Genetics and Molecular Biology Review: Inheritance, DNA Structure, and Biotechnology

Vocabulary flashcards covering Mendelian genetics, chromosomal inheritance, DNA structure and replication, transcription/translation, the genetic code, and biotechnology techniques.

Monohybrid cross

A cross involving a single gene with two alleles; typically shows a 3:1 phenotypic ratio in the F2 generation.

Dihybrid cross

A cross involving two genes; typically yields a 9:3:3:1 phenotypic ratio in the F2 generation and demonstrates independent assortment.

Allele

An alternate form of a gene at a given locus.

Homozygous

Having two identical alleles for a gene.

Heterozygous

Having two different alleles for a gene.

Dominant

An allele that is expressed in the phenotype when present in the genotype (often masks the recessive allele).

Recessive

An allele whose phenotype is masked by a dominant allele in a heterozygote.

Principle of Segregation

The two alleles for a gene segregate during gamete formation and reunite at fertilization.

Independent assortment

Alleles of different genes assort independently during gamete formation when genes are on different chromosomes.

Punnett square

A diagram used to predict genotype and phenotype frequencies from parental genotypes.

Testcross

Crossing an individual with an unknown genotype (dominant phenotype) to a homozygous recessive to reveal genotype.

Pedigree analysis

Using family trees to track inheritance patterns across generations.

Autosomal inheritance

Inheritance patterns on non-sex chromosomes (autosomes), not tied to sex.

X-linked inheritance

Inheritance patterns of genes on the X chromosome; often more apparent in males.

Dosage compensation

Mechanism that balances gene expression between sexes; in humans, X-inactivation in females.

Barr body

The condensed, inactivated X chromosome seen in female cell nuclei.

Morgan’s chromosomal theory

Genes reside on chromosomes; supported by experiments with fruit flies.

Hemophilia

An X-linked recessive disorder affecting blood clotting.

Down syndrome

Trisomy 21; aneuploid condition caused by nondisjunction.

Nondisjunction

Failure of chromosome pairs to separate during meiosis, leading to aneuploidy.

Karyotype

A display of an organism’s complete set of chromosomes used to detect abnormalities.

Transformation

Acquisition of new traits by a cell after uptake of external DNA; demonstrated by Griffith; DNA is genetic material.

DNA

Deoxyribonucleic acid; the genetic material with a double helix structure.

Chargaff’s rules

In DNA, the amount of adenine equals thymine and guanine equals cytosine.

Antiparallel

Two DNA strands run in opposite directions in the double helix.

Semiconservative replication

Each new DNA molecule consists of one old strand and one new strand.

Origin of replication

Specific DNA sequence where replication starts; helicase unwinds the helix.

Helicase

Enzyme that unwinds the DNA double helix at the replication fork.

DNA polymerase

Enzyme that synthesizes new DNA strands in the 5'→3' direction using a DNA template.

Central dogma

Genetic information flows from DNA to RNA to protein via transcription and translation.

mRNA (messenger RNA)

RNA that carries genetic information from DNA to the ribosome for protein synthesis.

tRNA (transfer RNA)

RNA that brings amino acids to the ribosome and has an anticodon that pairs with mRNA codons.

rRNA (ribosomal RNA)

RNA component of ribosomes, essential for protein synthesis.

Pre-mRNA and splicing

In eukaryotes, introns are removed and exons joined by the spliceosome; alternative splicing can produce multiple mRNA variants.

5' cap and 3' tail

Modifications added to eukaryotic mRNA for protection and initiation of translation.

Start codon

AUG; signals the start of translation.

Stop codon

UAA, UAG, or UGA; signals termination of translation.

Genetic code

Triplet codons in mRNA map to specific amino acids; codons are degenerate.

tRNA anticodon

Three-base sequence on tRNA that pairs with a complementary mRNA codon and carries the corresponding amino acid.

Translation

Synthesis of a protein by ribosomes using mRNA as template.

Spliceosome

RNA-protein complex that removes introns from pre-mRNA and splices exons together.

Alternative splicing

Different exons can be included or excluded to produce multiple proteins from one gene.

Recombinant DNA

DNA molecules formed by joining DNA from different sources.

Restriction endonucleases

Enzymes that cut DNA at specific sequences, producing fragments with sticky ends.

Gel electrophoresis

Technique to separate DNA, RNA, or proteins by size via an electric field; DNA migrates toward the positive pole.

DNA ligase

Enzyme that seals nicks in DNA by forming phosphodiester bonds to join fragments.

Plasmid vector

Circular DNA that carries foreign DNA into bacteria for cloning; contains origin of replication and selection markers.

Transformation (cloning)

Introduction of recombinant DNA into a bacterial host to propagate and amplify it.

cDNA

Complementary DNA synthesized from mRNA; used to study expressed genes.

RT‑PCR

Reverse transcription PCR; converts RNA to cDNA for amplification; used to measure gene expression.

PCR

Polymerase chain reaction; in vitro amplification of specific DNA sequences using primers and a DNA polymerase.

DNA sequencing

Determining the precise order of nucleotides in a DNA molecule.

DNA fingerprinting

Identification of individuals using DNA polymorphisms (RFLP, STR); used in forensics and paternity.

STR (short tandem repeat)

Repeating short DNA sequences; highly variable among individuals and used in profiling.

RFLP (restriction fragment length polymorphism)

Variation in DNA fragment lengths after restriction enzyme digestion, used for genetic analysis.

CODIS

Combined DNA Index System; database of DNA profiles for identification.

FISH (fluorescent in situ hybridization)

Technique using fluorescent probes to detect specific DNA/RNA sequences in cells or tissues.

Microarray (gene chip)

Technology to measure expression levels of thousands of genes simultaneously by hybridization to probes.

RNA interference (RNAi)

Noncoding RNAs guide silencing of specific mRNAs, reducing or silencing gene expression.

CRISPR

Genome-editing system using Cas9 nuclease guided by RNA to target DNA for mutation, deletion, or insertion.

Genome editing

Techniques (e.g., CRISPR) that alter DNA sequences in genomes.

Sickle cell disease (HBB mutation)

Hemoglobin beta chain mutation (Val instead of Glu) causing abnormal Hb and sickled RBCs.

Sickle cell trait

Heterozygous state for HBB mutation; often milder and can show codominant effects.