Bonus #2 due 11/25
Meiosis and Genetic Diversity
Is this the best I can do?Maybe I can find someone
with better genes or more genetic diversity.
Am I the only one? Am Ibetter off helping with these
kids or should I matewith someone else?
extremely lowgenetic diversity
greater geneticdiversity
vs.Asexaul Reproduction
SexaulReproduction
How does sexual reproduction generate genetic diversity?
Gene forblue eye pigment
Gene forbrown hair pigment
Gene forgrowth hormone
Haploidchromosomes
Gene forhemoglobin
Gene forDNA polymerase
Gene forhemoglobin
Gene forhair color
Gene forgrowth hormone
Allele forblack hair
Allele forblack hair
Allele forlow express(short)
Allele forhigh express(tall)
Allele for normal Hb
Allele forsickle cell Hb
Diploidchromosomes
Each pair of chromosomes is comprised of a paternal and maternal chromosome
Fig 1.5
meiosisDiploid Haploid
Fig 1.11
Fig 3.16
Meiosis splits apart the pairs of chromosomes.
X 23in humans
haploid
diploid
X 23in humans X 23
in humans
X 23in humans
Inheritance = The interaction between genes inherited from Mom and Dad.
Fig 3.12
sister chromatids= replicated DNA (chromosomes)tetrad= pair of sister chromatids
Fig 3.16
Meiosis splits apart the pairs of chromosomes.
X 23in humans
extremely lowgenetic diversity
greater geneticdiversity
vs.Asexual Reproduction
SexualReproduction
How does sexual reproduction generate genetic diversity?
Fig 3.10
DNA cut and religated
DNA cut and religated
Crossing-over(aka Recombination)
Crossing-over:Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
Fig 3.10
Fig 3.10Crossing-over:Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
Crossing-over:Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
Fig 3.10
extremely lowgenetic diversity
greater geneticdiversity
vs.Asexual Reproduction
SexualReproduction
How does sexual reproduction generate genetic diversity?
Fig 3.17 Independent Assortment(aka Random Assortment)
Independent Assortment
2 possibilities for each pair,
for 2 pairs22 = 4
combinations
Fig 3.17
Independent Assortment
2 possibilities for each pair, for 23 pairs
223 = 8,388,608
combinations
Fig 3.17
Crossing-Crossing-overover
Meiosis I
Meiosis II
4 Haploid cells, each unique
Meiosis:In humans, crossing-over and independent assortment lead to over 1 trillion possible unique gametes.(1,000,000,000,000)
(Ind. Assort.)(Ind. Assort.)
Fig 3.12
4 haploid cells
Fig 3.12
Sexual reproduction creates genetic diversity by combining DNA from 2 individuals, but also by creating genetically unique gametes.
{Producing more cells}
{Producing gametes}
haploid
diploid
X 23in humans X 23
in humans
X 23in humans
Inheritance = The interaction between genes inherited from Mom and Dad.
Do parents’ genes/traits blend together in offspring?
In many instances there is a unique pattern of inheritance.
Traits disappear and reappear in new ratios.
Fig 2.6
from DNA to Protein:from gene to trait
Fig 1.6
Cellular
Organism
Population
Molecular
from DNA to Protein:from gene to trait
Fig 1.7
Genotype Phenotype
Human blood types Fig 4.11
One gene with three alleles controls carbohydrates that are found on Red Blood Cell membranes
RBC
A A
A
A
AA
AA
A
RBCRBC
B B
B
B
BB
BB
B
Allele A = A carbs Allele B = B carbs Allele O = no carbs
Fig 4.11
Human blood types Fig 4.11
RBC
A A
A
A
AA
AA
A
We each have two versions of each gene…
So
Genotype could be A and AORA and O
RBC
A A
A
A
AA
AA
A
Recessive alleles do not show their phenotype when a dominant allele is present.
Genotype could be A and AORA and OSee Fig 4.2
What about…
Genotype = ??
RBC
What about…
Genotype = OO
RBC
RBC
AA
A
B
A A
B
B
B
What about…
B
RBC
AA
A
B
A A
B
B
B
What about…
B
Genotype = AB
Human blood types
AA orAO
AB
BB orBO
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?
possible
genotypes
Mom=B blood
BB or BO
Dad=A blood
AA or AO
Gametes all B / 50% B and50% O
all A / 50% A and50% O
possible
genotypes
Mom=B blood
BB or BO
Dad=A blood
AA or AO
Mom=B blood
BB or BO
Dad=A blood
AA or AO
Gametes all B / 50% B and50% O
all A / 50% A and50% O
Possiblegenotypes
Frank can be BO= B blood …no worries
Mom=B bloodBB or BO
Dad=A bloodAA
Gametes all B / 50% B and50% O
all A
possible
genotypes
Frank can be BO or BB= B blood …Uh-Oh
GrandparentsAB and AB
Pedigree, tracing the genetic past
Dom. Rec. Rec. Dom.
Fig 2.11
We can also predict the future
Fig 2.6
Mom = AB Dad = AB
Inheritance of blood types
Mom = AB Dad = AB
Gametes: A or B A or B
Inheritance of blood types
Mom = AB Dad = AB
Gametes: A or B A or B
A or B
A or B
AA
AB BB
AB
Chance of each phenotype for each offspring25% AA50% AB25% BB
Mom
Dad
Inheritance of blood types
Single genes controlling a single trait are unusual. Inheritance of most genes/traits is much more complex…
Dom. Rec. Rec. Dom.
PhenotypeGenotype
Genes code for proteins (or RNA). These gene products give rise to traits…
Human blood types
AA orAO
AB
BB orBO
OO
Fig 4.11
PhenotypeGenotype
Genes code for proteins (or RNA). These gene products give rise to traits…
It is rarely this simple.
Incomplete dominance
Fig 4.3
Fig 4.4
Bonus #2 due 11/25
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