ANTH 1001 Week 3
ANTH 1001 Week 3 Anth 1001
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This 6 page Class Notes was uploaded by Aafreen Afzal on Friday January 22, 2016. The Class Notes belongs to Anth 1001 at George Washington University taught by Shannon C. McFarlin in Spring 2016. Since its upload, it has received 9 views. For similar materials see Biological Anthropology in anthropology, evolution, sphr at George Washington University.
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Date Created: 01/22/16
Class 4 Lecture Notes ➔ (contd.) Receptions of Darwin’s book ◆ By Darwin’s death in 1882, his funeral was held at Westminster Abbey so it showed that he had become well respected as he was buried close to Newton, kings, queens, etc. ➔ MECHANISMS OF INHERITANCE: Mendel and his experiments ◆ Pre-DNA Concepts of Heredity: Blending Theory of Inheritance ◆ Gregor Mendel (1822-1884) ◆ He undertook a systematic investigation of inheritance using very large numbers of pea plants ◆ Demonstrated particulate inheritance ◆ The Garden Pea Plant - he chose it because it was easy to control pollination and because it showed variation in a number of different traits. ◆ Pure breeding lines could be identified ❖ MENDEL’S CONCLUSIONS ➢ PARTICULATE INHERITANCE ■ Each hereditary characteristic is controlled by particulate unit factors, which exist in pairs in individual organisms; one factor is inherited from each parent ■ These factors remain discrete, i.e: unchanged, regardless of external appearance ➢ DOMINANCE ○ When 2 different unit factors relate to a characteristic, only one is expressed (dominant) while the other is not (recessive) ○ There must be two copies of the recessive factor present for a recessive form to be expressed. TERMS AND DEFINITIONS ❏ Phenotype: The observable or detectable expression (e.g. appearance) of a trait ❏ Genotype: The full set of genetic factors that interact in determining the phenotype ❏ Homozygous: When two copies of the same genetic factor controlling a trait are present in an individual (=true breeding lines) ❏ Heterozygous: When two different genetic factors for a trait are present in an individual (=Hybrid) Chromosome ● Gene: Genetic material that encodes for the expression of a particular trait ● Locus: Location of a gene on a chromosome ● Allele: Alternative versions of a gene -one gene, but two or more alleles ● Both chromatids in a chromosome are identical (the result of the replication of the DNA molecule) ● Both homologous chromosomes in a pair are different (one comes from the father and one from the mother) They have the same loci but may have different alleles. Human Karyotype ● 46 chromosomes (23 pairs) ● Autosomes (1-22) Traits other than sex, eye and hair colour ● Sex Chromosomes (Pair 23 X and Y) (Female XX) (Male XY) Each species has a particular number of chromosomes in somatic cells ● Indian fem = 1,260 ● Garden peas = 14 ● Roundworm = 2 ● Boa constrictor CELL DIVISION ➔ Mitosis: Somatic Cells ➔ Meiosis Mitosis ● Mitosis is cell division in somatic cells ● Occurs during growth and repair/replacement of tissues ● The result of mitosis is two identical daughter cells, which are genetically identical to the original cell (2 diploid cells) ● Interphase, Prophase, Metaphase, Anaphase, Telophase ● I. Interphase: DNA replication (90-95% of their life cycle), nucleus is visible there and the chromosomes exist in a spaghetti like form, appear as chromatin, uncondensed form. The DNA replicates itself to produce an identical copy. ● II. Prophase: Replicated DNA is now in a condensed form that looks more like the chromosome appearance. Chromosome contains 2 identical sister chromatids. ● III. Metaphase: This is where there are some distinctions between Mitosis and Meiosis. In Mitosis (somatic cells), chromosomes line up single file along the equator of the cell containing one sister chromatid on one side of the equator and the other sister on the other side. ● IV. Anaphase: The two sister chromatids separate and one copy of the genetic material goes to one side and the other copy goes to the other ● V. Telophase: Results in two daughter cells (diploid) with identical copies of genetic material. Final stage of Mitosis. Meiosis ● Production of gametes (sex cells) ● Characterized by two rounds of division that result in four daughter cells, each of which contains 23 chromosomes (4 haploid cells) in humans ● Fertilization restores the full complement of chromosomes (diploid number of 46) to the zygote. ● I. Interphase: DNA Replication. ● II. Prophase: Crossing over genetic combination. Homologous pairs find each other. Two sister chromatids look different now because there is a crossover of genetic material. Reshuffling of genetic info. ● III. Metaphase I: Chromosomes align in homologous pairs; random assortment of chromosome members with respect to either side of the equator. ● IV. Anaphase I: Members of chromosome pairs separate (reduction division) ● V. Telophase I ● Interkinesis I: ● Result of Meiosis division 1: Each daughter cell inherits half as many chromosomes as the original cell, only one member of each homologous pair (i.e. haploid) ● Each chromosomes has two chromatids, but they are different because of crossing over ● There has been recombination of genetic material from the mother and father. ● Metaphase II: Chromosomes line up single file at equator (similar to Mitosis metaphase) Mendel’s laws of particulate inheritance ➔ Law of Segregation ◆ Paired hereditary factors segregate randomly during formation of the gametes ➔ Law of Independent Assortment ◆ Factors controlling for inheritance of different traits assort independently of one another ● Exception: Applies to genes located on different chromosomes but genes Evolutionary Significance of Meiosis ● Meiosis increases genetic variation ○ Crossing over (genetic recombination) ○ Random assortment (genetic recombination) ○ Mutation (source of new variants) only mutations occurring during Meiosis are heritable. Provides the raw materials for natural selection to act upon. Genetics II: From Genotype to Phenotype Outline Mechanisms of Inheritance: Mendel and his experiments Biological role of genetic material: 1. Accurate replication 2. Stable structure 3. Capable of coding for diverse information, including proteins 4. Capable of transmitting this information, to regulate development and normal cell functioning\ ➔ DNA ◆ Nucleic acid ◆ resides in the nucleus of the cell ◆ stores and transmits information ◆ made up of smaller structures called nucleotides ◆ Each nucleotide contains 1 of 4 different bases with one exception ◆ Structural difference between purines and pyrimidines have important consequences for nucleotide matching. ◆ Bases: Adenine = Thymine. Cytosine = Guanine ◆ Functions Replication, Protein S DNA replication ● occurs during cell division ● Original polynucleotide strands separate, leaving their bases exposed. ● Original strands -> Templates for two complementary strands. ● Results in two identical copies of the DNA molecule Protein Synthesis (from genotype to phenotype) ● Genotype = underlying genes ● Phenotype = physical outcome ○ Proteins may serve as structural components of body tissues or play active functional roles. Amino acids, polypeptide chains and proteins ● Amino acids subunits are linked together to form linear polypeptide chains ● 20 different amino acids gene: sequence of DNA bases that carries information for synthesizing a particular protein, and occupies a specific chromosomal locus. Protein synthesis takes place outside the nucleus. RNA - Ribonucleic acid is formed from the template strand of a DNA molecule. Protein Synthesis 1: ● Happens inside the nucleus ● DNA splits in region of gene and attracts complementary ribonucleotides. DNA Mutation - An alternation in the genetic code; source of new variants - Chromosomal mutations: Change in chromosome number, usually happens in cell division - Point mutations: AGC TCC CTA -> AGG TCC CTA - Duplication: AGC TCC CTA -> AGC AGC TCC CTA - Inversion: AGC TCC CTA -> CGA TCC CTA - Deletions (frameshift) AGC TCC CTA T… -> ACT CCC TAT When mutation occurs at the level of the nucleotide base, it may or may not alter function - Synonymous mutation: - AGC TCC CTA -> AGG TCC CTA - Change to a functionally equivalent amino acid DNA Mutation ● Mutations are constantly occurring at random; they may also be induced by other agents ● Mutations may be functionally irrelevant; of those that are functionally significant, many are lethal or have negative consequences. Others may be neutral. ● A small proportion may be beneficial and confer selective advantages ● If the mutation occurs during meiosis, it may be passed to the next generation Mendelian inheritance: ● single gene, autosomal, dominant-recessive model useful for examining traits with qualitative variation (discrete categories) ● Codominance: Both alleles in the heterozygous condition are fully expressed with neither being dominant over the other ● ABO blood system ● Sex Linkage (X-linked traits): Controlled by genes on the X chromosome, more commonly expressed in males. As males (XY) have only one X chromosome, any allele will be expressed, whether dominant or recessive ● Polygenic traits with quantitative (continuous) variation, influenced by two or more genes - stature, skin color, eye color. Many genes contribute to a single effect. ● Pleiotropy: A single gene influences the expression of multiple traits simultaneously - Marfan syndrome. Genetics beyond Mendel (The Complex Genome) Types of Genes ● Structural genes ● Regulatory genes ○ Homeotic genes ● Introns and exons ● Non protein coding regions: Introns, Pseudogenes
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