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Question
What is the peculiarity of the ‘DNA’ structure?
Solution
Peculiarities of the DNA structure:
- DNA is a double helical structure having nucleotides.
- These nucleotides are made of deoxyribose sugar, phosphoric acid and nitrogenous bases such as adenine, thymine, cytosine and guanine.
- The nucleotide sequence of the DNA molecule is called a gene.
- Genes are present on DNA.
- A type of gene is responsible for the synthesis of a particular protein.
- Changes in the gene can alter the characteristics of the organisms.
RELATED QUESTIONS
The F2 progeny of a monohybrid cross showed phenotypic and genotypic ratio as 1:2:1 unlike that the Mendel’s monohybrid F2 ratio. With the help of a suitable example, work out a cross and explain how it is possible.
Select the most appropriate option
Which one of the following has the smallest number of chromosomes?
(a) Onion
(b) Mouse
(c) Monkey
(d) Ascaris
Give the ratio of phenotype of these crosses.
Why did Mendel select pea plants for his experiment?
Define Mendel’s law of segregation.
Why law of segregation is also called the law of purity of gametes?
RR (Red) Antirrhinum is crossed with white (rr) one. Offspring (Rr) are pink. This is an example of ______.
The material used for conducting experiments on genetic traits by Mendel was ______.
Which of the following statement is incorrect?
Two pea plants one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds produce F1 progeny that have round, yellow (RrYy) seeds. When F1 plants are selfed, the F2 progeny will have new combination of characters. Choose the new combination from the following
- Round, yellow
- Round, green
- Wrinkled, yellow
- Wrinkled, green
Give reasons for the appearance of new combinations of characters in the F2 progeny.
Mendel selected pea as material for his experiments because:
A gene showing dominance has:
How many pairs of contrasting characters in pea bad were chosen by Mendel?
In Mendel's experiments, colour of seed coat, nature of flower, position of flower, colour of pod, height of stem, are called
Assertion: Height in pea plants is controlled by the efficiency of enzymes and is thus genetically controlled.
Reason: Cellular DNA is the information source for making proteins in the cell.
A green stemmed tomato plant denoted by (GG) is crossed with a tomato plant with purple stem denoted by (gg).
- What colour of the stem would you expect in their F1 progeny?
- In what ratio would you find the green and purple coloured stem in plants of F2 progeny?
- What conclusion can be drawn for the above observations?
In parents, mendelian factors occur in pairs, but they segregate during ______.
Purity of gametes is linked to ______.
