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.