DNA and Chromosomes Review

A set of 80 vocabulary flashcards covering the history of genetics, DNA structure, chromosome organization, and chromatin regulation based on lecture materials.

Charles Darwin (1859)

Proposed the theory of evolution by natural selection.

Gregor Mendel (1865)

Discovered that heredity is transmitted in discrete units.

Frederick Miescher (1869)

First to isolate DNA from cells, which he called nuclein.

Frederick Griffith (1928)

Discovered the phenomenon of transformation in bacteria using Streptococcus pneumoniae.

Pathogenic strain (S)

A lethal strain of pneumococcus encased in a slimy, glistening polysaccharide capsule.

Harmless strain (R)

A non-pathogenic strain of pneumococcus that lacks a protective polysaccharide coat.

Avery, MacLeod, and McCarty (1944)

Demonstrated that the transforming principle responsible for changing R-strain into S-strain is DNA.

Rosalind Franklin and Maurice Wilkins (1953)

Used X-ray crystallography to determine DNA is a double helix with phosphates on the outside.

Watson, Crick, and Wilkins (1953)

Constructed a DNA model showing complementary bases and the antiparallel nature of the strands.

Human Genome Sequencing completion

Achieved in the year $2003$.

Radioactive Phosphorous ($32P$)

The isotope used by Hershey and Chase to label viral DNA.

Radioactive Sulfur ($35S$)

The isotope used by Hershey and Chase to label viral proteins.

Waring Blender Experiment

The experiment by Hershey and Chase that definitively showed genes are made of DNA.

DNA Double Helix components

Consists of two complementary chains of nucleotides with sugar-phosphate backbones and inward-projecting nitrogenous bases.

$A=T$ Base Pair

A nitrogenous base pair held together by two hydrogen bonds.

$G=C$ Base Pair

A nitrogenous base pair held together by three hydrogen bonds.

Major and Minor Grooves

Regions of the DNA helix lined by potential hydrogen bond donors and acceptors that interact with molecules.

Protein-coding DNA percentage

Only about $1.5$ percent of human DNA encodes proteins and functional RNAs.

Mobile DNA elements

DNA sequences that make up over $45$ percent of human DNA and contribute to genome evolution.

Introns

Non-coding sequences in eukaryotic genes that are removed during the creation of functional RNA.

Fluorescence in situ hybridization (FISH)

A multi-color technique, also known as spectral karyotyping, used to paint and identify chromosomes.

Reciprocal chromosomal translocation

A genetic alteration where a segment of one chromosome is swapped with a segment from another.

$$t(4;6)(q22;q15)$$

A specific chromosomal translocation identified as a recurrent genetic alteration in prostate cancer.

Indian muntjac

A species with a diploid chromosome number of $7$ in males and $6$ in females.

Chinese muntjac

A species closely related to the Indian muntjac but having $23$ diploid chromosomes.

Genome size of Homo sapiens

$3200 \times 10^6$ nucleotide pairs.

Genome size of Mus musculus

$2800 \times 10^6$ nucleotide pairs.

Genome size of Drosophila melanogaster

$180 \times 10^6$ nucleotide pairs.

Genome size of Arabidopsis thaliana

$157 \times 10^6$ nucleotide pairs (referenced as $103 \times 10^6$ or $100 \times 10^6$ in provided table counts).

Genome size of Caenorhabditis elegans

$100 \times 10^6$ nucleotide pairs.

Genome size of Saccharomyces cerevisiae

$12.5 \times 10^6$ nucleotide pairs.

Number of protein-coding genes in humans

Approximately $19,000$ genes.

Number of protein-coding genes in Mus musculus

Approximately $22,000$ genes.

Number of protein-coding genes in Drosophila melanogaster

Approximately $14,000$ genes.

Number of protein-coding genes in Arabidopsis thaliana

Approximately $28,000$ genes.

Number of protein-coding genes in Caenorhabditis elegans

Approximately $22,000$ genes.

Number of protein-coding genes in Saccharomyces cerevisiae

Approximately $6600$ genes.

Interphase

The cell cycle phase where DNA replicates at origins of replication and the cell expresses genes.

M phase

The cell cycle phase where chromosomes condense and are attached to the mitotic spindle.

Centromere

The specialized DNA sequence where compact chromosomes attach to the mitotic spindle during mitosis.

Mitosis

The process where chromosomes condense, one set is pulled to each end of the cell, and the cell divides.

Interphase Nucleus distribution

Chromosomes occupy non-overlapping territories rather than being randomly distributed.

Nucleolus

The most prominent structure in the interphase nucleus, containing over $400$ copies of ribosomal RNA genes.

Total DNA length in a human cell

Approximately $2$ meters.

Nucleus diameter

Typically less than $10\,\mu m$.

Nucleosome

The basic unit of eukaryotic chromosome structure, consisting of DNA wrapped around histone proteins.

Histone octamer

The protein core composed of eight histone molecules around which DNA is wrapped.

$147$ nucleotide pairs

The length of DNA that wraps around the histone octamer nearly twice.

$$0.34\,nm$$

The distance between each base pair in a double strand helix according to Watson and Crick.

$$280\,Mb$$

The average number of nucleotides in an individual human chromosome.

Chromatin-remodeling complexes

Protein complexes that use ATP hydrolysis to loosen nucleosomal DNA and expose specific sequences.

Heterochromatin

A highly condensed, dark-staining form of chromatin that is transcriptionally inactive.

Euchromatin

A more extended, light-staining form of chromatin that includes most transcribed regions.

Histone N-terminal tails

The parts of histone proteins that undergo various post-translational modifications to regulate chromatin structure.

Histone Acetyltransferases (HAT)

Enzymes that add acetyl groups to histone lysine residues using an acetyl CoA cofactor.

Histone Deacetylases (HDAC)

Enzymes that remove acetyl groups from histone tails, strengthening interactions between DNA and histones.

Transcriptional Activators (TA)

Proteins recruited to DNA when histone acetylation exposes the sequence.

Transcriptional Repressor (TR)

Complexes that interact with HDACs to remove acetyl groups and silence gene expression.

K9 Trimethylation

A specific modification on histone $H3$ that recruits heterochromatin-specific proteins.

K9 Acetylation

A modification on histone $H3$ that blocks methylation and acts as a barrier to heterochromatin expansion.

Rubinstein–Taybi syndrome

A condition caused by a deficiency in a histone acetyltransferase (HAT).

Barrier DNA

A DNA sequence that prevents the invasion of heterochromatin into neighboring gene regions.

Anemia (Genetic context)

Can occur when the beta globin gene region is invaded by heterochromatin due to deleted barrier DNA.

Lyonization

The process of X-chromosome inactivation in mammalian females via heterochromatin formation.

Mary F. Lyon (1961)

The British geneticist who discovered the phenomenon of X-chromosome inactivation.

Calico cat coat color

A mosaic pattern dictated by the random inactivation of one of the two X chromosomes during development.

Histone H3 Hallmark Lysines

The specific residues $K9$, $K14$, $K18$, $K23$, and $K27$ that are targets for acetylation.

$3$ billion base pairs

The approximate number of base pairs in a single strand of the human genome.

Distance between base pairs

$0.34\,nm$.

Phosphorylation (P)

One of the three main types of modifications that histone $H3$ tails can receive.

Methyl groups (M)

Modifications on histone tails that, when imbalanced with acetylation, can affect neurodevelopment.

ATP hydrolysis in mitosis

During this phase, many chromatin-remodeling complexes are inactivated.

Ribosomal RNAs

Functional RNAs encoded by genes located within the nucleolus.

Scanning electron micrograph (SEM)

A microscopy method used to show the two chromatids of a mitotic chromosome tightly joined.

Pathogen

The result of harmless bacteria taking up the 'transforming principle' from heat-killed infectious bacteria.

Sugar-phosphate backbone

The outer structure of the DNA double helix from which nitrogenous bases project inward.

Hydrogen Bond Acceptors/Donors

Molecular groups located in the major and minor grooves that interact with external proteins.

Noncoding DNA

Interspersed sequences found in excess in many eukaryotic genes.

Nuclear Envelope

The structure that forms around each chromosome set during the final stages of mitosis.

Origins of Replication

The specific DNA sites where DNA replication begins during the interphase of the cell cycle.