Heredity and Continuity of Life - Genetics Review

Comprehensive practice flashcards covering DNA structure, organization, protein synthesis, replication, and mutations based on the Unit 4 Heredity lecture transcript.

Deoxyribonucleic acid (DNA)

The hereditary material in all organisms that is arranged in a twisted spiral configuration known as a helical structure or double helix.

Nucleotide

The basic building block of nucleic acids, consisting of a pentose sugar (5-carbon ring), a phosphate group, and a nitrogenous base.

Purines

A class of nitrogenous bases consisting of a six-membered ring fused to a five-membered ring, including Adenine ($A$) and Guanine ($G$).

Pyrimidines

A class of nitrogenous bases consisting of a single six-membered ring, including Cytosine ($C$), Thymine ($T$) in DNA, and Uracil ($U$) in RNA.

Complementary base pairing

The phenomenon where Guanine ($G$) always hydrogen bonds to Cytosine ($C$) and Adenine ($A$) always bonds to Thymine ($T$).

Antiparallel

The orientation of the two strands in a DNA double helix where one chain runs $5'-3'$ while the other runs $3'-5'$.

Chromosome

A structure composed of a single length of DNA and proteins called histones, which carries instructions for making specific proteins.

Homologous pairs

A pair of chromosomes in eukaryotic cells where one chromosome is inherited from each parent, containing the same genes at the same loci.

Karyotype

An image that shows the full set of chromosomes in an organism ordered from largest to smallest.

Sister chromatids

The two identical copies of a single chromatid formed by DNA duplication, often appearing in an X-shape joined at a centromere.

Centromere

A waist-like constriction in a chromosome required for attachment to spindle fibres during cell division.

Gene locus

The specific physical location of a gene on a chromosome.

Alleles

Different versions of the same gene resulting from slight variations in the DNA base sequence.

Telomeres

Stretches of repetitive DNA bases at the ends of chromosomes that provide a safe distance to minimize DNA damage.

Histones

Eight proteins around which a DNA strand is wound at intervals to organize the DNA and prevent tangling.

Nucleosome

A DNA-histone complex formed when a segment of DNA is wrapped approximately $1.7$ times around a core of histone proteins.

Chromatin

The combination of DNA and histone proteins, divided into heterochromatin (tightly condensed) and euchromatin (loosely wound).

Introns

Non-coding regions within a gene that are removed from the genetic code during RNA processing.

Exons

Coding regions within a gene that are joined together during RNA splicing to be expressed as a protein.

Promoter region

A regulatory non-coding DNA sequence located upstream (before) a gene that can encourage gene expression.

Plasmids

Small, circular, double-stranded DNA molecules found in prokaryotes, mitochondria, and chloroplasts that are not bound to histones.

Transcription

The first stage of protein synthesis where a messenger RNA (mRNA) molecule is formed against the template strand of a DNA molecule in the nucleus.

RNA polymerase

An enzyme that binds to the promoter region and synthesizes RNA from a DNA template during transcription.

5' Capping

The addition of a guanine nucleotide attached by three phosphates to the beginning of a pre-mRNA transcript to protect it and direct it out of the nucleus.

Poly-A tail

A series of adenosine molecules added to the $3'$ end of an mRNA transcript to protect it from degradation.

RNA splicing

A post-transcriptional process where a spliceosome removes introns and joins exons together to form mature mRNA.

Translation

The process by which ribosomes use the codon sequence of mRNA to assemble amino acids into a polypeptide chain.

Codon

A group of three RNA bases that codes for a specific amino acid.

Anticodon

A specific three-base nucleotide sequence on a tRNA molecule that pairs with a complementary codon on the mRNA.

Transfer RNA (tRNA)

RNA molecules that carry specific amino acids to the ribosome during translation.

DNA Helicase

An enzyme that separates the two strands of parent DNA by breaking the hydrogen bonds between nitrogen bases during replication.

DNA Polymerase

An enzyme that joins adjacent nucleotides in a $5'$ to $3'$ direction to form new DNA strands.

Semi-conservative replication

The process of DNA replication where each new double-helix contains one original parent strand and one newly synthesised daughter strand.

Okazaki fragments

Short, separate sections of DNA synthesized discontinuously on the lagging strand during DNA replication.

DNA Ligase

An enzyme that joins neighboring Okazaki fragments together on the lagging strand to form a continuous DNA strand.

Mutagen

An agent, such as ionizing radiation or certain chemicals, that induces a permanent change to the genetic material of an organism.

Point mutation

A mutation that occurs when a single nucleotide is permanently substituted with another incorrect nucleotide.

Silent mutation

A point mutation that still codes for the same amino acid due to degeneracy in the genetic code, resulting in no change to the polypeptide.

Nonsense mutation

A point mutation that results in a stop codon, prematurely terminating the synthesis of the polypeptide chain.

Frameshift mutation

A mutation caused by the insertion or deletion of a nucleotide, which changes the reading frame and typically results in a non-functional protein.