DNA, rNA, Protein Synthesis, and Mutations Test

What is DNA?

Deoxyribonucleic Acid

• determines an organism’s traits (ex. hair colour, eye colour)

• holds the information for life

List the nitrogenous bases

Purines:

• Adenine (A)

• Guanine (G)

Pyrimidines:

• Thymine (T)

• Cytosine (C)

What is Chargraff’s Rule?

Adenine MUST pair with Thymine

Guanine MUST pair with Cytosine

What are nucleotides?

Repeating units of large DNA molecules

What is a nucleotide composed of?

1 sugar, 1 phosphate, 1 nitrogen base (A,T,C,G in DNA; U,A,G,C in RNA)

Enzyme

macromolecule acting as a catalyst to speed up a chemical reaction in our bodies

Helicase

An enzyme that unzips the DNA molecule by breaking the hydrogen bonds between base pairs

DNA polymerase

Adds new nucleotides to build the new complementary strand; checks for mistakes

Double Helix

twisted-ladder shape of DNA formed by two strands

Ligase

enzyme that joins pieces of DNA together

Template Strand

The original DNA strand serving as as guide for building a new complementary strand

What is the name of the process shown in the diagram?

DNA replication

When does DNA replication occur?

DNA replication occurs during the process of meiosis and mitosis

Why does DNA replication happen?

growth and repair

First step of DNA replication:

1. Enzyme (helicase) breaks hydrogen bonds between base pairs

Second step of DNA replication:

DNA helix unwinds — two strands separate (unzip)

Third step of DNA replication:

Free nucleotides from the cytoplasm enter the nucleus with the help of DNA polymerase; they bond to complementary bases on the DNA strands

Result of DNA replication?

two identical DNA molecules that are EXACT copies of the original

What is semiconservative?

Two DNA molecules that each consist of one “old” strand and one “new” strand.

What is antiparallel?

One strand goes 5’ to 3’; the other goes 3’ to 5’

What is recombinant DNA?

A technique used in genetic engineering; to make large quantities of the product coded by the gene

Define vector.

Vector: a plasmid (bacterial DNA) or virus. Something to “host” the gene of interest

List the examples of rDNA:

• Gene therapy

• Cloning

• Transgenic “pharm” animals

• Transgenic/GMOs

Gene therapy

Inserting a functioning gene to help an individual with a dysfunctional gene (ex. fixing defective genes to help sick people get better)

Cloning

Making copies of genes and/or inserting genes into cells (ex. making an exact copy of an animal (Dolly the Sheep))

Transgenic “pharm” animals

Using animals/bacteria to make vaccines and drugs (ex. goats producing medicine (anti-clotting factors) in milk)

Transgenic/GMOs

Giving organisms traits they don’t naturally possess (ex. Golden Rice containing extra vitamin A)

Contrast DNA and RNA

DNA:

• double-stranded helix

• deoxyribose

• ATCG

• nucleus

• permanent

RNA:

• single-stranded

• ribose

• UAGC

• nucleus and cytoplasm

• temporary

Compare DNA and RNA

• both are nucleotides

• both has adenine, guanine, and cytosine

• both carry genetic information

• both are needed for making proteins

What is protein synthesis?

• process of making proteins

• involves transcription and translation

What is transcription?

• mRNA (messenger RNA)

• DNA → mRNA

• process of making mRNA from a DNA template to take the DNA info outside of the nucleus

  • DNA too fat to leave nucleus

• mRNA carries info encoded in DNA out of nucleus to the ribosomes located in the cytoplasm in a cell

First step of transcription:

DNA strands unwind and separate

Second step of transcription:

DNA strand containing a specific gene serves as a template strand

Third step of transcription:

RNA nucleotides are matched to complementary DNA bases

Fourth step of transcription:

mRNA molecule is complete and DNA rewinds

DNA and RNA

DNA: A T C G

=

RNA: U A G C

PRACTICE: CTG TAC GGA

GAC AUG CCU

What is translation?

• mRNA → protein

• process of making proteins from info on mRNA

• mRNA travels out of nucleus to the ribosomes located (rRNA), which “reads” the mRNA as a series of 3 letter words called codons

Define codon.

3-base code on mRNA that codes for a specific amino acid

Define protein.

peptide bonds connecting amino acids

Define mutation

A change in the DNA sequence

How can mutations occur?

• errors during DNA replication

• radiation

• chemicals

• viruses

What are ways mutations can occur?

• Substitution

• Deletion

• Insertion

• Inversion

• Reciprocal translocation

• Chromosomal rearrangements

Substitution

base is replaced by one of the other three bases (ex. A → G)

Deletion

a base is removed (ex. ATC → AC)

Insertion

a new base is added (ex. ATC → ATGC)

Inversion

a section of DNA flips around 180°

Reciprocal translocation

two chromosomes change places (ex. chromosome 1 gives part of its DNA to chromosome 3)

Chromosomal rearrangements

big mutations that change the structure or order of parts of a chromosome

What are the consequences of mutations?

• Missense mutation

• Nonsense mutation

• “Silent” mutation

• Frameshift mutation

Missense mutation

changes an amino acid to another amino acid

Nonsense mutation

changes an amino acid to a STOP codon; premature termination of translation

“Silent” mutation

doesn’t change an amino acid, but in some cases can still have a phenotypic effect (ex. speeding up or slowing down protein synthesis)

Frameshift mutation

deletion or insertion of a number of bases that is not a multiple of 3. Usually introduces premature STOP codons in addition to lots of amino acid changes

Mutation impact on protein function

• loss of function

  • complete loss of the protein

• gain of function

  • increase in the protein’s function