Student Genetics PDF

10/3/24 SPECIES HEREDITY ▣ The genetic endowment that members of a species have in...

10/3/24 SPECIES HEREDITY ▣ The genetic endowment that members of a species have in common, including genes that influence maturation and aging processes. EVOLUTION, GENETICS, □ Ex. Human can feel guilty but cannot fly. and DEVELOPMENT 2 1 2 THEORY OF EVOLUTION THREE MAIN ARGUMENTS ▣ There is genetic variation in a species ▣ the single most influential theory in the □ Some members of the species have different genes biological sciences. (and therefore different genetically influenced ▣ first to amass a large body of supporting traits) than other members of the species do evidence and the first to suggest how ▣ Some genes aid adaptation more than others do. □ Those with the genes for strength and intelligence evolution occurs would likely be better able to adapt to their environment 3 4 3 4 THREE MAIN ARGUMENTS Theory of Evolution ▣ Genes that aid their bearers in adapting to their NATURAL SELECTION FITNESS environment will be passed to future generations the member of each species vary Ability of an organism to survive greatly in their structure, and contribute its genes to the more frequently than genes that do not. physiology, and behavior and that next generation. □ natural selection—the idea that nature “selects,” or the heritable traits associated allows to survive and reproduce, those members of with high rates of survival and a species whose genes permit them to adapt to reproduction are the most likely ones to be passed on to future their environment generations 5 6 5 6 1  10/3/24 INDIVIDUAL HEREDITY FUNDAMENTALS OF GENETICS 7 8 7 8 Chromosomes: Reproduction and Human Genome Project Recombination Determination of Sex ▣ Chromosomes ▣ Gametes -> meiosis Genetic Code and Gene FUNDAMENTAL ▣ Fertilization -> genetic recombination Expression □ Identical twins GENETICS □ Fraternal twins Sex Chromosomes and Sex- linked Traits Polygenetic Inheritance 9 10 9 10 Human Genome Project DETERMINATION OF SEX ▣ The father dictates the sex of the child ▣ Male Child: XY chromosomes ▣ Female Child: XX Chromosomes 11 12 11 12 2  10/3/24 Translation and Expression of Genetic Code GENE EXPRESSION ▣ Genotype – genetic makeup a person inherits ▣ Because all of a person’s cells have the same genes on the same chromosomes, what makes brain, blood, and other cells different ▣ Phenotype – characteristics or trait the person from each other is not what genes they contain but which of those genes are expressed. eventually has. ▣ Gene Expression - the activation of particular genes in particular cells ▣ Environment influences combine with of the body at particular times; only if a gene is “turned on” is it influential genetic influences to determine how a particular genotype is translated into a particular phenotype 13 14 13 14 MECHANISM OF INHERITANCE Sickle-Cell Disease ▣ Single gene-pair inheritance – human ▣ About 9% affected in U.S. characteristics are influenced by one pari of □ Homozygous recessive (ss) genes ▣ Heterozygous: (Ss) “carriers” ▣ Dominant gene – it will be expressed when □ Can transmit gene to offspring paired ▣ Incomplete dominance ▣ Recessive gene – weaker gene that can be □ Will not have the disease dominated □ May have sickling episodes 15 16 15 16 Sex-linked Inheritance ▣ Single genes located on sex ▣ Incomplete dominance chromosomes ▣ Actually X-linked ▣ Codominance ▣ Males have no counterpart on Y chromosome ▣ Females have counter on second X □ Requires gene on both X’s for trait ▣ Hemophilia, Colorblindness, Duchene MD 17 18 17 18 3  10/3/24 CHROMOSOMES: STRUCTURE AND POLYGENIC INHERITANCE REPLICATION ▣ Polygenic traits - they are influenced by multiple pairs of genes, interacting with environmental factors, rather than by a single pair of genes. DNA Replication ▣ Most human characteristics □ Height, weight, intelligence, temperament □ Multiple pairs of genes Errors in Replication □ Normally distributed ▣ Mutations: Change in structure/arrangement □ Produces new phenotype □ Sperm more likely than ova Mutations □ Harmful or beneficial 19 20 19 20 Chromosomal Abnormalities Sex Chromosome Abnormalities ▣ Errors in chromosome division: Meiosis ▣ Turner’s syndrome: 1/3000 females □ Too many or too few chromosomes □ Single X chromosome (XO) ▣ Most spontaneously aborted □ Small, stubby fingers, sterile ▣ Down syndrome: Trisomy 21 ▣ Klinefelter syndrome: 1/200 males □ Physical deformities □ XXY, tall, sterile, feminine traits □ Mental retardation ▣ Fragile X syndrome: mental retardation □ Related to age of parents □ Leg of X barely connected □ Sex-linked: affects mostly males 21 22 Genetic Diagnosis and Counseling Behavioral Genetics ▣ Tay-Sachs disease ▣ Genetic/environment cause of trait □ Cause: recessive gene pair ▣ Heritability estimates (genetic) □ European Jews/French Canadians ▣ Methods of studying ▣ Huntington’s Disease □ Experimental and selective breeding □ Single dominant gene Tryon’s maze-bright rats ▣ Learn about risk to unborn child □ Twin, adoption, family studies ▣ Learn about nature, inheritance and effects of Reared together or apart genetic disorders in family history Concordance rates 23 24 4  10/3/24 Estimating Influences ▣ Genetic similarity □ Degree of trait similarity in family members ▣ Shared environmental influences □ Living in the same home ▣ Nonshared environmental influences □ Unique experiences Figure 3.4 25 26 Accounting for Individual Differences ▣ Correlations highest in identical twins □ Genetic factors determine trait ▣ Correlations higher if twins reared together □ Environmental factors ▣ Correlations are not perfect □ Nonshared experiences ▣ Identical twins more alike with age 27 28 Temperament and Personality Psychological Disorders ▣ Temperament correlations ▣ Schizophrenia concordance rates □ MZ twins =.50 to.60 □ MZ = 48%: DZ=17% □ DZ twins = 0 □ Affected parent increases risk: 13% ▣ Personality correlations similar ▣ Inherited predisposition □ DZ shared environment unimportant □ Environmental factors – triggers □ Same home - different personalities □ Prenatal exposure to infection suspected □ Nonshared environment and genes important 29 30 5  10/3/24 Gene/Environment Correlations Genetic Influences on Environment ▣ Finding: Parents who read to their children have ▣ E.g., Sociable genes brighter children. Why? □ Passive G/E correlations □ Environment: reading to child makes them Parents create social home brighter □ Evocative G/E correlations □ Genetic: brighter parents more informed or they enjoy reading themselves Smiley baby gets more social stimulation ▣ Finding: Aggressive children have hostile parents. □ Active G/E correlations □ Genetic: inherited behaviors Child seeks parties, friends, groups, etc. □ Environment: growing up with negative, hostile parents causes the behavior 31 32 Controversies Surrounding Genetic Research ▣ Identification of carriers of diseases and disorders ▣ Giving information which leads to abortion ▣ Experimenting with techniques for genetic alteration ▣ Better parenting if child’s genetic predispositions understood 33 6