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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