Inheritance & Traits
What is the term for the passing of traits from parents to offspring?
Heredity or inheritance.
What is a mutation?
A mutation is a change in the DNA sequence or genetic material.
Which scientist is most famous for developing the theory of natural selection?
Charles Darwin
Name one technology scientists use to study DNA or genes.
Acceptable answers include DNA sequencing, genetic engineering, CRISPR, gel electrophoresis, polymerase chain reaction, genetic testing, or cloning.
In a monohybrid cross, what does each parent contribute to the offspring?
Each parent contributes one allele for the trait.
What molecule carries genetic information in most organisms?
DNA, or deoxyribonucleic acid.
If a parent has the genotype Bb for brown eyes, where B represents brown and b represents blue, what two alleles could the parent pass to an offspring?
The parent could pass either
BB
or
bb
Name two ways genetic variations can occur in offspring.
Genetic variations can occur through different combinations of inherited alleles and through mutations in DNA.
What does the phrase “survival of the fittest” mean in natural selection?
Organisms with traits that are better suited to their environment are more likely to survive and reproduce.
What is genetic engineering?
Genetic engineering is the process of directly changing an organism’s DNA to give it new traits or characteristics.
If T represents tall plants and t represents short plants, what percentage of offspring will be tall in the cross TT×tt?
All offspring will have genotype Tt and will be tall because T is dominant.
What is the difference between genotype and phenotype?
Genotype is an organism’s genetic makeup, including its alleles. Phenotype is the organism’s observable traits or characteristics.
In a Punnett square cross between two heterozygous parents,
Bb×Bb, what percentage of offspring will be homozygous recessive, bb?
25%, or 1 out of 4 offspring.
True or false: All mutations are harmful to organisms. Explain your answer.
False. Mutations can be harmful, beneficial, or neutral. Some mutations provide advantages that help organisms survive and reproduce.
A population of beetles includes green and brown individuals. After a forest fire, the ground is covered in dark ash. Which color beetle is likely to increase in the population, and why?
Brown beetles are likely to increase because they are better camouflaged against the dark ash. Predators may have more difficulty seeing them, allowing them to survive and reproduce more often.
Describe one positive effect genetic research has had on human lives.
Acceptable answers include producing medicines such as insulin, detecting or preventing diseases, improving crop yields, developing gene therapies, or using DNA evidence in forensic science. The response should include an explanation.
In pea plants, yellow seeds, Y, are dominant to green seeds, y. If two heterozygous yellow plants are crossed, Yy×Yy, what is the probability of getting a green seed?
25% or 1 out of 4
How is selective breeding by humans similar to natural selection in nature?
Both processes cause certain traits to become more common over generations. In selective breeding, humans choose which organisms reproduce. In natural selection, the environment influences which organisms survive and reproduce more successfully.
Explain why two brown-eyed parents can have a blue-eyed child using genetic terminology.
Both parents must be heterozygous, with the genotype Bb, If each parent passes the recessive bb allele, the child inherits bb and may have blue eyes.
Explain how a mutation in a gene could lead to a different trait being expressed in an organism.
A mutation changes the DNA sequence. This may alter the instructions for making a protein. The changed protein can result in a different physical trait or characteristic.
Explain four conditions necessary for natural selection to occur in a population.
1. Variation exists among individuals.
2.Some traits are heritable.
3. More offspring are produced than can survive.
4. Individuals with advantageous traits survive and reproduce more successfully.
Describe one negative effect or ethical concern related to genetic research or technology.
Acceptable answers include concerns about designer babies, genetic discrimination, unknown long-term effects of genetic modification, environmental effects of genetically modified organisms, unequal access to technology, or privacy concerns involving genetic data. The response should include an explanation.
In guinea pigs, black fur, B, is dominant to white fur, b, and short hair, S, is dominant to long hair, s. What is the genotype of a guinea pig that is heterozygous for both traits?
BbSs
A rabbit population lives in a snowy environment. Over many generations, the population changes from mostly brown rabbits to mostly white rabbits. Explain this change using mutation, inheritance, and natural selection.
A mutation for white fur may have occurred in some rabbits. The trait could be inherited by their offspring. In the snowy environment, white rabbits would be better camouflaged from predators, so they might survive and reproduce more often than brown rabbits. Over many generations, natural selection would cause white fur to become more common.
A trait is controlled by three alleles, A, B, and i, for blood type. If one parent is Type AB and the other is Type O, with genotype ii, what blood types are possible in their children, and why?
Only Type A, with genotype Ai, or Type B, with genotype Bi, is possible. The AB parent can pass either A or B, while the Type O parent can pass only i. The A and B alleles are codominant with each other and dominant over i.
Compare and contrast inherited genetic variation with variation caused by mutations. Give an example of each.
Inherited variation results from combining alleles from both parents during reproduction. For example, an offspring may inherit one allele for curly hair from one parent and another hair-texture allele from the other parent. Mutation-based variation results from a change in DNA that may not have been present in either parent. Both processes create genetic diversity.
Use a model to explain how natural selection could lead to a decrease in a specific trait over time. Provide an example.
If a trait becomes disadvantageous because of an environmental change, individuals with that trait may survive and reproduce less often. As a result, the trait becomes less common over generations. For example, if tree bark becomes darker because of pollution, light-colored moths may be easier for predators to see. Fewer light-colored moths survive and reproduce, so the proportion of light-colored moths decreases.
Explain how advances in DNA sequencing technology have furthered genetic research. Give one example of something scientists can do now that was difficult or impossible in the past.
DNA sequencing has become faster, less expensive, and more accurate. Scientists can now sequence entire genomes much more quickly, identify genes linked to diseases, compare the DNA of different species, and develop treatments tailored to a person’s genetic information.
Using the following guinea pig traits, what fraction of offspring will have black fur and long hair in the cross BbSs×bbss?
1/4 , or 25%. The offspring must have at least one B allele and two s alleles, producing a genotype such as Bbss.
.
CRISPR gene-editing technology allows scientists to cut and modify DNA sequences. Construct an argument supporting either the benefits or the risks of using this technology on human embryos to eliminate genetic diseases. Use at least two pieces of evidence.
Possible argument supporting the benefits: CRISPR could eliminate serious genetic diseases before birth, potentially preventing lifelong suffering. It could also correct disease-causing DNA in every cell of the developing individual.
Possible argument emphasizing the risks: CRISPR could produce unexpected changes or long-term effects that might be passed to future generations. It could also increase inequality if only wealthy families could access the technology or lead to attempts to create “designer babies.”