GENETICS
What do you remember about genetics? List key terms that come to mind….
The branch of human Biology that deals with inheritance Often referred to as the science of heredity and variation in living organisms.
TWO MAJOR DIVISIONS OF GENETICS
Mendelian Gentics • Founded by Gregor Mendel • Developed the basic concepts of heredity by applying knowledge of inheritance of characteristics Modern Genetics • Currently being studied today • Seeks to understand the mechanisms( reasons/modes) for inheritance
DNA and its Structure n DNA stands for Deoxyribonucleic acid Located in the nucleus of each cell. n n Video Role: to maintain genetic continuity and carry all genetic info of the cell
n n Aim: How are genetic traits passed from parent to offspring? DN: n n n What is an organelle – give an example. What is an active site? What is it specific to? Which reproductive structure is responsible for the “exchange of materials” between mother and fetus? What type of molecule is capable of mutating? HW: Review book pages 50 -51 q’s 23 -31
Chromosomes: package DNA
DNA: n n Code of Life Housed in nucleus Controls all cell activities Is replicated when passed from one generation to the next or when cells divide (mitosis)
The structure of DNA was discovered by two scientist known as Watson and Crick. How would you describe a DNA molecule?
A DNA MOLECULE LOOKS LIKE A TWISTED LADDER. n This Twisted ladder structure is known as a double helix.
Job Description of DNA Must store information n Must be “copy-able” n Must be strong and stable n Must be capable of mutating, or changing, slightly to produce variation – which leads to evolution n
Some History… Mendel performed experiments on pea plants n Discovered “Genes” are located at a specific area on a chromosome. n Alleles two genes associated with a specific trait – (one from mom, one from dad) n
Aim: How are genetic traits passed from parent to offspring? n n DO NOW: Review book p 9 #20 -35 Homework: Castle learning “Genetics 1 & 2”
DNA n is a polymer (large molecule) made up of repeating chemical units called nucleotides.
Nucleotide n Composed of three separate subunits: n n n Phosphate group Deoxyribose: 5 carbon sugar Nitrogenous bases: Adenine (A) Thymine (T) Guanine (G) Cytosine (C)
What is a gene? n A gene n n gene n Is a section of the DNA molecule that codes for the production of a specific protein. Determines characteristics of the organism. Inherited
What are Genes? Genes = code language for protein, and proteins give your physical traits n A chromosome contains many genes n A gene is made up of lots of DNA. Put the following terms in order from n Big-------- Small: Nucleus, Cell, DNA, Genes, Chromosomes
An Allele Can Either be: n Dominant the expressed allele n n CAPITAL LETTER Recessive the covered up allele (unless both alleles are recessive) n lowercase letter
Let's Test Your Ability to See Colors?
n n n Phenotype physical traits (observable) an organism has Genotype the actual alleles (genes) an organism has Homozygous person has two identical alleles for a particular trait (TT or tt) (“purebred”) Heterozygous person has two different alleles for a particular trait (Tt) (“hybrid”) Polygenic Inheritance a trait controlled by two or more genes (ex. Eye color, skin color, blood group)
Summary of Genetics: n During fertilization there is random recombination of traits from each parent Random separation and distribution of paired chromosomes occurs during 1. 2. 3. 4. cleavage mitotic cell division fertilization meiotic cell division
n 1. 2. 3. 4. Two genes for two same traits located on the different chromosome are said to be homozygous independently assorted mutagenic agents linked
The diagram below represents the organization of genetic information within a cells nucleus. The circle labeled Z most likely represents a. ) chromosomes Nucleus b. ) amino acids Z c. ) vacuoles Genes d. ) molecular base n
4 Nitrogenous Bases 1. 2. 3. 4. Adenine Thymine Guanine Cytosine
Base Pair Rule: n n n Adenine (A) bonds to Thymine (T) n A-T or T-A Guanine (G) bonds to Cytosine (C) n G-C or C-G DNA Chains are COMPLEMENTARY
Practice
More Practice: If a DNA chain consists of the sequence ATTACGGCA What is its complementary sequence?
Answer…
When Can You Best See Your Chromosomes? n During Mitosis – all DNA is tightly coiled for accurate cell division!
What is DNA Replication? Process that creates an exact copy of DNA before a cell divides. n
DNA Replication n n Start with an original “template” Untwist “template” Template “unzips” by DNA Polymerase (enzyme) breaking hydrogen bonds that hold bases together Free-floating bases in nucleus attach to exposed bases Result two identical double strands – each made up of one ‘old’ and one ‘new’ strand
DNA unwinds, unzips and base pairs match up.
DNA Replication
Remember: Untwist Unzip Add the Bases Re-Twist!
Aim: How do the DNA and RNA molecule differ? Do Now: Which of the following arrangements lists the structures from largest to smallest? a chromosome a nucleus a gene 1. gene - chromosome - nucleus 2. gene - nucleus - chromosome 3. nucleus - gene - chromosome 4. nucleus - chromosome - gene
A researcher recently discovered a new species of bacteria in the body of a tubeworm living near a hydrothermal vent. He compared the DNA of this new bacterial species to the DNA of four other species of bacteria. The DNA sequences came from the same part of the bacterial chromosome of all four species. According to these data, the unknown bacterial species is most closely related to 1. 2. 3. 4. species III species IV
RNA - Ribo. Nucleic. Acid n n nucleotides ribose instead of deoxyribose Uracil(U) instead of Thymine (T) 3 types n n n messenger (m. RNA) n carries info from DNA transfer (t. RNA) n carries amino acids ribosomal (r. RNA)
DNA vs. RNA DNA • Double stranded molecule • Sugar = deoxyribose • Bases: A= adenine T= thymine G= guanine C= cytosine RNA • Single stranded molecule • Sugar = ribose • Bases: A= adenine U= uracil G= guanine C= cytosine
DNA vs. RNA
Protein Synthesis n n Protein synthesis is the process by which a cell synthesizes (makes) proteins from DNA (deoxyribonucleic acid). Process begins in the nucleus of the cell. Happens with the help of RNA (ribonucleic acid) The synthesis of the proteins takes place outside the nucleus in the ribosomes
Types of RNA n There are different types of RNA present in the cell Messenger RNA (m. RNA) and transfer RNA (t. RNA) n * Predict the functions of these types of RNA.
Transcription n The copying of a genetic message into a molecule of messenger RNA (m. RNA) is called transcription. Reads the message on the DNA molecule in groups of 3 bases called CODONS while in the nucleus. m. RNA then Carries the message to the ribosome in the cytoplasm.
Transcription
For the following DNA base sequences, write the complimentary messenger base sequence: n n DNA: TAT CGT AAC GGA TCG RNA: __________ n Answer: DNA: TAT CGT AAC GGA TCG RNA: AUA GCA UUG CCT AGC n ***Identify a codon? n
n n DNA: CCG ATA GGG TAA GCT RNA: __________ Answer: DNA: CCG ATA GGG TAA GCT RNA: GGC UAU CCC AUU CGA *Now Identify the Codon
Transfer RNA (t. RNA) n n Brings amino acids to the ribosome. Dependent on the codon sequence of m. RNA
Steps of Protein Synthesis n n n Begins in the nucleus DNA is copied and a strand of m. RNA is made. (transcription) m. RNA travels to the ribosomes in the cytoplasm. The codons are “read” by the ribosomes. This process is called translation. t. RNA transfers the proper amino acid (based on the codon sequence) to the ribosome for protein assembly. A protein (could be hundreds or thousands of amino acids long) is made.
Protein Synthesis
Protein Synthesis w x v Identify the parts. Is this transcription or translation?
Translation n The language of m. RNA consists of 4 letters: A, U, C, G. n n n Each word is only made up of 3 letters or bases. Every three bases is called a codon. A CODON codes for a specific amino acid that must be added to the polypeptide chain or protein. n There are 64 different codons for 20 amino acids.
m. RNA CODONS
Translation n n The START CODON is AUG and it codes for Methionine, which signals the beginning of translation. 3 STOP CODONS: UAA, UAG, UGA. DO NOT CODE FOR AN AMINO ACID. n n n They signal the end of a protein chain. t. RNA (transfer) is responsible for deciphering the codon and transferring the amino acid to the protein. Each t. RNA contains an anti-codon attached to one end and three bases called an anti-codon that are complimentary to the codon on the m. RNA.
Protein Synthesis Transcription Translation DNA ----- RNA ----- Protein Analogy: Pair the correct genetics term with the construction site examples given. Construction Site Analogy Blueprint to build house t. RNA DNA Workers carrying materials to house m. RNA The construction site Ribosome Messenger who brings instructions to worksite.
Changes in DNA: n Changes occur due to recombination, mutations & genetic engineering
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