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Today: Meiosis, producing genetically diverse offspring, and inheritance {Meiosis: producing gametes} For life to exist, the information (genes) must be passed on. {Mitosis: producing more cells} Voles Prairie Montane • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly Voles Prairie • Monogamous • Both parents care for young Montane • Nonmonogamous • Mother cares for young briefly Same levels of oxytocin and vasopressin • More receptors • Less receptors Why might these voles use different reproductive strategies? Prairie voles: Montane voles: Resource poor Resource rich habitat habitat • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly haploid X 23 in humans X 23 in humans diploid X 23 in humans Sexual Reproduction = The combination of genes inherited from Mom and Dad. Asexual Reproduction extremely low genetic diversity vs. Sexual Reproduction greater genetic diversity Asexual Reproduction genetically identical to parent (this tree can reproduce both sexually and asexually) Why does sexual reproduction exist? Cons: • Need two individuals • Hard to find mate • Diseases/Competition Pros: • Genetic diversity Screw worm flies F M sterile Sterile male screw worm flies led to decreased populations because of screw worm monogamy. F M sterile In most other species, because females mate with multiple males, introduction of sterile males has little effect. Sterile male screw worm flies led to decreased populations because of screw worm monogamy. F M sterile In most other species, because females mate with multiple males, introduction of sterile males has little effect. Hi, want to study biology together? M F fertile F M sterile 10-40% of offspring in “monogamous” bird species are fathered by an extra-pair male •Social Monogamy = pair lives/works together, but not “faithful” •Sexual Monogamy = pair raise young and only copulate with each other In mammals, child-rearing is most commonly done by the female. She provides milk. Less than 0.01% of mammals are monogamous Do Males and Females have different attitudes toward sex and relationships? On a college campus an attractive male or female asked the opposite sex: “I have been noticing you around campus. I find you very attractive…” Female answers: Male answers: …Would you go out …Would you go out with me tonight? with me tonight? = 50% yes = 50% yes On a college campus an attractive male or female asked the opposite sex: “I have been noticing you around campus. I find you very attractive…” Female answers: Male answers: …Would you go out with …Would you go out with me tonight? me tonight? = 50% yes = 50% yes …Would you come to …Would you come to my apartment my apartment tonight? tonight? = 6% yes = 69% yes On a college campus an attractive male or female asked the opposite sex: “I have been noticing you around campus. I find you very attractive…” Female answers: Male answers: …Would you go out with …Would you go out with me tonight? me tonight? = 50% yes = 50% yes …Would you come to …Would you come to my apartment tonight? my apartment tonight? = 6% yes = 69% yes …Would you go to bed …Would you go to bed with me tonight? with me tonight? = 0% yes = 75% yes Why do Males and Females have different attitudes toward sex and relationships? The male perspective on monogamy Eggs require large resource input. A clutch of bird eggs can be ~20% of bird’s weight. Sperm are cheap. Human Females: ~1 egg/month Human Males: 250,000,000 sperm/ ejaculation The female reproductive system Sperm competition: Sperm can survive for several days in a woman’s reproductive tract. In Great Britain in a survey of 4,000 women… 0.5% had sex with 2 different men within 30 minutes… 30% within 24 hours = sperm competition. The female reproductive system Female mammals provide additional resources in form of milk. Mating pairs share genetic information and possibly help in child-rearing What are the consequences of the different male and female attitudes toward sex and relationships? Zebra Finch Zebra finch pairs were allowed to mate ~9 times Then a new male was brought in and allowed to mate with the female once. Last male advantage The last male that only mated once fathered 54% of offspring Original male (mated 9 times) fathered 46% of offspring Last male advantage To ensure fatherhood males mate guard and produce copious quantities of sperm Purple Martins After successfully mating, male purple martins call and attract younger males The older males then cuckold the younger male’s females Younger males with nests near older males only father 29% of eggs in their nests. Older males produce 4.1 offspring with their mate and 3.6 by younger neighbor’s mate. Younger males with nests near older males only father 29% of eggs in their nests. Older males produce 4.1 offspring with their mate and 3.6 by younger neighbor’s mate. What advantage is their for females to accept or solicit EPCs? Gunnison’s Prairie Dogs Sexually monogamous female squirrels have a 92% chance of successfully giving birth. Gunnison’s Prairie Dogs Sexually monogamous female squirrels have a 92% chance of successfully giving birth. Non-monogamous females have a 100% chance of giving birth Can females detect compatible genes? http://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html How can a female know which male has successful genes? Females may choose traits, like large displays, that are disadvantageous for male survival. How can females determine “good” males? Color: Bright coloring can be correlated with health… But a male with a mate is judged as being high quality even if he is less colorful How does evolution work for a behaviors such as monogamy? monogamous bye non-monogamous Voles Prairie • Monogamous • Both parents care for young Montane • Nonmonogamous • Mother cares for young briefly Same levels of oxytocin and vasopressin • More receptors • Less receptors How does evolution work for a behaviors such as monogamy? monogamous bye non-monogamous How does evolution work for a behaviors such as monogamy? After several generations… monogamous non-monogamous •Males must choose between having more offspring (more mates) or helping to raise fewer offspring (sperm do not require many resources) •Females choose males that can provide “good” genes or resources for offspring (eggs, gestation, and/or lactation require high resource input) Am I the only one? Am I better off helping with these kids or should I mate with someone else? Is this the best I can do? Maybe I can find someone with better genes or more genetic diversity. Asexaul Reproduction extremely low genetic diversity vs. Sexaul Reproduction greater genetic diversity How does sexual reproduction generate genetic diversity? Gene for growth hormone Gene for brown hair pigment Gene for blue eye pigment Gene for hemoglobin Gene for DNA polymerase Haploid chromosomes Allele for low express (short) Gene for growth hormone Allele for high express (tall) Allele for black hair Gene for hair color Allele for black hair Allele for sickle cell Hb Gene for hemoglobin Allele for normal Hb Diploid chromosomes Fig 1.5 Each pair of chromosomes is comprised of a paternal and maternal chromosome Fig 1.11 Diploid meiosis Haploid Fig 3.16 Meiosis splits apart the pairs of chromosomes. X 23 in humans haploid X 23 in humans X 23 in humans diploid X 23 in humans Inheritance = The interaction between genes inherited from Mom and Dad. sister chromatids= replicated DNA (chromosomes) tetrad= pair of sister chromatids Fig 3.12 Fig 3.16 Meiosis splits apart the pairs of chromosomes. X 23 in humans Asexaul Reproduction extremely low genetic diversity vs. Sexaul Reproduction greater genetic diversity How does sexual reproduction generate genetic diversity? Fig 3.10 Crossing-over (aka Recombination) DNA cut and religated DNA cut and religated Crossing-over: Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes. Fig 3.10 Crossing-over: Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes. Fig 3.10 Crossing-over: Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes. Fig 3.10 Asexaul Reproduction extremely low genetic diversity vs. Sexaul Reproduction greater genetic diversity How does sexual reproduction generate genetic diversity? Fig 3.17 Independent Assortment (aka Random Assortment) Fig 3.17 Independent Assortment 2 possibilities for each pair, for 2 pairs 22 = 4 combinations Fig 3.17 Independent Assortment 2 possibilities for each pair, for 23 pairs 223 = 8,388,608 combinations Crossingover Meiosis: In humans, crossing-over and (Ind. Assort.) independent assortment lead to over 1 trillion possible unique gametes. (1,000,000,000,000) Meiosis I Meiosis II 4 Haploid cells, each unique Fig 3.12 Fig 3.12 4 haploid cells {Producing gametes} Sexual reproduction creates genetic diversity by combining DNA from 2 individuals, but also by creating genetically unique gametes. {Producing more cells} haploid X 23 in humans X 23 in humans diploid X 23 in humans Inheritance = The interaction between genes inherited from Mom and Dad. Do parents’ genes/traits blend together in offspring? Fig 2.6 In many instances there is a unique pattern of inheritance. Traits disappear and reappear in new ratios. Fig 1.6 from DNA to Protein: from gene to trait Fig 1.7 from DNA to Protein: from gene to trait Molecular Cellular Organism Population Genotype Phenotype Human blood types Fig 4.11 Fig 4.11 One gene with three alleles controls carbohydrates that are found on Red Blood Cell membranes A A A A A RBC A A A A Allele A = A carbs B B B B B RBC B RBC B B B Allele B = B carbs Allele O = no carbs Human blood types Fig 4.11 We each have two versions of each gene… A So A A A A RBC A A A A Genotype could be A and A OR A and O Recessive alleles do not show their phenotype when a dominant allele is present. A A A A A RBC A A A See Fig 4.2 A Genotype could be A and A OR A and O What about… RBC Genotype = ?? What about… RBC Genotype = OO What about… B A A B A RBC B A B B A What about… B A A B A RBC B A B Genotype = AB B A Human blood types AA or AO BB or BO AB OO Fig 4.11 If Frank has B blood type, his Dad has A blood type, And his Mom has B blood type… Should Frank be worried? Mom=B blood possible BB or BO genotypes Dad=A blood AA or AO possible genotypes Mom=B blood Dad=A blood BB or BO AA or AO Gametes all B / 50% B and all A / 50% A and 50% O 50% O possible genotypes Mom=B blood Dad=A blood BB or BO AA or AO Gametes all B / 50% B and all A / 50% A and 50% O 50% O Frank can be BO = B blood …no worries Grandparents AB and AB Mom=B blood possible BB or BO genotypes Gametes all B / 50% B and 50% O Frank can be BO or BB = B blood Dad=A blood AA all A …Uh-Oh Pedigree, tracing the genetic past Dom. Rec. Rec. Dom. Fig 2.11 We can also predict the future Fig 2.6 Inheritance of blood types Mom = AB Dad = AB Inheritance of blood types Mom = AB Gametes: A or B Dad = AB A or B Inheritance of blood types Mom = AB Gametes: A or B A or B Dad A or B A AA Mom or B AB Dad = AB AB BB Chance of each phenotype for each offspring 25% AA 50% AB 25% BB Single genes controlling a single trait are unusual. Inheritance of most genes/traits is much more complex… Dom. Rec. Rec. Dom. Genotype Phenotype Genes code for proteins (or RNA). These gene products give rise to traits… Human blood types AA or AO BB or BO AB OO Fig 4.11 Genotype Phenotype Genes code for proteins (or RNA). These gene products give rise to traits… It is rarely this simple. Fig 4.3 Incomplete dominance Fig 4.4 Wednesday: Mapping and Epigenetics