Mitosis
State one purpose of mitosis in multicellular organisms.
Growth, repair of tissues, or asexual reproduction.
State the number of daughter cells produced by meiosis.
Four haploid daughter cells
Describe the difference between genotype and phenotype.
Genotype is an organism's allele combination, while phenotype is the observable characteristic produced by the genotype and environment.
In a pedigree, what does a shaded symbol represent?
An individual expressing the trait being studied.
Define evolution.
Evolution is a change in allele frequencies within a population over many generations.
During which stage do chromosomes line up at the equator of the cell?
Metaphase
During which stage of meiosis does crossing over occur?
Prophase I
A heterozygous individual has which combination of alleles?
Two different alleles (e.g. Aa).
Autosomal dominant traits usually show which pattern across generations?
They typically do not skip generations.
State the ultimate source of genetic variation in a population.
Mutation. Mutations create new alleles that can be acted on by evolutionary processes.
Describe the events that occur during anaphase.
Sister chromatids separate at the centromere and are pulled to opposite poles by spindle fibres.
Explain how independent assortment increases genetic variation.
Maternal and paternal chromosomes are distributed randomly into gametes, creating different combinations of alleles.
Two heterozygous parents (Aa × Aa) produce offspring. State the probability of producing a homozygous recessive offspring.
25%
Which inheritance pattern is suggested when more males than females are affected and affected fathers do not pass the trait to their sons?
X-linked recessive inheritance.
Explain how natural selection can increase the frequency of a beneficial allele in a population.
Individuals with advantageous traits survive and reproduce more successfully, passing those alleles to offspring. Over generations, the frequency of the beneficial allele increases.
Explain why DNA replication during S phase is essential before mitosis begins.
DNA replication ensures each daughter cell receives a complete and identical set of chromosomes.
Compare the chromosome number of the parent cell and daughter cells produced by meiosis.
The parent cell is diploid (2n) while the daughter cells are haploid (n) and contain half the number of chromosomes.
A mother has blood group AB and a father has blood group O. State the possible blood groups of their offspring.
Type A and Type B only
An affected father passes a trait to all daughters but none of his sons. Which inheritance pattern is most likely?
X-linked dominant inheritance.
Compare natural selection and genetic drift as mechanisms of evolution.
Natural selection is a non-random process driven by selection pressures that favour advantageous traits. Genetic drift involves random changes in allele frequencies and has the greatest effect in small populations.
Explain how metaphase and cytokinesis help maintain genetic continuity in daughter cells.
Metaphase ensures chromosomes align correctly and attach to spindle fibres. Cytokinesis then divides the cytoplasm, producing two genetically identical daughter cells with the same chromosome number as the parent.
Explain the roles of both crossing over and independent assortment in producing genetic variation.
Crossing over exchanges genetic material between homologous chromosomes in Prophase I, while independent assortment randomly distributes maternal and paternal chromosomes during Metaphase I. Together they create unique allele combinations in gametes.
Explain the difference between codominance and incomplete dominance using an example of each.
In codominance, both alleles are fully expressed, such as blood group AB. In incomplete dominance, the heterozygote has an intermediate phenotype, such as pink flowers produced from red and white parents.
Explain how you would distinguish between autosomal recessive and autosomal dominant inheritance using a pedigree.
Autosomal dominant traits generally do not skip generations and affected individuals usually have an affected parent. Autosomal recessive traits can skip generations and affected offspring may be born to unaffected carrier parents.
Explain how geographic isolation could eventually lead to the formation of a new species.
Geographic isolation prevents gene flow between populations. Over time, genetic drift, mutations and natural selection cause populations to accumulate genetic differences. If reproductive isolation develops and the populations can no longer produce fertile offspring together, speciation has occurred.