BSC 101 Unit 1: How does inheritance work?

dominant allele

-An allele whose trait always shows up in the organism when the allele is present. -an allele that is fully expressed in the phenotype of a heterozygote -ex) widow's peak

gene

-a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring. -A segment of DNA on a chromosome that codes for a specific trait

methyl group

A chemical group consisting of a carbon bonded to three hydrogen atoms. The methyl group may be attached to a carbon or to a different atom.

unreplicated chromosome

A chromosome that consists of a single copy (in eukaryotes, a single "thread")

replicated chromosome

A chromosome that has been copied; consists of two identical chromatids, each containing one double-helical DNA molecule

codominance

A condition in which neither of two alleles of a gene is dominant or recessive.

Pleiotropy

A single gene having multiple effects on an individuals phenotype

recessive allele

An allele that is masked when a dominant allele is present

heterozygous

An organism that has two different alleles for a trait -Aa

homozygous

An organism that has two identical alleles for a trait -AA or aa

genotype

An organism's genetic makeup, or allele combinations.

phenotype

An organism's physical appearance, or visible traits.

homologus chromosomes

Chromosomes that have the same sequence of genes and the same structure

allele

Different forms of a gene

blending inheritance

Early concept of heredity proposing that offspring possess a mixture of the traits from both parents

law of independent assortment

Mendel's second law, stating that allele pairs separate from one another during gamete formation

law of segregation

Mendelian law stating that two alleles for each trait separate during meiosis

incomplete dominance

Situation in which one allele is not completely dominant over another allele

epigentic inheritance

patterns of inheritance that are due to something other than differences in DNA sequences

locus (loci - plural)

the physical location of a gene on a chromosome

discrete traits

traits that are clearly different from each other

polygenetic inheritance

two or more genes contribute to the phenotypic expression of a single characteristic