Cell Division, Genetics, and Patterns of Inheritance

Vocabulary flashcards covering the cell cycle, mitosis, meiosis, chromosomal abnormalities, Mendelian genetics, non-Mendelian inheritance patterns, and pedigrees based on the lecture notes.

Mitosis

Eukaryotic body-cell division that nuclear division usually produces two genetically identical daughter cells.

Meiosis

Eukaryotic cell division that produces four genetically different haploid cells for sexual reproduction.

Binary fission

Cell division in prokaryotes, such as bacteria.

Interphase

The portion of the cell cycle comprising the $G_1$, S, and $G_2$ phases together.

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S phase

The cell cycle stage where DNA is copied (replicated).

G2

The cell cycle stage where the cell grows more and prepares to divide.

Chromatin

DNA and associated proteins in a loose, uncondensed form.

Chromosome

A DNA molecule packaged with proteins that becomes more condensed and visible during cell division.

Chromatid

One of the two copies of a replicated chromosome; joined at the centromere until separation.

Centromere

The region where sister chromatids are joined until they separate.

Tetrad

Two homologous replicated chromosomes paired together, containing four chromatids in total.

Homologous chromosomes

Matching chromosomes, one from each parent, that carry the same genes at corresponding locations but may have different alleles.

Genome

An organism's complete genetic material.

Synapsis

The pairing of homologous chromosomes during Prophase I of meiosis.

Crossing over

The exchange of DNA between nonsister chromatids of homologous chromosomes during Prophase I.

Cytokinesis

The division of the cytoplasm, forming a cleavage furrow in animal cells or a cell plate in plant cells.

Diploid ($2n$)

Having two sets of chromosomes, equal to 46 in typical human body cells.

Haploid ($n$)

Having one set of chromosomes, equal to 23 in human sperm and egg cells.

Gamete

A haploid reproductive sex cell, such as a sperm or egg.

Zygote

The diploid cell formed when sperm and egg unite during fertilization.

Fertilization

The fusion of two haploid gametes to restore the diploid chromosome number.

Karyotype

An organized display of an individual's chromosomes, arranged in matching pairs by characteristics such as size and shape.

Independent assortment

The random lining up of homologous chromosome pairs in Metaphase I, allowing approximately $2^{23}$ possible combinations in human gametes.

Nondisjunction

The failure of chromosomes or sister chromatids to separate properly during meiosis.

Trisomy ($2n + 1$)

A condition characterized by one extra chromosome, resulting in 47 chromosomes in humans.

Monosomy ($2n - 1$)

A condition characterized by one missing chromosome, resulting in 45 chromosomes in humans.

Chromosomal deletion

A structural chromosome mutation in which a chromosome segment is lost.

Chromosomal duplication

A structural chromosome mutation in which a segment is copied and repeated.

Chromosomal inversion

A structural chromosome mutation where a segment breaks off, reverses, and reattaches.

Chromosomal translocation

A structural chromosome mutation where a segment moves to a different chromosome, often a nonhomologous one.

Benign tumour

A noncancerous tumour that generally stays localized and does not invade distant tissues.

Malignant tumour

A cancerous tumour that can invade nearby tissue and may spread to other parts of the body.

Metastasis

The spread of cancer cells from the original site to another part of the body.

Genetics

The study of heredity and variation — how characteristics are passed from parents to offspring and why individuals differ.

Gene

A section of DNA that contributes to a functional product or influences a trait.

Allele

An alternative version of a gene.

Autosome

Any chromosome that is not a sex chromosome; typically 22 pairs in humans.

Genotype

The specific alleles an organism carries, such as $BB$, $Bb$, or $bb$.

Phenotype

The observable physical characteristic of an organism, such as brown eyes or a particular flower colour.

True-breeding

Organisms that produce offspring with the same trait when self-pollinated under the relevant conditions.

Law of Segregation

Mendel's principle stating that an individual's two alleles for a gene separate during gamete formation, with each gamete receiving one allele.

Law of Independent Assortment

Mendel's principle stating that alleles of different genes assort independently into gametes when genes are unlinked or sufficiently far apart.

Incomplete dominance

An inheritance pattern where neither allele completely masks the other, producing an intermediate phenotype in the heterozygote.

Codominance

An inheritance pattern where both alleles are fully expressed in the heterozygote, such as the $I^AI^B$ genotype in the ABO blood group.

Polygenic inheritance

An inheritance pattern where multiple genes contribute to one trait, often creating a wide range of phenotypes.

Linked genes

Genes located on the same chromosome that tend to be inherited together unless separated by crossing over.

Pedigree

A family-tree diagram used to track how a trait is inherited across generations.

Carrier

An individual who carries an allele associated with a recessive condition but usually does not express the condition.