Gene Expression - Explanation

Describe the structure of DNA

composed of a deoxyribose sugar, phosphate group, and a nitrogenous base. H is located at carbon 2. It is double stranded

Describe the structure of RNA

composed of a ribose sugar, phosphate group and a nitrogenous base. OH is located at Carbon 2. It is single stranded

Impact of single/double stranded and importance

DNA ia double stranded so therefore it is more chemically stable than RNA. This is important because DNA contains genetic information

How long is mRNA

around the length of the single gene it encodes

Brief notes on mRNA

takes a copy of genetic information from nucleus to cytoplasm

Brief (rRNA)

makes ribosomes which are the site of protein synthesis

Brief note of tRNA

brings amino acids to ribosome

Difference in base pairing rule for DNA compared to RNA

A binds to U

3 regions of a gene

Promoter, Coding Sequence, Terminator

What happens before mRNA leaves the nucleus

It is proessed, meaning the non-coding regions are edited out and the coding regions are joined (spliced) together.

5 reasons for why transcription is necessary (producing mRNA)

DNA needs to be protected from external damage. Proteins would be too large to move through the nucleus. Many protein molecules can be made from mRNA. DNA is too large to leave nucleus. Ribosomes are only found in the cytoplasm

Process of Transcription

RNA Polymerase unwinds and unzips DNA by breaking the hydrogen bonds, binds to the promoter region of a gene. Adds nitrogenous bases according to complimentary base pairing rule. Stops transcription when reached terminator region. Pre-mRNA is processed by slicing out the non-coding regions. mRAN leaves the nucleus to the cytoplasm

Process of translation

mRNA binds to a ribosome. The ribosome reads the mRNA in codons (3 consecutive bases). tRNA’s carry the corressponding amino acid, each tRNA’s has a anti-codons which is complementary to the codon on the mRNA strand,  ensuring that the correct amino acid is added to the growing polypeptide chain. The ribosome catalyzes the formation of peptide bonds between amino acids, which links them into a polypeptide chain. When the ribosome reaches a stop codon translation ends. The completed polypeptide is released and folds into a functional protein. 

What does the START and STOP codon do

tells ribosome when to start making and when to stop making the protein

Why is the genetic code redundant

Because some amino acids can be specified by more than one 3-letter code

Why is translation important

allows the genetic information to be accurately converted into functional proteins, which are essential for the structure and function of all living cells.

What determines the properties of proteins

Amino acids that make up the protein and the order of amino acids

Explain the primary structure of proteins

• Linear sequence of amino acids linked together

• Order determined by DNA sequence

Explain the Secondary structure of Proteins

• Polypeptide chain folded into structures (helices or sheets) 

• Held together by hydrogen bonds

• H-bonds can be easily broken by high temperatures or pH changes

Explain the Primary Structure of Proteins

Compact structure of protein resulting from 3-D coiling of already folded chain of amino acids

• Held in place by:

  • hydrogen bonds

  • disulfide bonds

  • ionic bonds

  • hydrophilic / phobic interactions

Explain the Quaternary structure of Proteins

Some proteins are made up of 2 or more polypeptide chains. Chains held together by same bonds as described in tertiary structure

Why are proteins essential

Mediate most of the chemical reactions in our cells

Determine our genetic traits 

Are required for the structure, function, and regulation of the body’s tissues and organs

Explain a silent mutation

No change to protein, because of the redundancy of genetic code 

Explain a nonsense mutation

Results in a STOP codon. It prematures shortening of the polypeptide chain, This has a severe impact on protein structure (and ultimately function) 

Explain a missense (conservative) mutation

Results in a change in amino acid that doesn’t change the shape/function of the protein. The new amino acid is similar to the old one

Explain a missense (non-conservative) mutation

Results in a change in amino acid that does change the shape/function of the protein. The new amino acid is different to the old one

Mutations impact on gene expression order

Mutation > Change in protein Structure > Change in Protein Function > Change in Phenotype

Role of enzymes in metabolic pathways

crucial for the proper functioning of metabolic pathways because they speed up chemical reactions that would otherwise occur too slowly to support life.

Relationship between genes, enzymes, and metabolic pathways

metabolic reactions are catalysed by specific enzymes, which are coded for by specific genes

Mutations and Metabolic pathways and affect

A mutation could lead to a dysfunctional protein (enzyme), leading to the accumulation of some products and a shortage of others. Also the final product of the metabolic pathway might not be produced. There might be a toxic buildup of intermediate substrates. These changes may affect the phenotype of the individual

What does the final product in a metabolic pathway act as and name of process

Enzyme inhibitor. Once the final product starts to build up, it inhibits the original enzyme, so the pathway stops until the concentration of the product is used up. Called negative feedback.

Benefits of metabolic pathways

controlled by negative feedback (prevents toxic build-up of product), allows sophisticated reactions to occur so that complex molecules are made, intermediate products can be used in multiple pathways

What affects phenotype

genotype and environment

Changing gene expression

Environmental factors can switch genes on or off. This alters which proteins are produced and can lead to changes in traits

Not allow an organism to reach full genetic potential

Even if an organism has the genes to grow to a certain size or develop specific traits, environmental conditions can prevent it from reaching its full potential

Effect on the function of a protein or enzyme coded for by a gene

Proteins and enzymes are sensitive to environmental conditions such as pH, temperature,. Changes in these conditions can reduce enzyme activity, which can disrupt metabolic pathways and change the physical traits of an organism.

Genotype + Environmental Factors + Phenotypes

the genotype provides the potential for traits, while environmental factors can influence gene expression, protein function, and growth. This means the phenotype reflects both genetic instructions and environmental effects