Chapter 2- Genetics

Slipped mispairing

Misalignment of DNA strands during replication leading to insertion or deletion mutations

Trinucleotide repeats

Repeated sequences of three nucleotides in DNA, associated with certain genetic disorders

Anticipation

Phenomenon where the severity of a genetic disorder increases or appears at an earlier age in successive generations

Mutagen

Agent causing genetic mutations

Deamination

Removal of an amino group from a molecule, often affecting DNA bases

Depurination

Loss of a purine base from DNA, leading to mutations

Mismatch repair

Cellular process correcting errors in DNA replication

Nucleotide excision repair

DNA repair mechanism removing bulky DNA lesions

NHEJ

Non-homologous end joining, a DNA repair process

Homologous recombination

DNA repair using a homologous sequence as a template

Missense

Type of mutation where a single nucleotide change results in a different amino acid

Nonsense

Mutation causing premature termination of protein synthesis

Silent

Mutation that does not alter the amino acid sequence

Frameshift

Mutation caused by insertion or deletion of nucleotides, shifting the reading frame

Null mutation

Mutation resulting in complete loss of function

Temperature sensitivity

Phenomenon where a mutation's effects are influenced by temperature

Lethal mutation

Mutation causing death or severe harm to an organism

“Essential” gene

Gene critical for an organism's survival or development

Haploinsufficient

Condition where a single copy of a gene is not sufficient for normal function

Transposable element/transposon

DNA sequence capable of changing its position within the genome

Transposition

Movement of a transposable element within the genome

Dominant-negative

Mutant allele that interferes with the function of the wild-type allele

Single nucleotide polymorphism

Variation in a single nucleotide in the DNA sequence among individuals

Genetic polymorphism

Variation in DNA sequence among individuals in a population

Wildtype

The most common form of a gene in a population

Fidelity (referring to DNA polymerase)

Accuracy of DNA replication by DNA polymerase

Exonuclease site

Region in DNA polymerase responsible for proofreading during replication

“Proof-reading”

Mechanism by which DNA polymerase corrects errors during DNA replication

Hypermorph

Mutation causing increased gene activity

Neomorph

Mutation resulting in a novel gene function

Germ cell

Cell giving rise to gametes (sperm or egg)

Germline mutation

Mutation occurring in germ cells, heritable to offspring

Somatic cell

Any cell in the body except germ cells

Somatic mutation

Mutation occurring in somatic cells, not passed to offspring

Homologous chromosome

Pair of chromosomes with the same genes in the same order

Allele

Different forms of a gene

Sister chromatid

Identical copies of a chromosome produced during DNA replication

Quiescence

State of inactivity in the cell cycle

Interphase

Phase of the cell cycle between cell divisions

G1, S, G2, M phases

Phases of the cell cycle (Gap 1, Synthesis, Gap 2, Mitosis)

Mitosis

Cell division resulting in two identical daughter cells

Meiosis

Cell division producing gametes with half the chromosome number

Cytokinesis

Division of the cytoplasm following cell division

Bivalent/tetrad

Pair of homologous chromosomes physically connected during meiosis

Metaphase plate

Plane where chromosomes align during metaphase

Ploidy

Number of sets of chromosomes in a cell

Haploid

Cell with one set of chromosomes

Diploid

Cell with two sets of chromosomes

Polyploid

Cell with more than two sets of chromosomes

Karyotype

Number and appearance of an organism's chromosomes

Autosome

Chromosome not involved in determining sex

Sex Chromosome

Chromosome involved in determining sex

Centromere

Region of a chromosome where spindle fibers attach during cell division

Mitotic spindle

Structure organizing and separating chromosomes during cell division

Prophase

First stage of mitosis, chromosomes condense

Metaphase

Chromosomes align at the metaphase plate during mitosis

Anaphase

Sister chromatids separate and move to opposite poles during mitosis

Telophase

Last stage of mitosis, chromosomes