Biology Advanced Unit 4: Meiosis and Punnet Squares

Allele

An alternative form that a single gene can have for a particular trait.

Autosome

A chromosome that is not a sex chromosome

Chromosome

Condensed DNA containing structure that carries genetic material from one generation to another

Codominance

Non-mendelian pattern of inheritance that occurs when neither allele is dominant and both alleles are not expressed

Crossing Over

Exchange of chromosomal segments between a pair of homologous chromosomes during prophase 1 of mitosis

Dihybrid Cross

Cross of 2 individuals differing in 2 traits; looking at the resulting offspring's genotype and phenotype

Diploid

Having 2 copies of each chromosome; represented as (2n); these are body/somatic cells

Dominance

Relationship between alleles in which the phenotype of one allele masks the phenotype of the other allele

Dominant Trait

Mendel's name for a specific trait that appeared in the F1 generation

F1 (Filial) Generation

The first generation of offspring produced by a set of parents

Fertilization

The process by which a haploid sperm combines with the haploid egg/ovum

Gamete

Haploid sex cell, formed by meiosis; male=sperm; female=egg/ovum

Gene

Functional unit of DNA that controls inherited trait expression that is passed from one generation to another

Genome

Entire set of DNA found in the nucleus of each cell of an organism

Genotype

An organism's allele pairs

Haploid

Cell with half the number of chromosomes as a diploid cell; these are gametes/sex cells and are represented as (n)

Heterozygous

Organism with two different alleles for a specific trait

Homologous

Paired chromosomes, one from each parent, that are similar in size and location of centromere and carry genes for the same traits at the same location; they are similar but not identical

Homozygous

Organism with two of the same alleles for a specific trait (also referred to as purebred)

Incomplete Domicance

Non-mendelian inheritance in which heterozygous phenotype is intermediate / a blend between those of the two homozygous parent organism

Inherited Trait

A trait passed from parent to offspring, determined by genes

Law of Independent Assortment

Mendelian law stating that a random distribution of alleles occurs during the formation of gametes

Law of Segregation

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

Meiosis

Reproductive process that occurs only in sex cells (gametes) in which one diploid cell produced four haploid cells that are genetically unique

Monohybrid Cross

Cross of 2 individuals differing in one trait and looking at the resulting offspring's genotype and phenotypes

Multiple Alleles

Having more than 2 alleles for a trait (for example the A,B,O blood type)

Non-Mendelian Inheritance

Inheritance of traits that have more complex genetic basis than complete dominant and recessive relationships between the alleles

Phenotype

Observable characteristic that is expressed as a result of an allele pair

Punnet Square

Square diagram that is used to predict the genotypes of a particular cross or breeding experiment

Recessive

Mendel's name for specific trait hidden or masked by a dominant allele

Sex Cell

Haploid reproductive cells of an organism that are the product of Meiosis; also called gametes

Sex Chromosome

X or Y chromosome; paired sex chromosomes determine the gender of an individual (XX = female; XY = male)

Sex-linked Trait

Characteristic/trait controlled by genes on the X chromosome (also called X-linked trait)

Sister Chromatid

A structure that contains identical DNA copies and is formed during DNA replication

Tetrad

A 4 part structure that forms during prophase 1 of meiosis consisting of 2 homologous chromosomes, each composed of 2 sister chromatids

Zygote

Cell formed by the union of two gametes