Cell division

• What is coded as genetic information in cells?

  Genes
• How is variation passed on in living organisms?

  Through genes from one generation to the next
• Where are chromosomes located in living cells?

  In the nuclei
• What are chromosomes composed of?

  A single DNA molecule wrapped around histones
• What form do chromosomes take when a cell is not dividing?

  Chromatin threads
• What happens to chromosomes when a cell begins to divide?

  They become shorter and thicker
• How many chromosomes does each human cell have?

  46 chromosomes
• What is the diploid number of chromosomes?

  It is the total number of chromosomes in a body cell, represented as 2n
• What are homologous pairs of chromosomes?

  Pairs of chromosomes that are similar in shape, size, and genetic composition
• How many pairs of chromosomes do humans have?

  23 pairs
• What are genes?

  Specific sections of chromosomal DNA that control characteristics
• How many genes does each human body cell have?

  Over 30,000 genes
• What do genes control in cells?

  The production of proteins, mainly enzymes
• Why is each individual unique in terms of genes?

  Because no two individuals have the same combination of genes
• What happens to some genes within a cell?

  Some genes are active while others are inactive
• What are daughter cells?

  Cells produced when a parent cell divides
• What are the two types of cell division?

  Mitosis and meiosis
• What is the result of mitosis?

  Two daughter cells with the same number and kind of chromosomes as the parent cell
• In which cells does mitosis occur?

  In all body (somatic) cells except gametes
• What is a clone?

  Cells produced by mitosis from a single parent cell
• What are the important functions of mitosis?

  • Ensures each daughter cell has the same number and type of chromosomes
  • Ensures each daughter cell has an identical combination of genes
  • Essential for growth and repair of damaged tissues
  • Method of asexual reproduction
• What happens to chromosomes during mitosis?

  They shorten, thicken, duplicate, and become visible
• What forms between the centrioles during mitosis?

  Spindle fibres
• What happens to the nuclear membrane during mitosis?

  It disintegrates
• What do spindle fibres do during mitosis?

  They pull chromatids to opposite poles of the cell
• What happens to chromatids at the end of mitosis?

  They reach opposite poles and are called chromosomes
• What forms around each group of chromosomes after mitosis?

  A nuclear membrane
• What is the result of meiosis?

  Four daughter cells with half the number of chromosomes as the parent cell
• Where does meiosis occur?

  In the reproductive organs during gamete production
• What is the haploid number of chromosomes?

  Half the diploid number of chromosomes
• What are the important functions of meiosis?

  • Each gamete has the haploid number of chromosomes
  • Restores diploid number at fertilization
  • Each gamete has a different combination of genes
  • Leads to variation among offspring
• What happens to chromosomes during meiosis?

  They shorten, thicken, and become visible
• What forms between centrioles during meiosis?

  New spindles at right angles to the first spindle
• What happens to the nuclear membranes during meiosis?

  They disappear
• What occurs at the crossover points during meiosis?

  Chromatids exchange genetic material
• What happens to homologous chromosomes during meiosis?

  They separate and are pulled to opposite poles of the cell
• What forms around each group of chromosomes after meiosis?

  A nuclear membrane
• What is the final outcome of meiosis?

  Four daughter cells with different genetic compositions
• What happens to chromosomes after meiosis?

  They become long and thin and are no longer visible
• What are the vocabulary terms often confused in biology?

  Chromosome, chromatid, chromatin, transcription, translation