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Published byVirgil Leonard Modified over 9 years ago
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Today: Meiosis, producing genetically diverse offspring, and inheritance
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For life to exist, the information (genes) must be passed on.
{Meiosis: producing gametes} For life to exist, the information (genes) must be passed on. {Mitosis: producing more cells}
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Voles Prairie Monogamous Both parents care for young Montane
Nonmonogamous Mother cares for young briefly
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Voles Prairie Monogamous Both parents care for young More receptors
Montane Nonmonogamous Mother cares for young briefly Less receptors Same levels of oxytocin and vasopressin
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Why might these voles use different reproductive strategies?
Prairie voles: Resource poor habitat Monogamous Both parents care for young Montane voles: Resource rich habitat Nonmonogamous Mother cares for young briefly
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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.
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Asexual Reproduction Sexual Reproduction vs. extremely low genetic diversity greater genetic diversity
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Asexual Reproduction genetically identical to parent
(this tree can reproduce both sexually and asexually)
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Why does sexual reproduction exist?
Cons: Need two individuals Hard to find mate Diseases/Competition Pros: Genetic diversity
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Screw worm flies
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F M sterile Sterile male screw worm flies led to decreased populations because of screw worm monogamy.
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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
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Hi, want to study biology together?
In most other species, because females mate with multiple males, introduction of sterile males has little effect. Hi, want to study biology together? F M F M fertile sterile
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10-40% of offspring in “monogamous” bird species are fathered by an extra-pair male
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Social Monogamy = pair lives/works together, but not “faithful”
Sexual Monogamy = pair raise young and only copulate with each other
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In mammals, child-rearing is most commonly done by the female
In mammals, child-rearing is most commonly done by the female. She provides milk.
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Less than 0.01% of mammals are monogamous
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Do Males and Females have different attitudes toward sex and relationships?
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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: …Would you go out with me tonight? = 50% yes Male answers: …Would you go out with me tonight? = 50% yes
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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: …Would you go out with me tonight? = 50% yes …Would you come to my apartment tonight? = 6% yes Male answers: …Would you go out with me tonight? = 50% yes …Would you come to my apartment tonight? = 69% yes
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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: …Would you go out with me tonight? = 50% yes …Would you come to my apartment tonight? = 6% yes …Would you go to bed with me tonight? = 0% yes Male answers: …Would you go out with me tonight? = 50% yes …Would you come to my apartment tonight? = 69% yes …Would you go to bed with me tonight? = 75% yes
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Why do Males and Females have different attitudes toward sex and relationships?
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The male perspective on monogamy
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Eggs require large resource input.
A clutch of bird eggs can be ~20% of bird’s weight. Sperm are cheap.
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Human Females: ~1 egg/month Human Males: 250,000,000 sperm/ ejaculation
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The female reproductive system
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Sperm competition: = 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.
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The female reproductive system
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Female mammals provide additional resources in form of milk.
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Mating pairs share genetic information and possibly help in child-rearing
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What are the consequences of the different male and female attitudes toward sex and relationships?
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Zebra Finch
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Zebra finch pairs were allowed to mate ~9 times
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Then a new male was brought in and allowed to mate with the female once.
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Last male advantage Original male (mated 9 times) fathered 46% of offspring The last male that only mated once fathered 54% of offspring
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Last male advantage To ensure fatherhood males mate guard and produce copious quantities of sperm
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After successfully mating, male purple martins call and attract younger males
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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.
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Older males produce 4. 1 offspring with their mate and 3
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.
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What advantage is their for females to accept or solicit EPCs?
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?
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Gunnison’s Prairie Dogs
Sexually monogamous female squirrels have a 92% chance of successfully giving birth.
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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
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Can females detect compatible genes?
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How can a female know which male has successful genes?
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Females may choose traits, like large displays, that are disadvantageous for male survival.
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How can females determine “good” males?
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Color: Bright coloring can be correlated with health…
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But a male with a mate is judged as being high quality even if he is less colorful
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How does evolution work for a behaviors such as monogamy?
bye monogamous non-monogamous
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Voles Prairie Monogamous Both parents care for young More receptors
Montane Nonmonogamous Mother cares for young briefly Less receptors Same levels of oxytocin and vasopressin
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How does evolution work for a behaviors such as monogamy?
bye non-monogamous monogamous
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How does evolution work for a behaviors such as monogamy?
After several generations… monogamous non-monogamous
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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)
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better off helping with these kids or should I mate with someone else?
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.
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How does sexual reproduction generate genetic diversity?
Asexaul Reproduction Sexaul Reproduction vs. extremely low genetic diversity greater genetic diversity How does sexual reproduction generate genetic diversity?
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Gene for growth hormone Gene for brown hair pigment Gene for hemoglobin Gene for DNA polymerase Gene for blue eye pigment Haploid chromosomes
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Gene for growth hormone Gene for hair color Gene for hemoglobin
Allele for low express (short) Allele for black hair Allele for sickle cell Hb Gene for growth hormone Gene for hair color Gene for hemoglobin Diploid chromosomes Allele for high express (tall) Allele for black hair Allele for normal Hb
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Fig 1.5 Each pair of chromosomes is comprised of a paternal and maternal chromosome
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Fig 1.11 meiosis Diploid Haploid
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Meiosis splits apart the pairs of chromosomes.
Fig 3.16 X 23 in humans Meiosis splits apart the pairs of chromosomes.
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haploid X 23 in humans X 23 in humans diploid X 23 in humans Inheritance = The interaction between genes inherited from Mom and Dad.
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sister chromatids= replicated DNA (chromosomes)
tetrad= pair of sister chromatids Fig 3.12
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Meiosis splits apart the pairs of chromosomes.
Fig 3.16 X 23 in humans Meiosis splits apart the pairs of chromosomes.
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How does sexual reproduction generate genetic diversity?
Asexaul Reproduction Sexaul Reproduction vs. extremely low genetic diversity greater genetic diversity How does sexual reproduction generate genetic diversity?
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Crossing-over (aka Recombination) Fig 3.10 DNA cut and religated
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Fig 3.10 Crossing-over: Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
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Fig 3.10 Crossing-over: Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
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Fig 3.10 Crossing-over: Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
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How does sexual reproduction generate genetic diversity?
Asexaul Reproduction Sexaul Reproduction vs. extremely low genetic diversity greater genetic diversity How does sexual reproduction generate genetic diversity?
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Fig 3.17 Independent Assortment (aka Random Assortment)
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2 possibilities for each pair, for 2 pairs
Fig 3.17 Independent Assortment 2 possibilities for each pair, for 2 pairs 22 = 4 combinations
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2 possibilities for each pair, for 23 pairs
Fig 3.17 Independent Assortment 2 possibilities for each pair, for 23 pairs 223 = 8,388,608 combinations
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Crossing-over Meiosis: In humans, crossing-over and independent assortment lead to over 1 trillion possible unique gametes. (1,000,000,000,000) Meiosis I (Ind. Assort.) Meiosis II 4 Haploid cells, each unique
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Fig 3.12
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Fig 3.12 4 haploid cells
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{Producing gametes} Sexual reproduction creates genetic diversity by combining DNA from 2 individuals, but also by creating genetically unique gametes. {Producing more cells}
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haploid X 23 in humans X 23 in humans diploid X 23 in humans Inheritance = The interaction between genes inherited from Mom and Dad.
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Do parents’ genes/traits blend together in offspring?
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In many instances there is a unique pattern of inheritance.
Fig 2.6 In many instances there is a unique pattern of inheritance. Traits disappear and reappear in new ratios.
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from DNA to Protein: from gene to trait
Fig 1.6 from DNA to Protein: from gene to trait
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from DNA to Protein: from gene to trait
Fig 1.7 from DNA to Protein: from gene to trait Molecular Cellular Organism Population
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Genotype Phenotype
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Human blood types Fig 4.11
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Fig 4.11 One gene with three alleles controls carbohydrates that are found on Red Blood Cell membranes A A B RBC A B RBC RBC B A B A B A A B B A A B B Allele O = no carbs Allele A = A carbs Allele B = B carbs
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Human blood types Fig 4.11
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We each have two versions of each gene…
RBC A A A So A A A A Genotype could be A and A OR A and O
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Recessive alleles do not show their phenotype when a dominant allele is present.
RBC A A A A A A A Genotype could be A and A OR A and O See Fig 4.2
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What about… RBC Genotype = ??
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What about… RBC Genotype = OO
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What about… A B RBC B A A B B A A B
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What about… A B RBC B A A B B A A B Genotype = AB
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Human blood types Fig 4.11 AA or AO BB or BO AB OO
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If Frank has B blood type,
his Dad has A blood type, And his Mom has B blood type… Should Frank be worried?
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Mom=B blood BB or BO Dad=A blood AA or AO possible genotypes
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Mom=B blood BB or BO Dad=A blood AA or AO all B / 50% B and 50% O
possible genotypes all B / 50% B and 50% O all A / 50% A and 50% O Gametes
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Mom=B blood BB or BO Dad=A blood AA or AO Gametes all B / 50% B and
possible genotypes Gametes all B / 50% B and 50% O all A / 50% A and 50% O Frank can be BO = B blood …no worries
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Mom=B blood BB or BO Dad=A blood AA Gametes all B / 50% B and 50% O
Grandparents AB and AB Mom=B blood BB or BO Dad=A blood AA possible genotypes Gametes all B / 50% B and 50% O all A Frank can be BO or BB = B blood …Uh-Oh
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Pedigree, tracing the genetic past
Dom. Rec. Rec. Dom.
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Fig 2.11
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We can also predict the future
Fig 2.6
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Inheritance of blood types
Mom = AB Dad = AB
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Inheritance of blood types
Mom = AB Dad = AB Gametes: A or B A or B
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Mom = AB Dad = AB A or B A or B Gametes: Dad A or B 25% AA 50% AB
Inheritance of blood types Mom = AB Dad = AB A or B A or B Gametes: Dad A or B Chance of each phenotype for each offspring 25% AA 50% AB 25% BB AA A or B AB Mom AB BB
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Single genes controlling a single trait are unusual
Single genes controlling a single trait are unusual. Inheritance of most genes/traits is much more complex… Dom. Rec. Rec. Dom.
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Genotype Phenotype Genes code for proteins (or RNA). These gene products give rise to traits…
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Human blood types Fig 4.11 AA or AO BB or BO AB OO
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Genotype Phenotype Genes code for proteins (or RNA). These gene products give rise to traits… It is rarely this simple.
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Fig 4.3 Incomplete dominance
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Fig 4.4
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Wednesday: Mapping and Epigenetics
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