Cellular Reproduction

Chromosomes

Structures that contain genetic info in the form of DNA

Homologous chromosomes

The two chromosomes in a diploid pair present in a genome; one from the mother and one from the father for their traits to be inherited

Genome

All of the DNA possesssed by an individual organism

Haploid

Only one pair of DNA in the cell

Gametes

Type of cell only involved in sexual reproduction

Genes

Sequences of DNA that code for proteins

Locus

The location of genes on a chromosome

Chromatin

Unpackaged DNA, not prepared for cell division; the entire complex of DNA and associated proteins

Mitosis

The stage of the cell cycle where the cell divides; somatic cell division for growth, maintenance, and development

Meiosis

Cell division specific to the production of gametes (sex cells)

Interphase

The majority of time a cell spends during the cell cycle (90%)

• Cell normally performing its function

• Undergoes preparation for mitosis

G1 Phase

First gap: little change while the cell is preparing to replicate chromosomes

S Phase

Synthesis: DNA replication stage; diffuse chromatin condenses into sister chromatids and centrosomes begin creating mitosis spindle

G2 Phase

Second gap: final preparations for mitosis stage; organelles duplicate and cytoskeleton dismantles

Prophase

• Chromosomes condense and become visible

• Mitotic spindle made of fibers called microtubules emerge from centrosomes

• Nuclear envelope breaks down

• Centrosomes move toward opposite poles

Prometaphase

• Chromosomes continue to condense

• Kinetochores appear at the centromeres

• Mitotic spindle microtubules attach to the kinetochores

Metaphase

• Chromosomes line up at an imaginary line called the metaphase plate

• Each sister chromatid is attached to a spindle fiber originating from opposite poles

Anaphase

• Centromeres split in two

• Sister chromatids pulled apart are now chromosomes

• Certain microtubules/spindle fibers begin to elongate the cell

Telophase

• Chromosomes arrive at opposite poles and begin to de-condense

• Nuclear envelope material surrounds each set of chromosomes

• Mitotic spindle breaks down

• Spindle fibers continue to push the poles apart

Cytokinesis

• Animal cells: a cleavage furrow separates the daughter cells

• Plant cells: a cell plate, the precursor to a new cell wall, separates the daughter cells

Purines

Adenine and Guanine; have 2 rings

Pyrimidines

Thymine and Cytosine; have 1 ring

Origin of replication

Where replication starts on a DNA strand

• Specified by a particular nucleotide sequence

• Where proteins attach to separate the double helix

• Replication proceeds in both directions to create a replication bubble

Leading strand

Strand made continuously by DNA polymerase

Lagging strand

Strand made in fragments (Okazaki fragments) by DNA polymerase

Diploid dominant

Life cycle of animals; multicellular organisms with diploid somatic cells (2n) and only sperm and egg are gametes (n)

Haploid dominant

Life cycle of fungi; sexual reproduction results in zygospore (2n) formation and the rest of the cycle is haploid (n)

Alteration of generations

Life cycle of plants

• Diploid sporophyte produces spores

• Spores become a haploid gametophyte

• Gametophyte produces sperm and egg

• Sperm fertilizes the egg and together form a diploid zygote

• Zygote grows grows into a sporophyte

Heredity

The transmission of traits from one generation to the next

Genetics

The study of heredity

Genotype

The genetic composition of an organism

Phenotype

An organism’s physical appearance based on genotype

Law of Segregation of Chromosomes

• Pairs of alleles segregate during gamete formation

• Monohybrid cross

• AA x aa → Aa x Aa

• Results in AA, Aa, Aa, aa

• 3:1

Law of Independent Assortment

• “How one allele pair separates is independent of how other alleles separate”

• Dihybrid cross

• AABB x aabb

• 9:3:3:1