Lecture 1: Mendelian Genetics and Monogenic Inheritance – Vocabulary Flashcards

A vocabulary-style set of flashcards covering key Mendelian genetics concepts, cell division, chromosome behavior, inheritance patterns, and foundational theories from the lecture notes.

Mendelian genetics

Principles describing how traits are transmitted from parents to offspring, including the Law of Segregation and Law of Independent Assortment.

Monogenic inheritance

A trait controlled by a single gene (one locus).

Wild-type (WT)

The normal or standard form of a trait in a population.

Mutant

A variant form of a trait that differs from the wild-type.

Arabidopsis thaliana

A model plant used to study genetic traits such as floral development.

Neurospora crassa

A fungal model organism used to study growth and branching patterns in genetics.

Pangenesis

Hippocratic idea that seeds are produced by all body parts and transmitted to offspring at conception.

Preformationism

Theory that a miniature organism (homunculus) resides in the sperm or egg and unfolds during development.

Spermists

Proponents who believed hereditary traits reside in the sperm.

Ovists

Proponents who believed hereditary traits reside in the egg.

Blending inheritance

Idea that parental traits blend together in offspring and are transmitted to future generations.

Law of Segregation

During gamete formation, paired alleles segregate so that each gamete receives one allele.

Law of Independent Assortment

Alleles of different genes assort independently during gamete formation (except when linked).

Gene

A discrete hereditary unit; exists in alternative forms called alleles.

Allele

One of the alternative forms of a gene.

Homozygous

Having two identical alleles for a gene.

Heterozygous

Having two different alleles for a gene.

Genotype

The specific allelic composition of an individual for a gene.

Phenotype

The observable physical and functional traits of an individual.

Dominant

Allele whose effect is visible in the phenotype when present with another allele.

Recessive

Allele whose effect is masked in the presence of a dominant allele.

Gamete

A haploid reproductive cell (sperm or egg).

Diploid

A cell or organism with two sets of chromosomes (2n).

Haploid

A cell or organism with a single set of chromosomes (n); typical of gametes.

Interphase

Cell-cycle phase before division, consisting of G1, S, and G2.

S phase

DNA synthesis phase during which chromosomes are replicated.

Mitosis

Nuclear division producing two genetically identical diploid daughter cells.

Meiosis

Cell division that reduces chromosome number by half and increases genetic diversity.

Sister chromatids

Two identical copies of a chromosome held together at the centromere.

Centromere

Region where sister chromatids are held together and where the spindle attaches.

Homologous chromosomes

Chromosome pairs containing the same genes in the same order but possibly different alleles.

Chiasmata

Points where crossing over occurs between homologous chromosomes.

Synaptonemal complex

Protein structure that forms between homologous chromosomes during prophase I to facilitate pairing.

Crossing over

Exchange of genetic material between homologous chromosomes during meiosis.

Recombination

Genetic exchange creating new allele combinations.

Ploidy

Number of chromosome sets in a cell (e.g., diploid 2n, haploid n).

Tetrad

Four chromatids formed during meiosis in diploids, a product of meiosis I.

Meiosis I vs Meiosis II

Meiosis I reduces chromosome number and introduces recombination; Meiosis II separates sister chromatids.

Zygote

Diploid cell formed by the fusion of two gametes.

Saccharomyces cerevisiae

Baker’s yeast, used to study haploid/diploid life cycles and meiosis.

RFLP

Restriction Fragment Length Polymorphism; method to detect DNA variation via restriction enzyme patterns.

Southern blot

Technique to detect specific DNA sequences by transferring fragments to a membrane and probing.

PKU

Phenylketonuria; autosomal recessive disorder due to deficiency of phenylalanine hydroxylase.

PAH

Phenylalanine hydroxylase gene; mutations cause PKU.

Propositus

Index case in a pedigree—the first family member with the phenotype that draws genetic attention.

Autosomal recessive

Disorder appearing in the progeny of unaffected parents; can affect males and females equally.

Autosomal dominant

Disorder that typically appears in every generation; often seen in heterozygotes.

Huntington disease

Late-onset autosomal dominant neurodegenerative disorder.

Polydactyly

Autosomal dominant condition characterized by extra digits.

Piebald spotting

Autosomal dominant pigment pattern variation.

Autosomal polymorphisms

Two or more common phenotypes inherited as alleles of a single autosomal gene.

X-linked inheritance

Genes located on the X chromosome; inheritance patterns differ between sexes.

X-linked recessive

More males affected; affected males do not pass to sons; daughters may be carriers.

Hemophilia

X-linked recessive bleeding disorder due to clotting factor deficiency.

X-linked dominant

Pattern where affected males pass to all daughters; affected females pass to some offspring; rare.

Y-linked inheritance

Genes on the Y chromosome; passed from father to son; males only.

SRY gene

Sex-determining region on the Y chromosome that initiates male development.

Dioecious plants

Plants with separate male and female individuals; sex-related chromosomal patterns observed.

Mating types (yeast)

In Saccharomyces, mating types (commonly MATa and MATα) determine sexual compatibility.

Pedigree

Family tree used to analyze inheritance patterns across generations.

Probability (P) in genetics

Measure of the chance that a genetic event will occur; used to predict offspring outcomes.

Sum Rule

Probability that at least one of several mutually exclusive events occurs; add their probabilities.

Product Rule

Probability that two or more independent events both occur; multiply their probabilities.

Patterns of Mendelian segregation

Autosomal and sex-linked inheritance patterns observed in pedigrees.

Synapsis

Paring of homologous chromosomes during prophase I before recombination.

Crossing over frequency

Rate at which recombination occurs between loci; relates to independent assortment.

Ascus

Membranous sac containing four haploid products (tetrad) in fungi like yeast.

Spore

A reproductive cell produced by meiosis in fungi and plants.