Anthro 101: Human Biological Evolution Lecture 3: Genetics ...
Transcript of Anthro 101: Human Biological Evolution Lecture 3: Genetics ...
![Page 1: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/1.jpg)
Anthro 101: Human Biological Evolution Lecture 3: Genetics & Inheritance Prof. Kenneth Feldmeier [email protected] [email protected]
![Page 2: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/2.jpg)
What is Genetics???
○ Genetics is the scientific study of heredity.
○ Heredity is what makes each species unique.
![Page 3: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/3.jpg)
Who was the man when it came to genetics?
○ http://www.youtube.com/watch?v=NWqgZUnJdAY
!3
![Page 4: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/4.jpg)
Gregor Mendel
○ Austrian Monk ○ Famous for his work with pea plants ○ He is known as the father of
genetics
![Page 5: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/5.jpg)
Mendel’s Work○ Mendel used true-breeding plants which means if
they were left to breed with themselves they would produce offspring identical to themselves.
○ Mendel studied 7 different traits in pea plants. ○ A trait is a specific characteristic that varies from
one individual to another.
![Page 6: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/6.jpg)
Mendel showed simple genetic principles• Segregation
• Traits determined jointly by pairs of alleles
• Either allele can end up in a gamete
• Zygotes get 1 allele from mom, 1 allele from dad
!!• Dominance
• Sometimes, two different alleles at a gene loci (heterozygous) only one is expressed
![Page 7: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/7.jpg)
More on Mendel’s Work
○ Hybrids are offspring from parents with different traits.
○ Genes are the chemical factors that determine a trait.
○ The different forms of a gene are called alleles.
![Page 8: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/8.jpg)
Lets get down to the basics Somatic cells & Gametes both contain DNA
nucleus
mitochondria DNA in nucleus, mtDNA in mitochondria
![Page 9: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/9.jpg)
DNA Basics• 99.99% of all DNA in
the nucleus of a cell
!• DNA long strands of
biochemical information (legos or beads)
!• Sections of DNA form
functional units = genes
• Genes are recipes for proteins
• Proteins serve functions in the body = traits
![Page 10: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/10.jpg)
Phenotype: observable traits
The proteins that are built using the recipe.
Genotype: the alleles you carry
The recipe in your DNA.
Genotype / Phenotype
![Page 11: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/11.jpg)
Universal Genetic Code
• All living organisms have DNA made of the same material that serves similar functions !
• The universality of the genetic code implies a common ancestry for all life on the planet !
• Organisms differ in the amount of DNA !
• BUT the most important differences are in the arrangement of the DNA. ◆ Different order of nucleotides à different proteins
![Page 12: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/12.jpg)
What the heck is DNA?http://www.youtube.com/watch?v=8kK2zwjRV0M
!12
![Page 13: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/13.jpg)
Chromosomes = packages of DNA Cells have 2 versions of each chromosome – we have 23 homologous pairs, 46 total
Homologous Chromosomes
![Page 14: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/14.jpg)
Genes are segments on chromosomes• Genes on chromosomes like
beads on a string !
• Each gene has a specific location = locus ◆ Gene loci !
• There can be different versions of the same kind of gene: these are called alleles !
• Homologous alleles work together to produce phenotype
![Page 15: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/15.jpg)
Homozygous vs. Heterozygous Genotypes
• Homozygous: the same allele at the same locus on both versions of the chromosome
!!• Heterozygous: a
different allele at a particular locus on each chromosome
![Page 16: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/16.jpg)
Dominant & recessive alleles
• 2 different alleles (heterozygous) = Aa !
• Sometimes one of the alleles “overrides” the effects of other: this is called dominance = A > a !
• A dominant allele overrides the effects of a recessive allele
Aa
AA or aa
![Page 17: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/17.jpg)
Cell Division: Sharing the recipe
• DNA replicates before cell division ◆ Two types of replication: !
• Mitosis: makes a new somatic (body) cell
!• Meiosis: makes gametes (sex cells,
sperm and eggs) used in sexual reproduction
![Page 18: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/18.jpg)
Mitosis: replication of somatic cells
• When somatic cells divide chromosomes are doubled !
• Doubles are split between two daughter cells !
• Each daughter cell has an identical set of chromosomes to the original cell
![Page 19: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/19.jpg)
Meiosis: production of gametes
• Gametes (eggs and sperm) have only 1 copy of each chromosome !
• Chromosome pairs duplicate and divide into singles, distributed between 4 gametes !
• When gametes fuse during sexual reproduction, they create a zygote with full set of chromosomes
![Page 20: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/20.jpg)
To make a new organism
Parents make gametes
Gametes from two parents fuse to form offspring
For each chromosome, offspring carry two copies:
one from each parent
![Page 21: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/21.jpg)
Punnett Square Method
Genotypes • 4 Aa !Phenotypes • 4 Yellow
Aa Aa
Aa Aa
A
a
a
A
![Page 22: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/22.jpg)
Punnett Square Method
Genotypes • 1 AA • 2 Aa • 1 aa !Phenotypes • 3 Yellow • 1 Green
AA Aa
Aa aa
A
A
a
a
![Page 23: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/23.jpg)
• Recombination ◆ shuffling of alleles during meiosis = unique gametes
Independent assortment of alleles at different gene loci ◆ Mixing of alleles during sexual reproduction = unique offspring !
• The fate of a new mutation is unrelated to other traits ◆ New traits can spread independently in a population !
• Novel combinations of traits can appear in offspring ◆ This provides new phenotypes for natural selection to act upon
Recombination is important for evolution
![Page 24: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/24.jpg)
Mendel studied discontinuous (discrete) traits
Darwin observed continuous variation
Before Selection
Frequencyof each
Beak Depth
Beak Depth
![Page 25: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/25.jpg)
MOST traits vary along a continuum
Continuous Traits • Height • Weight • Skin color
Discontinuous Traits • Finger number • Litter size • Rolling tongue
![Page 26: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/26.jpg)
• Lots of traits are linked and so get inherited as a package deal ◆ Linked (same chromosome) !
• Lots of alleles for a gene aren’t clearly dominant/recessive ◆ Codominance: Sickle-cell anemia ◆ Complex dominance: ABO blood type !
• Lots of single genes controls multiple traits ◆ Pleiotropy !
• Lots of genes work together to affect the same trait = Polygenic inheritance
Simple Mendelian inheritance is rare (discontinuous traits)
![Page 27: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/27.jpg)
Linked traits are inherited together
![Page 28: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/28.jpg)
Codominance: Two alleles, three phenotypes
Sickle-cell anemia • Normal hemoglobin (A) allele • Sickling hemoglobin (S) allele !
• Three genotypes and three phenotypes: ◆ AA = normal blood cells ◆ SS = sickled blood cells ◆ AS = slightly impaired blood
cells, greater defense against malaria
![Page 29: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/29.jpg)
Complex Dominance: ABO Blood Type
• Three alleles: A, B & O !
• O recessive to A & B !
• A & B co-dominant
Genotype Phenotype Compatibility
AAType A
Rec.: A or O Don.: A or ABAO
AB Type AB Universal recipient
BBType B
Rec.: B or O Don.: B or ABBO
OO Type O Universal donor
![Page 30: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/30.jpg)
Pleiotropy: One gene controls two traits
• In Darwin’s finches, beak traits are correlated !
• Depth & width vary together ◆ Deeper & wider ◆ Shallow & narrow !
• Correlations arise when one gene affects multiple traits
![Page 31: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/31.jpg)
Polygenic Traits: Many genes, continuous variation
• Many genes affect each trait • Each one has small effect • Generates a continuous range of variation
in the trait
• Height ◆ So far approx 10 genes ◆ Affect about 30% of
variation in height
![Page 32: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/32.jpg)
All this variation! Where does it come from?
• Mutation • Meiosis
◆ Recombination of alleles into unique gametes ◆ increases genetic variation at a faster rate than mutation
• Sexual Reproduction ◆ Recombination of alleles from unique gametes into unique
offspring ◆ New phenotypes for NS to act upon
• Complex genetic inheritance ◆ Polygenic traits ◆ Environment interacts with genotype
![Page 33: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/33.jpg)
Polygenic Traits + Environment: Beak Depth
• Multiple genes interact to determine the actual beak phenotype
• Environmental effects blur across genetic differences producing a range of phenotypes
![Page 34: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/34.jpg)
Polygenic Traits shaped by many genes + environment
Phenotypes are almost ALWAYS the product of genes & environment interacting
Adjusted Mean Intelligence Test Scores Across 5 Categories of Breastfeeding
Duration
99
100.8
102.5
104.3
106
IQ S
core
37
38
39
40
41
Duration of Breastfeeding
<=1 2 to 3 4 to 6 7 to 9 > 9
WAIS Verbal IQBPP Test
![Page 35: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/35.jpg)
Variation is maintained in the DNA
• Intermediate types common, but genetic variation is maintained ◆ MOST individuals have some + and some – alleles for height
• Recessive alleles hidden by dominant alleles ◆ Still passed into gametes & remain in population
• Much of the variation is “hidden” from selection ◆ If a trait is affected by genes at many loci ◆ Many different genotypes may have similar selective fate ◆ Some variation is protected
• Neutral mutations can be hidden
Variation is essential for Natural Selection – without differences in traits, nothing to “select” & survival is random
![Page 36: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/36.jpg)
Speciation: Moving beyond existing variation
How can chihuahuas be smaller than the smallest wolves?
![Page 37: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/37.jpg)
Solution: Hidden Variation
• Normal sized wolves carry some alleles for small body size (some – alleles, and many + alleles)
• As big wolves die (or people prefer small ones), frequency of – alleles increases
• Variation is shuffled, some new combinations arise • As – alleles become more common, more – alleles likely
to be combined in a single individual • New combinations with more – alleles will be outside
initial range of variation
![Page 38: Anthro 101: Human Biological Evolution Lecture 3: Genetics ...](https://reader033.fdocuments.us/reader033/viewer/2022041617/62534d0b74eff8361d42bb74/html5/thumbnails/38.jpg)
What is the nature of variation?
+
+
• Variation is (usually) continuous • Continuous traits are generated via many genes and environmental
effects to produce the phenotype !
• Variation is generated and extended by: ◆ Mutation ◆ Meiosis ◆ Sexual reproduction ◆ Hidden alleles ◆ Polygenic inheritance + environment