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Questions and Answers
What is the primary function of DNA?
What is the primary function of DNA?
Which nitrogen base pairs with adenine in DNA?
Which nitrogen base pairs with adenine in DNA?
Which phase of mitosis involves the alignment of chromosomes along the equatorial plane?
Which phase of mitosis involves the alignment of chromosomes along the equatorial plane?
What type of cells contain a diploid number of chromosomes?
What type of cells contain a diploid number of chromosomes?
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In the structure of DNA, what forms the backbone of the DNA molecule?
In the structure of DNA, what forms the backbone of the DNA molecule?
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What occurs during the S phase of interphase?
What occurs during the S phase of interphase?
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How many chromatids are present in a chromosome after DNA replication during prophase?
How many chromatids are present in a chromosome after DNA replication during prophase?
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Which type of nucleic acid is found in prokaryotic cells?
Which type of nucleic acid is found in prokaryotic cells?
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During which phase of meiosis do homologous chromosomes separate?
During which phase of meiosis do homologous chromosomes separate?
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What is the purpose of cytokinesis?
What is the purpose of cytokinesis?
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What happens during Telophase I of meiosis?
What happens during Telophase I of meiosis?
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In which phase do the chromosomes reach the poles of the mitotic spindle?
In which phase do the chromosomes reach the poles of the mitotic spindle?
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At which point in meiosis does crossing over occur?
At which point in meiosis does crossing over occur?
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What is formed around the equator of the cell during cytokinesis in animal cells?
What is formed around the equator of the cell during cytokinesis in animal cells?
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What is the ploidy of the cells at the end of meiosis?
What is the ploidy of the cells at the end of meiosis?
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Which phase of meiosis is most similar to mitosis?
Which phase of meiosis is most similar to mitosis?
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Study Notes
Cell Division: Mitosis
- Mitosis is a process where a single cell divides into two identical daughter cells
- The genetic material (DNA) is replicated before mitosis begins
- DNA is Deoxyribonucleic acid
- Eukaryotic DNA is composed of multiple molecules of double-stranded linear DNA, while prokaryotic DNA is double-stranded and circular
DNA Function
- DNA carries and stores genetic information passed from one generation to the next through chromosomes
- DNA is a large molecule composed of nucleotides
DNA Structure
- DNA is structured as a large number of nucleotides arranged in a single strand
- Nucleotides consist of a sugar (5 carbon sugar), a phosphate group, and nitrogen bases (purine or pyrimidine)
Nitrogen Bases
- Purines: Adenine (A) and Guanine (G), with double-cycle structures
- Pyrimidines: Thymine (T) and Cytosine (C), with single-cycle structures
- Two strands coil around each other to form a double helix
- The two strands are held together by hydrogen bonds between complementary base pairs (A with T, and G with C)
Chromosome Number
- The number of chromosomes exists as pairs except in germ cells (sex cells)
- Somatic cells (body cells) contain two sets of chromosomes, also called diploid (2n; 46 in humans)
- Reproductive cells (gametes; sperm and ova) contain a single set of chromosomes, or haploid (n; 23 in humans)
- Chromatin consists of a single, long DNA double helix, plus histone and nonhistone proteins (chromosomal proteins) scattered in the nucleus
Cell Division Purposes
- Cell growth
- Reproduction
- Tissue repair
Mitosis Phases
- Interphase: The period between cell divisions, consisting of G1, S (DNA synthesis and replication), and G2 sub-phases. Time varies
- Prophase: Replicated chromosomes condense, nuclear envelope breaks down, nucleolus disappears, mitotic apparatus (spindle) forms
- Metaphase: Replicated chromosomes align at the cell's equator (middle) attached to the microtubules of the mitotic spindle
- Anaphase: Duplicated chromatids separate at the centromere, and move to opposite poles of the mitotic spindle
- Telophase: Chromosomes reach the poles of the mitotic spindle, the nuclear envelope reforms, and the cell completes division
- Cytokinesis: Cytoplasm divides, creating two new diploid cells, following telophase. In animal cells, cytokinesis begins during early anaphase.
Meiosis
- Meiosis is a specialized cell division occurring in sex organs to produce gametes (sex cells; e.g., oocyte and spermatocyte).
- Meiosis reduces the chromosome number from diploid (2n) to haploid(n)
- Meiosis has two steps:
- Reductional division (Meiosis I): Homologous chromosomes separate, producing two haploid daughter cells
- Equational division (Meiosis II): Sister chromatids separate, producing four haploid daughter cells
Meiosis I: Prophase I
- Prophase I is the longest stage taking a day to complete
- The nucleolus and nuclear membrane disappear
- Chromatin material replicates to form chromosomes
- Synapsis and tetrad formation: Homologous chromosome pairs come together and may exchange portions of chromatids called crossing over
Meiosis I: Metaphase I
- All tetrad chromosomes line up at the equator of spindles
Meiosis I: Anaphase I
- Homologous chromosomes move to the opposite poles.
- Sister chromatids do not separate
Meiosis I: Telophase I
- Chromosomes reach the poles
- Nuclear envelope reforms
- Cytoplasm divides
- Four haploid daughter cells are produced
Meiosis II: Prophase II
- DNA does not replicate
- A new spindle forms in the two cells
Meiosis II: Metaphase II
- Chromosomes align along the equator of the spindles
Meiosis II: Anaphase II
- Sister chromatids separate and move apart to opposite poles
Meiosis II: Telophase II
- Nuclear envelopes form
- Cytokinesis occurs
- Four haploid nuclei (n=23 chromosomes) form.
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Description
Test your knowledge on cell division, specifically the process of mitosis, and explore the intricacies of DNA structure and function. This quiz covers essential concepts such as nucleotide composition and the role of nitrogen bases in genetic information. Perfect for students studying biology and genetics!
