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Questions and Answers
In a scenario where a breeder is using artificial selection to increase the size of apples, which approach would be MOST effective?
In a scenario where a breeder is using artificial selection to increase the size of apples, which approach would be MOST effective?
- Consistently breeding the largest apples with each other over several generations. (correct)
- Breeding the smallest apples to encourage a reduction in average apple size and observe any mutations.
- Randomly selecting apples from the orchard to breed from, ensuring genetic diversity.
- Selecting apples based on color rather than size, as color is a more heritable trait.
Why is it important to consider a large number of offspring when determining phenotypic ratios in genetic crosses?
Why is it important to consider a large number of offspring when determining phenotypic ratios in genetic crosses?
- To reduce the number of possible genotypes.
- To increase the accuracy of observing the expected ratios, as random chance has less impact with larger sample sizes. (correct)
- To ensure that the parents are true breeding.
- To follow Mendel’s original experimental design precisely.
If all the F1 progeny of a monohybrid cross resemble one of the parental strains, what does this suggest about the alleles involved?
If all the F1 progeny of a monohybrid cross resemble one of the parental strains, what does this suggest about the alleles involved?
- The alleles exhibit incomplete dominance.
- The trait is sex-linked.
- One allele is completely dominant over the other. (correct)
- Both parental strains are heterozygous.
How do differences in nucleotide sequence between different alleles affect the phenotype?
How do differences in nucleotide sequence between different alleles affect the phenotype?
In a cross between two individuals with the genotypes AaBb and Aabb, where A and B represent different genes, what is the probability of producing an offspring with the genotype AAbb, assuming independent assortment?
In a cross between two individuals with the genotypes AaBb and Aabb, where A and B represent different genes, what is the probability of producing an offspring with the genotype AAbb, assuming independent assortment?
In natural selection, what determines whether a new trait will become more common in a population?
In natural selection, what determines whether a new trait will become more common in a population?
What is a key difference between natural selection and artificial selection?
What is a key difference between natural selection and artificial selection?
A farmer notices that a particular variety of corn consistently produces higher yields in dry conditions compared to other varieties. If the farmer saves seeds from these plants to plant the following year, this is an example of what?
A farmer notices that a particular variety of corn consistently produces higher yields in dry conditions compared to other varieties. If the farmer saves seeds from these plants to plant the following year, this is an example of what?
In a cross between two heterozygous plants (Aa) where orange (A) is dominant to blue (a), what is the probability of producing an orange offspring?
In a cross between two heterozygous plants (Aa) where orange (A) is dominant to blue (a), what is the probability of producing an orange offspring?
If you cross two dihybrid plants (YyRr), where Y is yellow, y is green, R is round, and r is wrinkled, and assuming that the genes are unlinked, what proportion of the offspring will be yellow and wrinkled?
If you cross two dihybrid plants (YyRr), where Y is yellow, y is green, R is round, and r is wrinkled, and assuming that the genes are unlinked, what proportion of the offspring will be yellow and wrinkled?
A dihybrid cross involves individuals that are heterozygous for two different genes. Which of the following genotypes represents a dihybrid individual?
A dihybrid cross involves individuals that are heterozygous for two different genes. Which of the following genotypes represents a dihybrid individual?
In a dihybrid cross where both genes exhibit simple dominance, what phenotypic ratio is expected in the F2 generation?
In a dihybrid cross where both genes exhibit simple dominance, what phenotypic ratio is expected in the F2 generation?
The law of independent assortment describes the behavior of alleles for different genes during gamete formation. Which of the following statements best describes this law?
The law of independent assortment describes the behavior of alleles for different genes during gamete formation. Which of the following statements best describes this law?
What does the law of segregation describe?
What does the law of segregation describe?
A plant breeder crosses two pea plants, one with round and yellow seeds (RRYY) and another with wrinkled and green seeds (rryy). What genotypes will the $F_1$ generation have?
A plant breeder crosses two pea plants, one with round and yellow seeds (RRYY) and another with wrinkled and green seeds (rryy). What genotypes will the $F_1$ generation have?
In a test cross with a dihybrid individual showing dominant phenotypes, what genotype would the other parent typically have?
In a test cross with a dihybrid individual showing dominant phenotypes, what genotype would the other parent typically have?
Using the law of sum, determine the probability of dice throw resulting in 2 or 4.
Using the law of sum, determine the probability of dice throw resulting in 2 or 4.
Considering a dihybrid cross, what does it mean if new phenotypic combinations appear in the offspring that were not present in the parental generations?
Considering a dihybrid cross, what does it mean if new phenotypic combinations appear in the offspring that were not present in the parental generations?
Which of the following scenarios best exemplifies natural selection?
Which of the following scenarios best exemplifies natural selection?
What is the primary difference between natural selection and artificial selection?
What is the primary difference between natural selection and artificial selection?
How did the fox domestication experiment demonstrate the potential for rapid evolutionary change?
How did the fox domestication experiment demonstrate the potential for rapid evolutionary change?
Which of the following is a common characteristic often observed in animals undergoing domestication, known as 'domestication syndrome'?
Which of the following is a common characteristic often observed in animals undergoing domestication, known as 'domestication syndrome'?
How might inbreeding, often practiced in artificial selection, impact the genetic makeup of a population?
How might inbreeding, often practiced in artificial selection, impact the genetic makeup of a population?
What advantage did Mendel gain by using pure-breeding lines of pea plants in his experiments?
What advantage did Mendel gain by using pure-breeding lines of pea plants in his experiments?
What was the significance of Mendel's reciprocal crosses in disproving previous theories of inheritance?
What was the significance of Mendel's reciprocal crosses in disproving previous theories of inheritance?
In Mendel's monohybrid crosses, what consistently occurred in the F1 generation?
In Mendel's monohybrid crosses, what consistently occurred in the F1 generation?
How did Mendel’s findings challenge the previously held belief that parental traits become mixed and forever changed in offspring?
How did Mendel’s findings challenge the previously held belief that parental traits become mixed and forever changed in offspring?
What is the relationship between genotype and phenotype?
What is the relationship between genotype and phenotype?
In natural selection, what determines which traits become more common in a population over time?
In natural selection, what determines which traits become more common in a population over time?
Which of the following describes the process of artificial selection?
Which of the following describes the process of artificial selection?
How does the domestication of dogs from wolves provide evidence for both natural and artificial selection?
How does the domestication of dogs from wolves provide evidence for both natural and artificial selection?
What is the role of random DNA mutations in the context of both natural and artificial selection?
What is the role of random DNA mutations in the context of both natural and artificial selection?
If a plant breeder wants to develop a new variety of drought-resistant wheat, which approach would be most aligned with artificial selection?
If a plant breeder wants to develop a new variety of drought-resistant wheat, which approach would be most aligned with artificial selection?
Flashcards
Family with 4 children
Family with 4 children
In family with 4 kids, expect statistically about 2 males, 2 females.
3:1 Phenotypic Ratio
3:1 Phenotypic Ratio
The ratio observed in the F2 generation when crossing monohybrids with simple dominant/recessive traits.
Monohybrid Crosses
Monohybrid Crosses
Crosses involving parents that differ in only one trait.
First Filial (F1)
First Filial (F1)
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Second Filial (F2)
Second Filial (F2)
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Punnett Square
Punnett Square
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DNA Level Allele Differences
DNA Level Allele Differences
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Genotype
Genotype
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Natural Selection
Natural Selection
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Artificial Selection
Artificial Selection
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Domestication Through Selection
Domestication Through Selection
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Domestication Syndrome
Domestication Syndrome
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Gregor Mendel
Gregor Mendel
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Gametes
Gametes
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Dominant Traits
Dominant Traits
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Recessive Traits
Recessive Traits
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Pure-Breeding Lines
Pure-Breeding Lines
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Inheritance
Inheritance
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F1 Generation
F1 Generation
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F2 Generation
F2 Generation
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Law of Sum
Law of Sum
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Dihybrids
Dihybrids
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Dihybrid Cross
Dihybrid Cross
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Dihybrid Cross Outcomes
Dihybrid Cross Outcomes
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Law of Independent Assortment
Law of Independent Assortment
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Law of Segregation
Law of Segregation
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Branching Diagrams
Branching Diagrams
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Test Cross
Test Cross
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9:3:3:1 Phenotypic Ratio
9:3:3:1 Phenotypic Ratio
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Law of Segregation
Law of Segregation
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Study Notes
- Learning objectives include comparing natural and artificial selection.
- Understanding segregation and independent assortment laws is also a key learning objective
- A further objective is to Describe molecular mechanisms of dominant and recessive alleles
- Using Punnett squares to figure out gametes, genotypes and phenotypes of offspring is another objective
- Using key terms including genotype, phenotype, allele, gene, test cross, dihybrid, monohybrid, pure breeding, gamete,
Genetic Traits
- Genetic traits pass from one generation to the next
- Natural selection involves individuals with certain traits that are more likely survive
- Those individuals are also more likely to reproduce in a given environment
- Artificial selection involves choosing which individual plants/animals reproduce
Domestication
- Domesticated plants include Pepo Squash, Maize, and Common Bean at varying times Before Present (BP).
- Domesticated animals Goat (10,500 yrs), Dog (15,000-36,000 yrs), Sheep (11,000 yrs), Cow (10,300 yrs)
- Queen Anne's Lace has been bred into the modern carrot for desirable traits (phenotypes).
- Teosinte ancestor has 5-12 kernels encased and wrapped, ear disarticulates and is protected from digestion
- Modern corn has 500+ kernels.
- Modern corn has unprotected kernels that remain attached
Artificial Selection
- Random DNA mutations causes small phenotypic (observable) changes.
- Humans choose which organisms reproduce which accumulates over time
- Dogs are domesticated wolves (same species)
- Human-compatible wolves were successful in domestication
- Self-domestication occurs in dogs
- Dogs have lots of genetic variation and inbreeding, making models for disease
- Dogs have more variation in skeletal size and proportion and more variation than any other mammal
Fox Domestication
- Dmitry Belyayev's fox domestication experiment selected foxes for tameness
Domestication syndrome
- Domestication (animals) includes floppy ears and variations in coat color
- Domestication also involves shorter muzzle and smaller tooth size.
- Prolonged juvenile behaviour and extended breeding cycle change hormonal behaviors
Gregor Mendel
- Gregor Mendel (1822-1884) was an expert Augustinian monk and expert plant breeder (Austria 1800s).
- Mendel experimented with garden peas (not allowed to experiment using mice)
- Garden peas are self-fertile and are easy to cross-fertilize and have a large number of offspring
- Another key feature is that they have a short growing season
Genetics
- Clear alternative forms of particular traits exist in genetics
- Pure-breeding lines produce offspring with the same traits as parents, as they are inbred
- Breeding is carefully controlled
- Gametes (reproductive cells) are male (ơ): pollen/sperm and female (♀): ovules/eggs
- Each pea is a separate individual
- Dominant traits are yellow, round, purple
- Recessive traits are green, wrinkled and white
- Prior to Mendel, they were the theories that one parent contributes most to an offspring's inherited features and parental traits become mixed and forever changed
Monohybrid Crosses
- Monohybrid crosses are matings between individuals that differ in only one trait
- ALL F₁ progeny resembled one of the parental strains
- In F2 progeny, the lost trait reappeared in a 3:1 ratio
Phenotypes and Genotypes
- Phenotype = observable characteristic (largely determined by genotype)
- Phenotype is commonly referred to as a trait
- Genotype = genetic make-up and descriptions of the genetic make-up of an individual
- DNA wasn't discovered at the time Mendel was working
Genes
- Discrete units of inheritance are alleles of genes
- Alleles are alternative forms of a single gene
- A hypothetical feature of the gene HERC2 for eye pigment corresponds to alleles of brown or blue
- For skin pigment, an allele can also be albino or pigmented
- For height, an allele can be tall or short. For hair and seed texture, alleles can be curly/straight or smooth/wrinkled
- Traits are determined by multiple genes with multiple alleles in humans
- Genes/alleles are always designated by italics
- In all populations, there will always be different forms of every gene (alleles)
- A gene has several alleles that normally exist in a population
- An individual has two or more versions known as polymorphic
- Some genes have one allele in a population: monomorphic
- Xenopus laevis is tetraploid
Mendel's Law of Segregation
- Mendel's law of segregation is how alleles of 1 gene behave,
- It means the two alleles for each trait separate (segregate) during gamete formation
- Alleles unite at random from each parent at fertilization
- The symbols doesn't really matter as long as they make sense (W for wrinkled or R for rough)
Punnett Square
- The Law of Segregation can be demonstrated via punnett square
- Specific allele exists
- Phenotype genotype carries 2 copies of each gene
- Each individual receives one from each parent
- Punnett square shows the POSSIBILITIES
Genetic Ratios
- With enough offspring, the approximate ratio is 3:1 for simple dominant/recessive traits
- These traits result from a cross between monohybrids (one gene)
- Punnett square can determine possible gamete possibilities
- The squares can be cross-referenced to work out possible genotypes
Product Rule
- Product Rule: The likelihood of independent events, occurring together in genetics
- e.g., if parents (Aa), product chance = a and a = 1/2 * 1/2 = 1/4 chance
Law of Sum
- The law of sum means the probability of either of two mutually exclusive events occurring
- Law of Sum is the sum of individual probabilities e.g., dice roll 2 or 4 or 6 = 1/6 + 1/6 + 1/6 = 1/2
- Law of Sum e.g. Aa or aA with heterozygous offspring= 1/2 * 1/2 + ½ = 3/4
Dihybrids
- Dihybrids are individuals that carry the different alleles of 2 genes
- Do not assume dihybrids are produced with parentals that are not homozygous
- With dihybrids, new phenotypic combinations may arrive and parental allele expression occurs
- Law of Sum: phenotype is one not seen in parents, so the traits act independently
- Law of segregation describes single gene behavior
- Law of independent assortment describes "different" alleles of different genes
- A dihybrid cross ratio is 9:3:3:1
- The formula for number of genes examined is n= 2 to the power of 2 Test crosses against a recessive homozygous phenotype will highlight any genetic ratios
Multihybrids
- With multiple genes, do multiple, smaller Punnett Squares!
- Multihybrid crosses are matings between individuals that differ in three or more traits
- Multihybrid: use the law of segregation with each gene independently
- Multihybrid: also use the law of independent assortment for different genes
- This lets humans apply probability laws
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