Chromosomes

• What are chromosomes made of?

  DNA
• Where are chromosomes found in cells?

  In the nucleus of cells
• How many chromosomes do humans have in body cells?

  46 chromosomes
• What are the key facts about chromosomes?

  • Made of DNA
  • Contain genes that code for proteins
  • Found in the nucleus of cells
  • Exist in pairs in diploid cells
• What is the chromosome number in human body cells?

  46 (23 pairs)
• What is the chromosome number in human gametes?

  23 chromosomes
• What type of cells have two sets of chromosomes?

  Diploid cells
• What type of cells have one set of chromosomes?

  Haploid cells
• What do chromosomes consist of before cell division?

  Two identical sister chromatids
• What happens to chromosomes during mitosis?

  Chromatids are pulled apart to form new cells
• What are the key terms related to chromosomes?

  • Chromosome: Long DNA molecule containing genes
  • Gene: Section of DNA coding for a protein
  • Allele: Different version of a gene
  • Homologous chromosomes: Pair from each parent
  • Sister chromatids: Identical copies after replication
  • Centromere: Point where chromatids are joined
• What is a karyotype?

  A picture of all chromosomes in a cell
• What determines the sex in humans?

  The 23rd pair of chromosomes
• What chromosome combination indicates a female?

  XX
• What chromosome combination indicates a male?

  XY
• What can chromosome disorders result from?

  Incorrect numbers of chromosomes
• What is Down syndrome caused by?

  An extra chromosome 21
• What occurs before cell division during interphase?

  • Chromosomes duplicate to form sister chromatids
  • DNA is checked for errors
• What happens during mitosis?

  • Chromosomes line up
  • Chromatids are pulled apart
  • Two identical diploid cells are formed
• What occurs during meiosis?

  • Chromosomes swap genetic material (crossing over)
  • Gametes with half the chromosome number are produced
  • Each gamete is genetically different
• How do humans inherit chromosomes?

  One from each parent in every pair
• What leads to genetic differences among humans?

  Variations in genes called alleles