Genetic pedigrees In these diagrams, people are represented by symbols, usually circles for female and squares for male, and the bottom line represents the children of the couple above. For simplicity, 4 offspring are shown in these examples. However, in practice the number, proportion and order of birth are likely to vary. Obviously, the same technique of family trees can be used to show the results of animal breeding. It is customary to use dark symbols to indicate someone affected with a genetic condition, and unfilled symbols for those who are unaffected. Dominant allele, e.g. Genetic explanation Since the condition is shown in some of the first generation offspring but not in some others, this is not a simple cross between 2 different homozygotes. Note also that in this case the appearance of the condition is independent of the sex of the individual. Genetic diagram Recessive allele, e.g Cystic fibrosis Genetic diagrams For the first section (parents giving rise to the first generation): Example 1 Example 2
Cell Differentiation | BioNinja Understanding: • Specialised tissues can develop by cell differentiation in multicellular organisms • Differentiation involves the expression of some genes and not others in a cell’s genome Differentiation Differentiation is the process during development whereby newly formed cells become more specialised and distinct from one another as they mature All cells of an organism share an identical genome – each cell contains the entire set of genetic instructions for that organism The activation of different instructions (genes) within a given cell by chemical signals will cause it to differentiate Cell Specialisation via Differential Gene Expression Gene Packaging Within the nucleus of a eukaryotic cell, DNA is packaged with proteins to form chromatin Active genes are usually packaged in an expanded form called euchromatin that is accessible to transcriptional machineryInactive genes are typically packaged in a more condensed form called heterochromatin (saves space, not transcribed)
NOVA | Cracking the Code of Life Cracking the Code of Life PBS Airdate: April 17, 2001 ROBERT KRULWICH: When I look at this—and these are the three billion chemical letters, instructions for a human being—my eyes glaze over. But when scientist Eric Lander looks at this he sees stories. ERIC LANDER (Whitehead Institute/MIT): The genome is a storybook that's been edited for a couple billion years. And you could take it to bed like A Thousand and One Arabian Nights, and read a different story in the genome every night. ROBERT KRULWICH: This is the story of one of the greatest scientific adventures ever, and at the heart of it is a small, very powerful molecule, DNA. For the past ten years, scientists all over the world have been painstakingly trying to read the tiny instructions buried inside our DNA. J. ROBERT KRULWICH: And what it's telling us is so surprising and so strange and so unexpected. ERIC LANDER: How different are you from a banana? ERIC LANDER: You may feel different... ROBERT KRULWICH: I eat a banana. We asked Dr.
Gene Expression | BioNinja Understanding: • Gene expression is regulated by proteins that bind to specific base sequences in DNA Transcriptional activity is regulated by two groups of proteins that mediate binding of RNA polymerase to the promoter Transcription factors form a complex with RNA polymerase at the promoter RNA polymerase cannot initiate transcription without these factors and hence their levels regulate gene expression Regulatory proteins bind to DNA sequences outside of the promoter and interact with the transcription factors Activator proteins bind to enhancer sites and increase the rate of transcription (by mediating complex formation)Repressor proteins bind to silencer sequences and decrease the rate of transcription (by preventing complex formation) The presence of certain transcription factors or regulatory proteins may be tissue-specific Additionally, chemical signals (e.g. hormones) can moderate protein levels and hence mediate a change in gene expression Differential Gene Expression Control Elements
DNA- The ins and outs! Watson and Crick's Paper Watson and Crick published a paper that described the complementary structure of DNA. This paper rocked the science world and illuminated the structure of DNA! Check out their Paper below! Watson and Crick published a paper that described the complementary structure of DNA. This paper rocked the science world and illuminated the structure of DNA! Watson and Crick's Paper The Complementary Structure of DNA-The paper The Complementary Structure of DNA-The paper [ DNA Replication-Explanation and Video DNA Replication-Explanation and Video Chapter 16 Outline Below is an outline of Chapter 16. Chapter 16 Outline Below is an outline of Chapter 16. Chapter 16 Outline The Cell Craft Challenge Install and Play CellCraft until you complete the 5th level. Download Cell Craft from here As you play the game, keep track of your success by filling out the cell craft worksheet (attached below).
Epigenetics | BioNinja Understanding: • Nucleosomes help to regulate transcription in eukaryotes Eukaryotic DNA is wrapped around histone proteins to form compact nucleosomes These histone proteins have protruding tails that determine how tightly the DNA is packaged Modification of Histone Tails Typically the histone tails have a positive charge and hence associate tightly with the negatively charged DNA Adding an acetyl group to the tail (acetylation) neutralises the charge, making DNA less tightly coiled and increasing transcriptionAdding a methyl group to the tail (methylation) maintains the positive charge, making DNA more coiled and reducing transcription Acetylation of Nucleosomes Types of Chromatin When DNA is supercoiled and not accessible for transcription, it exists as condensed heterochromatin When the DNA is loosely packed and therefore accessible to the transcription machinery, it exists as euchromatin Nucleosome Packaging in Euchromatin and Heterochromatin Skill: Epigenetics Adapted from:
Blog - Ricki Lewis Insights From Identical Twins Chromosome 3 pairs in each set of twins are digitally superimposed. One twin's epigenetic tags are dyed red and the other twin's tags are dyed green. When red and green overlap, that region shows up as yellow. The insight we gain from studying twins helps us to better understand how nature and nurture work together. Depending on the study and the particular trait of interest, data is collected and compared from identical or fraternal twins who have been raised together or apart. Twin studies have identified some traits that have a strong genetic component, including reading disabilities like dyslexia.