AI - DNA Structure and Function

Flashcards covering essential concepts related to DNA Structure and Function, including genomic composition, chromatin structure, genetic disorders, and molecular techniques.

Human Genome Composition

Humans possess 46 chromosomes (23 pairs), consisting of 22 pairs of autosomes and 1 pair of sex chromosomes (XX or XY). There are approximately 20,000–25,000 known genes.

Mitochondrial DNA Characteristics

Mitochondrial plasmids encode 37 genes (13 for energy production proteins, 22 tRNAs, and 2 rRNAs), follow a maternal inheritance pattern, and have higher mutation rates than chromosomal DNA.

Karyotype

The complete set of all chromosomes in a cell.

Diploid vs Haploid

Diploid (2n): Found in somatic cells, containing two full sets of chromosomes. Haploid (1n): Found in sex cells (sperm/egg), containing only one set of chromosomes.

G-banding

In G-banding cytogenetics, dark bands represent AT-rich regions (heterochromatic) while light bands represent GC-rich regions (euchromatic).

Nucleosome

The simplest level of chromatin, consisting of eight histone proteins around which DNA wraps 1.65 times.

Chromatosome

Consists of a nucleosome plus the H1 histone.

Euchromatin

Loosely packed chromatin that allows access for transcription.

Heterochromatin

A tightly condensed version of chromatin that is generally transcriptionally inactive.

Acetylation

The addition of acetyl groups to histone tails that opens the chromatin structure and promotes transcription.

Methylation

The addition of methyl groups to DNA or histones that condenses chromatin and reduces gene activity.

Aneuploidy

An abnormal number of chromosomes typically caused by nondisjunction during cell division.

Down’s Syndrome Genetic Causes

Classic Trisomy (three copies of chromosome 21), Translocation (4% of cases involving chromosomes 14 and 21), and Mosaicism (only a subset of cells harbor genetic change).

Philadelphia Chromosome

A chromosomal rearrangement formed by a t(9;22) translocation, creating a BCR-ABL1 fusion gene, associated with chronic myelogenous leukemia (CML).

Rubinstein-Taybi Syndrome

An autosomal dominant disorder typically caused by mutations in CREBBP or EP300, characterized by short stature, intellectual disability, and broad thumbs.

PCR Stages

1. Denaturation: Heat separates the DNA strands. 2. Annealing: Primers bind to the target sequence. 3. Extension: DNA polymerase synthesizes new strands.

Taq Polymerase

Heat-stable but lacks proofreading, leading to occasional errors.

Pfu Polymerase

Possesses proofreading activity, resulting in a lower error rate compared to Taq.

Analogy for DNA Packaging

DNA is a long thread fitting into the nucleus by wrapping around spools (nucleosomes), then stacked and folded into coils and chromosomes.