Chapter 1: The molecular basis of heredity, variation and evolution (Vocabulary Flashcards)

Vocabulary flashcards covering key terms and definitions from Chapter 1 topics.

Genetics

The study of heredity and variation; how genetic information is encoded in DNA and expressed in organisms.

Gene

A basic unit of heredity; a factor that Mendel called a gene.

Allele

Alternative forms of a gene.

DNA

Deoxyribonucleic acid; the molecule that carries genetic information; composed of a sugar–phosphate backbone with nitrogenous bases; antiparallel strands.

RNA

Ribonucleic acid; nucleic acid involved in transcription and translation; contains ribose and uses uracil instead of thymine.

Homologous chromosomes

Pairs of chromosomes, one from each parent, that carry the same genes in the same order.

Sister chromatids

Identical copies of a duplicated chromosome held together at the centromere.

Genotype

The genetic makeup of an individual.

Phenotype

The observable physical/biochemical traits of an individual.

Central Dogma

Flow of information from DNA to RNA to protein; with reverse transcription as an exception.

Transcription

Process of copying DNA into messenger RNA (mRNA).

Translation

Process of converting mRNA sequence into a polypeptide (protein).

DNA replication

Copying of DNA to produce identical DNA molecules; semi-conservative process.

DNA polymerase

Enzyme that adds nucleotides to synthesize new DNA strand in the 5′→3′ direction.

Semi-conservative replication

Each new DNA double helix contains one original strand and one new strand.

Nucleotide

The basic unit of DNA/RNA consisting of a sugar, phosphate, and a nitrogenous base.

Antiparallel

DNA strands run in opposite directions (5′→3′ on one strand and 3′→5′ on the other).

Purines

Adenine (A) and Guanine (G); larger nitrogenous bases.

Pyrimidines

Cytosine (C) and Thymine (T) in DNA; Uracil (U) in RNA.

Base pairing

A pairs with T (or U in RNA); G pairs with C.

Hydrogen bonds

Weak bonds between base pairs; A–T has 2; G–C has 3 in DNA.

Phosphodiester bond

Bond backbone linking nucleotides in DNA/RNA.

5′ to 3′ direction

Direction of DNA synthesis by DNA polymerase.

Genome

The total amount of heritable material in an organism.

Karyotype

Image/depiction of the chromosomes in a genome.

Diploid

Organism or cell with two copies of each chromosome.

Haploid

Organism or cell with one copy of each chromosome.

Polyploid

More than two copies of the genome.

Mutation

A change in the DNA sequence that introduces variation.

Genetic variation

Differences in nucleotide sequences among individuals.

Evolution

Change in allele frequencies in a population over time.

Natural selection

Differential reproductive success based on adaptive traits.

Genetic drift

Random changes in allele frequencies due to chance.

Gene flow (Migration)

Movement of individuals that changes allele frequencies between populations.

Sickle-cell anemia

Disease caused by abnormal β-globin alleles; heterozygotes have some protection against malaria.

TYR gene

Gene encoding tyrosinase; mutations can cause albinism (often recessive).

Albinism

Condition with reduced melanin production due to TYR mutations; typically recessive.

Malaria

Disease that exerts selective pressure influencing sickle-cell allele frequencies.

Heterozygous advantage

Advantage of heterozygotes in malaria regions, maintaining the sickle-cell allele.

Codon

A three-nucleotide sequence in mRNA that codes for an amino acid or stop signal.

Start codon AUG

Codon that signals the start of translation and codes for methionine.

Stop codons

UAA, UAG, UGA; signal termination of translation.

mRNA

Messenger RNA; carries genetic information from DNA to the ribosome.

tRNA

Transfer RNA; delivers amino acids to the ribosome during translation.

rRNA

Ribosomal RNA; structural and catalytic component of ribosomes.

miRNA

MicroRNA; small regulatory RNA molecules that regulate gene expression.

Reverse transcription

Synthesis of DNA from an RNA template; used by retroviruses.

Retrovirus

RNA virus that uses reverse transcription to integrate into the host genome.

Mendel

Gregor Mendel, founder of genetics; rediscovered in 1900; proposed genes/factors.

Mendel's Law of Segregation

Alleles separate during gamete formation so offspring inherit one allele per gene.

Mendel's Law of Independent Assortment

Genes on different chromosomes assort independently into gametes.

5' end / 3' end

Ends of nucleic acids; directionality affecting synthesis and reading frames.