Bio Test

allele

gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes

autosomes

any of of the non-sex chromosomes

dihybrid

result of a cross between two true-breeding parents that express different traits for two characteristics

dominant

trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait

epistasis

antagonistic interaction between genes such that one gene masks or interferes with the expression of another

F₁

The first filial generation in a cross; the offspring of the parental generation

F₂

second filial generation produced when F1 individuals are self-crossed or fertilized with each other

Genotype

underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organisme

heterozygous

having two different alleles for a given gene on the homologous chromosome

homozygous

having two identical alleles for a given gene on the homologous chromosome

law of independent assortment

genes do not influence each other with regard to sorting of alleles into gametes; every possible combination of alleles is equally likely to occur

law segregation

paired unit factors (ie genes) segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors

monohybrid

result of a cross between two true-breeding parents that express different traits for only one characteristic

P₀

parental generation in a cross

phenotype

observable traits expressed by an organism

Punnett square

visual representation of a cross between two individuals in which the gametes of each individual are denoted along the top and side of a grid, respectively ,and the possible zygotic genotypes are recombined at each box in the grid

recessive

trait that appears “latent” or non-expressed when the individual also carries a dominant trait for that same characteristic; when present as two identical copies, the recessive trait is expressed

reciprocal cross

paired cross in which the respective trait of the male and female in one cross become the respective traits of the female and male in the other cross

sex-linked

any gene on a sex chromosome

test cross

cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual; the offspring phenotypes indicate whether the unknown parent is heterozygous or homozygous for the dominant trait

trait

variation in the physical appearance of a heritable characteristic

x-linked

gene present on the X, but not the Y chromosome

helicase

during replication, this enzyme helps to open up the DNA helix by breaking the hydrogen bonds

lagging strong

during replication, the strand that is replicated in short fragments and away from the replication fork

leading strand

strains that is synthesized continuously in the 5’-3’ direction, which is synthesized in the direction of the replication fork

ligase

enzyme that catalyzes the formation of a phosphodiester linkage between the 3’ OH and 5’ phosphate ends of the DNA

Okazaki fragment

DNA fragment that is syntheseized in short stretched on the lagging strand

primase

enzyme that synthesizes the RNA primer; the primer is needed for DNA pol to start synthesis of a new DNA strand

primer

short stretch of nucleotides that is required to initiate of replication, in the case of replication, the primer has RNA nucleotides

replication

Y-shaped structure formed during initiation of replication

single-strand binding protein

during replication, protein that binds to the single-stranded DNA; this helps in keeping the two strands of DNA apart so that they may serve as templates

topoisomerase

enzyme that prevents overwinding of DNA when DNA replication, is taking place