BIO 120 Midterm III Review

DNA Replication

1. Enzyme Involved:

   • DNA polymerase is the enzyme involved in DNA replication.

2. Direction of Synthesis:

   • DNA polymerase works in the 5' to 3' direction.

3. De Novo Synthesis:

   • DNA polymerase does not synthesize de novo, meaning it cannot start a new strand from scratch; it can only add nucleotides to an existing strand.

4. Enzymes for Opening DNA:

   • Helicase opens up the DNA double helix.

   • Topoisomerase relieves the torsional stress caused by the unwinding of DNA.

5. Origin of Replication:

   • The origin of replication is the region on the DNA where replication begins. These regions are typically rich in adenine (A) and thymine (T) base pairs.

6. Enzyme Joining Okazaki Fragments:

   • Ligase joins Okazaki fragments together on the lagging strand.

7. Enzyme Creating RNA Primer:

   • Primase creates the RNA primer, which provides a starting point for DNA polymerase.

8. Enzyme Destroying RNA Primer:

   • RNase removes or destroys the RNA primer.

9. Proteins Preventing Single-Stranded DNA Re-annealing:

   • Single-strand binding proteins (SSBPs) prevent single-stranded DNA from coming back together during replication.

10. Telomeres:

    • Telomeres are repeat sequences at the ends of chromosomes that resolve the “end-replication problem.” Bacteria do not have this problem because their DNA is circular.

11. Telomerase:

    • Telomerase is the enzyme that solves the end-replication problem by extending the telomeres.

12. Replication Fork Review:

    • Understand the parts of the replication fork, including:

      • Leading strand

      • Leading strand template

      • Lagging strand template

      • Okazaki fragments

      • RNA primers

      • Direction of opening

Mitosis

1. Parts of a Condensed Chromosome:

   • CEN: Centromere

   • p-arm: Short arm of the chromosome

   • q-arm: Long arm of the chromosome

2. Diploid Number (2n):

   • The number of chromosomes in a somatic cell, which is the number of homologous pairs of chromosomes in a somatic cell.

3. Haploid Number (n):

   • The number of chromosomes in a germ cell (sperm or egg).

4. Difference Between Germ Cells and Somatic Cells:

   • Somatic cells: 2n (diploid), most cells in the body (muscle, liver, adipose, brain).

   • Germ cells: n (haploid), sperm or egg cells.

5. Difference Between Homologous Pairs and Sister Chromatids:

   • Homologous pairs: Chromosomes that have the same genes in the same order, but may have different alleles (versions of those genes).

   • Sister chromatids: Exact copies of the same chromosome, nucleotide for nucleotide.

6. Stages of Mitosis:

   • Interphase

   • Prophase

   • Prometaphase

   • Metaphase

   • Anaphase

   • Telophase

7. Events at Each Stage:

   • Review the events that occur during each stage of mitosis.

8. Cytokinesis:

   • The end of mitosis where the cell itself divides into two.

9. Cytokinesis in Animal vs. Plant Cells:

   • Animal cells: Cleavage furrow forms.

   • Plant cells: Cell plate forms.

10. Stages of the Cell Cycle:

    • G1-S-G2-M

11. Events at Each Stage of the Cell Cycle:

    • G1 and G2: “Growth” or “gap” phases.

    • S: Synthesis (DNA synthesis/replication).

    • M: Mitosis (all the stages of mitosis).

12. Correspondence Between Cell Cycle Stages and Mitosis Stages:

    • Interphase: G1, S, and G2 phases.

    • Mitosis Stages: M phase (prophase, prometaphase, metaphase, anaphase, telophase).

13. Decision Points During the Cell Cycle:

    • G1 to S: “Restriction point” or commitment step.

    • G2 to M

14. Factors Monitored at Decision Points:

    • G1 to S: Is the environment favorable? Is my DNA okay (undamaged)?

    • G2 to M: Has my DNA finished replicating?

Meiosis

1. Difference Between Sexual and Asexual Reproduction:

   • Sexual reproduction: Pass on half your DNA.

   • Asexual reproduction: Pass on all your DNA.

2. Life Cycle:

   • The sequence of stages from generation to generation, from conception to production of offspring.

3. Life Cycle Differences Among Animals, Plants, and Fungi:

   • Animals: Dominant diploid multicellular form.

   • Fungi: Haploid multicellular.

   • Plants: Both diploid multicellular and haploid multicellular forms (alternation of generations).

4. Purpose of Meiosis:

   • Reduce chromosome number from 2n to n.

5. First Stage Differing from Mitosis:

   • Anaphase I: Sister chromatids do not separate; they remain intact as they move to the poles of the cell.

6. Independent Assortment:

   • Maternal and paternal sets of chromosomes can assort independently.

7. Formula for Calculating Independent Assortment:

   • 2^n = number of possibilities

Genetics

1. P, F1, F2 Generations:

   • P = Parental generation

   • F1 = First filial generation (second generation)

   • F2 = Grandfilial generation (third generation)

2. True Breeding Plants:

   • Breeding with itself always produces the same phenotype; these plants are genotypically homozygous.

3. Allele:

   • Different versions of a gene.

4. Locus:

   • Physical location of a gene on a chromosome (plural is loci).

5. Dominant Allele:

   • In the heterozygote, the allele whose phenotype you see.

6. Recessive Allele:

   • In the heterozygote, the allele whose phenotype you don’t see.

7. Mendel’s Law of Segregation:

   • Two alleles for a character separate during gamete formation and end up in different gametes.

8. Punnett Square:

   • Review Punnett square basics.

9. Homozygous:

   • Two identical alleles for a particular gene.

10. Heterozygous:

    • Two different alleles for a particular gene.

11. Genotype:

    • The genetic makeup of an individual; which alleles a particular individual has.

12. Phenotype:

    • Observable physical properties of an organism.

13. Testcross:

    • Cross an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype.

14. Mendel’s Law of Independent Assortment:

    • Alleles of two or more genes get sorted into gametes independently of one another.

15. Incomplete Dominance:

    • The recessive allele is nonfunctional, so you see half the effect of the dominant allele (quantitative difference).

16. Codominance:

    • See both of the alleles in equal amounts.

17. ABO Blood Groups:

    • A and B are codominant.

    • A is dominant over O.

    • B is dominant over O.

    • Review which blood type can receive transfusions from which blood type.