Biology: Cell Division, Genetics, and Reproduction Key Concepts

Cell division

The process by which a parent cell divides into two or more daughter cells.

Asexual reproduction

A mode of reproduction that does not involve the fusion of gametes, resulting in offspring genetically identical to the parent.

Sexual reproduction

A mode of reproduction that involves the fusion of male and female gametes, resulting in genetically diverse offspring.

Chromosome

A structure composed of DNA and proteins that carries genetic information.

Chromatin

The complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells.

Sister chromatids

Identical copies of a chromosome that are connected by a centromere.

Cell cycle

The series of events that take place in a cell leading to its division and duplication.

Interphase

The phase of the cell cycle where the cell prepares for division, including growth and DNA replication.

Mitosis

The process of cell division that results in two genetically identical daughter cells.

Cytokinesis

The final stage of cell division where the cytoplasm divides, resulting in two separate cells.

Prophase

The first stage of mitosis where chromosomes condense and the nuclear envelope begins to break down.

Metaphase

The stage of mitosis where chromosomes line up at the cell's equatorial plane.

Anaphase

The stage of mitosis where sister chromatids are pulled apart to opposite poles of the cell.

Telophase

The final stage of mitosis where chromosomes de-condense and the nuclear envelope re-forms.

Cell plate

A structure that forms during cytokinesis in plant cells, leading to the separation of the daughter cells.

Centrioles

Cylindrical structures that play a role in cell division by organizing the mitotic spindle.

Spindle

A structure made of microtubules that segregates chromosomes during cell division.

Centromere

The region of a chromosome where sister chromatids are joined together.

Allele

Different forms of a gene that can exist at a specific locus on a chromosome.

Principle of dominance

The principle stating that some alleles are dominant and others are recessive.

Segregation

The separation of alleles during gamete formation, leading to offspring inheriting one allele from each parent.

Gamete

A reproductive cell (sperm or egg) that carries half the genetic information of an organism.

Genetic

Pertaining to genes or heredity.

Fertilization

The fusion of male and female gametes to form a zygote.

Trait

A specific characteristic of an organism that can be inherited.

Hybrid

An organism that has two different alleles for a trait.

Gene

A segment of DNA that codes for a specific protein or trait.

Probability

The likelihood of a particular genetic outcome occurring.

Homozygous

An organism that has two identical alleles for a particular trait.

Heterozygous

An organism that has two different alleles for a particular trait.

Genotype

The genetic makeup of an organism, represented by its alleles.

Phenotype

The observable physical or biochemical characteristics of an organism, determined by its genotype.

Punnett squares

A diagram used to predict the outcome of a genetic cross.

Independent assortment

The principle stating that alleles for different traits segregate independently of one another during gamete formation.

Monohybrid cross

A genetic cross between individuals that differ in one trait.

Dihybrid cross

A genetic cross between individuals that differ in two traits.

Incomplete dominance

A form of inheritance where the phenotype of a heterozygote is intermediate between the phenotypes of the homozygotes.

Codominance

A form of inheritance where both alleles in a heterozygote are fully expressed.

Multiple alleles

The presence of more than two alleles for a genetic trait within a population.

Polygenic traits

Traits that are controlled by multiple genes, resulting in a range of phenotypes.

Homologous chromosome pairs

Pairs of chromosomes that have the same structure and carry genes for the same traits.

Diploid

A cell that contains two complete sets of chromosomes, one from each parent.

Haploid

A cell that contains only one complete set of chromosomes.

Meiosis

A type of cell division that reduces the chromosome number by half, producing four haploid cells.

Tetrad

A structure formed during meiosis consisting of four chromatids (two homologous chromosomes).

Crossing over

The exchange of genetic material between homologous chromosomes during meiosis.

Zygote

The fertilized egg that results from the union of sperm and egg.

Nucleotide

The basic building block of DNA, consisting of a sugar, a phosphate group, and a nitrogenous base.

Complementary

Referring to the relationship between DNA strands where the bases pair specifically (A with T, C with G).

Helix

A spiral structure, such as the shape of DNA.

Double helix

The structure of DNA, consisting of two intertwined strands.

Sequence (of DNA)

The order of nucleotides in a DNA molecule.

DNA replication

The process by which a cell duplicates its DNA before cell division.

DNA polymerase

An enzyme that synthesizes new DNA strands by adding nucleotides to a growing chain.

Replication fork

The Y-shaped region where the DNA is split into two strands for replication.

Telomeres

The protective caps at the ends of chromosomes that prevent degradation.

What is DNA replication?

The process by which a DNA molecule makes a copy of itself, occurring during the S phase of the cell cycle.

What is DNA polymerase?

An enzyme that synthesizes new DNA strands by adding nucleotides to a growing DNA chain during replication.

What is a replication fork?

The Y-shaped region where the DNA double helix is unwound and separated into two single strands during replication.

What are telomeres?

The repetitive nucleotide sequences at the ends of chromosomes that protect them from deterioration or fusion with neighboring chromosomes.

When does DNA replication occur in the cell cycle?

DNA replication occurs during the S phase of interphase, before cell division.

Where does DNA replication occur in prokaryotes?

In prokaryotes, DNA replication occurs in the cytoplasm.

Where does DNA replication occur in eukaryotes?

In eukaryotes, DNA replication occurs in the nucleus.

Why does DNA replication need to occur?

DNA replication is necessary to ensure that each daughter cell receives an identical copy of the DNA during cell division.

What happens during the 'unzipping' process?

The DNA double helix unwinds and separates into two single strands, allowing each strand to serve as a template for new DNA synthesis.

What are the two jobs of DNA polymerase?

DNA polymerase adds nucleotides to the growing DNA strand and proofreads the newly synthesized DNA to correct errors.

What is the job of the enzyme telomerase?

Telomerase extends the telomeres of chromosomes, preventing them from shortening during DNA replication.

How do the number of chromosomes in prokaryotes compare to eukaryotes?

Prokaryotes typically have a single circular chromosome, while eukaryotes have multiple linear chromosomes.

Why are prokaryotic chromosomes circular?

Prokaryotic chromosomes are circular to facilitate replication and to fit within the smaller size of prokaryotic cells.

Why are eukaryotic chromosomes linear?

Eukaryotic chromosomes are linear to accommodate the larger amount of DNA and complex organization within the nucleus.

What is messenger RNA (mRNA)?

A type of RNA that carries genetic information from DNA to the ribosome, where proteins are synthesized.

What is ribosomal RNA (rRNA)?

A type of RNA that forms the core of the ribosome's structure and catalyzes protein synthesis.

What is transfer RNA (tRNA)?

A type of RNA that transports amino acids to the ribosome during protein synthesis, matching them to the appropriate codons in mRNA.

What is transcription?

The process of synthesizing RNA from a DNA template, resulting in the formation of mRNA.

What is RNA polymerase?

An enzyme that catalyzes the synthesis of RNA from a DNA template during transcription.

What is a promoter?

A specific DNA sequence that signals the start of a gene and is recognized by RNA polymerase to initiate transcription.

What is an intron?

A non-coding sequence of RNA that is removed during RNA processing before translation.

What is an exon?

A coding sequence of RNA that remains in the final mRNA molecule after introns are removed.

What is a polypeptide?

A chain of amino acids linked by peptide bonds, which folds into a functional protein.

What is the genetic code?

The set of rules by which information encoded in mRNA is translated into proteins, consisting of codons.

What is a codon?

A sequence of three nucleotides in mRNA that specifies a particular amino acid.

What is translation?

The process by which ribosomes synthesize proteins using the information carried by mRNA.

What is an anticodon?

A sequence of three nucleotides in tRNA that pairs with a complementary codon in mRNA during translation.

What is gene expression?

The process by which information from a gene is used to synthesize a functional gene product, typically a protein.

What are mutations?

Changes in the DNA sequence that can lead to alterations in gene function or expression.

What is a point mutation?

A mutation that involves a change in a single nucleotide in the DNA sequence.

What is a frameshift mutation?

A mutation caused by insertions or deletions of nucleotides that shifts the reading frame of the genetic code.

What is a mutagen?

An agent, such as radiation or chemicals, that causes changes in the DNA sequence.

What is polyploidy?

A condition in which an organism has more than two complete sets of chromosomes, often seen in plants.

What is evolution?

The change in the heritable characteristics of biological populations over successive generations.

What is a fossil?

The preserved remains or traces of ancient organisms, providing evidence of past life and evolutionary change.

What is artificial selection?

The process by which humans breed plants and animals for specific traits.

What are acquired traits?

Characteristics that are not inherited genetically but are developed during an organism's lifetime.

What is adaptation?

A trait that enhances an organism's ability to survive and reproduce in its environment.

What is fitness?

The ability of an organism to survive and reproduce in its environment, contributing to the gene pool of the next generation.

What is natural selection?

The process by which organisms better adapted to their environment tend to survive and produce more offspring.

What is the struggle for existence?

The competition among organisms for limited resources such as food, space, and mates.

What is a common ancestor?

A species from which two or more different species have evolved.

What is biogeography?

The study of the distribution of species and ecosystems in geographic space and through geological time.

What are homologous structures?

Anatomical features in different species that share a common ancestry, even if they have different functions.