Question 1
In mitosis, the number of chromosomes before and after cell division do not change. Mitosis results in daughter cells are having a diploid number of chromosomes as the parent cells.
Question 2
Mitosis is divided into four phases:
Prophase- in this phase, the chromosomal material (chromatin) condenses forming compact chromosomes which are seen as two chromatids joined together at the centromere. The mitotic spindle also starts to assemble with the help microtubules
Metaphase- In this phase, the spindle fibres become attached to the kinetochores of chromosomes. Chromosomes move to the equator and are aligned along the metaphase plate via spindle fibres to opposite poles.
Anaphase- In this phase, centromeres split making the chromatids separate. Also, chromatids move to opposite poles.
Telophase- In telophase, chromosomes are clustered at opposite poles of the cell and they appear as discrete elements. Around the chromosomes, nuclear envelope develop. Lastly, golgi apparatus, nucleolus, and endoplasmic reticulum begin to form.
Question 3
Diploid cells contain two sets of chromosomes (2n) while haploid cells contain one set of chromosomes (n) i.e. half the number as diploid.
Fertilization is the fusion of male gametes and female gametes forming a zygote.
Gametes are cells involved in reproduction.
Sexual reproduction is a type of reproduction involving the fusion of female and male gametes forming a zygote. On the other hand, asexual reproduction does not involve fusion of gametes; the offspring arise from the cells of a single parent.
Question 4
Meiosis I- Has four phases:
Prophase I- Chromosomes shorten and thicken hence becoming visible. Also, nucleolus disappears, crossing over occurs, mitotic spindle forms, and nuclear membrane disappears.
Metaphase I- In this phase, bivalent chromosomes become aligned on the equatorial plate. Microtubules originating from opposite poles of the spindles become attached to homologous chromosomes.
Anaphase I- In this phase, the homologous chromosomes separate, but sister chromatids are still joined at their centromeres.
Telophase I- in this phase, the nuclear membrane and nucleolus are formed. This is followed by cytokinesis, and this is referred to as a diad of cells.
Meiosis II- Has four phases:
Prophase II- Chromosomes shorten and thicken and nuclear membrane disappears.
Metaphase II- Chromosomes are aligned at the equator. Microtubules arising from opposite poles of the spindles are attached to the kinetochores.
Anaphase II- The centromere of each chromosome splits thus setting free the chromatids. Chromatids move to opposite poles of the cell.
Telophase II- Two group of chromosomes, are enclosed by a nuclear envelope. This is followed by cytokinesis resulting in four daughter cells.
Question 5
Synapsis- Pairing of two homologous chromosomes in meiosis.
Crossing Over- Exchange of genetic material between two homologous chromosomes.
Nondisjunction events- Failure of homologous chromosomes or sister chromatids to separate during cell division.
Cytokinesis- the Physical process of cell division involving the division of the cytoplasm of the parent cell forming two daughter cells.
Question 6
Sister Chromatids- Are either of the two identical copies of chromatids arising from replication of a chromosome. They are joined at the centromere.
Homologous Chromosomes- Are members of any chromosome pair. One member of the homolog is the chromosome derived from the mother while the other form the father.
Centromeres- Are parts of the chromosome joining the chromatids.
Centrioles- A small set of microtubules arranged in a particular way.
Asters- A star-like cellular structure that is formed around each centromere in mitotic cell division.
Kinetochore- A proteinous structure found on the chromatids and is where spindles fibres are attached during cell division thus enabling sister chromatids to be pulled apart.
Spindle fibers- These are the microtubules, centromeres, and other structures formed during cell division in eukaryotic cells.
Question 7
p53- A gene coding for a protein that regulates cell cycle and hence works as a tumor suppressor.
Mutagenic agents- Physical or chemical agents that alter the genetic make-up of an individual.
Apoptosis- Programmed cell death occurring in multicellular organisms.
Tumors- Are abnormal mass of tissues which are usually fluid-filled or solid.
Benign are tumors that do not spread to other parts of the body while malignant tumors spread to other parts of the body.
Question 8
Stem cells determination is the progressive restrictions in the developmental potentials of the cells while differentiation is the change of the cell from one cell type to another.
Question 9
Genotype is the overall genetic make-up of an individual while the phenotype is the outward expression of the genotype. A monohybrid cross involves mating of two individuals whose alleles are different at one genetic locus of interest.
Question 10
The homozygous state arises when an individual has the same set of alleles while the heterozygous condition is when an individual has a different set of alleles.
Mendel came up with two laws: The principle of segregation and the principle of independent assortment. The principle of independent assortment states that two members of a gene pair separate from each in the process of forming gametes. The principle of independent assortment states that genes for different traits assort themselves independently in the formation of gametes.
Question 11
Genes- Are functional units of heredity
Locus/loci- the location of a gene along a chromosome
Alleles- Alternative pair of genes
Allele frequency- The frequency of an allele at a specific locus in a population.
Genomes- An organisms full set of DNA
Gene pools- Set of all genes in a population
Pleiotropy- This is a phenomenon characterized by one gene influencing two or more unrelated phenotypic traits
Dominant gene expresses itself phenotypically both in homozygous and heterozygous states while a recessive expresses itself phenotypically only in the homozygous state.
Carrier- An organism is having a recessive allele for a certain genetic trait or mutation but does not show the trait or symptoms of a disease.
Question 12
Complete dominance arises when one allele completely masks the effect of the other in the heterozygous state while incomplete dominance arises when the phenotypic traits of a heterozygous offspring is an intermediate of the phenotypes of the homozygous parents. On the other hand, co-dominance arises when the contribution of both alleles can be seen in the phenotype of an offspring. Polygenic inheritance takes place when a single characteristic is controlled by more than one gene.
Question 13
Genetic engineering- This refers to the modification of an organism’s genetic make-up by transferring the genes.
Genetic recombination- refers to the production of offspring exhibiting combination of traits not found in both parents.
Gene therapy- A technique involving the use of a gene to prevent a disease
PCR- Is a technological approach in molecular biology used to amplify few (or a single) copies a piece of DNA to generate thousands or millions of copies of a specific DNA sequence
Electrophoresis- A laboratory technique utilized to separate macromolecules depending on size.
Clones and cloning- Clones refer to organisms having the same genetic make-up while cloning is the procedure of producing clones.
Question 14
Gene Sequencing- Refers to the process of figuring out the correct order of nucleotides in a DNA molecule.
Proteomics- This refers to the collection of all proteins that the organism synthesizes.
Genomics- refers to a discipline in the field of genetics that applies recombinant DNA, DNA sequencing methods, and bioinformatics to order, assemble and evaluate the role and structure of genomes.
Transcriptomics- the study of a complete set of RNA transcripts produced by the genome.
Bioremediation- Refers to a treatment approach that utilizes naturally occurring organisms to oxidize toxic substances into less toxic or harmless substances.
Question 15
Restriction endonucleases are enzymes that cut a DNA molecule at specific nucleotide sequences while DNA polymerases are enzymes that create DNA molecules by assembling nucleotides.
Helicases are enzymes that bind and/or remodel nucleic acid while ligases are enzymes that facilitate joining of Deoxyribonucleic acid strands together by speeding up the formation of a phosphodiester bond.
VNTRs refers to a short sequence of DNA repeated at a specific chromosomal locus.
Introns are sections of RNA transcript that are non-coding while exons are sections of genes that eventually become part of mature RNA.
Question 16
Genetic diversity in neighboring populations is reduced due to the effect of gene flow. Genetic diversity in founding populations is low due to the loss of genetic variation that comes as a result of the formation of a new population by a small number of individuals derived from a larger population. Large populations have a greater genetic variation as compared to small populations. This is known as population size effects.
Question 17
Genetic bottleneck- Refers to genetic drift that takes place after an event greatly decreases the size of a population.
Genetic drift refers to changes in gene types in a population as a result of random nature of reproduction
High genetic diversity occurs when there are a large variety of genes within a species while low genetic diversity is characterized by a low variety of genes within a species.
Allele frequency- The frequency of an allele at a specific locus in a population.
Founder Effect- Refers to the loss of genetic variation occurring when a new population is established by a small number of individuals derived from a larger population.
Question 18
Interspecific hybridization is a hybridization between organisms of distinct species while intraspecific hybridization is between different sub-species within a particular species.
Question 19
Traits- Are characteristics seen in organisms.
Acquired characteristics- Are characteristics that come about as a result of environmental effects and thus cannot be passed from parents to offspring.
Variation- Differences seen in cells or organisms caused by genetic differences or by environmental factors.
Polyploidy- a state in which an organism has sets of chromosomes more than the diploid number.
Question 20
Natural selection refers to differences in survival and reproduction rates of individuals due to differences in their phenotypic characteristics while the directional selection refers to changes in population genetics whereby extreme values for a particular characteristic are favored.
Sexual selection is a type of natural selection where members of a particular biological sex choose mates of opposite sex with whom to mate while disruptive selection refers to the selection of individuals at the center of a distribution of a certain trait are selected against while those occurring at the extreme are selected for.
Stabilizing selection is a type of natural selection characterized by a decrease in genetic diversity and stabilization of population mean on a certain trait value.
Selective agent is any environmental factor acting on a population.
Question 21
Fitness of an organism/population- Refers to the ability of an organism to survive, reach reproductive age, and mate to produce viable offsprings.
Adaptive radiation- Refers to the diversification of organisms from ancestral species into many new forms as a result of a change in the environment.
Question 22
Darwin- Is considered the father of genetics. He conducted first experiments on inheritance.
Wallace- He came up with the use of human mitochondrial DNA.
Lamarck- He came up with the theory of natural selection.
Question 23
Divergent evolution occurs when two species originate from a common ancestor but do not have the same characteristics while convergent evolution occurs when two species which do not have a common ancestral origin develop similar traits.
Analogous structures are structures having the same functions but have no structural similarity while homologous structures are structures having similar anatomy and morphology but perform different functions.
Question 24
Gradualism refers to the selection and variation happening gradually while in punctuated equilibrium, change happen in spurts.
Question 25
Ecosystem structure- An ecosystem consist of biotic and abiotic factors.
Food webs- Are interconnection of food chains.
Trophic levels- Feeding levels of an organism.
Biomass- Total dry weight of an organism.
Question 26
Energy flow in a food web- The sun> Producers> Primary consumers > Secondary consumers > Tertiary consumers > Quaternary consumers > Decomposers.
2nd Law of Thermodynamics- states that energy of all kinds tends to change itself into a more dispersed form.
