype

An organism's physical appearance, or visible traits

Gregor Mendel

Austrian monk and botanist whose experiments in breeding garden peas led to his eventual recognition as the "father of genetics" (1822-1884)

What environmental conditions may effect the genotype?

Body temperature, carbon dioxide levels in blood, external temperature, and/or amount of sunlight

Homozygous dominant

Both alleles (factors) for a trait are the same and dominant (AA)

Homozygous recessive

Both alleles for a trait are the same and recessive (aa)

How do alleles in a gene arise?

By mutation, a change in the DNA that makes up a protein

Mendelian traits

Controlled by a single gene and unaffected by environmental conditions

Dominant

Describes an alelle that covers over, or dominates, another form of that trait, hindering that gene from appearing in the phenotype. Represented by a capital letter

Alleles

Different forms of a gene

F1 generation

Filial one generation, the first generation of offspring obtained from an experimental cross of two organisms

F2 generation

Filial two generation, the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation

Homozygous

Having two identical alleles for a particular gene (BB)

Genetic trait

A genetically determined condition or characteristic

Polygenic traits

Traits controlled by two or more genes

Invariant traits

Traits that are the same in all individuals of a species

Variable traits

Traits that vary in the population due to differences in alleles carried by different individuals

Chromosome theory of inheritance

A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns

Biochemical traits

A characteristic due to specific chemical processes of an individual, such as the level of a particular enzyme

Dihybrid cross

A cross between individuals that have different alleles for the same gene

Punnett Square

A diagram that can be used to predict the genotype and phenotype combinations of a genetic cross.

Genotypic ratio

The probable ratio of genotypes produced by a cross. The most dominant trait goes first.

Phenotypic ratio

The ratio of phenotypes produced by a cross. Dominant traits always go first.

Bred true

The trait stayed the same generation after generation

How are Mendel's laws used?

They describe how genes are passed from parents to offspring. These laws allow us to use parental genotypes to predict offspring phenotypes and genotypes.