What is Variation?.This documents goes in the inner depths of how our genetic information are passed on from our parents to us , how our features are decided , what causes cystic fibrosis and polydactyly and are we able to design our baby through genetic modification and more....
What causes Variation?
Variation, the differences among individuals within a species, can
be caused by several factors:
Genetic Variation: Each individual has a unique genetic
makeup, derived from the DNA inherited from their parents.
Mutations, the permanent alterations in the DNA sequence of
a gene, can also introduce new genetic variations. Genetic
recombination, which occurs during sexual reproduction as
chromosomes exchange segments, further contributes to
genetic diversity.
Environmental Influences: Conditions in an individual’s
environment can greatly influence their physical and
behavioural traits. For instance, differences in climate,
availability of food, and exposure to pollutants can cause
variations in size, coloration, and survival strategies among
individuals within the same species.
Gene-Environment Interaction: The expression of genes
can be influenced by environmental conditions, meaning that
the same genotype (genetic makeup) can result in different
phenotypes (observable traits) under different environmental
circumstances. This interaction can lead to considerable
variation within a population.
Epigenetic Factors: These are changes that affect gene
expression without altering the DNA sequence. Epigenetic
changes can be caused by environmental factors and can be
inherited by the next generation in some cases. This leads to
variation in how genes are expressed in different individuals.
Developmental Noise: Random variations during the
development of an organism, such as slight differences in cell
division or small fluctuations in hormone levels, can lead to
differences among individuals.
,The combination of these factors ensures a high level of diversity
within populations, which can be critical for adaptation and survival
in changing environments. This diversity is a key element in the
process of natural selection, as it provides a pool of traits from
which advantageous ones can be selected.
What is the structure of DNA?
The structure of DNA (deoxyribonucleic acid) is famously known as
a double helix, a discovery that was made by James Watson and
Francis Crick in 1953, with crucial contributions from Rosalind
Franklin and Maurice Wilkins.
Here’s how the DNA structure is organised:
Double Helix: DNA consists of two long strands that wind
around each other like a twisted ladder. The sides of the
ladder are formed by alternating sugar (deoxyribose) and
phosphate groups. These two strands are antiparallel,
meaning they run in opposite directions.
Nucleotides: Each "rung" of the DNA ladder is made up of a
pair of nitrogenous bases. The nucleotide itself is a basic unit
of DNA, consisting of a phosphate group, a sugar molecule
(deoxyribose), and a nitrogenous base. There are four types
of nitrogenous bases in DNA:
● Adenine (A)
● Thymine (T)
● Cytosine (C)
● Guanine (G)
Base Pairing: The nitrogenous bases on one strand form
hydrogen bonds with the bases on the opposite strand.
, These bases pair in a very specific way: adenine always pairs
with thymine (A-T) and cytosine always pairs with guanine (C-G).
This specific pairing (known as complementary base pairing) helps
to maintain the consistent width of the double helix and allows for
the DNA to be copied accurately during cell division.
Major and Minor Grooves: The spiralling of the double helix
creates spaces that are referred to as major and minor
grooves. These grooves are pathways that allow regulatory
proteins to access the bases and influence gene expression.
The structure of DNA is crucial for its function. It allows DNA to
carry genetic information, replicate accurately, and evolve over time
through mutations. Each twist of the helix typically contains about
ten base pairs. The overall structure is highly stable, protecting the
genetic code it carries within the sequences of its bases. This code
is essential for directing the synthesis of proteins, which in turn
dictates the structure and function of the body’s cells and tissues.
Inside The Cell: Cell - Nucleus - Chromosome - DNA - Gene
(Segment of DNA)
When a sperm fertilises the egg, the two nuclei fuse together to
form a single nucleus.This nucleus contains 46 chromosomes. Our
chromosomes are made up of strands of DNA.
DNA is found inside the nucleus of each cell. One very long.Coiled
up molecule of DNA is called a chromosome.
Human cells have 46 chromosomes in total.
Each DNA molecule contains two strands that are connected by a
pair of substances called bases. It looks like a ladder, where the
, bases form the rungs. In addition, the ladder is wound and looks a
bit like a spiral staircase. We call this wound-ladder structure of
DNA a "double helix".
This double helix structure of DNA was discovered by the British
scientists James Watson and Francis Crick who received the Nobel
Prize for their work in 1962,
There are four bases in DNA, adenine, thymine, cytosine and
guanine, normally just called A, T, C and G. When forming pairs to
make the rungs of the ladder, A always pairs with T and C with G.
We call this complementary base pairs.
Furthermore, each base is attached to a sugar which in turn bonds
to a phosphate group. The sugars and phosphate form the
backbone of the DNA strands.
A gene is one section of DNA that codes for one single
characteristic or protein. We all have very small differences in our
genes caused by slightly different orders of the bases in our DNA.
This means that everyone's DNA is unique. It allows scientists to
match DNA from cells to specific people. For example, it helps
scientists to find out how people are related or it can be used by
forensic scientists to identify criminals.
How to predict the genetic outcomes?
Predicting genetic outcomes typically involves understanding how
genes are transmitted from parents to offspring through the
processes of inheritance. Several methods and principles derived
from genetics are used to predict these outcomes:
Punnett Square: This is a simple and commonly used tool to
predict the probability of the genotypes and phenotypes of
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