ANTB14 CH2.odt

6 Pages
Unlock Document

University of Toronto Scarborough
Michael Schillaci

CHAPTER 2: MICROEVOLUTION & EVOLUTIONARY ANTHROPOLOGY Microevolution: small changes in biological evolution, such as a population's gene pool over a succession of generations -an understanding of inheritance allows know exactly what is going on at the genetic level -there are two types of cells: eukaryotic and prokaryotic >eukaryotic cells contain a nucleus whereas a prokaryotic cell does not >nucleus: part of a eukaryotic cell containing genetic material >w/in a nucleus is chromosomes which are double-stranded DNA molecule in nucleus of eukaryotic cells that carries genes and functions in the transmission of hereditary information -each eukaryotic cell can duplicate itself in a process known as mitosis which is a cellular division resulting in two identical daughter cells w the same number of chromosomes as the parent cell -important to inheritance and evolutionary processes: meiosis is a process in which cellular division results in the formation of haploid cells that determine an organism's sex (sex cells or gamete-sperm or egg) >meiosis provides the hereditary material passed bw generations in sexually reproducing species (i.e., humans & mammals) -humans have 23 pairs of chromosomes in diploid cells-one set inherited from father & and the other from mother-->of these pairs, 2 determine sex of offspring -each human has the same version of each gene • humans don't pass on 23 pairs of chromosomes to reproduce from biological mother & father. What actually happens is that each gamete (egg or sperm) has only half the total number of chromosomes (23 unpaired in humans) known as the haploid number. When the germ cells are joined, the baby receives the normal 23 matched pairs—therefore, each gamete contains 22 autosomes which are chromosomes not involved in determining sex and one sex chromosome (X&Y) Mitosis and meiosis. Mitosis is how most cells make copies of themselves whereas meiosis produces sex cells. In meiosis, the daughter cells contain only a single set of chromosomes (i.e., half the normal number of chromosomes). The red and blue colours indicate differing alleles. During meiosis, genetic material may cross over from one section of a chromosome to another. During production of sex cells: recombination or cross over takes place, this is a process by which two homologous (23 chromosomes) exchange genetic material during gamete production >this happens BEFORE fertilization takes place >gene mixing during gamete production results in each baby's inheriting a unique combination of genes from its forebears >recombination important for biological evolution bc it can introduce new combinations of genes every generation BUT it can also break up “good combinations” of genes • -the hereditary material in the nucleus is called deoxyribonucleic acid (DNA), which is a double stranded helix and looks like a twisted step ladder. The outside eails are strongly held by a “chemical glue”, sugar-phosphate chemical bonds which form backbone of DNA >the rungs of the ladder (where I would step) are composed of four nucleotide bases [adenine (a), cytosine (c), thymine (t), and guanine (g)] which is a building block of DNA consisting of a base, sugar and phosphate group >the sequence of four nucleotide base pairs is the genetic blueprint for every creature that has ever lived on Earth -in the nucleus, DNA doesm't just float around but rather is wrapped tightly a spool-like protein known as HISTONES -the centre of a chromosome contains a CENTROMERE which plays critical role in cell division and expression -each chromosome is crapped by a special section of DNA called TELOMERE which protects endings of chromosomes from damage *tight packaging is required to fit DNA molecules into the small nucleus w/in a cell FUNCTION of DNA: it contains the genetic “blueprint” necessary for specifying the sequence of amino acids (one of a class of 20 molecules that are combined to form proteins in living things) that comprise proteins (a large molecule composed of a specific sequence of amino acids) -structural proteins form basic building blocks of every part of one's body from brain cells to skeleton to skin -prof says protein in turn is responsible for expression of phenotype Protein formation is 2 step process involving transcription and translation -transcription: process by which genetic information from DNA is tranferred into RNA >in essence, it is the biological means of copying the DNA code in the nucleus and then getting it out into the cytoplasm where protein formation takes place -think of NUCLEUS as head office for protein-building contract, the DNA as blueprint for producing protein -DNA cannot leave head office so therefore the cell needs a copy made of the blueprint (nucleotide sequence) on one side of the DNA strand so the rungs (nucleotides) of the DNA are unzipped, -a special form of RNA (ribonucleic acid) often called messenger of mRNA makes a mirror image of the blueprint (nucleotide sequence) -->remember: the THYMINES on DNA are replaced with uracils (u) on the mRNA this replacement serves principally to protect the DNA from errors during protein formation -genetic info encoded in DNA is transferred to mRNA which acts as a messenger carrying the genetic blueprint (the nucleotide sequence) out of head office (nucleus) and into the cytoplasm of the cell, where TRANSLATION occurs Definitions RNA: single-stranded nucleic acid. The primary function of RNA in a cel is the step between DNA and protein synthesis Cytoplasm:internal fluid (called cytosol), dissolved materials, and cellular organelles in a cell, except for the nucleus. The cytoplasm is the primary sitre for chemical activity in the cell. Translation: process by which information coded in sequence of mRNA is translated into sequence of amino acids in a protein (SECOND STEP OF PROTEIN FORMATION) Translation: Process involves mRNA, ribosomes (factories), tRNA (factory workers) and amino acids Ribosomes: are the factories in the cell; w/in a factory, the amino acids that constitute each protein are specified by a sequence of THREE nucleotides in mRNA, known as a codon, which is a sequence of three base pairs that codes for specific amino acid -there are multiple codons for each of the 20 standard amino acids in proteins i.e., CGU, GGG, GGC -a final RNA molecule is needed to transfer a specific amino acid to the growing protein, which is typically called transfer RNA or tRNA >think of tRNA as the “factory worker” who reads the blueprint (nucleotide sequence) provided by the messenger (mRNA) and assembles the “building materials” (amino acids) in the factory (ribosomes) >each factory worker has an anticodon, which is a unit made up of three nucleotides that correspond to the sequence of three bases of the codon on the mRNA-->therefore, the anticodon decodes the genetic information on the messenger >each factory worker also has a receptor site for one amino acid specific to an anticodon therefore the tRNA w the code AATTGC has the following two anticodons: AAT and TGC. The protein factory (ribosome) moves along the blueprint (nucleotide sequence) provided by the messenger (mRNA). The worker tRNA then “reads” (translates) this information and brings in the correct “building materials” (amino acids). The building materials (amino acids) are joined together at the factory (ribosome) to form a protein Definitions -ribosome: a structure w/in cells that manufactures proteins by linking together amino acids according to the coded sequence on a strand of mRNA -codon: genetic information encoded in a sequence of three nucleotides (in mRNA) -anticodons: a complementary three nucleotide site on the tRNA that recognizes and binds to a specific codon on the mRNA during protein synthesis -mutation: an error or alteration of a nucleotide sequence, which represents the ultimate source of new genetic material in populations -results from 4 things: 1) copying errors in the genetic material during cell division 2) exposure to ultraviolet or ionizing radiation—UV radiation produced by or tanning beds is most related to human health 3) chemical mutagens 4) viruses -not all mutations are directly relevant to evolutionary processes in populations thus there are two classes of mutation 1)somatic cell mutations are changes to the nucleotide sequence of the genetic material in body cells expect those in sperm or egg, they cannot pass from one generation to the next so the genetic changes have little relevance to evolutionary processes 2)germ cell mutations: are changes to the nucleotide sequence of the genetic material in sex cells, they involve heritable materials and can therefore be passed on to descendans— -mutations are random & do not serve needs of an organism -mutations can either be neutral, beneficial, or harmful (most are neutral and typically result from a change in the nucleotide sequence of a DNA strand but do not alter the genetic code for an amino acid) >however a mutation in one nucleotide sequence can produce a diff amino acid and protein which can be harmful to the host -there are few direct relationships among a gene, a mutation or a trait >discontinuous variation refers to genetic characters that are either di
More Less

Related notes for ANTB14H3

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.