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Questions and Answers
In a cross between two heterozygous black fur mice (Bb), what percentage of offspring is expected to have the homozygous recessive genotype (bb)?
In a cross between two heterozygous black fur mice (Bb), what percentage of offspring is expected to have the homozygous recessive genotype (bb)?
- 0%
- 75%
- 25% (correct)
- 50%
If a black fur mouse (Bb) is crossed with a white fur mouse (bb), what is the probability of the offspring having black fur?
If a black fur mouse (Bb) is crossed with a white fur mouse (bb), what is the probability of the offspring having black fur?
- 25%
- 50% (correct)
- 0%
- 75%
A man and woman, both with brown eyes, have a blue-eyed child. What are the genotypes of the man and woman?
A man and woman, both with brown eyes, have a blue-eyed child. What are the genotypes of the man and woman?
- BB and BB
- BB and Bb
- Bb and Bb (correct)
- Bb and bb
In mice, black fur (B) is dominant to white fur (b). If you cross two hybrid mice (Bb), what is the resulting phenotypic ratio of black fur to white fur?
In mice, black fur (B) is dominant to white fur (b). If you cross two hybrid mice (Bb), what is the resulting phenotypic ratio of black fur to white fur?
Consider a cross where one parent is Bb and the other parent is also Bb. What is the genotypic ratio of the offspring?
Consider a cross where one parent is Bb and the other parent is also Bb. What is the genotypic ratio of the offspring?
In genetics, what is the relationship between genes and chromosomes?
In genetics, what is the relationship between genes and chromosomes?
If 'Y' represents the dominant allele for yellow seeds and 'y' represents the recessive allele for green seeds, what phenotype would a plant with the genotype 'Yy' exhibit?
If 'Y' represents the dominant allele for yellow seeds and 'y' represents the recessive allele for green seeds, what phenotype would a plant with the genotype 'Yy' exhibit?
What is the significance of homologous pairs in the context of genetics?
What is the significance of homologous pairs in the context of genetics?
In a certain species, the allele for tall plants (T) is dominant over the allele for short plants (t). If a heterozygous tall plant (Tt) is crossed with a homozygous short plant (tt), what is the probability of producing a short plant?
In a certain species, the allele for tall plants (T) is dominant over the allele for short plants (t). If a heterozygous tall plant (Tt) is crossed with a homozygous short plant (tt), what is the probability of producing a short plant?
What is the difference between genotype and phenotype?
What is the difference between genotype and phenotype?
Why is it important to use the same letter to represent different alleles of the same gene (e.g., 'T' and 't' for tall and short, respectively)?
Why is it important to use the same letter to represent different alleles of the same gene (e.g., 'T' and 't' for tall and short, respectively)?
In Mendelian genetics, what does the Principle of Independent Assortment state?
In Mendelian genetics, what does the Principle of Independent Assortment state?
A plant breeder crosses two pea plants. One plant is homozygous dominant for purple flowers (PP) and the other is homozygous recessive for white flowers (pp). What is the expected phenotype of the F1 generation?
A plant breeder crosses two pea plants. One plant is homozygous dominant for purple flowers (PP) and the other is homozygous recessive for white flowers (pp). What is the expected phenotype of the F1 generation?
Flashcards
Heterozygous
Heterozygous
A genetic condition where two different alleles are present for a trait (e.g., Bb).
Homozygous
Homozygous
A genetic condition where two identical alleles are present for a trait (e.g., bb or BB).
Genotypic Ratio
Genotypic Ratio
The proportion of different genotypes (genetic makeup) in a population (e.g., 1 BB : 2 Bb : 1 bb).
Phenotypic Ratio
Phenotypic Ratio
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Recessive Trait Appearance
Recessive Trait Appearance
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Genetics
Genetics
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Independent Assortment
Independent Assortment
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Gene
Gene
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Homologous Pairs
Homologous Pairs
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Alleles
Alleles
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Dominant Gene
Dominant Gene
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Study Notes
- Gregor Mendel: The father of genetics
- Principle of Independent Assortment: Inheritance of one trait will not affect the inheritance of another trait
Traits
- Genetics: The study of how traits are passed from parent to their offspring
Genes and Chromosomes
- Traits are determined by genes on chromosomes
- A gene is a segment of DNA that determines a trait
Homologous Chromosomes
- Chromosomes come in homologous pairs, so genes also come in pairs
- Homologous pairs are matching genes; one comes from the female and one from the male parent
- Humans have 46 chromosomes or 23 pairs
- One set from dad is in sperm (23)
- One set from mom is in egg (23)
Alleles
- Alleles are different genes for the same triat, for example, the possibilities for eye color
Dominant and Recessive Genes
- A dominant gene prevents the other from showing
- A recessive gene will not show even if it is present
- Dominant genes are symbolized by an uppercase letter
- Recessive genes are symbolized by a lowercase letter
Dominant Example
- The straight thumb is dominant to the hitchhiker thumb
- T = straight thumb
- t = hitchhiker thumb
- Straight thumb genotypes: TT or Tt
- Hitchhikers thumb genotype: tt
- For a recessive trait to show, the gene must have two recessive alleles
Homozygous vs Heterozygous
- Homozygous or Purebred: Both genes of a pair are the same.
- TT = homozygous dominant
- tt = homozygous recessive
- Heterozygous or Hybrid: One dominant and one recessive gene
- Tt
Genotype and Phenotype
- Genotype: Combination of genes an organism has
- Examples: TT, Tt, tt
- Phenotype: Physical appearance due to gene make-up
- Examples: hitchhiker's thumb or straight thumb
Punnett Square and Probability
- The Punnett Square is used to predict the possible gene makeup of offspring
- Example: Black fur(B)is dominant to white fur (b) in mice
- Cross a heterozygous male with a homozygous recessive female
- Male gametes go on the left side of the punnett square (one gene in sperm)
- Female gametes go on the top of the punnett square (one gene in egg)
- Female gametes are N
- Male gametes are N The possible Offspring are 2N
Genotypic Ratio
- Homozygous dominant: heterozygous: homozygous recessive
Phenotypic Ratio
- Dominant: recessive
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