DNA

Flashcards for DNA test

DNA structure

• DNA is a double helix.

• Made up of Nucleotides (monomers)

• Contains a phosphate group, sugar (deoxyribose), and molecular bases (adenine, thymine, guanine, cytosine).

Chargraff’s Rule

• There are equal amounts of Adenine and Thymine and of Guanine as Cytosine.

• A-T / G - C

• Difference in percentages of nitrogenous bases can be caused by…

  • Mutations - A Change in the DNA sequence

  • Radiation such as X-rays and ultraviolet

Polymer and Monomer

Monomer - Nucleotides

Polymer - Nucleic Acid (DNA/RNA)

Rosalind Franklin

• Used x-ray crystallography

• Helped discover DNA structure by Wilkins

Watson and Crick

Created the first model of what DNA’s structure looked like.

DNA replication

• DNA enters through the left side of the helicase.

• The DNA is then spun as fast as a jet and unwinds the double helix into 2 strands.

• One strand is copied continuously while the other side is copied backwards.

  • The strand being copied backwards is drawn out repeatedly in loops and copied one section at a time.

DNA replication structures

Origin - Where DNA replication starts.

Okazaki Fragments - Leading and Lagging Strands

Leading strand - The strand being copied continuously

Lagging Strand - The strand being copied backwards and in sections.

Helicase

“The Unzipping Enzymes”

• Unzips the 2 DNA strands by breaking the hydrogen bonds between the nucleotides

DNA polymerase

“The Builder”

• Enzyme that replicates DNA molecules to build a new strand of DNA

Primase

“The Initializer”

• Makes the primer so that DNA polymerase so DNA can figure out where to go to start to work

Ligase

“The Gluer”

• Helps glue the DNA fragments together

Anti-parallel

• DNA polymerase builds the new strand in the 5’ → 3’ direction.

DNA vs. RNA

DNA:

• Double-stranded

• Sugar: Deoxyribose

• Uses Thymine

RNA:

• Single-stranded

• Sugar: Ribose

• Uses Uracil

Transcription

• Occurs in Nucleus

• DNA → mRNA

• Use DNA as a template to make mRNA

Transcription Steps

1. Factors assemble at the start of the genes.

2. As it goes down the DNA strand, it unzips, copies hydrogen, and reads the genes for production.

3. RNA is released and matched with DNA.

4. Molecules go into the intake hole to create the RNA strand.

Translation

• Occurs in ribosomes

• mRNA → amino acids → proteins

• Amino acids are building blocks of proteins.

• mRNA is the template for the amino acids.

Translation Steps

1. After RNA is copied, it escapes into the outer part of the cell.

2. Forms a ribosome to translate genetic information into amino acids.

3. Bring the amino acid to the ribosome.

4. Each transfer molecule (tRNA) carries a 3-letter code matched with the RNA machine (ribosome).

5. RNA is pulled through, read off 3 letters at a time, and matched with 3 corresponding letters.

6. Amino acid is carried onto the chain and produces hemoglobin, which other organisms can receive.

Codons

• 3 bases within an mRNA molecule that code for an amino acid.

Anti-Codon

• A 3-base code within a tRNA molecule that is complementary to a specific codon

• Ex. If the codon is A U G, then the anti-codon is U A C.

Different kinds of DNA replication

• Conservative - The original DNA remains, and a new one is created

• Semi-conservative - means each new DNA has one old strand and one new strand.

• Dispersive - means the new DNA strands are mixed pieces of old and new DNA all along the strand.

Hemoglobin

The molecule in red blood cells that ferries (carries) oxygen through the body.

Mutation

• A change in DNA sequence

• A genetic mutation can alter a person’s hemoglobin.

  • However, they are not harmful as long as you have one normal copy of the two genes.

• Mutated genes are passed down from generation to generation

1 mutated gene

• They were not harmed and were protected from malaria.

2 mutated genes

• Can’t produce normal hemoglobin.

  • As a result, blood cells will take on a sickle shape and become defective → This led to clogged blood vessels.

• This is called the sickle cell anemia

• Leads to extreme pain, difficulty with breathing, kidney failure, and even strokes.