Notes

• What type of information do both DNA and RNA carry?

  DNA holds genetic information, while RNA transfers this genetic information.
• What are the components of a nucleotide?

  Nucleotides consist of a pentose sugar, a nitrogen-containing organic base, and a phosphate group.
• What are the components of a DNA nucleotide?

  A DNA nucleotide consists of deoxyribose, a phosphate group, and one of the organic bases adenine, cytosine, guanine, or thymine.
• How are adenine and guanine classified in terms of their structure?

  Adenine and guanine have double ring structures and are classified as purine bases.
• What are the components of an RNA nucleotide?


  An RNA nucleotide consists of ribose, a phosphate group, and one of the organic bases adenine, cytosine, guanine, or uracil.
• How are thymine, uracil, and cytosine classified in terms of their structure?

  Thymine, uracil, and cytosine have single ring structures and are classified as pyrimidines.
• How do nucleotides join together?

  Nucleotides join together by phosphodiester bonds formed in condensation reactions.
• What is the structure of a DNA molecule?

  A DNA molecule is a double helix composed of two polynucleotides joined together by hydrogen bonds between complementary bases.
• What is the structure of RNA?

  RNA is a relatively short polynucleotide chain.
• What is the genetic code?

  The genetic code is the order of bases on DNA, consisting of triplets of bases that code for particular amino acids known as codons.
• What is a codon?


  A codon is a triplet of bases that codes for a particular amino acid.
• What is a gene?


  A gene is a sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain.
• What is the locus of a gene?

  The locus of a gene is its location on a chromosome.
• What are introns and exons?

  Introns are non-coding sections of DNA, while exons are coding regions.
• How many nucleotide bases code for how many different amino acids?

  There are four nucleotide bases that code for 20 different amino acids.
• How many possible triplets are there?

  There are 64 possible triplets (4^3).
• What does it mean that the genetic code is non-overlapping?

  It means that each triplet is only read once and triplets don’t share any bases.
• What does it mean that the genetic code is degenerate?

  It means that more than one triplet codes for the same amino acid.
• How do mutations affect the amino acid sequence?

  A change in the base sequence of DNA alters the amino acid sequence and the protein, which can have various effects.
• What are some examples of harmful mutations?

  Examples include mutations that lead to cystic fibrosis or sickle cell anemia.
• What are start and stop codons?

  Start and stop codons are specific sequences in the genetic code that signal the beginning and end of protein synthesis.
• Where is DNA found in eukaryotic cells?

  In eukaryotic cells, DNA is found in the nucleus and is long and linear.
• What are chromosomes in eukaryotic cells?

  Chromosomes are structures formed by DNA associated with proteins called histones, visible at the start of cell division.
• How many chromosomes do humans have in each cell?

  Humans have 46 chromosomes in every cell in the body.
• What is a homologous pair of chromosomes?

  A homologous pair consists of two chromosomes that carry the same genes but may have different alleles.
• What determines the sex of an individual in humans?

  The 23rd chromosome determines the sex of the individual, with females having two X chromosomes and males having one X and one Y chromosome.
• What is an allele?


  An allele is an alternative form of the same gene, with every gene existing in two or more possible forms.
• How many alleles does an individual inherit for every gene?

  Every individual inherits two alleles of every gene from their parents.