Biology Practice: Cell Growth, Genetics, DNA, and Evolution

Flashcards covering terminology from Chapters 11-18 of the biology curriculum, including cell division, genetics, molecular biology, biotechnology, and evolution.

Cell division

The process by which a cell divides into new daughter cells, addressing the difficulties a cell faces as it grows.

Asexual reproduction

A form of reproduction involving a single parent that results in offspring that are genetically identical to the parent.

Sexual reproduction

A form of reproduction involving two parents that results in offspring inheriting genetic information from both parents.

Surface area:volume ratio

A calculation used to explain why a cell must divide; this ratio decreases as a cell grows.

Chromosome

Structures that package DNA; they are circular in prokaryotes and linear in eukaryotes.

Chromatin

A substance found in eukaryotic chromosomes consisting of DNA tightly coiled around histones.

Sister chromatids

Two identical parts of a duplicated chromosome.

Cell cycle

A series of events characterized by interphase and cell division (mitosis and cytokinesis).

Interphase

The stage of the cell cycle occurring between divisions, consisting of three main stages.

Mitosis

The division of the cell nucleus, occurring in four phases: prophase, metaphase, anaphase, and telophase.

Cytokinesis

The division of the cytoplasm that causes daughter cells to split apart after mitosis.

Cell plate

A structure that forms during cytokinesis in plant cells to separate the two daughter cells.

Centrioles

Structures in animal cells that help organize the spindle during cell division.

Spindle

A fanlike system of microtubules that helps separate the chromosomes during mitosis.

Centromere

The region of a chromosome where the two sister chromatids attach.

Allele

The different forms of a gene; an individual typically has $2$ for a trait, one inherited from each parent.

Principle of dominance

Mendel's second conclusion, which states that some alleles are dominant and others are recessive.

Segregation

The separation of alleles during the formation of gametes.

Gamete

A specialized cell (egg or sperm) that passes on only one allele for a trait.

Fertilization

The process in sexual reproduction in which male and female reproductive cells join to form a new cell.

Trait

A specific characteristic of an individual.

Hybrid

Offspring of crosses between parents with different traits.

Gene

A factor that is passed from parent to offspring; the basic unit of heredity.

True breeding

Organisms that always produce offspring identical to themselves; used by Mendel for the P generation.

Probability

The likelihood that a particular event will occur; used in genetics to predict the outcomes of crosses.

Homozygous

Having two identical alleles for a particular gene (e.g., $TT$ or $tt$).

Heterozygous

Having two different alleles for a particular gene (e.g., $Tt$).

Genotype

The genetic makeup of an organism.

Phenotype

The physical characteristics or observable traits of an organism.

Punnett squares

Diagrams used to predict the genotypes and phenotypes of a genetic cross.

Independent assortment

The principle that genes for different traits can segregate independently during the formation of gametes.

Monohybrid cross

A genetic cross looking at a single trait at a time.

Dihybrid cross

A genetic cross looking at two traits simultaneously, resulting in a phenotypic ratio that adds up to $16$.

Incomplete dominance

A situation in which one allele is not completely dominant over another, resulting in a pink phenotype ($AB$) from red ($A$) and white ($B$) parents.

Codominance

A situation in which the phenotypes produced by both alleles are clearly expressed, such as an organism being half red and half white.

Multiple alleles

A gene that has more than two alleles (e.g., human blood types).

Polygenic traits

Traits controlled by two or more genes, which typically show more variation than single-gene traits.

Homologous chromosome pairs

Pairs of chromosomes that are similar but not identical because they carry the same genes but possibly different alleles.

Diploid

A cell containing two complete sets of chromosomes, one from each parent; skin cells are an example.

Haploid

A cell containing only a single set of chromosomes; eggs and sperm are examples.

Meiosis

The process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes.

Tetrad

A structure containing four chromatids that forms during meiosis when homologous pairs join.

Crossing over

A process in meiosis where homologous chromosomes exchange portions of their chromatids.

Zygote

A fertilized egg.

Nucleotide

The monomer of DNA consisting of three parts: a sugar (deoxyribose), a phosphate group, and a nitrogenous base.

Nitrogenous bases

The four types of bases in DNA: adenine, thymine, cytosine, and guanine; adenine pairs with thymine, and cytosine pairs with guanine.

Covalent bonds

Strong bonds that hold the parts of a single DNA strand together.

Hydrogen bonds

Weak bonds that hold the two complementary strands of a DNA molecule together.

Chargaff

Scientist who discovered the base-pairing rules (e.g., if DNA is $14\%$ cytosine, it must also be $14\%$ guanine).

Rosalind Franklin

Scientist who used X-ray diffraction to contribute information about the structure of DNA.

Watson and Crick

Scientists who built the double helix model of DNA.

DNA replication

The process occurring before cell division where DNA is copied, creating two identical molecules.

DNA polymerase

The principal enzyme involved in DNA replication that joins nucleotides and proofreads the new strand.

Replication fork

The Y-shaped region where the two strands of DNA are unzipped to allow replication to occur.

Telomeres

The tips of eukaryotic chromosomes; the enzyme telomerase helps replicate them.

Messenger RNA (mRNA)

The type of RNA that carries instructions for protein synthesis from the nucleus to the ribosome.

Transcription

The process where RNA polymerase uses DNA as a template to make a complementary mRNA strand.

RNA polymerase

The enzyme that binds to promoters to initiate transcription.

Intron

A portion of RNA that is edited out and discarded before the molecule becomes functional.

Exon

The remaining pieces of RNA that are spliced back together to form the final mRNA.

Genetic code

The system of reading mRNA bases in groups of three (codons) to determine the amino acid sequence.

Codon

A group of three nucleotide bases in mRNA that specifies a particular amino acid.

Translation

The process where the ribosome reads the mRNA code to assemble a polypeptide chain.

Central dogma

The molecular biology principle that information flows from DNA to RNA to Protein.

Mutation

A change in the genetic material of a cell.

Point mutation

A gene mutation in which a single base pair in DNA has been changed.

Frameshift mutation

A mutation that shifts the "reading frame" of the genetic message by inserting or deleting a nucleotide.

Selective Breeding

A method of breeding that allows only those individual organisms with desired characteristics to produce the next generation; includes hybridization and inbreeding.

Polyploidy

A condition in which an organism has extra sets of chromosomes; often used to produce larger, stronger plants.

Polymerase chain reaction (PCR)

A technique used by scientists to make many copies of a particular DNA sequence.

Recombinant DNA

DNA produced by combining DNA from different sources.

Clone

A member of a population of genetically identical cells produced from a single cell.

Evolution

Change over time; in genetic terms, a change in the frequency of alleles in a population.

Fossil

Preserved remains or traces of ancient organisms which Darwin used to support his theories.

Artificial selection

Selective breeding by humans to enhance desired traits in plants or animals.

Adaptation

A heritable characteristic that increases an organism's ability to survive and reproduce.

Fitness

How well an organism can survive and reproduce in its environment.

Natural selection

The process by which organisms with variations most suited to their environment survive and leave more offspring.

Homologous structures

Structures that are shared by related species and have been inherited from a common ancestor.

Analogous structures

Body parts that share a common function, but not structure (e.g., a bird's wing and a bee's wing).

Vestigial structures

Structures inherited from ancestors but which have lost much or all of their original function, such as the pelvic bones of modern whales.

Gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time.

Allele frequency

The number of times an allele occurs in a gene pool compared to the total number of alleles in that pool for the same gene.

Genetic drift

A random change in allele frequency, often occurring in small populations.

Bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population.

Founder effect

A change in allele frequency as a result of the migration of a small subgroup of a population.

Directional selection

Selection that occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end.

Stabilizing selection

Selection that occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end.

Disruptive selection

Selection that occurs when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle.

Genetic equilibrium

A situation in which allele frequencies in a population remain the same.

Speciation

The formation of a new species resulting from isolation.

Reproductive isolation

When some members of a population stop breeding with others, leading to the splitting of the gene pool into two species; includes behavioral, geographic, and temporal isolation.