Classic Experiments and Genetics Key Terms

Vocabulary flashcards covering landmark experiments in molecular genetics, basic genetic terms, and Mendelian cross ratios based on lecture notes.

Mendel

Scientist who used pea plants to discover the basic principles of inheritance, showing that traits are passed from parents to offspring through genes as dominant and recessive traits.

Miescher (Friederich Miescher)

Scientist who isolated "nuclein" from cell nuclei (later recognized as DNA) and discovered that DNA contained $PO_4^-$.

Morgan

Scientist who used fruit flies (Drosophila) to show that genes are located on chromosomes, discovered sex-linked inheritance, and proved that chromosomes contain more than one gene.

Levene

Scientist who identified the basic components of nucleotides: sugar, phosphate, and nitrogenous base.

Beadle and Tatum

Scientists who used Neurospora (bread mold) to show that genes control enzyme production, establishing the "one gene one enzyme" hypothesis.

Griffith

Scientist who used bacteria and mice to demonstrate bacterial transformation and introduced the concept of the "transforming principle".

Avery, MacLeod and McCarty

Scientists who showed that DNA was the transforming material by selectively destroying protein, RNA, and DNA, providing direct evidence that DNA carries genetic information.

Chargaff

Scientist who established Chargaff's rules in DNA, stating that $A = T$ and $G = C$.

Hershey and Chase

Scientists who used bacteriophages to prove that DNA, and not protein, is the genetic material that enters bacteria.

Franklin and Wilkins

Scientists who used X-ray diffraction to help reveal the physical structure of DNA.

Watson and Crick

Scientists who proposed the double helix model of DNA, highlighting its antiparallel nature and helical dimensions.

Meselson and Stahl

Scientists who demonstrated that DNA replication is semiconservative using $N^{15}$ and $N^{14}$, showing that each new DNA molecule consists of one old strand and one new strand.

Crick and Brenner

Scientists who used frameshift mutations to demonstrate that the genetic code is read in groups of 3 nucleotides (codons).

Nirenberg

Scientist who helped decipher the genetic code by determining which codons correspond to specific amino acids.

Sanger

Scientist who developed a method for determining the nucleotide sequence of DNA.

Gene

A segment of DNA that contains information for a functional product, such as a protein or RNA.

Allele

A different version or sequence variant of the same gene at a specific chromosome region (e.g., purple allele vs. white allele).

Chromosome

A long DNA molecule packed with proteins that contains many genes.

Genome

All the genetic material (DNA) of an organism, which is made up of chromosomes.

Central Dogma

Describes the general flow of genetic information: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$ via transcription and translation.

Intergenic Region

A non-coding region in DNA that does not code for any functional product.

Homologous Pair

A pair of chromosomes of the same type containing the same genes, with one chromosome coming from the mother and one from the father.

Phenotype

The observable physical traits or appearance of an organism.

Chromatid

One of two identical copies of a replicated chromosome, joined to its sister chromatid at the centromere.

Tetrad

A structure formed during meiosis consisting of two homologous chromosomes, each composed of two sister chromatids.

Test Cross

A cross where an organism with an unknown genotype is crossed with an organism exhibiting the recessive phenotype to examine the offspring phenotypes.

Loci

The specific physical location of a gene within the genome.

Monohybrid Cross

A genetic cross between individuals involving a single characteristic (e.g., $Pp \times Pp$), producing a $3:1$ phenotypic ratio and a $1:2:1$ genotypic ratio in the $F_2$ generation.

Dihybrid Cross

A genetic cross involving individuals heterozygous for two traits (e.g., color $\times$ shape), producing a characteristic $9:3:3:1$ phenotypic ratio.

Trihybrid Cross

A cross involving three traits, where the number of gametes is calculated using $2^n$ ($2^3 = 8$ gamete types, each with a frequency of $\frac{1}{8}$).