Week 3 - Cellular Level of Organisation Flashcards
Question
Answer
What is the cell cycle?
The cell cycle is an orderly sequence of events in which a somatic cell duplicates its contents and divides into two identical cells.
What are somatic cells?
Somatic cells include all body cells except for germ cells (egg and sperm).
How many chromosomes do human somatic cells have?
Human somatic cells contain 23 pairs of chromosomes, totaling 46 chromosomes.
What are homologous chromosomes?
Homologous chromosomes are pairs of chromosomes, with one chromosome inherited from the mother and the other from the father.
What are the two major periods of the cell cycle?
Interphase and the mitotic phase.
What happens during interphase?
The cell prepares for division, including growth, replication of organelles and DNA, and synthesis of proteins and enzymes.
What occurs in the G1 phase of interphase?
The cell grows, replicates its organelles and cytosolic components, and the metabolic rate increases. Centrosome replication begins.
What happens during the S phase of interphase?
DNA is replicated, forming chromatids.
What occurs in the G2 phase of interphase?
The cell continues to grow, synthesizes proteins and enzymes, and completes centrosome replication.
What are the stages of the mitotic phase?
Prophase, Metaphase, Anaphase, Telophase.
What occurs during prophase in mitosis?
Chromatin fibers condense into paired chromosomes, the nucleolus and nuclear envelope disappear, and the mitotic spindle forms. Centrosomes move to opposite poles.
What happens during metaphase in mitosis?
Chromatid pairs line up along the metaphase plate.
What occurs during anaphase in mitosis?
Centromeres split, and identical sets of chromosomes move to opposite poles of the cell. Cytokinesis begins with the formation of a cleavage furrow.
What happens during telophase in mitosis?
Nuclear envelopes and nucleoli reappear, chromosomes revert to chromatin form, and the mitotic spindle disappears. The cytoplasm divides, resulting in two identical daughter cells.
What is meiosis?
Meiosis is a type of cell division in the gonads that produces four haploid gametes from a diploid cell.
What are the main stages of meiosis?
Meiosis I and Meiosis II.
What occurs during prophase I of meiosis?
Chromosomes condense, nuclear envelope and nucleoli disappear, the mitotic spindle forms, and homologous chromosomes pair up and exchange genetic material (crossing over).
What happens during metaphase I of meiosis?
Tetrads line up along the metaphase plate.
What occurs during anaphase I of meiosis?
Homologous chromosomes separate and move to opposite poles.
What happens during telophase I of meiosis?
Nuclear envelopes reappear, and the cytoplasm divides, resulting in two haploid cells.
What is interkinesis?
Interkinesis is a brief phase between Meiosis I and Meiosis II where no chromosome duplication occurs, but centrosomes duplicate.
What occurs during prophase II of meiosis?
The mitotic spindle forms, and the nuclear membrane disappears.
What happens during metaphase II of meiosis?
Chromosomes line up along the metaphase plate.
What occurs during anaphase II of meiosis?
Centromeres split, and sister chromatids separate, moving to opposite poles.
What happens during telophase II of meiosis?
Nuclear membranes reappear, and the cytoplasm divides, resulting in four haploid cells.
How do mitosis and meiosis differ in the type of cells they affect?
Mitosis affects somatic cells, while meiosis affects gametes.
How many divisions occur in mitosis and meiosis?
Mitosis has 1 division; meiosis has 2 divisions.
Do both mitosis and meiosis include interphase?
Yes, but in meiosis, interphase occurs only before Meiosis I.
Are tetrads formed in mitosis or meiosis?
Tetrads are formed in meiosis.
How many cells are produced at the end of mitosis and meiosis?
Mitosis produces 2 cells; meiosis produces 4 cells.
How many chromosomes are present in cells produced by mitosis and meiosis?
Mitosis produces cells with 46 chromosomes (diploid, 2n); meiosis produces cells with 23 chromosomes (haploid, n).
What is protein synthesis?
Protein synthesis is a crucial cellular function that determines physical and chemical characteristics of cells by assembling proteins for various roles such as forming the plasma membrane, cytoskeleton, organelles, and acting as hormones, antibodies, enzymes, and contractile elements in muscle tissue.
What is gene expression?
Gene expression is the process by which a gene’s DNA is used as a template to synthesize a specific protein.
What are the sets of three nucleotides in DNA and RNA called?
In DNA, they are called base triplets, and in RNA, they are called codons.
What do each triplet or codon correspond to?
Each triplet or codon corresponds to a specific amino acid.
What are the nucleotide bases in DNA?
Adenine (A), Thymine (T), Guanine (G), Cytosine (C)
What nucleotide replaces thymine in RNA?
Uracil (U)
What base pairs form in DNA?
Adenine pairs with thymine, and guanine pairs with cytosine.
What is transcription?
Transcription is the first step in gene expression, occurring in the nucleus, where genetic information from DNA is copied to a complementary RNA sequence.
What happens during the initiation step of transcription?
The enzyme RNA polymerase binds to a promoter sequence on the DNA, initiating transcription.
What occurs during the elongation step of transcription?
RNA polymerase reads the DNA strand and synthesizes a complementary mRNA strand using base pairing rules (A-U, T-A, G-C, C-G).
What happens during the termination step of transcription?
Transcription ends at a terminator sequence, and the newly formed mRNA strand detaches.
What types of RNA are produced during transcription?
Messenger RNA (mRNA), Ribosomal RNA (rRNA), Transfer RNA (tRNA)
What is the role of mRNA?
Directs protein synthesis.