Correction L2 Exams

Why parents (P) have all the same

gametes F1 parents have four different

gametes. 

The F1 parent carries two different alleles for each gene, so the independent assortment of these alleles during meiosis leads to the formation of four equally likely types of gametes in the ratio 1:1:1:1.

Why does a frameshift (insertion/deletion) mutation generally have a severe effect on a protein's function?

It causes a shift in the reading frame, resulting in many amino acids changing down the line. This leads to a severe, change in the protein's primary structure, folding, and therefore, its ability to function (e.g., in oxygen transport).

Why does a substitution (point mutation) generally have a less severe effect on a protein's function (like oxygen transport)?

It typically affects only one amino acid in the primary structure. This small change may only slightly alter the protein's folding (tertiary structure), so the loss of function is less severe.

Define Natural Selection and explain its effect on a population's genes.

It is the process where individuals with 'fit' phenotypes survive and reproduce at a higher rate than less fit individuals. This results in the increase of beneficial allele frequency in the next generation.

Why must a cell divide as it grows larger?

As a cell grows, its Volume increases much faster than its Surface Area. This causes the SA:V ratio to decrease (become smaller). When the ratio is too small, the cell's surface area isn't large enough to support the required rate of diffusion for transporting materials (like oxygen and waste) across the membrane, so the cell must divide to restore a larger, more efficient SA:V ratio.

What are Linked Genes and how does this affect inheritance?

Since Linked genes inherited together, they cannot be separated by independent assortment during meiosis.

How can genetic variation be increased in an isolated population?

Introduce individuals from different populations to breed (crossbreed). This action causes gene flow and increases the number of beneficial alleles in the gene pool.

What is the primary benefit of Gene Flow (connecting sub-populations)?

It maintains genetic variation by increasing the effective population size. This brings in new alleles and prevents inbreeding, creating a more diverse and resilient gene pool

Why is losing genetic diversity dangerous for a small population?

Individuals become too genetically similar to each other. If the environment changes (e.g., a new disease or climate change), there is a low chance that anyone in the population will have the right alleles to survive. This severely lowers the chances of long-term survival or population recovery.

What is the main advantage of Incomplete Dominance inheritance?

It increases phenotype variation by producing three different phenotypes (e.g., Red, White, and Pink flowers) from two alleles.

What is the main disadvantage of Complete Dominance?

It masks/hides the recessive allele in heterozygous individuals. This results in only two phenotypes being expressed, reducing observable variation.

What is the advantage of a species having Multiple Alleles for a trait?

More alleles lead to more phenotypes being expressed. This provides more options for natural selection to act on, increasing the species' chances of survival if the environment changes.

Why do low and high pH levels stop an enzyme reaction?

Extreme pH causes the enzyme to denature. It disrupts the hydrogen bonds holding the protein together, making the active site change shape. The substrate no longer fits (it's no longer complementary), so the reaction stops.

How does Genetic Drift affect small populations?

It has a larger, faster effect. Random events (drift) are more likely to cause alleles to be fixed (100% frequency) or lost (0% frequency), leading to a quick reduction in genetic variation.

How does Genetic Drift affect large populations?

It has a smaller, slower effect. The larger number of individuals acts as a buffer, making it less likely for any single allele to be completely lost or fixed. Large populations, therefore, maintain more genetic variation.