Mendelian and Molecular Genetics Exam 1 Flashcards

Vocabulary practice flashcards covering Mendelian genetics, DNA replication, gene expression, and embryonic development.

Gene locus

The specific physical location of a gene on a chromosome.

Homologous chromosome pairs

Chromosomes that carry the same gene loci in the same order, although they may have different alleles.

True breeding

Organisms that always produce offspring with the same phenotype, which are usually homozygous.

Homozygous

An organism that possesses two identical alleles (e.g., AA or aa) for a gene.

Heterozygous

An organism that possesses two different alleles (e.g., Aa) for a gene.

Law of Segregation

Principle stating that two alleles of a gene separate during gamete formation in meiosis I.

Law of Independent Assortment

Principle stating that alleles of different genes assort independently if the genes are unlinked.

Genotype

The genetic makeup of an organism, represented by the alleles present.

Phenotype

The observable traits of an individual.

Incomplete dominance

A mode of inheritance where the heterozygote shows an intermediate phenotype.

Codominance

A mode of inheritance where both alleles are fully expressed.

Polygenic traits

Traits where many genes contribute additively; also known as quantitative traits.

Genetic linkage

The tendency of genes located close together on the same chromosome to be inherited together during meiosis.

Recombinant types

New combinations of phenotypes not seen in the parents, resulting from crossing over.

Recombination frequency

The proportion of recombinant gametes produced due to crossing over between two genes.

Purines

The nitrogenous bases Adenine (A) and Guanine (G).

Pyrimidines

The nitrogenous bases Cytosine (C) and Thymine (T) in DNA, or Uracil (U) in RNA.

Phosphodiester bonds

Covalent bonds forming the sugar-phosphate backbone by joining the $3'$ hydroxyl of one sugar to the $5'$ phosphate of the next nucleotide.

Antiparallel arrangement

The structural characteristic of DNA where the two strands run in opposite directions ($5'$ to $3'$ and $3'$ to $5'$).

Helicase

The enzyme that unwinds and separates the DNA strands during replication.

Topoisomerase

The enzyme that relieves twisting and supercoiling ahead of the replication fork.

Single strand binding proteins (SSBs)

Proteins that stabilize separated DNA strands to prevent them from re-annealing.

Primase

The enzyme that synthesizes short RNA primers.

DNA polymerase III

The main synthesizing enzyme that extends DNA from RNA primers.

DNA polymerase I

The enzyme that removes RNA primers and replaces them with DNA.

DNA ligase

The enzyme that seals gaps between DNA fragments like Okazaki fragments.

Okazaki fragments

Short DNA segments synthesized discontinuously on the lagging strand.

Central Dogma

The conceptual framework of genetic information flow: DNA to RNA to Protein.

Transcription factors

Proteins that help RNA polymerase bind to DNA and initiate transcription.

Alternative splicing

A process that allows different exon combinations from one gene, resulting in multiple distinct proteins.

Reading frame

The specific grouping of nucleotides into codons, determined by where translation begins at the start codon AUG.

Silent mutation

A point mutation where the codon changes but still codes for the same amino acid.

Missense mutation

A point mutation where the codon changes and results in a different amino acid.

Nonsense mutation

A point mutation where the codon changes to a stop codon.

Frameshift mutation

An insertion or deletion of nucleotides (not in multiples of $3$) that shifts the reading frame and alters all downstream amino acids.

Consensus sequences

Common nucleotide patterns in promoters, such as the TATA box, that ensure accurate transcription.

Introns

Noncoding regions of pre-mRNA that are removed during splicing.

Exons

Coding regions of mRNA that remain after splicing and are translated into protein.

Untranslated regions (UTRs)

Regions at the $5'$ and $3'$ ends of mRNA that are not translated into protein but affect regulation and stability.

Acrosomal reaction

A process where the sperm releases enzymes and an acrosomal process extends to penetrate the egg jelly.

Cortical reaction

A process where cortical granules release contents to form a fertilization envelope and prevent polyspermy.

Cleavage

Rapid mitotic divisions following fertilization with no growth between divisions, resulting in smaller cell sizes.

Blastula

A hollow ball of cells formed at the end of the cleavage stage.

Gastrulation

The reorganization of the blastula into distinct germ layers (ectoderm, endoderm, and sometimes mesoderm).

Organogenesis

The process by which organs form from the three germ layers after gastrulation.

Induction

The developmental process where one group of cells influences the fate of another group of cells.

Determination

The stage of development where a cell's fate becomes fixed and irreversible.

Amnion

An extraembryonic membrane that forms a fluid-filled sac to cushion the embryo.

Chorion

The outermost extraembryonic membrane used for gas exchange and contributing to the placenta in humans.

Inner Cell Mass (ICM)

The part of the blastocyst derived from the zygote that gives rise to the embryo proper.

Trophoblast

The outer layer of the blastocyst that gives rise to the chorion and placenta.

Epiblast

The structure derived from the inner cell mass that gives rise to all three germ layers.