Gene Regulationsand

Mutations

Gene Regulation

• Genes are regulated differently in prokaryotic cells vs. eukaryotic cells

• 21,000 genes in the human genome

• Expressed genes= genes that are turned into RNA

Prokaryotic Gene Regulation

• Operon/Operator- a functioning unit of DNA containing a multiple genes under the control of a single promoter – Usually only found in prokaryotes– turns the genes “on” or “off”

Prokaryotic Gene Regulation

• Repressor proteins stop the transcription process– RNA polymerase is blocked by the protein and

therefore cannot transcribe the gene.

Eukaryotic Gene Regulation

• Genes are controlled individually – Regulatory sequences are much more complex

then in prokaryotes• Genes are regulated by enhancer sequences

Enhancer region

Cell specialization

• Cell specialization requires genetic specialization– Specific cells must express specific proteins

• Pancreas= insulin protein• Skin cells= keratin protein• Blood cells= hemoglobin protein

• Only a small fraction of genes need to be expressed in any given cell– Prokaryotes are single celled and so they have to

express ALL genes

Development and Differentiation

• Cells don’t just grow and divide during development they also differentiate– specialized in structure and function

Hox Genes• Cells become specialized based on location in

the body and hox genes– Hox genes- control the body plan of cells in the

embryo

Mutations• Mutation= changes in the DNA code during

the replication process – DNA polymerase adds the wrong nucleotides

• Changes in the gametes effect the entire organism

• Changes in the body cells effect only that cell

Chromosomal Mutations

• Chromosomal mutations- changes to the whole chromosome

• Changes in the number or structure of chromosomes

Changes in Chromosome Number

• What is the normal number of chromosome in a human cell?– 46 (23 pairs)

Chromosomal mutations• Deletion

• Duplication

• Inversion

• Translocation

Gene Mutations

• Gene mutations- changes to a single gene

Types of Gene Mutations

1. Point mutation– one base pair is replaced by another– Changes in one or a few nucleotides

Types of Gene Mutations2. Frameshift mutations • Codon pairing changes,

changing the whole sequence of amino acids– Insertions: one or more base

pairs are added to the sequence

– Deletions: one or more base pairs are deleted from the sequence

Effect of Mutations

1. Silent Mutation- have not effect– Even though the RNA strand is effected the same

amino acid sequence is made– How is this possible?• 1 amino acid is created by more than 1 codon

Effects of Mutations

2. Substitution: base pair is substituted and the new codon codes for a different amino acid– There are still the same number of bases in the

RNA strand

Effects of Mutations

3. Premature Stop: substitution results in the formation of a STOP codon before all codons have been translated– UAA – UAG– UGA

Effects of Mutations

4. Codon Deletion or Insertion: A whole new amino acid is added, or one is missing from the protein– Caused by the addition or removal of bases in the

DNA strand

Practice Evaluating Mutations

Original DNA Strand:TACGGGTACGGCGGCATT

Original mRNA strand:

Original amino acid Sequence:

Mutated DNA Strand:TACGAUTACGGCGGCAUUOriginal mRNA strand:

Original amino acid Sequence:

Kind of Mutation:What is the Effect:

Significance of Mutations

• No impact– Most mutations are neutral

• Positive impact– Mutations provide genetic variability in organisms– Plant and animal breeders use beneficial

mutations to better crops and livestock • Negative tioimpact– Harmful mutans cause genetic disorders