BIOL 1030 Unit 3 Study Guide Flashcards

Comprehensive vocabulary flashcards covering Unit 3 of BIOL 1030, including molecular genetics, transcription, translation, gene regulation, biotechnology, the cell cycle, meiosis, and patterns of Mendelian and non-Mendelian inheritance.

Nucleotide

A subunit of nucleic acids consisting of three parts: a phosphate group, a five-carbon sugar (deoxyribose in DNA or ribose in RNA), and a nitrogenous base.

Antiparallel

The structural property of double-stranded DNA in which the two strands run in opposite orientations, one from $5'$ to $3'$ and the other from $3'$ to $5'$.

Phosphodiester bond

The covalent bond that connects adjacent nucleotides within an individual DNA or RNA strand.

Codon

A sequence of three consecutive mRNA bases that codes for a specific amino acid or a stop signal during translation.

Start codon

The specific mRNA codon ($\text{AUG}$) that initiates translation and codes for the amino acid methionine.

Stop codon

One of three mRNA codons ($\text{UAA}$, $\text{UAG}$, or $\text{UGA}$) that signals the termination of translation.

Transcription

The biological process in which RNA polymerase reads a DNA template strand from $3'$ to $5'$ and synthesizes a complementary mRNA transcript from $5'$ to $3'$.

Promoter

A specific nucleotide region on DNA where RNA polymerase binds and unwinds the double helix to initiate transcription.

Intron

A noncoding section of an RNA transcript that is cut out and removed during RNA processing.

Exon

A coding section of an RNA transcript that is preserved and spliced together to form mature mRNA.

Alternative splicing

The RNA processing mechanism where different combinations of exons are joined together, allowing a single gene to encode multiple distinct proteins.

Transfer RNA (tRNA)

An RNA molecule featuring an anticodon at one end and a specific bound amino acid at the opposite end, responsible for delivering amino acids to the ribosome.

Anticodon

A three-nucleotide sequence on a tRNA molecule that base-pairs complementarily with a corresponding codon on an mRNA transcript.

Gene expression

The multi-step process through which information encoded within a gene is used to produce a functional biological product, such as a protein.

Gene regulation

The cellular control mechanisms that determine when, where, and in what quantity a specific gene is expressed.

Epigenetics

Heritable or persistent modifications that alter gene expression without changing the underlying nucleotide sequence of DNA.

DNA methylation

An epigenetic modification involving the addition of methyl groups to DNA molecules, generally silencing gene transcription.

Histone modification

Chemical changes that alter how tightly DNA is coiled around histone proteins; tight coiling impedes transcription, whereas loose coiling facilitates it.

Mutation

Any change occurring in the nucleotide sequence of an organism's DNA.

Germ cell

A reproductive cell (sperm or egg), or one of the cells that produce them, in which a mutation must occur to be passed down to offspring.

Silent mutation

A point substitution mutation that alters a codon without changing the amino acid incorporated into the resulting polypeptide.

Missense mutation

A point substitution mutation that alters a single codon such that it codes for a different amino acid.

Nonsense mutation

A point substitution mutation that changes an amino acid codon into a stop codon, terminating protein translation prematurely.

Frameshift mutation

A mutation caused by insertions or deletions of nucleotides in amounts not divisible by three, altering the downstream triplet reading frame.

Pluripotent

The developmental ability of embryonic stem cells to differentiate into almost any cell type found in the body.

Multipotent

The developmental capacity of adult stem cells (such as bone marrow stem cells) to differentiate into a limited range of closely related cell types.

CRISPR-Cas9

A targeted gene-editing technology utilizing a guide RNA to direct the Cas9 endonuclease to cut a precise DNA sequence for modification.

Gene therapy

A clinical approach aimed at treating or preventing diseases by introducing or modifying genetic material within a patient's cells.

Transgenic organism

A genetically modified organism that contains recombinant DNA originating from a different species.

S phase

The specific synthesis phase of interphase during which chromosomal DNA is replicated, producing two copies of each chromosome.

Helicase

An enzyme that unwinds and separates double-stranded DNA by breaking the hydrogen bonds holding the nitrogenous bases together.

Primase

An enzyme that synthesizes short complementary RNA primers necessary for DNA polymerase to begin replication.

DNA polymerase

An enzyme that builds a new complementary DNA strand by adding nucleotides exclusively in the $5'$ to $3'$ direction.

Okazaki fragments

Short, discontinuous segments of synthesized DNA produced on the lagging strand during DNA replication.

DNA ligase

An enzyme that joins Okazaki fragments together on the lagging strand by forming covalent bonds between segments.

Semiconservative replication

The mode of DNA replication wherein each new double-stranded DNA molecule contains one original parent strand and one newly synthesized daughter strand.

Proto-oncogene

A normal regulatory gene promoting cell growth and division that, upon mutation or hyperactivation, becomes an oncogene capable of causing uncontrolled division.

Tumor-suppressor gene

A gene whose protein products normally function to slow cell division, repair damaged DNA, or induce apoptosis when appropriate.

Carcinogen

Any substance, organism, or form of radiation (such as solar radiation, processed meats, alcoholic beverages, or tobacco smoke) capable of causing cancer.

Benign tumor

A noncancerous mass of cells that does not invade surrounding tissues or spread to other parts of the body.

Malignant tumor

A cancerous growth capable of invading adjacent tissues and metastasizing to distant anatomical sites.

Metastasis

The biological process wherein cancerous cells detach from their site of origin and migrate to colonize distant tissues or organs.

Ploidy

The number of complete sets of chromosomes present within a biological cell.

Haploid ($n$)

A cell containing one complete set of unpaired chromosomes ($23$ individual chromosomes in human gametes).

Diploid ($2n$)

A cell containing two complete sets of chromosomes ($23$ pairs, totaling $46$ chromosomes in human somatic cells).

Homologous chromosomes

A pair of matched chromosomes (one maternal and one paternal) possessing identical gene loci, potentially containing different alleles.

Sister chromatids

Two identical copies of a single replicated chromosome joined together at the centromere.

Crossing over

The reciprocal exchange of corresponding DNA fragments between homologous chromosomes during prophase I of meiosis.

Recombinant chromosome

A chromosome that emerges from meiotic crossing over, carrying a novel combination of maternal and paternal genetic sequences.

Independent assortment

The random and independent orientation of homologous chromosome pairs along the cell equator during metaphase I of meiosis.

Nondisjunction

The failure of homologous chromosomes to separate during anaphase I or sister chromatids to separate during anaphase II of meiosis.

Down syndrome

A human genetic condition (also known as Trisomy 21) caused by meiotic nondisjunction that results in an individual possessing an extra copy of chromosome 21.

Locus

The specific physical location or address of a gene on a chromosome.

Allele

An alternative sequence variant of a specific gene.

Law of segregation

Mendelian principle stating that the two alleles for a gene separate during gametogenesis so that each gamete carries only one allele.

Carrier

A heterozygous individual ($Aa$) who carries a single recessive disease allele without exhibiting symptoms of the genetic disorder.

Incomplete dominance

An inheritance pattern wherein the heterozygous phenotype presents as an intermediate blend because neither allele is fully dominant over the other.

Codominance

An inheritance pattern wherein both alleles are simultaneously and fully expressed in the heterozygote, as seen in AB blood type.

Pleiotropy

A genetic phenomenon in which a single gene exerts regulatory control over multiple distinct phenotypic traits.

Polygenic trait

A phenotypic characteristic, such as human height, whose variation is governed by the additive effects of multiple independent genes.

Heterozygote advantage

An evolutionary scenario in which heterozygous individuals have higher fitness than either homozygote, exemplified by sickle cell trait carriers possessing resistance to malaria.