Genetics, Cell Division, and Population Dynamics

Comprehensive vocabulary flashcards covering cell biology, DNA structure, Mendelian and non-Mendelian inheritance, meiosis, sources of genetic variation, mutations, and evolutionary population dynamics.

Cell

The basic building blocks or units that make up all living organisms.

DNA (Deoxyribonucleic Acid)

The double-stranded molecule located in the nucleus that contains the genetic code.

Chromosome

A structure composed of a tightly wound $DNA$ molecule. Humans have $46$ chromosomes in total ($23$ from mum and $23$ from dad).

Gene

A specific section of $DNA$ that codes for a particular feature or characteristic.

Allele

Each distinct version or variant of a gene.

Nucleotide

The structural subunit of $DNA$, consisting of a phosphate group, a $5$-carbon sugar (pentose), and a nitrogenous base ($A$, $T$, $C$, or $G$).

Base-Pairing Rule

The complementary pairing of nitrogenous bases in $DNA$, where Adenine pairs with Thymine ($A - T$) and Cytosine pairs with Guanine ($C - G$).

Genotype

The combination of alleles an organism possesses for a particular gene (such as $AA$, $Aa$, or $aa$).

Phenotype

The physical expression or observable feature of a gene or genotype (such as short fur or brown eyes).

Homozygous Dominant

A genotype consisting of two identical dominant alleles (for example, $AA$).

Heterozygous

A genotype consisting of two different alleles for a specific gene (for example, $Aa$).

Homozygous Recessive

A genotype consisting of two identical recessive alleles (for example, $aa$).

Complete Dominance

A pattern of inheritance where one allele is completely dominant over another, completely masking the effect of the recessive allele in heterozygous individuals.

Incomplete Dominance

An inheritance pattern where neither allele is completely dominant or recessive, resulting in a heterozygous phenotype that is an intermediate blend of the parents' phenotypes.

Codominance

An inheritance pattern where both alleles of a gene pair in a heterozygote are fully and independently expressed simultaneously (such as in $AB$ blood type or red-and-white spotted flowers).

Antigen

A molecular marker on cells that causes the immune system to send antibodies to attack if recognized as foreign.

Dihybrid Cross

A genetic cross examining the inheritance of two different genes simultaneously.

Meiosis

The type of cell division that produces gametes containing half the original number of chromosomes (haploid cells).

Gametes

Haploid sex cells (sperm and egg) that carry a half set of chromosomes ($23$ in humans) and combine to form a zygote.

Homologous Chromosomes

A pair of matching chromosomes (one paternal, one maternal) that carry the same genes at the same locations, but may have different alleles.

Crossing Over (Recombination)

The process during meiosis where homologous chromosomes pair up and exchange small segments of $DNA$ with each other, generating new allele combinations.

Independent Assortment

The process during meiosis where homologous chromosome pairs line up randomly and independently along the cell equator before separation.

Segregation

The separation and distribution of chromosomes into separate gametes during meiosis, ensuring each gamete receives a unique combination of alleles.

Somatic Cells

All non-gametic body cells that contain a full diploid set of chromosomes ($46$ in humans). Mutations occurring in somatic cells cannot be passed down to offspring.

Gametic Cells

Sex cells (sperm and egg) containing a haploid set of chromosomes ($23$ in humans). Mutations occurring in these cells are inherited by offspring.

Mutation

A permanent, random change in the $DNA$ sequence; it serves as the only source of entirely new alleles in a gene pool.

Population

A group of interbreeding individuals belonging to the same species living in a specific geographical area.

Gene Pool

The total collection of all different genes and alleles present in an interbreeding population.

Allele Frequency

The occurrence or proportion of a specific allele relative to all alleles for that gene within a population.

Natural Selection

The process where individuals possessing phenotypes better suited to their environment have greater survival and reproductive success, passing their favorable alleles on to subsequent generations.

Migration

The movement of individuals and their alleles into or out of a population.

Immigration

The movement of individuals into an existing population, which can introduce new alleles and increase genetic variation.

Emigration

The departure of individuals leaving a population, which can decrease genetic variation by permanently removing alleles from the gene pool.

Genetic Drift

A change in allele frequencies within a population resulting purely from chance events, having a far greater impact on small populations than large ones.

Bottleneck Effect

A sharp decrease in population size to a small group of survivors following a catastrophic event (such as a natural disaster or climate change), dramatically altering allele frequencies.