Human Bio - 1.3 - Gene Expression

Define cell genotype

The genetic composition of a cell

What is cell genotype determined by?

the sequence of DNA bases in a cell’s genes

Define gene expression

how the cell genotype is shown in the cell phenotype

What is a cell’s phenotype determined by?

Proteins produced as a result of gene expression

Gene expression involves the regulation of…

transcription and translation of DNA sequences.

What does the order of bases on DNA determine?

The sequence of amino acids that are made

What is the structure, shape, and function of a protein determined by?

The sequence of amino acids joined together in polypeptide chains

Copying DNA and changing its code into a protein requires a second type of nucleic acid called…

RNA

What are the 3 main differences of RNA in comparison to DNA?

RNA nucleotides contain a ribose sugar

RNA uses the base Uracil as a partner with Adenine instead of Thymine

RNA is a single stranded molecule

What are the three types of RNA?

rRNA

tRNA

mRNA

Describe mRNA (Function, shape, # of strands and what it is complimentary to)

It is transcribed from DNA in the nucleus and posted out to the ribosomes for translation. 

It is a linear strand

It has one strand

mRNA codons are complementary to DNA triplets

Describe tRNA (Function, shape, # of strands, and what it is complementary to)

It is used to translate mRNA by the ribosomes, making a new polypeptide. It folds due to complimentary base pairing and carries the amino acids into position at the ribosome.

It is a clover-shaped loop structure

It has one strand

tRNA anticodons are complementary to mRNA codons and correspond to specific amino acids

What is the role of rRNA?

rRNA is the part of a ribosome which aids protein synthesis

Define transcription

It is the copying of the DNA code for a specific protein into mRNA

Where does transcription of DNA into primary and mature RNA transcripts occur?

in the nucleus

RNA polymerase can only add nucleotides to the BLANK of mRNA

3’ end

Describe the stages of transcription (5)

A promoter region of DNA initiates transcription

RNA polymerase enzyme moves to the specific section of DNA and moved along DNA , unwinding the double helix and breaking the hydrogen bonds between bases

RNA nucleotides pair with complementary DNA base pairs, forming RNA

RNA polymerase joins the nucleotides together to form a new sugar-phosphate backbone

The mRNA becomes separated from the DNA template, and is called the primary transcript of DNA

What are introns?

Non-coding regions of DNA

What are extrons?

Coding regions of DNA

What happens to introns?

They are cut out and removed from the primary transcript

What happens to exons? 

They are spliced together to form mRNA with a continuous sequence of nucleotides. This is called the mature transcript of mRNA

mRNA is linear and carries the DNA code in the form of…

mRNA codons

where is tRNA found?

In the cytoplasm

Why is tRNA folded in on itself?

Because of the hydrogen bonds forming between bases

tRNA exposes triplets of bases called…

tRNA anticodons

tRNA anitcodons have (BLANK) which bind to a specific amino acid

attachment site

mRNA codons and tRNA anticodons translate the genetic code into…

a sequence of amino acids

Describe the five stages of translation

mRNA binds to the ribosome

Each tRNA picks up specific amino acids in the cytoplasm and carries it to the ribosome

Each tRNA anticodon binds to a complementary codon on the mRNA lining up the amino acids in a specific order

Peptide bonds form between the amino acids to form a growing polypeptide chain

When the chain is complete, it detaches from the ribosome and will be modifiec

Translation begins at (BLANK) and ends at (BLANK 2)

a start codon

a stop codon

mRNA codon AUG complementary to tRNA anticodon UAC codes for the amino acid methionine (met) and…

acts as the start codon

mRNA codons (BLANK) do not code for amino acids, but they act as stop codons.

UAA, UAG and UGA

RNA splicing can result in…

different proteins being expressed from one gene

What does RNA splicing involve?

The primary mRNA transcript being spliced in a variety of ways, leading to a mix of different mature mRNA

RNA splicing depends on…

which RNA segments are treated as exons and introns

Alternative RNA splicing produces different mature mRNA transcripts depending on…

which exons are retained

Alternative cutting of exons leads to…

a variety of proteins

Once translation is complete, further modification may be required to…

enable a protein to  perform its specific function

Polypeptide chains fold to form (BLANK), held together by hydrogen bonds and other interactions between individual amino acids

the 3D shape of a protein