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Flashcards on Genetic Variation and Change
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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.