Module #6-Mendalian genetics, genes & chromosomes. Genes & alleles2.

P generation

the parental generation, true-breeding parents

multiple allele

The human ABO blood group.

Trait

A characteristic that an organism can pass on to its offspring through its genes.

For instance: Eye color

gametes contain

one allele for every gene

Mendel studied

pea plants and experimented with clearly contrasting phenotypes.

Phenotype

physical appearance.

self-pollinate

male and female gametes fertilize within the same flower

Genotype

genetic structure; "letters"

F1 generation

offspring of the P generation.

F2 generation

the second generation of offspring, obtained from an experimental cross between F1 individuals or by self-pollination of F1 individuals

Pedigree

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

Alleles

Alternative forms of a gene.

Dominent allele/trait

An allele whose trait always shows up in the organism when the allele is present.

Recessive allele/trait

An allele that is masked when a dominant allele is present

Gene

a DNA sequence that cotains the information to make an RNA or ptrotein product with a specific function.

Each gene is a segment of DNA molecule.

Principle of Segregation (Mendel's First Law)

states that before sexual production occcurs, the two alleles carried by an individual parent must become separarted.

Gametes

sex cells

homologous chromosomes

usually have the same genes, often with different alleles, that located in corresponding positions

monohybrid cross

the inheritence of two different alleles of a single gene

Homozygous

two identical alleles

Heterozygous

two different alleles

Principle of Independent Assortment

stats that memebers of any gene pair segregate from one another independently of the memebers of the other gene pairs.

human females have

two X chromosomes

Y chromosome

found in human males

Autosomes

Chromosomes that are not directly involved in determining the sex of an individual.

sex chromosomes

carries the major sex-determining genes.

dihybrid cross

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

Fertilization

Fusion of an egg and sperm cell

X-linked

Genes located in the X chromosome.

X chromosome

contains many numerous genes required by both sexes, yet a normal female has two copies

Punnett Square

form of a grid that represents the possible combinations of egg and sperm at fertilization.

Codominance

The alleles do not dominent one over another,

they make combination, a mixture.

Both alleles in the genotype are seen in the phenotype.

Incomplete dominance

Cases in which one allele is not completely dominant over another. "blended"

carrier

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

polygenic traits

traits controlled by two or more genes; example skin color

Hemophilia

An X-linked recessive disorder in which blood fails to clot properly, leading to excessive bleeding if injured.

Huntington's disease

A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms.

Hybrid

Offspring of crosses between parents with different traits