GED and HiSET science — DNA, heredity and evolution

Heredity and evolution are central to the life-science questions on the GED and HiSET science tests. A question might describe a family in which a disorder appears in a child of healthy parents, a museum display of fossils, or a table comparing the DNA of several species, and ask what it shows. This material takes the topic past the basics into the reasoning these questions require.

The quiz begins with the molecule itself: pairing the bases of a DNA strand (A with T, C with G), ordering the steps from DNA to messenger RNA to protein, and explaining why a single changed letter in the hemoglobin gene can cause sickle cell disease by changing one amino acid and with it the shape of the protein. It separates the mutations that can be passed to children (in egg and sperm cells) from those that cannot (in skin or lung cells), and compares mitosis, which makes two identical body cells with 46 chromosomes, with meiosis, which makes four different sex cells with 23. Punnett squares follow: the chance of a recessive trait from an Aa × aa cross, the chance that a child of two carriers will itself be a carrier, and the reasoning that two unaffected parents of an affected child must both carry the recessive allele. The last part turns to the evidence for evolution: a series of whale fossils running from four-legged land animals to aquatic forms with shrinking hind limbs, homologous bones in a human arm, a bat wing and a whale flipper, a table of DNA differences between species, and a cladogram described in words.

The flashcards review base pairing, transcription and translation, inherited and non-inherited mutations, mitosis and meiosis, carriers, transitional fossils, homologous structures, DNA similarity and cladograms.

The written work asks you to draw and explain Punnett squares, to trace a gene to a protein, to explain why a mutation in a skin cell is not inherited, and to weigh several lines of evidence for common ancestry. In the oral exam an examiner presents families, fossils and data one question at a time, asks you to explain your reasoning, and ends with short feedback on what to review.

All content reflects current mainstream biology. This is independent practice material based on the publicly described content of the two tests; it is not produced or endorsed by GED Testing Service or by ETS.

• Apply base-pairing rules and describe how DNA is transcribed and translated into protein
• Explain how a single mutation can change a protein, and which mutations are inherited
• Compare mitosis and meiosis by purpose, number of cells and chromosome number
• Use Punnett squares to find probabilities of traits and of carrier status
• Deduce carrier status from a family pattern
• Interpret fossil sequences, homologous structures, DNA comparisons and cladograms as evidence of common ancestry

Practice material written by Zestly, based on the published descriptions of the GED Science test (ged.com) and the HiSET Science subtest (hiset.org: life science — heredity and evolution).