BIO1011 Exam Review: Cell Biology, Genetics, and Evolution

Flashcards based on BIO1011 practice questions covering cell division, inheritance, molecular biology, and population genetics.

Eukaryotic chromosome

A structure composed of a long, linear DNA molecule tightly coiled and associated with proteins called histones.

DNA replication

The process of creating an identical copy of a DNA molecule, requiring a DNA template, DNA polymerase, primers, and nucleotides.

Leading strand

The DNA strand that is synthesised continuously in the $5'$ to $3'$ direction during DNA replication.

Lagging strand

The DNA strand synthesised discontinuously in short fragments, also in the $5'$ to $3'$ direction.

Okazaki fragments

Short DNA fragments synthesised on the lagging strand during DNA replication.

Mitosis

A process of cell division characterized by the separation of sister chromatids and result in two daughter cells; its phases are Prophase, Metaphase, Anaphase, and Telophase.

Meiosis

A "reduction division" that reduces the chromosome number from diploid ($2n$) to haploid ($n$), resulting in the production of four haploid cells.

Interphase

A phase of the cell cycle where cell growth and DNA replication occur, but chromosomes are not yet condensed for division.

Cell cycle regulation

The mechanisms, including checkpoints like G1 and S phase, that ensure accurate DNA replication and proper chromosome segregation to prevent mutations.

Prophase

The phase of mitosis in which chromosomes actively condense and become visible under a light microscope.

G1 checkpoint

A regulatory point in the cell cycle; if mutated, the cell may bypass the checkpoint and proceed to S phase even with DNA damage.

Crossing over

The process of homologous recombination in meiosis I that shuffles alleles between homologous chromosomes to increase genetic variation.

Mitotic spindle

A structure that functions to align chromosomes at the metaphase plate, separate sister chromatids, and move them to opposite poles, but does not condense them.

Telomeres

Structural components that prevent the degradation of DNA ends and maintain chromosome stability during division.

Telomerase

An enzyme that is more active in stem cells than somatic cells, functioning to maintain telomere length.

Cytokinesis

The physical division of the cytoplasm resulting in two separate daughter cells.

Aneuploidy

A condition where daughter cells have an abnormal number of chromosomes, often due to disruptions in mitotic spindle assembly.

Cyclins and Cyclin-dependent kinases (CDKs)

Regulators of the cell cycle where cyclins bind to and activate CDKs to phosphorylate target proteins; their concentrations fluctuate throughout the cycle.

Autosomal inheritance

The inheritance of genes located on non-sex chromosomes, known as autosomes.

Sex-linked inheritance

The inheritance of genes located on the sex chromosomes ($X$ and $Y$).

Monohybrid cross

A genetic cross between parents that differ in only one trait, typically yielding a $3:1$ phenotypic ratio in the F2 generation with complete dominance.

Dihybrid cross

A genetic cross between parents that differ in two traits.

Incomplete dominance

A form of intermediate inheritance where one allele is not completely expressed over its paired allele, resulting in a blending of traits or a third phenotype.

Codominance

A relationship between alleles where both contribute to the phenotype of the heterozygote and are fully expressed.

Epistasis

The interaction of genes at two or more loci where one gene masks the expression of another gene, such as the E gene masking the B gene in Labrador retrievers.

Penetrance

The proportion of individuals with a given genotype who express the associated phenotype.

Expressivity

The degree to which a phenotype is expressed in individuals with a specific genotype.

Allelic heterogeneity

A phenomenon where different mutations within the same gene can cause the same disease, such as mutations in the CFTR gene causing Cystic Fibrosis.

Locus heterogeneity

A phenomenon where mutations in different genes can cause the same disease phenotype, such as inherited deafness.

Pedigree

A diagram showing the occurrence and appearance of phenotypes of a particular gene and its ancestors across generations.

Linkage

The tendency of genes located close together on the same chromosome to be inherited together, causing deviation from Mendelian ratios.

Operon

A unit of linked genes including a promoter and operator that are regulated and transcribed together, typically found in prokaryotes.

Introns

Non-coding regions of a gene present in eukaryotic pre-mRNA that are removed during splicing.

Exons

The coding regions of a gene that are joined together after the removal of introns to form mature mRNA.

Transcription

The process by which genetic information in a DNA sequence is copied into a complementary RNA sequence.

mRNA splicing

The post-transcriptional process of removing introns from pre-mRNA and joining exons to form mature mRNA.

Transcription factors

Proteins that bind to specific DNA sequences (promoters or enhancers) to control the rate of transcription by activating or repressing RNA polymerase.

Differential gene expression

The process by which cells selectively activate or inactivate specific genes, leading to cell differentiation and specialization.

5' capping

A eukaryotic-specific mRNA modification involving the addition of a cap to the $5'$ end of the transcript.

Spliceosome

The cellular machinery responsible for removing introns from pre-mRNA.

Enhancer

A regulatory DNA sequence in eukaryotes that can be located far from the gene it regulates to control the rate of transcription.

Histone modifications

Changes such as acetylation or methylation that alter chromatin structure and affect DNA accessibility for transcription.

DNA methylation

The addition of methyl groups to DNA which typically represses gene transcription.

Translation

The process by which the genetic information encoded in mRNA is used by ribosomes to synthesise a polypeptide chain.

tRNA

Molecules that transport specific amino acids to the ribosome and match them to mRNA codons using anticodons.

Aminoacyl-tRNA synthetases

Enzymes that attach the correct amino acid to its corresponding tRNA molecule.

Methionine

The first amino acid brought to the ribosome by the initiator tRNA during translation initiation in eukaryotes.

Chaperone proteins

Proteins that assist in the proper folding of other proteins.

Ubiquitin

A protein that tags other proteins for degradation.

Point mutation

A mutation that changes a single nucleotide base in the DNA sequence.

Silent mutation

A point mutation that has no effect on the amino acid sequence of a protein.

Missense mutation

A point mutation that results in a codon coding for a different amino acid.

Nonsense mutation

A point mutation that results in a premature stop codon in the mRNA.

Frameshift mutation

A mutation caused by the insertion or deletion of nucleotides that shifts the reading frame and drastically alters the amino acid sequence.

Restriction enzymes

Tools used in biotechnology to cut DNA at specific recognition sites.

PCR (Polymerase Chain Reaction)

A technique used to amplify specific DNA segments to create many copies for analysis.

DNA ligase

An enzyme used to join DNA fragments together.

Gel electrophoresis

A method used to separate DNA fragments based on their size.

Transgenic organism

An organism that contains DNA from another species.

Sanger sequencing

A method using dideoxynucleotides (ddNTPs) to terminate DNA synthesis and determine the sequence of DNA fragments.

CRISPR-Cas9

A gene-editing technology using a guide RNA and the Cas9 protein to cut DNA at specific locations for disabling genes, fixing mutations, or inserting new genes.

Polymorphisms

Genomic variations between individuals, such as SNPs, that contribute to variations in traits within a population.

Evolution

A change in the allele frequencies of a population over time.

Natural selection

The process that increases the frequency of alleles conferring advantageous traits, leading to adaptation; it acts on individuals.

Genetic drift

The random fluctuation of allele frequencies due to chance events, such as the founder effect or bottlenecks, more pronounced in small populations.

Gene flow

The movement of genes between populations, which can introduce new alleles and increase genetic variation.

Hardy-Weinberg equation

The formula $p^2 + 2pq + q^2 = 1$ used to calculate allele and genotype frequencies in a population under equilibrium.

Hardy-Weinberg equilibrium assumptions

The required conditions: no mutation, random mating, no gene flow, no natural selection, and large population size.

SNP (Single Nucleotide Polymorphism)

A variation in a single nucleotide base in DNA between individuals.

Speciation

The evolutionary process by which new biological species arise when populations become reproductively isolated.

Stabilizing selection

A type of natural selection that favors average phenotypes, such as average birth weights in humans.

Heterozygote advantage

A situation where heterozygotes have higher fitness than either homozygote, such as the sickle cell trait providing malaria resistance.