Bio Test 8.4/8.5/ 8.6 AJ likes Men

April 4, 2023

DNA contains the information to _______?

Build proteins

Proteins are needed for __________?

Structure, function, and regulation of the body.

 Steps of Central Dogma?

1\. DNA Replication

2\. Transcription: Converts the DNA into a mRNA (message)

3\. Translation: Interprets an RNA message into a string of amino acids, called a polypeptide, which makes up a protein. 

In transcription RNA (Ribonucleic acid) acts as a __________?

Middleman between DNA and protein synthesis.

What is RNA?

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

__RNA differs from DNA in three major ways__?

 RNA has a ribose sugar.

RNA has uracil instead of thymine. ( A pairs with U)

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

Additionally, DNA codes for proteins, while RNA makes proteins.

Transcription/where

Nucleus

Transcription/purpose

Copy a sequence of DNA to produce a complementary strand of RNA.

Transcription/definition

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

RNA polymerase/definition

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

RNA polymerase moves in a ____________?

5'-3' direction

RNA polymerase also unwinds and unbinds the __________?

DNA double helix

RNA polymerase adds nucleotides to a new strand of _________?

RNA

Transcription produces three major types of RNA molecules?

mRNA

rRNA

tRNA

mRNA?

Intermediate message that is translated to form a protein.

rRNA?

Forms part of ribosomes, a cell’s protein factories.

tRNA?

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

Steps in transcription?

1\. INITIATION 

2\. ELONGATION 

3\. TERMINATION

(Honors) Initiation: TATA Box -

Promoter Sequence 

(Honors) RNA polymerase binds to a region of a gene called the_________?

Promoter

(Honors) Promoter/Definition?

A segment of DNA that allows a gene to be __found and transcribed__

(Honors) The promoter tells the RNA polymerase where on the DNA to begin______?

Transcribing

A TATAA box is?

A DNA sequence that indicates where a genetic sequence can be read and decoded. It is a type of promoter sequence, which specifies to other molecules where transcription begins.

Elongation?

Using the DNA strand as a template the RNA polymerase makes a complementary strand of RNA.

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

Termination?

After a gene has been transcribed, RNA polymerase will encounter a __terminator sequence__ and the RNA strand will be released. 

Termination/ End result

mRNA

Before the mRNA can leave the nucleus and be used it needs to be edited (__mRNA splicing__).

(Honors) Pre-mRNA Splicing?

RNA splicing is a process in molecular biology where a newly-made precursor messenger RNA (pre-mRNA) transcript is transformed into a mature messenger RNA (mRNA). It works by removing all the introns (non-coding regions of RNA) and splicing back together exons (coding regions).

mRNA must be processed before leaving the nucleus.

(Honors) mRNA Splicing process?

Exons are nucleotide segments that __code__ for parts of the protein. 

Introns are __non-coding__ nucleotide segments that intervene, or occur, between exons.

5' cap tail is added which helps preserve the mRNA and helps ribosomes bind to it.

Poly-A tail is added to help the mRNA leave the nucleus.

(Honors) 1.3' poly-A tail protects _________?

Protects mRNA from degradation

Aids in exporting the mature mRNA to the cytoplasm.

Involved in binding proteins to initiate translation.

(Honors) The 5' cap protects the __________?

newly-synthesized mRNA from degradation.

It also assists in ribosome binding to help initiating translation.

__Translation/Definition__

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

__Translation/Where__

Cytoplasm

Primary?

Amino acid sequence

Secondary structure?

Alpha helix, beta sheet and loops

Tertiary?

Phi-Psi angle

Quaternary?

Arrangement of several Polypeptide chains

The human genetic code only directly encodes _______?

20 amino acids

__Codon/definition__

A sequence of 3 nucleotides that codes for an amino acid

The genetic code matches each mRNA codon with its _________?

Amino acid or function

The __first two letters are the most important__ in coding for ____________?

Amino acids

Stop codons/definition

Signal the end of an amino acid chain.

Stop codons?

__UAA,UGA, and UAG__

Start codons/definition

Signals the start of translation. AUG which codes for methionine is the start codon. 

Reading frame

It's crucial that the mRNA is read correctly.

A misread mRNA could change the protein completely.

Could lead to mutations.

In molecular biology, a reading frame is a way of dividing the sequence of nucleotides in a nucleic acid (DNA or RNA) molecule into a set of consecutive, non-overlapping triplets.

Where these triplets equate to amino acids or stop signals during translation, they are called __codons.__

Universal Language 

The genetic code is shared by almost all living organisms.

Codons are said to be universal throughout all living organisms. This allows crossing species and genetic modification.

The genetic code is universal means the same codons code for the same amino acids in all forms of life that exists today. 

How to read the mRNA?

The mRNA is read by a ribosomal  subunit (rRNA) and a transfer RNA (tRNA).

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

The __large subunit__ holds onto the growing protein chain, while the __small subunit__ holds onto the mRNA.

tRNA carry free-floating amino acids from the cytoplasm to the ribosome.

It's L shaped, (tRNA) one side has an amino acid attached;  the other has a code called the anticodon.

The anticodon is a set of three nucleotides complementary to the mRNA.

mRNA: GGG

tRNA:    CCC (this is the anticodon for GGG)

Ribosome

Large Subunit

Binding sites

Small subunit binds to mRNA

tRNA

Amino acid

Anti-codon

What happens when proteins fail to work?

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.

The skin might also be affected—proteins enable skin regeneration, and if they do not work adequately, the skin might become dry and cracked. 

Mutation/definition

DNA change

Mutations can affect a __________?

single gene or an entire chromosome. 

Mutations can be good, bad, or neither. 

Proteopathy?

The condition when proteins fail to work.

__Point mutations/ Definition__

Substitute one nucleotide for another. This means that an incorrect nucleotide is put in the place of the correct nucleotide.

__Sickle Cell anemia/ Definition__

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

Examples of Gene mutations?

__Cystic Fibrosis__                  __Tay-Sachs__                __Cancer__

Silent Mutation:

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

Missense Mutation:

A missense mutation is 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 nonsense mutation, or its synonym, a stop mutation, is a change in DNA that causes a protein to terminate or end its translation earlier than expected.

__Frameshift mutations__:

Delete/insert nucleotides that don't belong

__Frameshift mutations/ examples__

Ex. THE CAT ATE THE RAT, delete the first E

      THC ATA TET HER AT

Ex. THE CAT ATE THE RAT

Insert an extra C

THE CCA TAT ETH ERA T

Insertion mutation examples:

Fragile X Syndrome

Huntington's disease

Deletion mutation examples:

Cri du Chat

Male infertility

Prader Willi syndrome

__Chromosomal mutations:__

Changes in structure or number of chromosomes.

__a.Duplication:__

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

__b.Translocation:__

A piece of one chromosome moves to a non-homologous chromosome

Duplications and Translocations occur in _________?

germ cells during Prophase I of meiosis.  

Duplication/ examples

Klinefelter syndrome

XXY syndrome 

Affects men only 

Translocation/ example

Down syndrome

Edwards syndrome

Not all mutations have an effect on an _________?

Organisms phenotype

Mutations that do not affect a resulting protein are called ___________?

__silent mutations__

Mutations can occur in all types of cells, but ________?

to affect an offspring it has to occur in __germ cells__ (gametes).

__Mutagens/ defintion__

Agents in the environment that can change DNA.  

 ndustrial chemicals

They can speed up replication rate or break DNA strands. 

Some mutagens occur naturally. Ex. : UV rays from sunlight, pesticides, nicotine, bacteria, viruses, etc...