Genetics
Module B, Anchor 3
Key Concepts:
- An individual’s characteristics are determines by factors that are passed from one
parental generation to the next.
- During gamete formation, the alleles for each gene segregate from each other so that each
gamete carries only one allele for each gene.
- Punnett squares use mathematical probability to help predict the genotype and phenotype
combinations in genetic crosses.
- The principle of independent assortment states that genes for different traits can segregate
independently during the formation of gametes.
- Mendel’s principles of heredity, observed through patterns of inheritance, form the basis
of modern genetics.
- Some alleles are neither dominant nor recessive. Many genes exist in several different
forms and are therefore said to have multiple alleles. Many traits are produced by the
interaction of several genes.
- Environmental conditions can affect gene expression and influence genetically
determined traits.
- The DNA that makes up genes must be capable of storing, copying, and transmitting the
genetic information in a cell.
- DNA is a nucleic acid made up of nucleotides joined into long strands or chains by
covalent bonds.
- DNA polymerase is an enzyme that joins individual nucleotides to produce a new strand
of DNA.
- Replication in most prokaryotic cells starts from a single point and proceeds in both
directions until the entire chromosome is copied.
- In eukaryotic cells, replication may begin at dozens or even hundreds of places on the
DNA molecule, proceeding in both directions until each chromosome is completely
copied.
- The main differences between DNA and RNA are that (1) the sugar in RNA is ribose
instead of deoxyribose; (2) RNA is generally single-stranded, not double-stranded; and
(3) RNA contains uracil in place of thymine.
- In transcription, segments of DNA serve as templates to produce complementary RNA
molecules.
- The genetic code is read three “letters” at a time, so that each “word” is three bases long
and corresponds to a single amino acid.
- Ribosomes use the sequences of RNA codons to assemble amino acids into polypeptide
chains.
- The central dogma of molecular biology is that information is transferred from DNA to
RNA to protein.
- Mutations are heritable changes in genetic information.
- The effects of mutations on genes vary widely. Some have little or no effect; some
produce beneficial variations. Some negatively disrupt gene function.
- Mutations often produce proteins with new or altered functions that can be useful to
organisms in different or changing environments.
