Module 2: Chromosomes & Genes

The three main components of DNA are nitrogenous bases, deoxyribose sugars, and phosphates, structured as nucleotides that link to form long strands.

Hydrogen bonds stabilize the pairing between adenine-thymine and guanine-cytosine, while phosphodiester bonds link the sugar-phosphate backbone of DNA.

Purines (adenine and guanine) pair with pyrimidines (thymine and cytosine), ensuring stable base pairing necessary for DNA's double-helix structure.

<p>Humans have nuclear DNA organized into 22 pairs of autosomes and two sex chromosomes, inherited from both parents.</p> Signup and view all the answers

<p>Mitochondrial DNA is circular, consists of about 17,000 base pairs, and is crucial for cellular metabolism, being inherited maternally.</p> Signup and view all the answers

<p>DNA condenses by wrapping around histone proteins to form nucleosomes, which further coil into fibers and loops for efficient packing in the nucleus.</p> Signup and view all the answers

<p>Nucleosomes, formed by DNA wrapping around histones, serve as the fundamental units of chromatin that aid in the compaction and organization of DNA.</p> Signup and view all the answers

<p>The antiparallel orientation of DNA strands enables complementary base pairing and hydrogen bonding, enhancing the overall stability of the double helix.</p> Signup and view all the answers

<p>Exons specify amino acids organized into codons for protein synthesis.</p> Signup and view all the answers

<p>The Central Dogma describes the flow of genetic information as DNA being transcribed into RNA, which is then translated into proteins.</p> Signup and view all the answers

<p>RNA polymerase II synthesizes mRNA by binding to the promoter region of a gene and transcribing the DNA into RNA.</p> Signup and view all the answers

<p>The 5′ cap protects mRNA from degradation, aids in its transport out of the nucleus, and is necessary for ribosome attachment.</p> Signup and view all the answers

<p>Introns are non-coding sequences in pre-mRNA that must be removed to produce a functional mRNA for translation.</p> Signup and view all the answers

<p>The mRNA is synthesized as a complementary strand to the DNA template strand, using A-U, T-A, C-G, and G-C base pairing.</p> Signup and view all the answers

<p>A termination sequence in the DNA signals the end of transcription.</p> Signup and view all the answers

<p>Signal transduction pathways regulate gene expression in response to external cues, influencing cell functions.</p> Signup and view all the answers

<p>Euchromatin is loosely packed and accessible for gene expression, while heterochromatin is densely packed and generally inactive.</p> Signup and view all the answers

<p>Telomeres are protective sequences at chromosome ends that prevent gene loss during replication, maintained by telomerase.</p> Signup and view all the answers

<p>Autosomes are identical in both sexes and carry genes that are not sex-specific, while sex chromosomes (XX in females, XY in males) determine sexual characteristics.</p> Signup and view all the answers

<p>Homologous chromosomes contain similar genes but can have different alleles, contributing to genetic diversity through recombination.</p> Signup and view all the answers

<p>A diploid organism has two complete sets of chromosomes (2n), while aneuploidy refers to an abnormal number of chromosomes, either missing or additional.</p> Signup and view all the answers

<p>The SRY gene is responsible for male sex determination, triggering pathways for male reproductive development.</p> Signup and view all the answers

<p>During transcription, DNA is copied into mRNA, which then undergoes splicing to remove introns, allowing for protein synthesis.</p> Signup and view all the answers

<p>The metacentric shape of the X chromosome, with a centrally located centromere, aids during cell division by ensuring proper segregation.</p> Signup and view all the answers

<p>The spliceosome facilitates the splicing together of coding regions, or exons, to form a continuous mRNA strand.</p> Signup and view all the answers

<p>The poly(A) tail enhances mRNA stability, aids in export from the nucleus, and initiates translation.</p> Signup and view all the answers

<p>tRNA molecules carry amino acids and have anticodons that are complementary to the mRNA codons, ensuring accurate amino acid incorporation.</p> Signup and view all the answers

<p>During initiation, the small ribosomal subunit binds to mRNA, identifies the start codon (AUG), and the initiator tRNA binds to it, followed by the large subunit's attachment.</p> Signup and view all the answers

<p>The ribosome moves along the mRNA, reading codons and recruiting tRNA molecules that bring specific amino acids, forming peptide bonds.</p> Signup and view all the answers

<p>Stop codons signal the termination of translation, leading to the release of the polypeptide chain from the ribosome.</p> Signup and view all the answers

<p>Two common modifications are phosphorylation, which can regulate protein activity, and glycosylation, which affects protein stability and cell signaling.</p> Signup and view all the answers

<p>Proteolytic cleavage, like the conversion of proinsulin to insulin, activates the protein and allows it to carry out its biological function.</p> Signup and view all the answers

<p>siRNAs and miRNAs regulate gene expression by guiding mRNA degradation or inhibiting translation.</p> Signup and view all the answers

<p>Lyon's Hypothesis explains that in female mammals, one of the two X chromosomes is randomly inactivated to ensure equivalent gene expression levels with males.</p> Signup and view all the answers

<p>Random X-chromosome inactivation results in a mosaic pattern of gene expression, leading to varying symptoms in female carriers of X-linked diseases.</p> Signup and view all the answers

<p>A Barr body is the condensed structure formed by the inactivated X chromosome in female cells.</p> Signup and view all the answers

<p>Alternative splicing allows approximately 95% of human genes to produce multiple protein isoforms, enhancing proteomic diversity.</p> Signup and view all the answers

<p>RNA-directed DNA synthesis is the process where RNA serves as a template for synthesizing DNA, exemplified by retroviruses.</p> Signup and view all the answers

<p>Semiconservative replication ensures each new DNA double helix consists of one parental and one new strand, maintaining genetic stability.</p> Signup and view all the answers

<p>X-inactivation promotes survival and adaptability by ensuring balanced gene expression and preventing dosage imbalance between sexes.</p> Signup and view all the answers