(2.1) An introduction to genetic variation

Reminders: A chromosome as a thread-like structure of DNA, carrying genetic information in the form of genes.

A gene is a length of DNA that codes for a protein. An allele as a version of a gene.

A genetic change is a mutation and how new alleles are formed.

Reminder that in the biological science of genetics, inheritance is the transmission of genetic information from one generation to the next generation by chromosomes of DNA, BUT, things are not that simple!.

 

Different species of plants or animals have different genes.

Individual species look different from each other because they have different combinations of genes.

The gene differences within a species are very similar, BUT, not absolutely identical, just look around and see the variation in the human species!

You see differences in height, eye colour, hair colour, height, skin colour, all of which are characteristic features within the same species.

Characteristic features can be inherited from your parents via the gene combination when an egg is fertilised (genetic factors), though some characteristic features can develop due to your surroundings and lifestyle (environmental factors).

This page will help you understand that ...

Genetic variants are caused by alterations in the common nucleotide sequences in the DNA of genes - specifically the change in base sequence from a mutation.

The term variant can be used to describe the result of a genetic alteration that may be benign (harmless), pathogenic (harmful), or of unknown significance.

 

Variation is the differences between individuals of the same species.

Variants are key to successful evolution because genotype changes (usually of the smaller type) can lead to changes in phenotype.

 

Human genetic variation is the genetic differences both within and among populations.

There may be multiple variants of any given gene in the human population, that is two different alleles, different genotypes.

The different alleles, different versions of a same gene, can lead to difference in phenotypes - the characteristics an organism displays.

A mutation may defined as any change in a DNA compared to normal that results in a rare and abnormal variant.

See the evolution page for lots more notes on variation - genetic and environmental

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Key biology points Source of information is based on the syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Introduction to Genetic Variation

Genetic variation refers to the differences in the DNA sequences among individuals within a species.

These differences are crucial for evolution, adaptation, and biodiversity.

Understanding genetic variation helps scientists and medical professionals study heredity, genetic disorders, and individual traits.

Key Terms to know:

• Variants: Variants are slight differences in the genetic sequence among individuals. They can arise due to mutations, recombination, or genetic inheritance.

• Genes: Genes are specific sequences of DNA that code for proteins and determine traits. They are inherited from parents and passed on to offspring.

• Alleles: Alleles are different versions of the same gene. For example, the gene for eye color has different alleles that can result in blue, brown, or green eyes.

• Chromosomes: Chromosomes are long structures made of DNA and proteins that store genetic information. Humans have 23 pairs of chromosomes, inheriting one set from each parent.

• Genotypes: A genotype refers to the genetic makeup of an individual for a particular trait. It consists of the specific alleles inherited from the parents.

• Phenotypes: A phenotype is the observable characteristics or traits of an individual, influenced by both genetic and environmental factors.

Importance in Human Biology

Genetic variation plays a critical role in shaping the diversity of traits among humans.

It affects susceptibility to diseases, response to medications, and even physical and behavioral characteristics.

Understanding genetic variation enables advancements in medical research, personalized medicine, and the study of inherited disorders.

It also aids evolutionary biology in explaining how populations adapt to changing environments.

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Summary of learning objectives and key words or phrases

Be able to explain what genetic variation is and refer to different organisms have different gene variants of their genotypes expressed as phenotypes.

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