Heredity and Evolution online mcq quiz
Heredity and Evolution boostup points
🡆 Heredity:
⤷ The passing of traits from the parents to offspring is called heredity.
⤷ This is heredity which is responsible for many commonly observable facts; like siblings looking similar in overall appearance.
⤷ Variation: The differences among the individuals of a species/population are called variations.
⤷ Genotype: The complete set of genes in an organism’s genome is called genotype.
🡆 Phenotype:
⤷ The observable characters in an organism make the phenotype.
⤷ Phenotype is a result of genotype’s interaction with the environment.
⤷ Due to this reason, many phenotypes are not inheritable.
🡆Acquired Traits:
⤷ Traits; which are acquired due to interaction with the environment; are called acquired traits.
⤷ Acquired traits are not inheritable.
⤷ Example; if a boxer develops bulging biceps, it does not mean that his son would be borne with bulging biceps.
🡆Inheritable Traits:
⤷ Traits; which can be expressed in subsequent generations; are called inheritable traits.
⤷ Such traits bring a change in the genotype of the organism and hence become inheritable.
🡆 Speciation
⤷ Micro evolution: It is the evolution which is on a small scale. Example: change in body color of beetles.
⤷ The process by which new species develop from the existing species is known as speciation.
⤷ Speciation: it is the process of formation of new species.
⤷ Species: A group of similar individuals within a population that can interbreed and produce fertile offspring.
⤷ Gene flow: It is exchange of genetic material by interbreeding between populations of same species or individuals
⤷ Speciation takes place when variation is combined with geographical isolation.
⤷ Gene flow : occurs between population that are partly but not completely separated
🡆 Genetic Drift:
⤷ It is the random change in the frequency of alleles (gene pair) in a population over successive generations.
⤷ The process by which nature selects and consolidate those organisms which
are more suitably adapted and possesses favorable variations
⤷ Genetic drift takes place due to
Severe changes in the DNA
Change in number of chromosomes
🡆 Accumulation of Variations During Reproduction:
⤷ Asexual reproduction involves a single parent and is hence not ideal ideal for facilitating variations.
⤷ Some minor variations do occur due to inaccuracies in DNA replication.
⤷ But the quantum of variations would be too little and would take too many years to show effect.
⤷ Sexual reproduction, on the other hand, is ideal for facilitating variations because two parents are involved in it.
⤷ The offspring’s genotype is contributed by two parents and hence chances of variations are very high.
🡆Rules of Inheritance
⤷ Gregor Johann Mendel conducted experiments on pea plants and proposed the rules of inheritance; based on his observations.
⤷ Mendel observed that characters are often present in pairs.
⤷ A pair of contrasting characters is called allele.
⤷ Possible Reasons of Pea Plants Used by Mendel:
🢝 Pea can be termed as biennial plant, i.e. two generations of a pea plant can grow in a given year.
🢝 This means that Mendel could get enough time to observe a larger number of generations.
🢝 Many easily identifiable and contrasting characters are present in pea plants.
🢝 Cross pollination can be easily induced in pea plants.
⤷ Monohybrid Cross: The cross in which just two contrasting characters are studied is
called monohybrid cross.
🡆 Mendel's First Law
⤷ Law of Segregation:
🢝 Every individual possesses a pair of alleles for a particular trait.
🢝 During gamete formation, a gamete receives only one trait from the alleles.
🢝 A particular trait can be dominant or recessive in a particular generation.
Dihybrid Cross: The cross in which two pairs of characters are studied is called dihybrid cross..
🡆 Mendel’s Second Law:
🢝 Law of Independent Assortment:
🢝 Alleles of different characters separate independent from each other during gamete formation.
🡆Sex Determination in Humans:
⤷ Somatic cells in human beings contain 23 pairs of chromosomes.
⤷ Out of them the 23rd pair is composed of different types of chromosomes which are named as X and Y chromosomes.
⤷ The 23rd pair contains one X and one Y chromosome in a male.
⤷ On the other hand, the 23rd pair in a female contains X chromosomes.
⤷ This means that all the eggs would have X chromosome as the 23rd chromosome, while a sperm may have either X or Y chromosome as the 23rd chromosome.
⤷ When a sperm with X chromosome fertilizes the egg, the resulting zygote would develop into a female child.
⤷ When a sperm with Y chromosome fertilizes the egg, the resulting zygote would develop into a male child.
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