Heredity, Genes, and DNA - The Cell - NCBI Bookshelf
different proteins produced by different alleles for the same gene; and Glossary of Genetic Terms, from Lecture Heredity and Meiosis Chromosomes consist of a very tightly wound molecule of DNA plus associated proteins (Hoefnagels pg , figure ) The Relationship Between Genes, Proteins, and Traits. Consequently, elucidation of the mechanisms of genetic transmission and One gene copy (called an allele) specifying each trait is inherited from each parent. genetic linkage, and the relationships between genes and chromosomes were proteins as well as DNA, and it was initially thought that genes were proteins. The central dogma of molecular biology: DNA → RNA → protein. How, exactly, does DNA direct the construction of a polypeptide? These relationships between codons and amino acids are called the genetic code. Alleles and genes .. If so, then exponentials can't be expressed in terms of any polynomial, linear or.
Review the answers and address student questions before moving on. A protein is a long train of amino acids linked together. Proteins have different functions; they can provide structure ligaments, fingernails, hairhelp in digestion stomach enzymesaid in movement musclesand play a part in our ability to see the lens of our eyes is pure crystalline protein. DNA Direct students to read pages 1—2 in the student handout and answer questions 1—7 with their partner.
Once they are finished, explain to students that they will use paper models to learn more about transcription and translation. They will model how a cell carries out transcription and translation to make the beginning of the hemoglobin molecule. Explain that hemoglobin is a protein-based component of red blood cells that is primarily responsible for carrying from the lungs to the tissues of the body. Hand out the following to each pair of students: Explain that a similar base pairing process takes place in transcription but instead of the A—T pairing found in DNA, in transcription, the base adenine pairs with uracil found in RNA.
Instruct students that you will guide them through the transcription process as follows: Students will work with partners to model the actual sequence of steps used by the cell to carry out transcription. Tell students that even though they will be able to think of a faster way to make the mRNA, they should follow the sequence of steps described in their hand-outs in order to learn how the cell actually makes mRNA. Have each pair of students complete the Transcription Modeling Procedure from their handouts on page 3.
Observe pairs to make sure students are following the procedures correctly and using the materials appropriately. Once they have completed the Transcription Modeling Procedures, have students review their answers in the questions document. Reviewing student responses for thoroughness and accuracy can show which students have a strong understanding of the concept and which students may need additional support.
Circulate through the class assisting groups in need of assistance.
This in turn determines the types and order of amino acids included in proteins. Specific three-letter groups of RNA nucleotides code for specific amino acids. The combination TTT, for example, codes for the amino acid phenylalanine.
Regulatory regions of the gene also contribute to protein synthesis by determining when the gene will be switched on or off.
DNA, Genes and Chromosomes
Sciencing Video Vault Proteins In active genes, genetic information determines which proteins are synthesized and when synthesis is turned on or off. These proteins fold into complicated three-dimensional structures, somewhat like molecular origami. These external factors can produce small modifications to DNA, such as addition of metal ions, addition or removal of acetyl groups or methyl groups to DNA or to the histones that control the wrapping and packing of DNA.
Attachment of methyl groups appears to reduce transcription or even shut it off; attachment of acetyl groups to histones turns genes on. These biological changes to the genome is known as 'epigenetic factors', i. In essence, the DNA in our cells provide the code for making functional proteins, and the epigenetic factors act as switches which turn genes off and on.
Epigenetic factors are likely to play many important roles, such as: Turning genes off and on as differentiation proceeds in a growing embryo. As a result, some cells in the pancreas become specialized to produce digestive enzymes, while others synthesis the hormone insulin.
Epigenetic factors in utero may have a lasting influence on phenotype years later.
If a pregnant agouti mouse is fed a folate enriched diet that provides methyl groups, it's offspring will have dark coats and be lean and healthy, because a particular gene is turned on; if the diet is poor in methyl groups, the offspring will be obese and light coats. In the winter of the German army set up a blockade to prevent food and fuel from reaching the western part of Belgium, reducing food consumption to exceptionally low levels for the winter.
Fifty years later researchers compared the children who were conceived to starved mothers during that period to mothers who were already in their second or third trimester when the blockade began. They found that the offspring of the starved mothers weighed 14 pounds more on average, had waist circumferences that were 1.
Intro to gene expression (central dogma) (article) | Khan Academy
Certain genes are know to predispose to certain types of cancer, such as breast and colon cancer. If is tantalizing to think about the possibility of turning such genes off epigenetically in order to reduce the risk of developing these cancers. Epigenetics and the Influence of Our Genes This is an Some environmental factors including our diet, our behaviors, and a myriad of environmental exposures influence our phenotype through non-genetic mechanisms.
For example, one might have a number of genes that predispose an individual to being lean; however, such an individual might still become overweight or obese despite their "lean genes" as a result of chronically overeating.
Yet other epigenetic factors from the environment can modify the genome in subtle ways without actually changing the code. For more information on epigenetics explore the following web site: Pink hydrangeas can be made to turn blue by adding aluminum sulfate to the soil.
Reproduction Binary Fission in Prokaryotes Prokaryotes reproduce by the relatively simple process of binary fission.
The single chromosome replicates and each copy attaches to a different location on the cell membrane. The cell membrane then begins to invaginate and eventually separates into two genetically identical bacteria.
A similar process is used to replicate mitochondria within eukaryotic cells, but the overall process of cell replication in eukaryotes is more complicated see below.
Mitosis Adapted from http: It is the process by which new cells are formed in the growing embryo and after birth, and mitosis also replaces cells that have died or been shed. In humans some cells retain the capacity to divide throughout life. These "stem cells" divide by mitosis and produce daughter cells which then differentiate into a particular cell type. This provides a way of replacing cells, such as skin cells; the epithelial cells that line the respiratory, digestive, and urogenital tracts; and blood cells.
Benign and malignant tumors also growth through mitosis. The Cell Cycle Cells normally follow a carefully controlled cell cycle, depicted below. Many of our cells are mature functioning cells that are not actively dividing. These are cells in the G0 phase; this is sometimes called the "resting phase," but these cells are actively functioning, and they are resting only in the sense that they aren't replicating. The phases in dividing cells are as follows: G1, when the cell grows in size in preparation for division S, when synthesis of new DNA replication takes place G2, when there is continued cell growth M, which stands for mitosis, i.
Loss of control mechanisms can result in abnormal cell division and a progression to to tumor formation. This is discussed in greater detail in the online module on cancer.
Meiosis Meiosis is the specialized process by which gametes sperm and eggs are produced for sexual reproduction in the ovaries and testes. Recall that humans have 22 pairs of homologous chromosomes and one pair of sex chromosomes; one member of each pair came from the mother, and the other from the father. The 46 chromosomes are referred to as the diploid 2n number, because there are two of each. In order for the fertilized egg to end up with the correct diploid number, sperm cells and eggs must be produced such that each has only one chromosome from each pair.
In other words, gametes have only 23 chromosomes referred to as the haploid number 1n.