DNA and chromosomes

• What is a gene?

  A section of the DNA that contains a code for making polypeptide and functional RNA.The code is a specific sequence of bases.
• What is a locus?

  Located at a particular site on a DNA molecule.
• What do polypeptides make?

  Proteins
• How do genes influence an organism?

  They determine the protein of an organism
• What is an allele?


  An allele is one of a number of alternatives forms of a gene.Most genes occur in two,different forms
• What does each individual inherit from their parents?

  One allele from each parent
• What can the two alleles inherited from parents be?

  They may be the same or different
• Why do alleles produce different polypeptides?

  Each allele has a different base sequence
• How does the base sequence of an allele affect its function?

  It leads to a different amino acid sequence
• What is produced as a result of different amino acid sequences from alleles?

  A different polypeptide is produced
• What are chromosomes made of?

  Tightly coiled up DNA
• Where are chromosomes located in eukaryotic cells?

  In the nucleus
• How many pairs of chromosomes do humans have?

  23 pairs
• What is the total number of chromosomes in humans?

  46
• What are homologous pairs of chromosomes?

  The two chromosomes that carry the same genes
• What is the significance of alleles in homologous pairs?

  They may have different versions of the same gene
• When do homologous pairs form?

  When the sperm and egg fuse
• Where does one chromosome of each homologous pair come from?

  From the mother in the egg
• Where is DNA stored in eukaryotic cells?

  Inside the nucleus as chromosomes
• What is the shape of chromosomes in eukaryotic cells?

  Linear in shape
• How is DNA organized to fit in the nucleus?

  It is tightly coiled around histones
• What is a nucleosome?

  A complex of DNA wrapped around histones
• How do prokaryotic cells carry DNA?

  In shorter, circular chromosomes
• How is prokaryotic DNA different from eukaryotic DNA?

  It does not wind around histones
• How does prokaryotic DNA fit in the cell?

  It supercoils to fit in the cell
• What type of DNA do mitochondria and chloroplasts contain?

  Short, circular DNA like prokaryotes
• How is the DNA in mitochondria and chloroplasts associated with proteins?

  It is not associated with proteins
• Explain how the considerable length of a DNA molecule is compacted into a chromosome?

  Double helix is tightly coiled around histone proteins
• What is the function of a histone protein?

  Histone proteins are tightly coiled of DNA to fit chromosomes into the nucleus
• What does a gene in a base sequence of DNA codes for?

  -The amino acid sequence of a polypeptide and functional RNA(including trna and rrna)
• what are some similarities with the DNA eukaryotic cells and prokaryotic cells?

  Nucleotides structure is identical and joined by a phosphodiester bond.