Bio Test 4

What is the purpose of mitosis?

The purpose of mitosis is to enable cell division, resulting in two identical daughter cells for growth, repair, and asexual reproduction.

What are the steps of DNA Replication?

Step 1: Formation of a Replication Fork

Step 2: Priming for DNA Replication

Step 3: Elongation of a Daughter Strand

Step 4: Removal of RNA Primers

Step 5: Replacing RNA Primer with DNA Nucleotides

Step 6: Sealing the gaps in Sugar/Phosphate Backbone

Describe Step 1 of DNA Replication

Step 1: Formation of a Replication Fork

DNA Helicase unwinds and “unzips” the double-stranded DNA, resulting in a replication fork.

• Breaks the Hydrogen Bonds between complementary base pairs

Describe Step 2 of DNA Replication

Step 2: Priming for DNA Replication

Primase uses RNA nucleotides to place a primer (starting point) on the DNA strand

Describe Step 3 of DNA Replication

Step 3: Elongation of a Daughter Strand

• DNA Polymerase adds DNA nucleotides on the primer in the 3’ to 5’ direction

• One daughter strand (Leading Strand) replicates continuously as the replication fork continues to unwind the DNA

  • 3’ to 5’

• Other daughter strand (Lagging Strand) replicates discontinuously

  • Unwinding in 5’ to 3’ direction creates small fragments of the Daughter Strand (Okazaki Fragments)

Describe Step 4 of DNA Replication

Step 4: Removal of RNA Primers

Once the daughter strands (leading + lagging strands) are done synthesizing, Exonuclease removes the RNA primers located on both strands

Describe Step 5 of DNA Replication

Step 5: Replacing RNA Primer with DNA Nucleotides

What are the stages of the cell cycle?

The stages of the cell cycle include Interphase (G1, S, G2), Mitosis (Prophase, Metaphase, Anaphase, Telophase), and Cytokinesis.

What are the three checkpoints of the cell cycle?

The three checkpoints are G1 checkpoint (checks for cell size and DNA damage), G2 checkpoint (checks for DNA replication errors), and M checkpoint (checks for proper chromosome alignment before division).

What is apoptosis?

Apoptosis is the process of programmed cell death that occurs in multicellular organisms, helping to eliminate damaged or unnecessary cells.

Define chromatin.

Chromatin is a complex of DNA and proteins found in the nucleus of eukaryotic cells, which condenses to form chromosomes during cell division.

What are sister chromatids?

Sister chromatids are identical copies of a single chromosome, connected by a centromere, that are formed during DNA replication.

What is the difference between cytokinesis in plant and animal cells?

In animal cells, cytokinesis occurs through cleavage furrow formation, while in plant cells, a cell plate forms to separate the two daughter cells.

What is the purpose of meiosis?

The purpose of meiosis is to produce gametes (sperm and eggs) with half the number of chromosomes, contributing to genetic diversity through sexual reproduction.

What is crossing over?

Crossing over is the exchange of genetic material between homologous chromosomes during prophase I of meiosis, leading to genetic variation in gametes.

What is independent assortment?

Independent assortment is the random distribution of homologous chromosome pairs during meiosis, contributing to genetic diversity in offspring.

Define diploid.

Diploid refers to a cell or organism that has two complete sets of chromosomes, one from each parent, typically represented as 2n.

Define haploid.

Haploid refers to a cell or organism that has one complete set of chromosomes, typically represented as n, as seen in gametes.

What is non-disjunction?

Non-disjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to gametes with abnormal chromosome numbers.

What is the significance of Punnett squares?

Punnett squares are used to predict the genotypes and phenotypes of offspring from genetic crosses, illustrating inheritance patterns.

What is codominance?

Codominance is a genetic scenario where both alleles in a heterozygote are fully expressed, resulting in offspring with a phenotype that is neither dominant nor recessive.

What is sex-linked inheritance?

Sex-linked inheritance refers to genes located on sex chromosomes, where traits are passed on differently based on the sex of the individual.

What are chromosomal mutations?

Chromosomal mutations are alterations in the structure or number of chromosomes, which can lead to genetic disorders or variations.

What are the causes of gene mutations?

Gene mutations can be caused by factors such as environmental influences (radiation, chemicals), errors during DNA replication, or inherited genetic changes.

What is genetic recombination?

Genetic recombination is the process by which genetic material is physically mixed during meiosis, resulting in offspring with combinations of traits different from those of the parents.

What is fertilization?

Fertilization is the process in which male and female gametes combine to form a zygote, initiating the development of a new organism.

What is the role of DNA helicase?

DNA helicase is an enzyme that unwinds the DNA double helix during DNA replication, allowing the strands to separate for copying.

What is the role of DNA polymerase?

DNA polymerase is an enzyme that synthesizes new DNA strands by adding nucleotides complementary to the template strand during DNA replication.

What is the role of exonuclease?

Exonuclease is an enzyme that removes nucleotides from the ends of DNA strands, playing a role in proofreading and repairing DNA.

What is the role of DNA ligase?

DNA ligase is an enzyme that joins Okazaki fragments on the lagging strand during DNA replication, sealing nicks in the sugar-phosphate backbone.

What is the role of primase?

Primase is an enzyme that synthesizes short RNA primers needed to initiate DNA replication on the template strand.