Heredity and Evolution: Meaning of Heredity, Aristotle՚S Model of Inheritance (For CBSE, ICSE, IAS, NET, NRA 2022)
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Introduction
- The passing on of traits from parents to their offspring is called Heredity.
- Heredity is also known as inheritance or biological inheritance.
- This takes place either through sexual reproduction or asexual reproduction.
- The genetic information of the parents is acquired by the offsprings.
- Genetics is the study of heredity in Biology.
- Cryptophasia is the language which can be understand only by the twins.
- Twin formation can be of two types:
Monozygotic
- The twins are the ones which are formed from one zygote.
- Splits into two embryos.
- Twins are identical to each other.
Dizygotic
- The twins are fraternal in dizygotic twins.
- The twins are not identical.
- Reproduced from separate eggs being released simultaneously from the ovary.
- Subtypes of twins:
- Boy-boy
- Boy-girl
- Girl-girl
Asexual Reproduction
- This reproduction involves the fusion of gametes or change in the number of chromosomes.
- It is the primary form of reproduction for single-celled organisms such as archaea and bacteria.
- Several eukaryotic organisms including plants, animals, and fungi can also reproduce asexually.
Types
Aristotle՚S Model of Inheritance
Modern Development of Genetics and Heredity
- The gap between experimental geneticists and naturalists was bridged by the modern synthesis.
- With known genetic mechanisms including the observational evidence of naturalists, all evolutionary phenomena can be explained.
- The evolution process is gradual:
- Small genetic changes
- Recombination ordered by natural selection
- Selection is overwhelmingly the main mechanism of change.
- The primacy of population thinking:
- The genetic diversity carried in natural populations.
- The strength of natural selection in the wild.
Common Genetic Disorders
Down Syndrome
- It is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21.
- It is also known as trisomy 21.
- It is usually associated with:
- Physical growth delays.
- Mild to moderate intellectual disability.
- Characteristic facial features.
Sickle Cell Disease
- It is a group of blood disorders typically inherited from a person՚s parents.
- Sickle cell anaemia (SCA) is the most common type.
- Sickle cell disease results in an abnormality in the oxygen-carrying protein haemoglobin.
Phenylketonuria
- PKU is an inborn error of metabolism.
- It is a genetic disorder inherited from a person՚s parents.
- It results in decreased metabolism of the amino acid phenylalanine.
- Untreated, PKU can lead to:
- Intellectual disability
- Seizures
- Behavioral problems
- Mental disorders