Exam 4 Review: DNA Replication, Mitosis, Meiosis, and Genetics

Comprehensive vocabulary flashcards covering DNA replication mechanisms, the mitotic cell cycle, meiosis, and Mendelian genetic principles.

Nucleotide

The monomer of a nucleic acid, consisting of three major components: phosphate group(s), a pentose sugar, and a nitrogenous base.

Phosphodiester Bond

The type of chemical bond that joins nucleotides together into polymers to create nucleic acid strands.

Semiconservative DNA Replication

The process of DNA replication wherein each newly formed double helix consists of one conserved parental strand and one newly synthesized strand.

Origin of Replication (ORI)

A specific sequence of DNA where the process of DNA replication is initiated.

Replication Fork

A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized.

Helicase

An enzyme required in the initiation phase of DNA replication that untwists and unwinds the parental DNA strands at the replication fork.

SSBs (Single-Stranded Binding Proteins)

Proteins that bind to and stabilize single-stranded DNA during initiation to prevent the strands from re-annealing.

Primase

An enzyme that synthesizes short RNA primers to provide a starting point for DNA polymerase to begin synthesizing DNA.

DNA Polymerase III (DNAPIII)

The primary enzyme in elongation that reads the template DNA strand in the $3' \rightarrow 5'$ direction and synthesizes new DNA in the $5' \rightarrow 3'$ direction.

Sliding Clamp

A protein required in elongation that tethers DNA polymerase III to the template strand, increasing its processivity.

Topoisomerase (DNA Gyrase)

A protein required during elongation that relieves torsional strain and prevents supercoiling ahead of the advancing replication fork.

Leading Strand

The new complementary DNA strand synthesized continuously toward the replication fork in the mandatory $5' \rightarrow 3'$ direction.

Lagging Strand

The discontinuously synthesized DNA strand that elongates away from the replication fork, produced as a series of Okazaki fragments.

Okazaki Fragments

Short segments of DNA synthesized discontinuously along the lagging strand during DNA replication.

DNA Polymerase I (DNAPI)

The enzyme in lagging strand synthesis that removes RNA primers and replaces them with complementary DNA nucleotides.

DNA Ligase

An enzyme that forms phosphodiester bonds to connect Okazaki fragments together on the lagging strand.

Chromosome

A cellular structure carrying genetic information, visible as a condensed unit of packaged chromatin during cell division.

Chromatid

One of two identical copies of a replicated chromosome joined together at a centromere.

Chromatin

The complex of DNA and associated proteins that composes eukaryotic chromosomes when the cell is not actively dividing.

Centromere

The specialized DNA region on a chromosome where sister chromatids are most closely joined together.

Centrosome

The microtubule-organizing center of the cell that houses the apparatus organizing the mitotic spindle during division.

Kinetochore

A specialized protein structure located at the centromere of each chromatid to which spindle microtubules attach during cell division.

Kinetochore Microtubules

Spindle microtubules that directly connect to kinetochore proteins on chromosomes to pull sister chromatids or chromosomes apart.

Polar Microtubules

Non-kinetochore microtubules of the mitotic spindle that overlap and push against each other to elongate the cell during division.

Cytokinesis (Animal Cells)

The physical division of the cytoplasm following mitosis, driven by the contractile action of actin and myosin proteins.

Somatic Cells

Any biological cells forming the body of an organism other than gametes or germ cells, typically possessing a diploid set of chromosomes.

Gametes

Haploid reproductive cells produced by meiotic cell division that carry half the normal number of chromosomes.

Homologous Chromosomes

A pair of chromosomes possessing the same genes at the same loci, with one member inherited from each parent.

Diploid

A cell or organism possessing two complete sets of chromosomes, one derived from each parent.

Haploid

A cell or organism possessing a single set of unpaired chromosomes.

Synapsis

The physical pairing and pairing up of duplicated homologous chromosomes during Prophase I of Meiosis.

Crossing Over

The reciprocal exchange of genetic material between non-sister chromatids of homologous chromosomes during Prophase I of Meiosis.

Gene

A discrete unit of hereditary information located at a specific locus on a chromosome that codes for a specific trait.

Allele

Any of the alternative versions of a gene that can exist at a single gene locus.

Genotype

The genetic makeup or specific combination of alleles present in an organism.

Phenotype

The observable physical or physiological traits of an organism, determined by its genotype and environment.

Homozygous

Having two identical alleles for a particular gene.

Heterozygous

Having two different alleles for a particular gene.

Dominant Allele

An allele that is fully expressed in the phenotype whenever it is present in either the homozygous or heterozygous state.

Recessive Allele

An allele whose phenotypic effect is fully masked in a heterozygote and only expressed when an organism is homozygous for that allele.

Law of Segregation

Mendel's principle stating that the two alleles of a single gene separate from each other during gamete formation in meiosis, ending up in different gametes.

Law of Independent Assortment

Mendel's principle stating that alleles from two separate genes segregate independently into gametes during meiosis, producing $2^{23}$ possible assortments in humans.

P Generation

The true-breeding parental generation from which offspring are produced in genetic crosses.

F1 Generation

The first filial hybrid offspring resulting directly from a cross between two individuals of the parental (P) generation.

F2 Generation

The second filial generation of offspring produced by intercrossing or self-pollinating individuals of the $F_1$ generation.

Testcross

Breeding an individual exhibiting a dominant phenotype (unknown genotype) with a homozygous recessive individual to determine the unknown genotype.

Incomplete Dominance

A non-Mendelian inheritance pattern where heterozygotes show an intermediate phenotype blended between the two homozygous parental phenotypes.

Codominance

A non-Mendelian inheritance pattern where both alleles for a gene are distinctly and fully expressed in the phenotype of a heterozygote.

Sex-Linked Genes

Genes located specifically on either the X or Y sex chromosomes.