Mutations
What do we call a change in the DNA sequence that may affect a single base pair?
point mutation
What does "epigenetics" study?
Epigenetics studies how behaviors, environment, and life experiences can switch genes "on" or "off" without changing the actual DNA sequence.
If tall (T) is dominant over short (t), what is the genotype and phenotype of a cross: TT × tt? (list genotype(s) and phenotype)
All offspring genotype Tt; phenotype all tall.
In human pedigrees, what shape indicates a male and what shape indicates a female?
Male = square, Female = circle
According to the gene‑chromosome theory, where are genes located?
Genes are located on chromosomes.
Name one environmental factor that can increase the rate of mutations.
UV radiation, sun, x-rays, extreme heat, smoking (any correct response)
Explain why an epigenetic change is not usually considered a mutation in one clear sentence.
Because epigenetic changes do not alter the DNA sequence, they alter expression via chemical tags.
Draw (describe) the four boxes of a Punnett square for a cross Tt × Tt and write the genotypic ratio.
Tt × Tt → Punnett: TT, Tt, Tt, tt → genotypic ratio 1:2:1 (TT:Tt:tt)
In an X‑linked recessive pedigree, who is more likely to express the trait: males or females?
males
How many chromosomes are normally found in human body (somatic) cells?
46
Explain the difference between a point mutation that is a silent mutation.
A silent mutation does not effect the protein that is being made. It does not change the amino acid.
Give a short classroom example of how diet or environment might change gene expression in twins.
If one twin has a diet rich in healthy foods and the other eats all processed foods, the twin with a poor diet may have genes expressed associated with inflammation (disease).
In pea plants, purple (P) is dominant to white (p). Parent cross: PP × Pp. List expected phenotypes
100% purple
Explain in one sentence what an allele is.
An allele is a version of a gene.
What is a frameshift mutation and how does adding or deleting one base affect the protein produced?
frameshift = insertion/deletion not multiple of three; shifts reading frame so most downstream amino acids change and often causes premature stop.
Give a reason why a goldfish in a tank will only grow to be a few inches long, yet a goldfish in a pond can grow much longer. Use the correct scientific terminology in your answer.
The goldfish in the pond has a larger environment impacting the gene expression allowing it to grow bigger given the extra space. The fish in the tank's body releases a chemical signal to slow growth due to environmental stress, leading to stunted growth.
Cross a heterozygous father and a homozygous dominant mother. Using R as the dominant allele and r as the recessive. List the genotypes of the offspring.
RR, RR, Rr, Rr
If two unaffected parents have an affected son and the trait is autosomal recessive, what are the most likely genotypes of the parents?
Parents likely both carriers (Aa × Aa) for an autosomal recessive trait; explanation: unaffected carriers can produce affected (aa) children.
What is meant by homologous chromosomes?
Homologous chromosomes are a matched pair (one from each parent) that carry the same genes in the same order.
Name the type of mutation:
ATA CGG TTA CGC
TAT GCA AAT GCG
Substitution
Name two environmental factors that can affect gene expression and explain how this happens.
Environmental factors like diet, stress, pollution, temperature, light, and toxins significantly alter gene expression by adding or removing epigenetic markers (like DNA methylation) or changing how genes are transcribed, impacting health, development, and disease risk (cancer, diabetes).
The pedigree shows a trait appearing in every generation and both males and females are affected about equally. Which inheritance pattern is most likely? Explain in one sentence.
Most likely autosomal dominant (appears every generation, both sexes equally affected).
Describe how crossing over during meiosis increases genetic variation.
Crossing over exchanges segments between homologous chromosomes during meiosis, producing new combinations of alleles and increasing genetic variation.