During metaphase, the chromosomes line up across the center of the cell. Each chromosome attaches to a spindle fiber at its centromere. During anaphase, the centromeres split, the two chromatids separate, and each chromatid becomes a new chromosome. During the last part of mitosis —— telophase, the chromosomes begin to stretch out and lose their rodlike appearance. A new nuclear envelope forms around each chromosomes.
During prophase, the chromosomes become visible under a light microscope as they super coil and therefore they get shorter and more bulky. The nuclear envelope disintegrates and the spindle microtubules grow and extend from each pole to the equator. At metaphase the chromatids move to the equator. The sister chromatids are two DNA molecules formed by DNA replication and are therefore identical. These sister chromatids are then separated in anaphase as the spindle microtubules attaches to centromere and pulls the sister chromatids to opposite poles.
Comparison chart | Meiosis | Mitosis | Definition: | A type of cellular reproduction in which the number of chromosomes are reduced by half through the separation of homologous chromosomes in a diploid cell. | A process of asexual reproductionin which the cell divides in two producing a replica, with an equal number of chromosomes in haploid cell | Function: | sexual reproduction | Cellular Reproduction & general growth and repair of the body | Type ofReproduction: | Sexual | Asexual | Occurs in: | Humans, animals, plants, fungi | all organisms | Genetically: | different | identical | Crossing Over: | Yes, mixing of chromosomes can occur. | No, crossing over cannot occur.
Cell division stops until p53 binds to DNA and repairs the damage. C. p53 is an example of an oncogene, and its expression causes uncontrolled cell division. D. activation of p53 leads to inhibition of the S-phase cyclin-CDK complex. 6. All of the following statements correctly describe M-Cdk, EXCEPT: A. M-Cdk causes the cell to enter S phase and begin DNA replication.
The circular DNA molecules in prokaryotes usually contain ____________________ replication forks during replication, while linear eukaryotic DNA contains many more. DNA Structure and Replication Answer Section TRUE/FALSE 1.
Which sex cells join together during fertilization is a random process. New combinations of genes occur, producing genetic variation 2. During meiosis, chromosome pairs sort themselves independently and randomly (this is called random segregation). This produces genetic variation also. 3.
stores proteins and alot of exporting (sending stuff out of the cell) 3. In which part of the cell would you expect to find nucleotides? building block for DNA, DNA found in the nucleus 4. Name the two organelles involved in energy conversion.chloroplast and mitochondria 5. What are the basic functions of the organelles in chapter 4?
The plasma membrane acts as a selective barrier between the cell and its environment, and is a structure that you will study in detail throughout the year. The nucleus consists of a limiting double bilayer nuclear envelope containing nuclear pores enclosing the nucleoplasm. Small, irregular particles scattered throughout the nucleus or accumulated adjacent to the nuclear envelope are clumps of condensed chromatin known as heterochromatin. They consist of protein and DNA and stain with basic dyes. When the chromatin is dispersed and not readily stainable, it is known as euchromatin.
14. What is going on during crossing-over events (this is somewhat complicated and obscure)? 10.3 Does crossing-over occur during meiosis I or meiosis II? Crossing over is when two chromosomes switch their genes around. (A 1 a, B 1 b, C 1 c, D 1 d).
The chromosomes condense and become visible Metaphase II- the chromosomes align down the center of the cell Anaphase II- the centromeres part and the separated sister chromatids move to opposite poles Telophase II- nuclear envelopes form, and cytokinesis then separates the nuclei into individual cell Crossing over- is a process in which two homologous chromosomes exchange genetic material Polyploid- an error in meiosis, gamete with one or more complete cells of extra chromosomes Nondisjunction- abnormality error, occurs when the chromosomes fail to separate at either the first or second meiotic