Mitosis/Meiosis/Genetics Definitions

Gametes

Reproductive cells

Somatic cells

Not reproductive cells

Sister Chromatids

A copy of each chromosome after replication

Centromere

Part of the chromosome that attaches to the cytoskeleton

Mitotic Spindle

Cytoskeletal structure consisting of microtubules and proteins, pulls sister chromatids apart

Centrosome

Hundreds of ring-shaped structures that are nucleation sites for microtubules

G1/G2 Phase

Cell growth and mRNA/protein synthesis

S Phase

DNA is replicated

G2 Checkpoint

Cell ensures DNA is duplicated properly- all cell contents must be duplicated

Prophase

DNA is beginning to condense into chromosomes, nucleolus disappears, centrosomes begin moving apart, mitotic spindle is beginning to form

Prometaphase

DNA is condensed more, nuclear envelope is in fragments, centrosomes are moving further apart, mitotic spindle begins to attach to chromosomes

Metaphase

Chromosomes are aligned at the metaphase plate, centrosomes are bi-orientated, mitotic spindle is fully attached to chromosomes

Anaphase

Chromosomes separate to opposite poles, centrosomes are bi-orientated, microtubules change in length to separate the sister chromatids

Telophase

Chromosomes relax into chromatin, nucleus begins to reassemble, mitotic spindle depolymerizes

Cytokinesis (Animals)

Use microfilaments and a contractile ring to separate the new cells

Cytokinesis (Plants)

The cell plate forms from vesicles delivering cell wall materials, the cell plate enlarges and fuses with the plasma membrane

Homologous Chromosomes

Paired chromosomes

Allele

Different versions of a gene that code the same trait

Genotype

Alleles present in an individual

Phenotype

An individuals observable traits

True-breeding Lineage

Offspring only have genotypes the same as parents

Hybrid

Offspring are a combination of different parent types

Polymorphisms

Any common genetic differences resulting from a mutation

Dyhybrid Cross

An experiment that looks at two traits

Law of Dominance

Heterozygotes always express the dominant trait

Law of Segregation

Parental alleles are randomly separated tot he gametes so that gametes contain only one allele of the pair

Law of Independent Assortment

Genes for different traits are sorted separately from one another so that the inheritance of 1 trait is not dependent on the inheritance of another

Linked Genes

Do not sort into gametes independently

Incomplete Dominance

Dominant allele does not completely mask the expression of another allele

Co-Dominance

both alleles are expressed in heterozygous conditions

Epistasis

Trait resulting from interactions among two or more gene pairs- one trait masks the other

X-Linked Genes

Traits reside on X-chromosome

Polygenic Inheritance

Traits are determined by multiple genes

Complex Traits

The more genes affecting the same trait, the more shades of variation are possible

Prophase 1

Chromosomes “cross over”

Metaphase 1

Chromosomes line up in the middle in pairs

Equational Divison

Meiosis 2- the number of chromosomes is not being reduced

Reductional Division

Meiosis 1- reduces the number of chromosomes in half