Question

a) List the mechanisms which create genetic variation in sexually reproducing organisms. 

b) List at least 4 conserved processes, molecules, or cell components which support the concept of a universal common ancestor. 

c) Define Mendel's two laws and state their cellular basis and limitations.

Answer 1

1-a)- the different mechanisms are as follows:-

• mutation.
• random mating between organisms.
• random fertilization.
• crossing over (or recombination) between chromatids of homologous chromosomes during meiosis

b)- the conserved processes or molecules which support the concept of a universal common ancestor are as follows:-

• DNA, based genetic code which is nearly universal
• RNA intermediates,
• Presence of codons that coded for 20 amino acids in the genetic code,
• ATP presence
• Presence of enzymes to catalyze chemical reactions,
• Presence of lipid membrane,
• Cell division.as a mode of reproduction

c)-

• The principle of segregation (First Law): The two members of a gene pair (alleles) segregate (separate) from each other in the formation of gametes. Half the gametes carry one allele, and the other half carry the other allele.
• The principle of independent assortment (Second Law): Genes for different traits assort independently of one another in the formation of gametes.

Cellular basis :- They can explain how many different characteristics are inherited, in a wide range of organisms including human beings.Since the chromosomes are a part of the cell so these laws frame the basis of the cellular inheritance also from the parents.

Limitations:-

• Law of segregation does not apply to incompletely dominant or co-dominant alleles.
• Law of independent assortment applies to only on those genes which are distantly located may be on the same chromosome or on different chromosome.
• Mendel's laws are not applicable to bacteria where sexual reproduction doesnot take place and also to haploid organisms .