Chapter 3 - Exam Notes
Chapter 3 - Exam Notes Typical Cell Nucleus: Contains 46 chromosomes in each somatic cell (23 from mother, 23 from father), stores majority of genetic information (DNA) Somatic Cell: Most cells in the body (not sex cells) --> 46 chromosomes Gametes: Sex cells (sperm and egg) --> 23 chromosomes Chromosomes: Long strands of tightly coiled DNA, paired structures, in nucleus * Each allele for a specific trait is located in same place on every chromosome * 2 alleles (1 mom, 1 dad) Human Genetics - 46 chromosomes (23 pairs) --> carry TONS of genes - Sperm has an X, Y (males determine sex of baby) - Number of chromosomes is different depending on species - Number of chromosomes is not related to amount of DNA - Some DNA non coding (can replicate and would not make a difference) Mitochondrial DNA Mitochondria: Power house of cell, generated most of energy - Mito. DNA found in cytoplasm - Inherited by mother --> eggs have mitochondria, sperm don't - Y chromosome only be passed from father to son (easier to trace line) DNA: Deoxyribonucleic Acid - Double helix - Genetic information stored in sequence of bases (nucleotides) * Adenine-Thymine * Guanine-Cytosine - Base pairs on sugar phosphate backbone - Order of base pairs that determines genetic code - Genes 'recipe' for making specific proteins * 'Recipe' passed down from generation to generation - Gene regulators can turn genes on and off DNA Replication - Identical copies are made - Happens before cell division - Parental strand is used as template for new daughter strands - Parent template separated by DNA polymerase into 2 identical daughter strands Cell Division a) Mitosis - Cell division to produce somatic cells (non-sex--> 46 chromosomes) - Undergone for growth and reproduction of body cells 1
- DNA is replicated - Replicated DNA (pairs of chromosomes) lineup down middle of cell - Cell divides, DNA separates (one goes to each new cell) - Produced 2 diploid daughter cells --> have 46 pairs of chromosomes b) Meiosis - Produces 4 haploid daughter cells --> 23 chromosomes * Reproductive cells * Half of each chromosomes pair in every egg and sperm Homologous Chromosomes: One chromosome from mom, one from dad Genetic Recombination: Some genes cross over at random points (reshuffled) - Sperm fertilizes the egg (2 complete sets of chromosomes) Building Proteins - Function of DNA - Genes (or genetic code) are copied (or transcribed) into mRNA (messenger RNA) - mRNA attached to a ribosome which uses info on mRNA to make proteins - mRNA is read 3 'letters' at a time --> called codons - Each codon is a code for an amino acid - Amino acids join together to make proteins - DNA codes for proteins --> genotype turns into a phenotype How Does Genetic Variation Arise? - Change in nucleotide sequence of DNA during cell division - DNA replication is not a perfect process (copying/translation errors) * Change in the structure of the DNA * Non-coding (doesn't represent a specific trait) - Some mutations can cause change in phenotype (but not all) Mutations - Random=spontaneous (copying errors during DNA replication) - Induced mutations (DNA damaged from environmental sources) - DNA repair slows as w age - Mutations can be inherited ONLY if occurs in a sex cell (sperm or egg) * Mutation on sex chromosomes will be passed onto next generation - Mutation is only source of new variation in populations a) Point Mutations --> incorrect base pairing (replacement of a single nitrogen base with another) Synonymous Point Mutation: Altered triplet in DNA, still codes for same amino acid Nonsynonymous Point Mutation: Altered triplet in DNA, codes for different amino acid b) Frame Shift Mutations --> Insertion of deletion of a nitrogen base
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Transposable Elements: Mobile pieces of DNA that copy themselves into new areas of chromosome What are SNP's - Single nucleotide polymorphism (single base pair substitution) - Difference in appearances - Develop diseases - Respond to drugs - Most lead to no observable differences between people How Does Evolution Occur? - Evolution required genetic variety - Mutations are the only source of genetic variation in a population - 4 forces that change gene frequencies 1. Mutation 2. Natural Selection - Trait must be inherited to have any importance in natural selection - Fitness (reproductive success) will change as conditions change - Pre-industry --> lichen covered trees = light colouring is adaptive - Post- industry --> dark trees= Dark colouring is adaptive 3. Genetic Drift 4. Gene Flow Genetic Drift - Random processes that effected gene frequencies in isolated populations - Reduce variation in population a) Founder Effect - Small population moves to a new locale and becomes isolated - ie. Red ladybugs get blown on island (basis of new population) b) Bottleneck Effect - An event (natural disaster, disease, predators) that reduced population to a smaller group - Population size may increase but diversity is lost * As population re-grows has very limited amount of genetic variability available - Mutations will give rise once again (slow process, will take time) Gene Flow - Genes pass from one gene pool from one population to another - Over time variation decreases between population a) Intermixture - Genes exchanges between populations (not actual movement of individuals) 3
b) Migration - Movement of gene pool in space (physical movement) Sickle Cell Anemia - Results from mutation on chromosome 11 - Abnormal haemoglobin -- reduced availability to transport oxygen - AS (one mutant allele) confers some resistance to malaria (adaptive) - SS (two mutant alleles) 'full' sickle cell disease - Cell tends to sickle when infected by malaria parasite Balances Polymorphisms Polymorphism: Occurrence of two or more genetic (or phenotypic) variants within a population Balance Polymorphism: When natural selection favours heterozygous (AS) individuals Misconceptions About Natural Selection - Natural selection/evolution do NOT have an 'ultimate goal' - Natural selection acts of variability within a population (cannot supply what an organism NEEDS) Evolution of New Species (Macroevolution) Theories for how species evolve (COMPETING IDEAS) 1. Phyletic Gradualism - Gradual changes in gene pool slowly accumulate over time (Slowly species A turns into B) - ie. Giraffe Necks 2. Punctuated Equilibrium - After long periods of time with little to no change and isolation event occurs, separate small population - With A different gene pool and burst of mutations, new species evolves - Genetic variation is essential for evolution to occur - Genetic variation produced through genetic recombination and mutation Evolution: A change in gene frequency in a population over time
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- DNA is replicated - Replicated DNA (pairs of chromosomes) lineup down middle of cell - Cell divides, DNA separates (one goes to each new cell) - Produced 2 diploid daughter cells --> have 46 pairs of chromosomes b) Meiosis - Produces 4 haploid daughter cells --> 23 chromosomes * Reproductive cells * Half of each chromosomes pair in every egg and sperm Homologous Chromosomes: One chromosome from mom, one from dad Genetic Recombination: Some genes cross over at random points (reshuffled) - Sperm fertilizes the egg (2 complete sets of chromosomes) Building Proteins - Function of DNA - Genes (or genetic code) are copied (or transcribed) into mRNA (messenger RNA) - mRNA attached to a ribosome which uses info on mRNA to make proteins - mRNA is read 3 'letters' at a time --> called codons - Each codon is a code for an amino acid - Amino acids join together to make proteins - DNA codes for proteins --> genotype turns into a phenotype How Does Genetic Variation Arise? - Change in nucleotide sequence of DNA during cell division - DNA replication is not a perfect process (copying/translation errors) * Change in the structure of the DNA * Non-coding (doesn't represent a specific trait) - Some mutations can cause change in phenotype (but not all) Mutations - Random=spontaneous (copying errors during DNA replication) - Induced mutations (DNA damaged from environmental sources) - DNA repair slows as w age - Mutations can be inherited ONLY if occurs in a sex cell (sperm or egg) * Mutation on sex chromosomes will be passed onto next generation - Mutation is only source of new variation in populations a) Point Mutations --> incorrect base pairing (replacement of a single nitrogen base with another) Synonymous Point Mutation: Altered triplet in DNA, still codes for same amino acid Nonsynonymous Point Mutation: Altered triplet in DNA, codes for different amino acid b) Frame Shift Mutations --> Insertion of deletion of a nitrogen base
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Transposable Elements: Mobile pieces of DNA that copy themselves into new areas of chromosome What are SNP's - Single nucleotide polymorphism (single base pair substitution) - Difference in appearances - Develop diseases - Respond to drugs - Most lead to no observable differences between people How Does Evolution Occur? - Evolution required genetic variety - Mutations are the only source of genetic variation in a population - 4 forces that change gene frequencies 1. Mutation 2. Natural Selection - Trait must be inherited to have any importance in natural selection - Fitness (reproductive success) will change as conditions change - Pre-industry --> lichen covered trees = light colouring is adaptive - Post- industry --> dark trees= Dark colouring is adaptive 3. Genetic Drift 4. Gene Flow Genetic Drift - Random processes that effected gene frequencies in isolated populations - Reduce variation in population a) Founder Effect - Small population moves to a new locale and becomes isolated - ie. Red ladybugs get blown on island (basis of new population) b) Bottleneck Effect - An event (natural disaster, disease, predators) that reduced population to a smaller group - Population size may increase but diversity is lost * As population re-grows has very limited amount of genetic variability available - Mutations will give rise once again (slow process, will take time) Gene Flow - Genes pass from one gene pool from one population to another - Over time variation decreases between population a) Intermixture - Genes exchanges between populations (not actual movement of individuals) 3
b) Migration - Movement of gene pool in space (physical movement) Sickle Cell Anemia - Results from mutation on chromosome 11 - Abnormal haemoglobin -- reduced availability to transport oxygen - AS (one mutant allele) confers some resistance to malaria (adaptive) - SS (two mutant alleles) 'full' sickle cell disease - Cell tends to sickle when infected by malaria parasite Balances Polymorphisms Polymorphism: Occurrence of two or more genetic (or phenotypic) variants within a population Balance Polymorphism: When natural selection favours heterozygous (AS) individuals Misconceptions About Natural Selection - Natural selection/evolution do NOT have an 'ultimate goal' - Natural selection acts of variability within a population (cannot supply what an organism NEEDS) Evolution of New Species (Macroevolution) Theories for how species evolve (COMPETING IDEAS) 1. Phyletic Gradualism - Gradual changes in gene pool slowly accumulate over time (Slowly species A turns into B) - ie. Giraffe Necks 2. Punctuated Equilibrium - After long periods of time with little to no change and isolation event occurs, separate small population - With A different gene pool and burst of mutations, new species evolves - Genetic variation is essential for evolution to occur - Genetic variation produced through genetic recombination and mutation Evolution: A change in gene frequency in a population over time
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