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Questions and Answers
Why is Gregor Mendel considered the 'father of modern genetics'?
Why is Gregor Mendel considered the 'father of modern genetics'?
- He developed the theory of evolution by natural selection.
- He discovered the structure of DNA.
- He was the first to identify chromosomes.
- He was the first to use a quantitative experimental approach in genetics. (correct)
According to Mendel's Law of Dominance, what will happen when two organisms that are homozygous for two opposing traits are crossed?
According to Mendel's Law of Dominance, what will happen when two organisms that are homozygous for two opposing traits are crossed?
- The offspring will exhibit only the recessive trait.
- The offspring will exhibit only the dominant trait. (correct)
- The offspring will exhibit both traits equally.
- The offspring will exhibit a blend of both traits.
What process ensures that each gamete carries only one allele for each trait, as described by Mendel's Law of Segregation?
What process ensures that each gamete carries only one allele for each trait, as described by Mendel's Law of Segregation?
- Mitosis
- Fertilization
- Replication
- Meiosis (correct)
In a monohybrid cross between two heterozygous tall plants (Tt), what is the expected phenotypic ratio of tall to dwarf plants in the F2 generation?
In a monohybrid cross between two heterozygous tall plants (Tt), what is the expected phenotypic ratio of tall to dwarf plants in the F2 generation?
A plant breeder performs a testcross by crossing a plant with an unknown genotype to a homozygous recessive plant. If the offspring show both dominant and recessive phenotypes, what does this indicate about the genotype of the unknown plant?
A plant breeder performs a testcross by crossing a plant with an unknown genotype to a homozygous recessive plant. If the offspring show both dominant and recessive phenotypes, what does this indicate about the genotype of the unknown plant?
According to the Law of Independent Assortment, how do alleles for different traits located on separate chromosomes behave during gamete formation?
According to the Law of Independent Assortment, how do alleles for different traits located on separate chromosomes behave during gamete formation?
In incomplete dominance, if a red flower (RR) is crossed with a white flower (WW), and all the offspring are pink (RW), what phenotypic ratio would you expect in the F2 generation after crossing two pink flowers?
In incomplete dominance, if a red flower (RR) is crossed with a white flower (WW), and all the offspring are pink (RW), what phenotypic ratio would you expect in the F2 generation after crossing two pink flowers?
In codominance, such as with human MN blood groups, what happens when both alleles are present in an individual?
In codominance, such as with human MN blood groups, what happens when both alleles are present in an individual?
If a population has three alleles for a gene, how does this complicate predicting inheritance patterns compared to genes with only two alleles?
If a population has three alleles for a gene, how does this complicate predicting inheritance patterns compared to genes with only two alleles?
What term describes traits that are controlled by multiple genes, like skin color and height in humans?
What term describes traits that are controlled by multiple genes, like skin color and height in humans?
Why do males exhibit sex-linked recessive traits more frequently than females?
Why do males exhibit sex-linked recessive traits more frequently than females?
In sex-influenced inheritance, like pattern baldness in humans, how can the same genotype result in different phenotypes between males and females?
In sex-influenced inheritance, like pattern baldness in humans, how can the same genotype result in different phenotypes between males and females?
In pedigree analysis, if a trait is autosomal recessive, what must be true of the parents of an affected individual?
In pedigree analysis, if a trait is autosomal recessive, what must be true of the parents of an affected individual?
If a couple with normal vision has a color-blind son, what are the most likely genotypes of the parents, considering that color blindness is an X-linked recessive trait?
If a couple with normal vision has a color-blind son, what are the most likely genotypes of the parents, considering that color blindness is an X-linked recessive trait?
In sheep, white wool (W) is dominant to black wool (w). If two white wool sheep produce a black wool lamb, what can be concluded about the genotypes of the parents?
In sheep, white wool (W) is dominant to black wool (w). If two white wool sheep produce a black wool lamb, what can be concluded about the genotypes of the parents?
If a parent with genotype AaBb produces gametes, what are the possible combinations of alleles in the gametes, assuming the genes are unlinked?
If a parent with genotype AaBb produces gametes, what are the possible combinations of alleles in the gametes, assuming the genes are unlinked?
In humans, blood type is determined by multiple alleles, including $I^A$, $I^B$, and i. If a father has type AB blood and a mother has type A blood, which blood type is LEAST likely to be seen in their offspring?
In humans, blood type is determined by multiple alleles, including $I^A$, $I^B$, and i. If a father has type AB blood and a mother has type A blood, which blood type is LEAST likely to be seen in their offspring?
What is the probability that the next child will be a girl?
What is the probability that the next child will be a girl?
In fruit flies, normal wings (W) are dominant to vestigial wings (w). If a cross between two normal-winged flies produces some offspring with vestigial wings, what must be the genotypes of the parent flies?
In fruit flies, normal wings (W) are dominant to vestigial wings (w). If a cross between two normal-winged flies produces some offspring with vestigial wings, what must be the genotypes of the parent flies?
A trait that is passed only from fathers to sons is most likely which of the following?
A trait that is passed only from fathers to sons is most likely which of the following?
Flashcards
Who is the father of modern genetics?
Who is the father of modern genetics?
Mendel was the first to use a quantitative experimental approach in genetics.
What is a recessive trait?
What is a recessive trait?
The trait that remains hidden in an organism.
What is the Law of Dominance?
What is the Law of Dominance?
When two organisms, homozygous for two opposing traits, are crossed the offspring will be hybrid but will exhibit only the dominant trait.
What is the Law of Segregation?
What is the Law of Segregation?
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What is a monohybrid cross?
What is a monohybrid cross?
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What is a backcross or testcross?
What is a backcross or testcross?
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What is a dihybrid cross?
What is a dihybrid cross?
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What is the Law of Independent Assortment?
What is the Law of Independent Assortment?
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What is incomplete dominance?
What is incomplete dominance?
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What is codominance?
What is codominance?
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What are multiple alleles?
What are multiple alleles?
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What are polygenic traits?
What are polygenic traits?
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What are sex-linked genes?
What are sex-linked genes?
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What is Sex-influenced Inheritance?
What is Sex-influenced Inheritance?
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What is the pedigree?
What is the pedigree?
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Study Notes
Mendel Genetics
- Gregor Mendel is considered the father of modern genetics for quantitatively experimenting with genetics
- Mendel's works produced three laws: dominance, segregation, and independent assortment.
- Interbreeding increases the frequency of certain traits among offspring.
- True breeding involves mating individuals of the same breed, where offspring have the same phenotype.
Law of Dominance
- When crossing homozygous organisms with opposing traits, the offspring are hybrid, exhibiting only the dominant trait, while the recessive trait remains hidden.
Law of Segregation
- During gamete formation, the two traits carried by each parent separate.
Monohybrid Cross
- Crosses involve two organisms that are each hybrid for a single trait.
- A trait not evident in either parent can appear in the F1 generation.
Backcross or Testcross
- Used to determine if a dominant trait is homozygous (BB) or heterozygous (Bb).
- Cross an individual of unknown genotype with a homozygous recessive individual (bb) to determine the genotype.
- If a parent of unknown genotype is BB, no offspring can be white.
- If a parent of unknown genotype is hybrid, there is a 50% chance any offspring will be white.
- If any offspring show the recessive trait, the parent of unknown genotype must be hybrid.
Law of Independent Assortment
- This cross, also known as a dihybrid cross, is between two individuals that are hybrid for two traits on separate chromosomes.
Incomplete Dominance (Blending)
- Neither trait is dominant, so the genes are written using different capital letters.
- Crossing a red Japanese four o'clock flower with a white Japanese four o'clock flower produces all pink offspring (RW).
Co-Dominance
- Both traits are fully expressed.
- In humans, MN blood groups are based on two distinct molecules on the surface of red blood cells.
- MN genotype is not intermediate between M and N; both traits are fully expressed.
Multiple Alleles
- Most genes in a population exist as two allelic forms; more than two allelic forms are multiple alleles.
- In humans, there are four blood groups: A, B, AB, and O, determined by molecules on red blood cells.
- Three alleles determine the four blood types: A, B, and O.
- A and B are Co-dominant, O is a recessive trait.
Human Blood Types and Genotypes
- Type A blood can be homozygous (AA) or hybrid (Ai).
- Type B blood can be homozygous (BB) or hybrid (Bi).
- Type AB blood is heterozygous (AB).
- Type O blood is homozygous (ii).
Polygenic Inheritance
- Many traits are controlled by several genes and are called polygenic, like skin color, hair color, and height.
- This wide variation in genotypes always results in a bell-shaped curve in an entire population.
Sex-Linked Genes
- Traits carried on the X chromosome are called sex-linked.
- Linked genes are on the same chromosome.
- Females (XX) inherit two copies of sex-linked genes, while males (XY) inherit only one.
- If a sex-linked trait is due to a recessive mutation, a female will express it only if she carries two mutated genes (X-X-).
- If the male inherits a mutated X-linked gene (X-Y), he will express the gene.
- Recessive sex-linked traits are more common.
- Common recessive sex-linked traits are color blindness and hemophilia.
- A son has a 50% chance of inheriting a sex-linked trait from a carrier mother.
- It is uncommon for a female to express a sex-linked condition because she must inherit a mutant gene from both parents to be affected.
- All daughters of affected fathers are carriers.
- Sons cannot inherit an X-linked trait from the father.
- There is no carrier state for X-linked traits in males; if a male has the gene, he will express it.
Sex-influenced Inheritance
- Traits are affected by organism sex.
- Males and females express the gene for pattern baldness differently.
The Pedigree
- A family tree indicates the phenotype of one trait being studied for every family member.
- Females are represented by a circle, and males by a square.
- A half-shaded shape shows a carrier state.
- If a person exhibits the trait (as deafness), a shape is completely shaded in.
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