29 Questions
What is heredity?
The transmission of characteristics from one generation to the next
Which scientist is known as the 'Father of Genetics'?
Gregor Johann Mendel
What is an allele?
A version of a specific gene
Which term represents a dominant allele?
Indicated by a capital letter
Why did Gregor Johann Mendel choose garden peas for his experiments?
They have several contrasting characteristics
What causes variations in traits among individuals in a species?
Genetic mutations and environmental factors
What did Mendel observe when he crossed a tall pea plant with a short one?
All offspring in the first generation were tall.
What ratio of tall to short plants did Mendel observe in the second generation after self-pollinating the first-generation plants?
3:1
What led Mendel to conclude about the short trait in the first generation?
The short trait was present but unable to express itself in the first generation.
What did Mendel observe about shape and color traits in the second generation of his pea plant experiments?
New combinations alongside parental traits were observed, showing independent inheritance.
In Mendel's experiment with round and yellow seed pea plants, why did he self-pollinate the first-generation plants?
To understand what happened to the green and wrinkled traits.
What did Mendel's observation of new combinations in the second generation suggest about shape and color traits?
Shape and color traits are inherited independently.
How many pea plants did Mendel grow to generate the plants of the first hybrid generation?
1600
What is the genotype of a pea plant that is heterozygous for round shape of seeds?
Aa
In the first generation offspring when Aa is crossed with aa, what phenotype is most likely to be exhibited by the offspring?
Half will exhibit dominant phenotype, half will exhibit recessive phenotype
What would be the color of the puppies produced by Harsh's two golden retriever dogs, if one parent is black and the other parent is also black?
Black
How many seedlings would have germinated if Lokesh allowed a black dog and a homozygous black dog to mate, given that a total of four puppies were produced?
800
What is the reason intelligence and knowledge are not heritable traits?
They do not bring changes in germ cell DNA
In a tabular form, how can you distinguish between inherited traits and acquired traits?
Inherited traits are passed genetically, while acquired traits are due to environmental factors.
Why are characters like 'T' considered dominant traits in genetics?
They express themselves and suppress other traits
What happens to the number of chromosomes during gamete formation in sexually reproducing organisms?
The number halves
What advice did Lila give to Rekha regarding her skin color?
That skin color is determined by birth and should not be altered
Why might all the family members of Rekha's family have dark complexions?
Possible genetic inheritance of dark complexion trait
What is the likely genotype of the dogs with black coat color?
Bb
In the case of a homozygous tall F₂ plant, what genetic combinations would Mendel have observed upon self-pollination?
All TT
When a black dog with genotype BB mates with a black dog with genotype Bb, what will be the coat color of their offspring?
All black
If Harsh's two golden retriever dogs carry the recessive allele for black coat color (bb), what color puppy could they potentially produce?
Black
What does the 150:50 offspring ratio from dogs suggest about their alleles?
One parent is heterozygous and the other is homozygous dominant
In a cross between a tall and a dwarf plant where 250 puppies are obtained, out of which 124 display tall phenotype, what is the likely genotype of the parent plants?
Tt x Tt
Study Notes
Heredity and Genetics
- Heredity refers to the passing of traits from parents to offspring through genes.
- Gregor Johann Mendel is known as the 'Father of Genetics'.
Alleles and Traits
- An allele is a variant of a gene that occupies a specific location on a chromosome.
- A dominant allele is represented by a capital letter (e.g., 'B' for black coat color).
- Variations in traits among individuals in a species occur due to the combination of different alleles.
Mendel's Experiments
- Mendel chose garden peas for his experiments because they have a relatively simple genetic makeup and can be easily crossed and self-pollinated.
- When Mendel crossed a tall pea plant with a short one, he observed that all offspring in the first generation were tall.
- In the second generation, Mendel observed a 3:1 ratio of tall to short plants after self-pollinating the first-generation plants.
- The short trait in the first generation was not visible, leading Mendel to conclude that it was recessive.
- In the second generation, Mendel observed that shape and color traits were not always paired together, suggesting that they are separate traits.
Genotype and Phenotype
- The genotype of a pea plant that is heterozygous for round shape of seeds is 'Rr'.
- When 'Aa' is crossed with 'aa', the offspring are most likely to exhibit the 'aa' phenotype.
- The genotype of a dog with a black coat color is 'BB' or 'Bb'.
Inheritance of Traits
- Intelligence and knowledge are not heritable traits because they are influenced by environmental factors.
- Inherited traits are determined by genes, whereas acquired traits are influenced by environmental factors.
- Characters like 'T' are considered dominant traits because they are always expressed when paired with a recessive allele.
Chromosomes and Gamete Formation
- During gamete formation in sexually reproducing organisms, the number of chromosomes is halved.
Genetic Combinations
- In the case of a homozygous tall F₂ plant, Mendel would have observed the genetic combinations 'TT' or 'tt' upon self-pollination.
- When a black dog with genotype 'BB' mates with a black dog with genotype 'Bb', the offspring will have a black coat color.
- If Harsh's two golden retriever dogs carry the recessive allele for black coat color ('bb'), they could potentially produce a puppy with a black coat color.
Offspring Ratios
- The 150:50 offspring ratio from dogs suggests that the alleles are segregating in a 3:1 ratio.
- In a cross between a tall and a dwarf plant, a 3:1 ratio of tall to dwarf plants suggests that the parent plants are heterozygous for the tall trait.
Test your knowledge on inherited and acquired traits by distinguishing between them in a tabular form and providing examples. Explore the concept of dominant trait in pea plants and understand its significance.
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