Topic 5: Gene Expression and Enzymes

The function and location of Ribosomes and the Endoplasmic Reticulum

- Ribosomes manufacture a made to order protein. - They are manufactured in the ER - The endoplasmic reticulum is an extensive interconnected network of tubes and flatted sacs. The ER functions like a specialized department, preparing items for transport to other parts of the cell or export outside of the cell.

Gene Mutation

A change to the sequence of bases in an organism's DNA is called a mutation. Mutations can also occur when cells are exposed to mutagens (substances or energy sources that alter DNA). Mutations result in the formation of new alleles. A mutation is a change in the base sequence of an organism's DNA. Mutations can occur in three different ways; substitution, insertions, and deletions.

Genome

A genome is an organism's complete set of DNA, including all of its genes. Each genome contains all of the information needed to build and maintain that organism. In humans, a copy of the entire genome (which is more than 3 billion DNA base pairs) s contained in all cells that have a nucleus.

Point Mutation

A point mutation is a mutation in which a single base is altered

Polypeptide

A polymer of amino acids joined together by peptide bonds

A substrate is in a chemical reaction is:

A substrate is the substance upon which an enzyme acts in an enzymatic reaction. Enzymes are biological catalysts that increase the rate of chemical reactions by decreasing the activation energy required for that reaction. An enzyme catalyzes a chemical reaction converting a substrate reactant to a product. An individual enzyme generally has more than one substrate and may be specific to several reaction intermediates that are part of an over-all reaction.

List the four RNA nucleotides that make up RNA nucleic acids

Adenine (A) Guanine (G) Cytosine (C) Uracil (U)

Gene

DNA sequences that code for RNA

Extron

Exons are segments of a gene that actually code for the amino acids. Exons are preserved in the mature, translation0ready mRNA, and ribosomes manufacture a "made-to0-rder" protein according to the code carried by the exons in the mRNA

List the subunits that make up an RNA nucleotide

In RNA, nucleotides contain the sugar ribose rather than the sugar deoxyribose that is contained in DNA. The nucleotide is made up of a phosphate and a sugar ribose.

What is a product is in a chemical reaction?

In a chemical reaction, substances (elements and/or compounds) called reactants are changed into other substances (compounds and/or elements) called products. Chemical equations show the reactants and products, as well as other factors such as energy changes, catalysts, and so on. Reactants → Products

Gene Regulation

In gene mutation, a gene is transcribed and its mRNA is translated into a functional protein that has an effect on phenotype.

In the sickle cell activity lab, the frequency of the sickle cell allele ____ and the frequency of the normal hemoglobin allele _____ due to natural selection

Increased, Decreased Natural selection by the malaria parasite drive the increase in the sickle cell trait in the population over time since those carrying just one copy of the gene for sickle cell will not die of Malaria.

Insertion and Deletion Mutations

Insertion or deletion mutation occurs when a base is inserted into or deleted from a DNA sequence. When a single base insertion occurs, it causes a genetic frameshift. A frameshift mutation, whether it's caused by a point mutation or by a large insertion or deletion, alters the resulting protein so severely that it fails to function it most cases.

Intron

Most eukaryotic genes are interrupted by stretches of DNA, called Introns. Introns do not code for the amino acid sequence of proteins and must be spliced out of a newly made mRNA molecule.

What are the sources of genetic variation in a sexually reproducing population?

Mutation and crossing-over

RNA interference (RNAi):

RNA interference (RNAi), also known as Post-Transcriptional Gene Silencing, is an important pathway that is used in many different organisms to regulate gene expression. It's a conserved biological response to double-stranded RNA that mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.

The substance or molecule to which an enzyme binds at its active site is the

Substrate. Substrates bond for a short period of time so the enzyme so that the enzyme can perform a reaction and release the products (s) of the substrates (s). The enzyme can then go on to perform another chemical reaction on another substrate molecule.

Tertiary level of organization of enzymes

Tertiary structure of a protein is very specific three-dimensional shape. This shape is attained not merely through local patterns of folding, as in the secondary structure, but through interactions between distant segments of the polypeptide chain. Tertiary structure is stabilized by non-covalent associations such as ionic bonds, and often by covalent links between distant amino acids

Active Site

The binding of an enzyme to its particular substrate depends on a match between the three-dimensional shapes of both the substrate and the enzyme molecules. In the same way that a lock accepts only a key with just the right shape, each enzyme has an active site that fits only substrates with the correct three-dimensional shape and chemical characteristics.

Genetic Code

The genetic code specifics the "meaning" of every word in the language: which amino acid is encoded by a particular codon, and which codon act as signposts that communicate to the ribosomes where they should start or stop reading the mRNA

Codon

The information in an mRNA molecule is "read" by the ribosomes in sets of three bases, and each unique sequence of three bases is called a codon. When reading the code, a ribosome begins at a fixed starting point on an mRNA molecule, called a start codon (the codon AUG) and tends at one of three stop codons (UAA, UAG, or UGA).

Primary level of organization of enzymes

The primary structure of a polypeptide is its sequence of amino acids. A polypeptide most acquire a higher level of organization, beyond its primary structure, before it can function as a protein or part of a protein

Secondary level of organization of enzymes

The secondary structure of a protein is created by the local folding of the amino acid chain into specific three-dimensional patterns. Alpha helices and beta sheers are two of the most common types of secondary structures. An alpha helix is a spiral pattern and a beta sheer is created when a polypeptide backbone is bent into ridges and valleys as in a paper fan.

Transcription:

Transcription of a protein-coding gene involves copying the DNA sequence of the gene into mRNA. The base sequence of an mRNA is complementary to its DNA template, and it carries the code for the amino acid sequence of a specific protein.

Translation:

Translation is the process by which the mRNA code is turned into the precise sequence of amino acids that become covalently linked to form the protein product. Translation requires not only mRNA but also rRNA.

Transfer RNA (tRNA):

Transports the correct amino acid to the ribosome, using the information encoded in the mRNA; contains a three-base anticodon that pairs with a complementary codon revealed in the mRNA.

Homozygous Dominant

YY

Heterozygous

Yy

Ribosomal RNA (rRNA):

as a major component of ribosomes, assists in making the covalent bonds that link amino acids together to make protein.

Small Interfering RNA (siRNA):

small interfering RNAs (siRNAs) are yet another class of small RNAs. Although these molecules are only 21 to 25 base pairs in length, they also work to inhibit gene expression. Specifically, one strand of a double-stranded siRNA molecule can be incorporated into a complex called RISC. This RNA-containing complex can then inhibit transcription of an mRNA molecule that has a sequence complementary to its RNA component.

Messenger RNA (mRNA):

specifies the order of amino acids in a protein using a series of three-base codons, where different amino acids are specified by particular codons.

Homozygous Recessive

yy

Define enzyme and list the function of enzymes:

• Enzymes are biomolecules that speed up chemical reactions. Without the action of enzymes, metabolic reactions would be extremely slow and life as we know it could not exist. • The majority of enzymes are proteins. • Enzymes are catalysts, meaning that they are a chemical that speeds up chemical reactions without itself being chanced in the course of the reaction. • They are usually proteins • They increase the rate of chemical reactions, often by a million-fold or more. • They generally act on one or a few specific substances • Remain unchanged by the reaction • Are reused over and over, catalyzing the transformation of many substrate molecules • Are sensitive to temperature, pH, and salt concentration. • Many need the assistance of specific ions or molecules • Are usually tightly regulated within the cell or inside the body of a multicellular organism.

Describe how histone proteins regulate gene expression

• Histone proteins are essential for the packaging of DNA into chromosomes. • Histone gene expression is cell-cycle-regulated and coupled to DNA replication. • Control of histone gene expression occurs at the transcriptional and post-transcriptional level and ensures that a fine balance between histone abundance and DNA replication is maintained for the correct packaging of newly replicated DNA into chromosomes.

Briefly outline the steps in gene expression, starting with the gene and ending with an observable trait:

•In gene expression, a gene is transcribed and its mRNA is translated into a functional protein that has an effect of phenotype. •Cells receive signals that determine gene expression. •Some of these signals are sent from one cell to another, as when one cell released a signaling molecule that alter gene expression in another cell. •DNA packing •Regulation of transcription •RNA moves through the nuclear envelope and into the cytoplasm. •Break down of mRNA •Regulation of translation •Regulation after translation

Histone Proteins

•Proteins that act as spools upon which DNA wraps around •Responsible for the first and most basic level of chromosome organization: the nucleosome •Play a pivotal role in transcription factors depending on how tight or loose the DNA is wound around it •The number of Acetyl Groups on the histones determine how tight or loose the DNA is wrapped •The more Acetyl Groups there are, the looser the DNA The less Acetyl Groups there are, the tighter the DNA