Chapter 25: DNA Structure and Gene Expression
What are the three types of RNA involved in gene expression?
mRNA, tRNA, and rRNA
During which stage of interphase does DNA replication occur?
S Phase
What is the difference between genotype and phenotype?
Genotype: an individual's allele combination
Phenotype: the expressed or observable trait.
What does it mean when two genes are linked?
They are located on the same chromosome and tend to be inherited together.
Who proposed evolution by natural selection?
Charles Darwin
What enzyme unwinds and unzips DNA during replication?
DNA helicase
During which phase of mitosis do sister chromatids separate?
Anaphase
What is the difference between homozygous and heterozygous?
Homozygous means two identical alleles; heterozygous means two different alleles.
What is nondisjunction?
The failure of homologous chromosomes or sister chromatids to separate properly during meiosis.
What is the difference between Lamarck's and Darwin's explanations of evolution?
Lamarck proposed inheritance of acquired characteristics
Darwin proposed natural selection acting on inherited variation.
Why is DNA replication described as semiconservative?
Each new DNA molecule contains one original parent strand and one newly synthesized strand.
What are the two processes during meiosis that increase genetic variation?
Crossing over and independent assortment
Two heterozygous individuals (Aa × Aa) are crossed. What is the expected phenotypic ratio if A (brown eyes) is completely dominant to a (blue eyes)?
3 brown eyes : 1 blue eyes
What chromosomal abnormality causes Down syndrome?
Trisomy 21
What are the five conditions necessary for Hardy-Weinberg equilibrium?
No mutations, no migration, random mating, a very large population, and no natural selection.
What are the three steps of translation, in order?
initiation, elongation, termination
What is the difference between proto-oncogenes and tumor suppressor genes?
Proto-oncogenes promote cell division, while tumor suppressor genes inhibit cell division
A red flower and a white flower produce pink offspring. What type of inheritance does this demonstrate?
Incomplete dominance.
A mother is a carrier for X-linked recessive color blindness, and the father has normal vision. What percentage of their sons are expected to be colorblind?
50% of their sons.
What are the four major lines of evidence that support the theory of evolution?
Fossil evidence, biogeography, comparative anatomy, and molecular evidence.
What are the roles of DNA helicase, DNA polymerase, and DNA ligase during DNA replication?
DNA helicase: Unwinds and separates the DNA strands.
DNA polymerase: Adds complementary nucleotides to build new DNA strands.
DNA ligase: Seals breaks in the sugar-phosphate backbone.
A cell starts meiosis with 16 chromosomes. How many chromosomes will each daughter cell contain after meiosis I and after meiosis II?
8 chromosomes after meiosis I and 8 chromosomes after meiosis II
A parent with type AB blood and a parent with type O blood have children. What blood types are possible, and what are their percentages?
50% Type A
50% Type B
What is the difference between a chromosomal deletion, duplication, inversion, and translocation?
Deletion: Removes a chromosome segment.
Duplication: Repeats a chromosome segment.
Inversion: Reverses a chromosome segment.
Translocation: Moves a chromosome segment to another location.
A population of insects becomes separated by a mountain range. Over many generations, the two populations become unable to interbreed. What type of speciation has occurred?
Allopatric speciation.