Genetics Exam 2

pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family.

mode of inheritance

the pattern in which a genetic disease is inherited through generations

simple dominance

a pattern of inheritance in which there are only two alleles and the dominant trait is always expressed in a hybrid organism

dominant

Describes a trait that covers over, or dominates, another form of that trait.

genotype

genetic makeup of an organism

punnett square

A chart that shows all the possible combinations of alleles that can result from a genetic cross

forked-line diagram

a method for diagramming the probabilities of outcomes in a branching format

recessive

An allele that is masked when a dominant allele is present

allele

An alternative form of a gene.

phenotype

An organism's physical appearance, or visible traits.

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

mendel's principle of segregation

The two members of a gene pair (alleles) segregate (separate) from each other in the formation of gametes. Half the gametes carry one allele, and the other half carry the other allele.

independent assortment

One of Mendel's principles that states that genes for different traits can segregate independently during the formation of gametes

homozygous

An organism that has two identical alleles for a trait

heterozygous

An organism that has two different alleles for a trait

mutant

An organism genetically different from its parent

wildtype

the most common genotype/phenotype observed in a population

P1

parental generation

F1

first generation

F2

second generation

true-breeding

term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate

test cross

the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype

transposable element

Segment of DNA that can move spontaneously within or between chromosomes.

polymorphism

The coexistence of two or more distinct forms in the same population.

PCR

(polymerase chain reaction) a method used to rapidly make multiple copies of a specific segment of DNA; can be used to make millions of copies of DNA from a very small amount of DNA

meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

carrier

A person whose genotype includes a gene that is not expressed in the phenotype.

incomplete dominance

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

codominance

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

lethal allele

an allele whose expression results in the death of the individual organism expressing it

epistasis

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

genetic analysis

Determination of the function of cell RNAs and proteins based on the phenotype of cells in which the gene encoding the RNA or protein is mutated.

complement

something that completes or makes up a whole

3:1 ratio

heterzygous x heterozygous f2 generation phenotypic result

9:3:3:1 ratio

heterozygous x heterozygous f2 generation phenotypic result for dihybrid cross

autosome

Any chromosome that is not a sex chromosome

x-linked

referring to a gene located on the X chromosome

multiple alleles

three or more forms of a gene that code for a single trait

pleiotropy

The ability of a single gene to have multiple effects.

sex-limited

When expression of a gene depends on the sex of the individual.

sex-influenced

can be influenced by sex of individual carrying trait (e.g. Bb female not bald, Bb male is)

genetic anticipation

number of repeats increases in future generations causing symptoms to be worse

test cross

the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype

single crossover

leads to half recombinant, half non recombinant

double crossover

Chromosomes may trade a segment once and then trade back a sub-section of that segment so that each chromosome regains some of its own original genetic material.

linkage

occurs when different traits are inherited together more often than they would have been by chance along; it is assumed that these traits are linked on the same chromosome

recombinant

of or resulting from new combinations of genetic material

parental

characteristic of a mother or father

recombinant frequency

the proportion of offspring of a genetic cross that have phenotypes different from the parental phenotypes due to crossing over between linked genes during gamete formation

LOD score

The ratio of probabilities

that two genes are linked to the probability that they are not linked,

expressed as a log10. Scores of 3.0 or higher are taken as establishing

linkage.

Manhattan Plot

a graphical representation of DNA variants that may be associated