BIO110 DNA

BIO110 DNA

Chapter 6

DNA Basics

• DNA is short for Deoxyribose Nucleic Acid

• DNA is a nucleic acid made up of nucleotides

DNA Base Pairing Rules

• Adenine (A) can only bond with thymine (T)

• Guanine (G) can only bond with cytosine (C)

DNA Replication

• During DNA replication, a cell duplicates its chromosomes

• Happens during the S phase of Interphase in the Cell Cycle

• New DNA molecules are made up of one of the original parental strands plus a new half.

• As a result, DNA replication is called semi-conservative

Practicing DNA Replication

• If the parent DNA strand reads: TACGGTAAC

• The synthesized strand will read: ATGCCATTG

Multiple Choice

What is the DNA complement to the DNA strand ATCTGGACT

• ATCTGGACT

• TAGACCTGA

• TCAGGTCTA

• AGTCCAGAT

RNA Basics

• RNA is also a nucleic acid (like DNA)

• RNA has three major differences from DNA:

  1.It is single-stranded (not a helix)

  2.Sugar in RNA is ribose.

  3.Thymine (T) is replaced by uracil (U).

Multiple Choice

Now what is the RNA complement to the same DNA strand ATCTGGACT

• TAGACCTGA

• TCAGGTCTA

• AGUCCAGAU

• UAGACCUGA

The Flow of Genetic Information

Transcription

• Transcription Rewrites the DNA Code into RNA, Which Then Leaves the Nucleus

• Transcription follows the D N A base-pairing rules with one exception: Uracil (U) is used instead of thymine (T)

• The molecule that results from transcription is called messenger RNA (mRNA), which exits through a nuclear pore.

Translation

• In translation, the mRNA molecule made in transcription serves as instructions for making a protein

• At the ribosomes in the cytoplasm, each mRNA codon (group of 3) is translated into an amino acid to build a protein

• Translation occurs in 3 steps: 1-Initiation, 2-Elongation, and 3-Termination

Translation (cont)

• Translation involves three kinds of RNA: rRNA, mRNA, and tRNA

• Translation of the mRNA takes place in the cytoplasm within ribosomes

• Ribosomes are made from proteins and ribosomal RNA (rRNA)

• Transfer RNA (tRNA) molecules carry amino acids to the ribosome

Multiple Choice

Rewriting DNA into messenger RNA in the nucleus is

• Transcription

• Translation

Multiple Choice

Which type of RNA brings the correct amino acid to the translation complex?

• mRNA

• tRNA

• rRNA

Using the Genetic Code

Multiple Choice

Which amino acid would AAA code for?

• Lysine

• Serine

• Methionine

• Stop

Multiple Select

Which of the following are Stop codons?

• UAA

• UAG

• UAU

• UGA

Multiple Choice

Which is the Start codon?

• UGA

• AUG

• GAU

• AGU

Gene Expression

• Gene regulation is the process of turning genes on and off.

• Different cell types express different genes

• For example: skin cells express the gene for melanin (protein producing skin color pigment), while stomach cells have this gene turned off.

Gene Regulation in Transcription

• Special transcription factors must bind to DNA to “turn on” transcription

Gene Regulation Post-Transcription

• Before leaving the nucleus, the mRNA is modified

• A cap and tail are added

• Non-coding introns may be removed

• Protein-coding exons may be rearranged

Gene Regulation in Translation

• The cell can control the following:

• –Whether translation proceeds

• –How proteins are modified after translation

• –When proteins are broken down

Cell-to-Cell Communication Signalling Gene Expression

• Multicellular life depends on cell-to-cell signaling

• Molecules exit one cell and bind to a receptor protein on the outside of another cell

• A signal from another cell can regulate genes (turn on or off) in the receiving cell

Multiple Select

Which are types of gene regulation included in post-transcriptional modification?

• Adding a methylated cap

• Adding a poly-a tail

• Splicing out introns

• Recombining exons

Mutations

• A mutation is any change in the nucleotide sequence of DNA

• Replacing, deleting, or adding a nucleotide base can have a wide range of effects

• Mutations can be caused by mutagens or be spontaneous

• Mutations can be point mutations or frameshift mutations.

Point Mutations

• Point mutations occur at a single nucleotide

• Point mutations can have varying effects

• 3 types are Silent mutation, Missense mutation, or Nonsense mutation.

Frameshift Mutations

• Frameshift mutations are due to the addition or deletion of a nucleotide

• Frameshift mutations often result in different or defective proteins

Multiple Choice

What type of point mutation changes the amino acid sequence?

• Silent

• Missense

• Nonsense

Multiple Choice

What type of mutation comes from the addition or deletion of a nucleotide?

• Silent

• Missense

• Frameshift

• Nonsense

Cancer

• Loss of gene expression control can result in cancer

• Mutations can lead to a mass of body cells growing out of control, a tumor

• If a tumor spreads to other tissues, the person is said to have cancer

Proto-Oncogenes

• A cell cycle control system regulates the timing of cell duplication

• A proto-oncogene codes for proteins that tell the cell when to duplicate

• A mutated proto-oncogene fails to regulate cell division and is called an oncogene

• Cancer is caused by out-of-control cell growth due to a breakdown of the cell cycle control system

Gene Cloning

• In DNA cloning a human gene that produces an important protein is isolated

• It is then inserted into a piece of bacterial DNA called a plasmid

• As the bacteria multiply, large amounts of the gene, and thus the protein, are produced

Genetically Modified Organisms (GMOs) and Transgenic Organisms

• Genetically modified organisms (GMOs) are ones that have acquired one or more genes by artificial means

• If the transferred gene is from another species then the organism is called a transgenic organism

Summary

• DNA and RNA basics (complementary pairing rules for both)

• Transcription and Translation

• Gene Expression&Gene Regulation

• Mutations

• Cancer

• GMOs and Transgenic Organisms

• (Extra) PCR, DNA Profiling and STRs, Gel Electrophoresis, Genomics, Gene Therapy