CH9 // Pt1 Transcription and Translation Overview

Chapter 9

DNA Transcription and Translation

Genes

Segments of DNA that contain information about certain traits

  • Gives us proteins
      * Transcribed and translated to make proteins
  • Proteins make a visible phenotype, and the human body
  • Genes encode traits
      * Ex: hair and eye color, freckles, blood type
  • Genes give us the sexes
      * 800 genes encode for X chromosomes, which everyone has one of
      * 63 encode for Y chromosomes

SRY gene

  • Y chromosome determines sex due to SRY gene
  • Not found on X chromosomes
  • Without it fetus automatically develops as female
      * So having the SRY gene makes an organism male

Gene Expression

  • Instructions in genes making proteins
  • Physical traits
  • Gene expression = transcription and translation

Transcription

Copying gene information in DNA into RNA

RNA

Ribonucleic acid

Similar to DNA, ½ of DNA, single stranded, phosphate backbone

Nucleotides

  • Adenine
  • Cytosine
  • Guanine
  • Uracil

Types of RNA

rRNA

  • Ribosomal RNA
  • Part of ribosomes
  • Ribosomes make proteins from amino acids
  • Making proteins = whole point of gene expression

tRNA

  • Transfer RNA
  • Brings amino acids to ribosomes

mRNA

  • Messenger RNA
  • “Messenger” between DNA and protein
  • Tells ribosome what protein to make

Translation

Proteins assembles according to information in mRNA

DNA Mutations

Mutation = nucleotides incorrect, moved, deleted, added during DNA replication

  • DNA = sections of genes which give traits
  • DNA ( and mutations) transcribed to RNA
  • RNA translated to proteins which make up the human body

Most common cause for mutations

  • G-T bonds
  • Rule of base pairings: G-C, A-T
  • Why?
      * G-T pairing can change shape so DNA polymerase doesn’t identify it as incorrect
  • DNA mutation = gene mutations = physical trait mutations
      * Ex: down syndrome, Type I diabetes, lactose tolerance

Sex Chromosome can mutate too = intersex

  • Female
      * X - tuner syndrome
      * XXX - triple X syndrome
      * XY - swyer syndrome
  • Male
      * XXY - klinefelter syndrome
      * XYY syndrome
      * XX - De la Chapelle Syndrome

Not all mutations are scary diseases:

  • Needing glasses
  • Heterochromia
  • allergies

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