Flashcards in Reproduction Deck (64)
Are autosomal cells haploid or diploid?
Diploid (2n, contain two copies of each chromosome)
Are germ cells haploid or diploid?
Haploid (n, contain one copy of each chromosome)
What is Interphase?
-includes the first 3 stages of cell cycle (G1, S, G2)
-longest part of cell cycle
-2 centrioles come together to form a centrosome -- helps hold chromosomes apart
-chromosomes are uncondensed
-individual chromosomes are not visible with light microscopy b/c they are in chromatin form (less condensed form where DNA is available to RNA Poly for transcription)
What is the G0 stage?
stage where cells that do not divide spend all of their time, cell just performs its function
What happens during the G1 stage?
-cells create mitochondria, ribosomes, ER
-cells increase in size
-DNA is examined and repaired at restriction point (determines if cell can enter next stage)
What happens during the S stage?
-Synthesis of DNA
-cell replicates its DNA
-after replication each chromosome has 2 identical chromatids bound together at the centromere
-have 92 chromatids organized into 46 chromosomes organized into 23 homologous pairs
-2x as much DNA as cells in G1
What happens during G2 stage?
-cell continues to grow & replicates organelles in preparation for mitosis
-cell continues to perform its normal functions
-goes through 2nd quality control checkpoint
What happens during M stage?
-Mitosis (cell division)
-cytokinesis (splitting of the cytoplasm and organelles into two daughter cells)
What composes a chromatid?
a complete double-stranded molecule of DNA
What is a sister chromatid?
identical copies of eachother
When can the term chromosome be used in the cell cylce?
-before S phase when referring to a single chromatid
-after S phase when there is a pair of chromatids attached at the centromere
What is the result of division in autosomal cells?
2 genetically identical daughter cells
What is the result of division in germ cells
2 non-equivalent germ cells
When are the checkpoints in the cell cycle?
-between G1 and S phase
-between G2 and M phase
What occurs at the G1/S checkpoint?
-known as the restriction point
-cell determines if DNA is good enough for synthesis
-if there is damaged DNA then cell goes into arrest until DNA is repaired
What is the main protein in control during the G1/S checkpoint?
What occurs at the G2/M checkpoint?
-ensure the cell has achieved adequate size and organelles have been properly replicated
-makes proteins for mitosis
What protein plays a role during the G2/M checkpoint?
What molecules are responsible for the cell cycle?
cyclins & cyclin-dependent kinases (CDK)
Explain the process of cyclin & CDK binding and what they do
cyclins bind to CDKs to create an active CDK-cyclin complex (MPF - mitosis promoting factor) that can then phosphorylate transcription factors that promote transcription of genes required for the next stage of the cell cycle
How does cancer occur?
results when cell cycle control is deranged and damaged cells still undergo mitosis
What gene is most commonly mutated in cancer?
TP53 (gene that produces p53)
What is metastasis?
spread of cancerous cells through the blood stream or lymphatic system
What is mitosis?
-process by which two identical daughter cells are created from a single cell
-occurs in somatic cells
What are the phases of mitosis?
What is a centrosome?
contains two tubulin-based centrioles responsible for proper movement of chromosomes
(1) What occurs during prophase?
(2) What occurs during Prometaphase?
-condensation of chromatin into chromosomes -- chromosomes condense
-centriole pairs (located outside the nucleus in the centrosome) separate and move towards opposite poles of cell
-at opposite poles of cell the centrioles begin to form spindle fibers / mitotic spindle (made of microtubules)
-some microtubules form asters (anchor centrioles to cell membrane) and others extend toward middle of cell
-nuclear membrane dissolves so spindle fibers can contact the chromosomes
-kinetochores appear at centromere and serve as attachment points for fibers of the spindle apparatus that are called kinetochore fibers
What occurs during metaphase?
-centriole pairs located at opposite ends of cell
-chromosomes gather along metaphase plate in center of the cell under guidance of spindle apparatus
-chromosomes are madeup of two sister chromatids that are still attached to one another (pair of sister chromatids = one chromosome_
What occurs during anaphase?
-centromeres split so each chromatid has its own distinct centromere and sister chromatids can separate
-sister chromatids pulled toward the opposite poles of the cell by shortening of kinetochore fibers