Mutations and DNA Damage Repair

Flashcards covering mutations, DNA damage repair mechanisms, and mobile genetic elements like transposons and viruses, based on the provided lecture notes.

Sickle cell anemia

A condition caused by a single nucleotide change (A to T) in DNA, altering glutamic acid to valine.

Sickle cell trait

A genetic condition that worsens under low oxygen conditions, distinct from sickle cell disease.

Sickle cell disease

A severe genetic condition that worsens under low oxygen conditions, distinct from sickle cell trait.

Mutations

Changes in DNA, such as deletions, additions, or substitutions of nucleotides, leading to altered amino acid sequences.

Frameshift mutations

Mutations caused by deletions or additions of nucleotides, altering the reading frame during translation.

Depurination

A spontaneous chemical change in DNA where guanine and adenine bases are lost due to thermal collisions.

Deamination

A chemical change that can occur in DNA bases.

Thymine dimers

Covalently bonded DNA damage caused by UV rays, leading to replication errors if unrepaired.

Xeroderma pigmentosum (skin cancer)

A human disease caused by the lack of enzymes necessary to repair thymine dimers.

DNA repair

A basic three-step mechanism involving excision, resynthesis, and ligation to correct DNA damage.

Mismatch repair

A DNA repair mechanism that eliminates replication errors and restores the original DNA sequence.

Double stranded breaks

Severe DNA damage caused by ionizing radiation, oxidizing agents, or mishaps at replication forks.

Homologous recombination/homologous end joining

A flawless DNA repair mechanism for double-stranded breaks in newly synthesized, identical DNA duplexes, occurring in the S phase.

Homologous recombination (in meiosis)

A process occurring between similar DNA in prophase I, creating novel DNA sequences and genetic diversity.

Transposons/jumping genes/mobile genetic elements

Segments of DNA that can move to different positions within the genome, causing genetic rearrangements, mutations, or novel protein generation.

Provirus

A viral genome integrated into the host chromosome, allowing it to hide silently and potentially lead to abnormal protein expression.

Dr. Barbara McClintock

Nobel Prize winner in 1983 for her research on 'jumping genes' (transposons) in corn genetics.

Transposition

The process by which jumping genes (transposons) move from one DNA position to another within a cell.

Transposase enzyme

An enzyme encoded by most transposons that catalyzes their movement (transposition).

Inverted repeats

Nucleotide sequences often found at the ends of transposons, recognized by transposase.

Direct repeats

Host DNA sequences left behind as a signature after a transposon has moved.

DNA only transposons

A type of transposon that moves via cut-and-paste or replicative transposition mechanisms.

Retrotransposons

A type of transposon that moves via an RNA intermediate, replicating by forming RNA and then converting it to cDNA.

cDNA (complementary DNA)

DNA synthesized from an RNA template.

Cut-and-paste transposition

A mechanism of movement for DNA-only transposons where the transposon is excised and inserted elsewhere.

Replicative transposition

A mechanism of movement for DNA-only transposons where the transposon is copied, and the copy is inserted elsewhere while the original remains.

LINES (long interspersed nuclear element)

A major family of retrotransposons in the human genome, more abundant than SINES, which encode their own reverse transcriptase.

SINES (short interspersed nuclear elements)

A major family of retrotransposons in the human genome that do not encode reverse transcriptase.

Reverse transcriptase

An enzyme, often encoded by retrotransposons like LINES or retroviruses, that synthesizes DNA from an RNA template.

Retrotransposon movement

A process involving transcription into RNA, reverse transcription into double-stranded DNA, and insertion of the DNA copy into a new target site.

Viruses

Fully mobile genetic elements that can escape from cells, possessing DNA or RNA genomes, single or double stranded.

Retroviruses (RNA viruses)

Viruses that reverse the normal flow of genetic information by using reverse transcriptase to synthesize DNA from their RNA genome.

Integrase

An enzyme carried by retroviruses that facilitates the integration of viral DNA into the host chromosome.

Life cycle of a retrovirus

Includes reverse transcription of its RNA genome into DNA, and subsequent integration of this DNA (as a provirus) into the host cell's chromosome.

HIV (human immunodeficiency virus)

A single-stranded RNA retrovirus that causes AIDS (Acquired Immunodeficiency Syndrome).

AIDS

A condition that develops when HIV provirus DNA, integrated into host cells, is transcribed and translated into viral proteins by host cell machinery.

HIV drug targets

Key viral components targeted by drugs, including reverse transcriptase, envelope spike proteins, and integrase.