Genetic Variation and Change

Flashcards on Genetic Variation and Change

DNA

Units of genetic information

DNA

Deoxyribose nucleic acid; a polymer made of nucleotide subunits.

Nucleotide

The fundamental building block of DNA and RNA, consisting of a base, phosphate, and 5-carbon sugar.

Four Bases of DNA

Adenine, Thymine, Cytosine, Guanine

Polymer

A molecule made up of many nucleotide monomers.

Polymer

Many units.

Monomer

One unit.

Allele

Different forms of a gene coding for a trait; different versions of the same gene.

Chromosome

A structure within a cell that contains genetic information.

Genotype

Alleles that you inherit for a gene; the genetic makeup of an individual.

Phenotype

Physical characteristics of the genotype.

Genotype

Determine the phenotype.

Homologous Chromosomes

Two chromosomes which contain matching pairs of genes coding for the same trait (contain different alleles).

Non-homologous chromosomes

They are replicated chromosomes.

Sister Chromatids

Identical copies of a chromosome, joined by the centromere; have the same alleles.

Gene Mutation (Point)

Affects the base sequence of a single gene; forms new alleles.

Chromosome Mutations

Changes the structure of a chromosome; affects a whole group of genes.

Aneuploidy

Loss or gain of whole chromosomes.

Polyploidy

Loss or gain of a complete set of chromosomes; common in plants.

Missense / Substitution Mutation

Single base substituted by another, resulting in a new triplet that codes for a different amino acid.

Nonsense Substitution

Mutated DNA creates a stop codon which prematurely ends synthesis of the polypeptide chain.

Silent Substitution

One base is substituted for another but does not result in a different amino acid because of genetic code redundancy.

Mutations

The only source of new alleles and new genetic information.

Mutations

Can occur in somatic cells (not inherited) or gametic mutations occur in the cells of gonads (may be inherited).

Insertion and Deletion

A single base is either inserted or deleted, upsetting the reading sequence.

Prophase 1 (Meiosis)

Homologous chromosomes pair and exchange segments (crossing over).

Metaphase 1 (Meiosis)

Tetrads line up.

Anaphase 1 (Meiosis)

Pairs of homologous chromosomes split up.

Telophase 1 + Cytokinesis (Meiosis)

Two haploid cells form; chromosomes are still double.

Meiosis II

Sister chromatids separate and four haploid daughter cells result, containing single chromosomes.

Haploid

A cell that contains half the number of chromosomes.

Diploid

A cell that contains a full set of homologous chromosomes.