Genes and Proteins

Investigation 1 Genes and Proteins

DNA Genetic Information Chromosomes contain all of the information required to make a complete individual. Half of an individual’s chromosomes come from their father and half from their mother, Each individual is an entirely new combination of genetic information that, unless they have an identical twin, has never occurred before and will never occur again

Karyotypes Karyotypes view microscopic images of chromosomes and arrange them in pairs for analysis. Each human has 23 pairs of chromosomes. Thus, each normal human has a total of 46 chromosomes. Each chromosome pair contains genetic information from both the individual’s father and mother. The final pair of chromosomes, the 23rd pair, determines the sex of the individual. males have one “x” chromosome and one “y” chromosome, females have two “x” chromosomes.

Chromosomes

DNA Deoxyribonucleic Acid Long, double stranded, molecule made up of chemical building blocks called nucleotides Nucleotides consist of a phosphate, sugar, and one of four nitrogen bases Adenine (A) ̶ Cytosine (C) Guanine (G) ̶ Thymine (T) Different combinations of the nitrogen bases make up a person’s unique DNA

DNA DNA has the appearance of a ladder that has been twisted. It is called a Double Helix

DNA

Replication

DNA Each molecule of DNA consists of smaller segments called genes. Genes contain the information to make Proteins Proteins are large molecules that are made up of amino acids (building blocks) Cells convert info from genes into proteins with the help of RNA

RNA Ribonucleic Acid Single strand molecule, made up of nucleotides like DNA except thymine is replaced Adenine (A) ̶ Cytosine (C) Guanine (G) ̶ Uracil (U) RNA acts as messenger (mRNA) and carries DNA information to other parts of the cell that make proteins

DNA into RNA The conversion of DNA into RNA is known as TRANSCRIPTION Transcription takes place in the nucleus and it converts DNA into RNA When DNA is converted to RNA there is a set of rules that are followed. This rule is known as the Base Pairing Rule

Transcription

Base Pairing Rule Each base in DNA pairs or matches up with a base that will be used to create RNA After RNA is made it acts as a messenger and carries code from DNA in the nucleus to the ribosomes

Transcription DNA Double Helix unwinds and allows for base pairs to form RNA Once the RNA single strand is formed the DNA is twisted back together and the RNA prepares to leave the Nucleus

Translation RNA leaves the nucleus to ribosomes where the RNA code is translated into a protein RNA code is translated into proteins in groups of three base nucleotides called Codons Each codon group corresponds to a specific amino acid Each Amino Acid has at least one codon; some more than one There are codons that signal to stop the making of proteins

Translation

Protein Synthesis Transcription and Translation http://www.youtube.com/watch?v=8nQH0GqFn6k

Mutations Mutation is a change in the sequence of nucleotides in a gene Three Basic Mutations Substitution: one nucleotide is changed into a different nucleotide Insertion: one or more nucleotides are inserted (added) into the DNA sequence Deletion: one or more nucleotides are deleted (removed) from the DNA sequence

DNA Controls the Function of Organisms Genes contain DNA sequences that encode for proteins. The DNA sequence and its corresponding RNA sequence instruct the cell to build a specific protein. Each set of three nucleotides in the RNA (and DNA) corresponds to one amino acid in the protein. Proteins are responsible for most of the functions of an organism’s cells.

Mutations Causing Changes in Organisms Mutations may or may not lead to changes in an organism. If the mutation in DNA does not change the amino acid sequence of the protein, then no change in function of that protein will occur and no change will be seen in the organism. If the mutation in the organism does cause a change in amino acid sequence of the protein, then a change in function of the protein is possible and a corresponding change in the organism would be expected.

Investigation 2 Genes and Proteins

Proteins Once the RNA has been translated into Amino Acids the Amino form proteins Wild-Type Protein- a protein that is produced with no mutations

Proteins Proteins fold in certain ways in order to perform certain functions Proteins bind or attach to another molecule at a binding or active site Binding Sites are formed by neighboring amino acids that are positioned together to form a pocket into which fits a molecule Each Amino Acid has a different shape, so when they come together the pocket the form fits a specific molecule exactly.

Proteins- Primary Structure Primary Structure: This refers simply to the sequence of amino acids in a protein. This sequence, of course, is dictated by the DNA sequence of the gene. This amino acid sequence is sometimes referred to as a polypeptide chain. This is because the bonds that hold the amino acids together in a linear chain are call peptide bonds.

Secondary Structure Secondary Structure: Due to the physical properties of the individual amino acids (remember, there are 20 different amino acids), sections of the polypeptide chain may interact with each other to form local structures. For example, a stretch of amino acids may interact with each other to for a spiraling helix. They may also for zigzag structures and flat sheets. Such localized secondary structures may be important for a protein’s function.

Tertiary Structure Tertiary Structure: A completed protein may have many secondary structures and amino acid sequences that attract and interact with each other. Consequently, the overall amino acid chain often folds in upon itself in a very specific manner to form a tertiary structure. One important result of such tertiary structure is that the folded protein’s three-dimensional structure may form surface areas that recognize and bind to other molecules. Such a structure would clearly be important for the protein’s function. Oftentimes, mutations that affect protein function do so because a replaced amino acid, caused by the mutation, does not lead to the formation of functional binding sites on the protein molecule.

Quaternary Structure Quaternary Structure: Finally, many proteins are actually composed of more than one polypeptide chain. In such cases, two or more different polypeptide chains, each with their own tertiary structure, bind to each other in very specific arrangements. When this happens, the individual polypeptide chains within the final protein molecule are typically referred to as subunits of the protein

Mutations in DNA Yes. Mutations in DNA can lead to changes in the amino acid sequence of a protein. Changes in amino acid sequence can cause changes to protein structure. Changes in protein structure may cause changes in function. If a protein cannot function properly, some of the functions of the organism may be affected because functions of an organism often depend on the functions of the proteins within the organism. However, not all mutations cause changes in an organism. Some mutations in DNA do not cause changes in the amino acid sequence of a protein and therefore do not change a protein’s structure or function. Some mutations in DNA cause changes in amino acid sequences without changing the structure and function of a protein. Some mutations cause changes in the structure of a protein without affecting the function of a protein.

Investigation 3 Genes and Proteins http://www.mhhe.com/biosci/genbio/virtual_labs/BL_23/BL_23.html Genes and Proteins

DNA DNA is found in the nucleus of almost all body cells Inside the Nucleus the DNA is located in special structures called Chromosomes Chromosomes- contain many genes

Chromosomes Each body cell contains two copies of each chromosomes, these copies are called Homologous Chromosomes Each chromosome in a homologous pair came from each parent Homologous chromosomes contain the same genes but they are not identical, they contain different alleles or versions of the genes

Cell Division Cells in the body divide and produce new Cells in the process called the Cell Cycle The Cell Cycle is divided into different parts Interphase Mitosis Cytokinesis

Cell Cycle Step 1: Interphase Cell grows larger DNA is replicated Each chromosome in a pair is copied The two identical copies of each chromosome are called Sister Chromatids They are attached together by a structure called centromere Cells prepares for division

Centromere

Cell Cycle Step 2: Mitosis Mitosis is divided into 4 phases PMAT Prophase Metaphase Anaphase Telophase

Mitosis Phase 1: Prophase Prophase: the nuclear membrane dissolves Chromosomes condense into rod-like structures that can be seen with a microscope

Mitosis Phase 2: Metaphase Metaphase: spindle fibers have formed in the cell Chromosomes line up as pairs of duplicated homologous chromosomes in the center of the cell

Mitosis Phase 3: Anaphase Anaphase: chromatids separate and move down the spindle fibers to opposite ends of the cell

Mitosis Phase 4: Telophase Telophase: chromatids have moved to the ends of the spindle fibers and the spindle fibers disappear Nuclear membranes form around each set of chromosomes Cell is prepared to divide

Cell Cycle Step 3: Cytokinesis Third step in the Cell Cycle is Cytokinesis, cells divide into two separate new cells Telophase

Human Body Cells Human body contain many cells that scientist classify into two groups Somatic or Body Cells Gametes or Sex Cells

Human Body Cells Somatic Body Cells- Cells that make up different parts of the body such as: stomach, skin, muscles, and other organs Gametes or Sex Cells – cells that make up egg or sperm cells Gametes are responsible for passing on Genetic information from one generation to another Gametes cells divide through meiosis

Mutations in a Single Cell Affect Function of the Organism A mutation of the DNA in a gene in a single body cell will get copied when the chromosomes duplicate. All of the new body cells formed through mitosis will then have the mutation. If the mutation causes a change in a protein, all cells will produce the mutant protein. If the cells in an organ are producing mutant proteins, the organ may not function properly. Thus the organism may not function properly.

People to know

Rosalind Franklin and Maurice Wilkins In 1951 made a crystal of the DNA molecule.  DNA crystallized allowing them to make an x-ray pattern The pattern appeared to contain rungs, like those on a ladder between to strands that are side by side.   

James Watson and Francis Crick In 1953 using the X-ray picture from Franklin and Wilkins, made a double helix with little rungs connecting the two strands. These rungs were the bases of a nucleotide. Using the Base Pairing rule they were able to figure out the stability of the structure

DNA Structure

Nobel Prize 1962 Watson, Crick, and Wilkins Received the Nobel Prize in physiology and medicine for their 1953 determination of the structure of deoxyribonucleic acid  Rosalind Franklin was not awarded the prize because she had died a few years prior