DNA & Genetics Basics
What are the four bases of DNA?
Adenine, Thymine, Cytosine, Guanine.
If a heterozygous (Ee) dog mates with a homozygous recessive (ee) dog, what % of offspring will have floppy ears?
50%
What is the process that develops new types of life on Earth?
Evolution.
What does “extinction” mean?
The permanent loss of all members of a species.
What is the name of the theory explaining how organisms change over time through adaptation?
Natural selection.
Which base pairs with adenine in DNA?
Thymine.
Which type of allele is “hidden” in a heterozygous individual?
The recessive allele.
Who proposed the theory of natural selection?
Charles Darwin.
Name one cause of extinction.
Examples: climate change, habitat loss, invasive species, inability to adapt.
What is a gene pool?
All the genes present in a population.
What is a gene?
A unit of heredity, a segment of DNA that codes for a trait.
Right-handedness (R) is dominant over left-handedness (r). If a parent is Rr and another rr, what is the chance of left-handed offspring?
50%
What is meant by “survival of the fittest”?
Organisms best adapted to their environment survive and reproduce.
In which type of rock are fossils usually found?
Sedimentary rock.
What is one source of evidence for Darwin’s theory of evolution?
Fossils, comparative anatomy, embryology, or DNA evidence.
What is the difference between genotype and phenotype?
Genotype is the genetic makeup (alleles), phenotype is the observable characteristics.
What is a pedigree chart used for?
To trace inheritance of traits through generations.
Why have crocodiles barely changed in 200 million years?
They are very well adapted to their environment.
Why are some organisms preserved better in the fossil record than others?
Hard parts (bones, shells) fossilise more easily than soft tissue.
How did industrialisation affect the frequency of dark-coloured peppered moths?
Increased soot made dark moths better camouflaged, so their frequency rose.
How many chromosomes do human gametes have after meiosis?
23
If two white mice (recessive trait) are bred, can they produce a brown (dominant) offspring? Explain.
No, because they both carry only recessive alleles.
What must occur in a population for evolution to take place?
Genetic variation.
What is one piece of fossil evidence that supports evolution?
Transitional fossils showing gradual change (e.g., Archaeopteryx between reptiles and birds).
Why does natural selection not mean a theory is “just a guess”?
In science, a theory is a well-supported explanation based on evidence.