DNA Transcription, DNA Translation, and Mutations

What is the function of structure proteins?

It provides support to the tissues.

What is the function of transport proteins?

It transports substances and molecules in the cell.

What is the function of enzymes?

It provides chemical reactions.

What is the function of channel proteins?

It acts as a channel which molecules travel in the cell.

Central Dogma of Molecular Biology

States that information flows in one direction; DNA - RNA - Proteins

What are the steps of Central Dogma?

1. DNA Replication 2. Transcription 3. Translation

Transcription

Converts the DNA into a mRNA message

Translation

Interprets an RNA message into a string of amino acids

Polypeptide

A string of amino acids that make up proteins

In transcription, what does RNA act as between DNA and protein synthesis?

RNA acts as a middleman between DNA and protein synthesis.

RNA

a chain of nucleotides, each made of a sugar, a phosphate group, and a nitrogen base.

What are the three major ways in which RNA is different from DNA?

RNA has a ribose sugar, has uracil instead of thymine, and a single-stranded structure.

What does its single-stranded structure allow some types of RNA to do?

Its single-stranded structure allows some types of RNA to form complex 3D shapes, and as a result, some RNA molecules can catalyze reactions as much as enzymes do.

How are DNA and RNA different, when it comes to proteins?

DNA codes for proteins, while RNA makes proteins.

DNA Strand: AGTCGCTAGCTAA, what is the RNA strand?

UCAGCGAUCGAUU

DNA Strand: GCTTACGAATCGG, what is the RNA strand?

CGAAUGCUUAGCC

Where does transcription take place?

nucleus

What is the purpose of transcription?

It copies a sequence of DNA to produce a complementary strand of RNA.

Transcription

Process of copying a sequence of DNA to produce a complementary strand of RNA

What will the RNA strand later be used for?

The RNA strand will later be used to make a certain protein.

RNA Polymerase

Enzymes that bond nucleotides together in a chain to make a new RNA molecule.

What does RNA polymerase unwind and unbind?

RNA polymerase unwinds and unbinds the DNA double helix.

What does RNA polymerase add to a new strand of RNA?

RNA polymerase adds nucleotides to a new strand of RNA.

What are the three major types of RNA molecules?

Messenger RNA (mRNA), Ribosomal RNA (rRNA), and Transfer RNA (tRNA)

Messenger RNA (mRNA)

An intermediate message that is translated to form a protein.

Ribosomal RNA (rRNA)

Forms part of ribosomes

Transfer RNA (tRNA)

Brings amino acids from the cytoplasm to a ribosome to help make the growing protein.

What are the steps of Transcription?

1. Initiation 2. Elongation 3. Termination

What does RNA polymerase use as a template to make a complementary strand of RNA?

RNA polymerase uses the DNA strand as a template.

Elongation

The stage when the RNA strand gets longer, thanks to the addition of new nucleotides.

Termination

After a gene has been transcribed, RNA will encounter a terminator sequence and the RNA strand will be released.

What is the end result from termination?

mRNA and before the mRNA can leave the nucleus and be used it needs to be edited (mRNA splicing)

Translation

The process by which translates an mRNA message into a polypeptide chain (protein).

Where does translation take place?

Cytoplasm

Amino acids

the building block of proteins in living organisms

How many amino acids are found in nature?

over 500 amino acids

How many amino does the human genetic code directly encode?

20

How are essential amino acids obtained?

diet

Where are non-essential amino acids synthesized?

in the body

What foods are the amino acid lysine found in?

meat, eggs, black beans, quinoa, and pumpkin seeds

What foods have large amounts of the amino acid histidine?

meat, fish, poultry, nuts, seeds, and whole grains

What is the Triplet Code?

In the genetic code all "words" have only 3 letters.

Codon

a sequence of 3 nucleotides that codes for an amino acid

What does the genetic code match each mRNA codon with?

It matches each mRNA codon with its amino acid or function.

What are many amino acid coded by?

Many amino acids are coded by more than one codon.

What is Leucine coded by?

CUU, CUC, CUA, CUG, UUA, & UUG

What is the pattern of the codons?

They all share (most of the time) the first two letters.

What are the first two letter most important in?

They are most important in coding for an amino acid.

How could a misread mRNA affect the protein?

A misread mRNA could change the protein completely and lead to mutations.

Reading frame

A way of dividing the sequence of nucleotides in a nucleic acid (DNA or RNA) molecule into a set of consecutive, non-overlapping triplets.

What is the mRNA read by?

a ribosomal subunit (rRNA) and a transfer RNA (tRNA)

rRNA

composed of 2 subunits, large and small and together both pull the mRNA through reading one codon at a time.

What do the large and small subunit do for mRNA?

The large subunit holds unto the growing protein chain, while the small subunit holds unto the mRNA.

tRNA

carries free-floating amino acids from the cytoplasm to the ribosome

What is the shape of tRNA?

L-shaped; one side has an amino acid attached; the other has a code called the anticodon

anticodon

a set of three nucleotides complementary to the mRNA

If the codon for the mRNA is GGG, what is the anticodon from tRNA?

CCC

What happens when you don't eat enough proteins?

When dietary protein is in short supply, the body tends to take protein from skeletal muscles to preserve more important tissues and body functions. As a result, lack of protein leads to muscle wasting over time.

How is your skin affected by lack of protein?

Proteins enable skin regeneration, and if they do not work adequately, the skin might become dry and cracked.

If an mRNA molecule in the cytoplasm had 300 nucleotides. How many amino acids would be in the resulting protein?

100 amino acids

What is the connection between a codon and an amino acid?

One codon codes for one amino acid.

If a tRNA molecule had the anticodon AGU. What amino acid would it carry?

UCA

What is the start codon?

AUG

What are the stop codons?

UAA, UAG, and UGA

Mutation

DNA or RNA change; any change to the nucleotide sequence of a DNA molecule

What can mutations affect?

Mutations can affect a single gene or an entire chromosome.

Proteopathy

The condition when proteins fail to work.

What are many neurodegenerative diseases caused by?

Many neurodegenerative diseases are caused by wrongly folded proteins, which lead to mutations.

What diseases is protein misfolding believed to be the primary cause of?

Alzheimer's disease, Parkinson's disease, Huntington's disease, Creutzfeldt-Jakob disease, and cystic fibrosis.

Point Mutations

Substitutes one nucleotide from another. This means an incorrect nucleotide is put in the place of the correct nucleotide.

Sickle Cell anemia

Instead of coding for Glutamic acid, Valine is coded for when making the hemoglobin protein.

What diseases are caused by point mutations?

Cystic fibrosis, Tay-Sachs, and Cancer

What are the types of point mutations?

silent, missence, and nonsense

Silent mutation

Mutations in DNA that do not have an observable effect on the organism's phenotype.

Missense mutation

A mistake in the DNA which results in the wrong amino acid being incorporated into a protein because of change that single DNA sequence change, results in a different amino acid codon which the ribosome recognizes

Nonsense mutation

A change in DNA that causes a protein to terminate or end its translation earlier than expected.

Frameshift mutation

Delete/insert nucleotides that don't belong

THE CAT ATE THE RAT, what is the result if the first E is deleted?

THC ATA TET HER AT

THE CAT ATE THE RAT, what is the result if an extra C is inserted?

THE CCA TAT ETH ERA T

What diseases are the result of frameshift mutations?

Crohn's disease, some forms of cancer, resistance to infections such as HIV retrovirus, increased suspectability to certain cancers, classes of familial hypercholestrolemia, and Leigh disease.

What are examples of insertion mutations?

Fragile X Syndrome (X chromosome) and Huntington's disease (chromosome #4)

What are examples of deletion mutations?

Cri du Chat (chromosome #5), male infertility (Y chromosome), and Prader Willi syndrome (chromosome #5)

Chromosomal mutations

Changes in structure or number of chromosomes

Duplication mutations

One chromosome may have two copies of a gene(s)

Translocation mutations

A piece of one chromosome move to a non-homologous chromosome.

When and where does duplications and translocations occur?

Duplications and Translocations occur in germ cells during Prophase I of meiosis.

What are examples of Duplication mutations?

Kilnefelter syndrome and XXY syndrome (both affect only men)

What are examples of Translocation mutations?

Down syndrome (chromosome #21) and Edward's syndrome (chromosome #18)

True or False: Not all mutations have an effect on an organism's phenotype.

True

Where does mutations have to occur, in order to affect the offspring?

Germ cells (gametes)

What do studies suggest mutations are significant cause of?

aging