What is DNA?
What is a genome?
What is a gene?
How are they inherited?
What is a mutation?
What is a chromosome?
What is an autosome?
What is the chromosomal difference between men and women?
What are the four main forms of inheritance conditions?
What is Autosomal dominant inheritance?
What is Autosomal recessive inheritance?
What does it mean to be a carrier of a disease?
What is an X-linked condition?
What Mitochondrial inheritance?
What is chromosomal inheritance?
What is Epigenetic inheritance?
What are the three main categories for Epigenetic Inheritance?
What is polygenic inheritance?
What is DNA?
DNA is a long molecule made up of a combination of four chemicals: adenine, thymine, cytosine and guanine, represented as letters A, T, C and G. These “letters” are ordered in particular sequences within your genes. They contain the instructions to make a particular protein, in a particular cell, at a particular time
What is a genome?
Your genome is all 3.2 billion letters of your DNA which contains around 20,000 genes.
What is a gene?
A section of DNA that codes for a specific protein. Much of genetics is concerned with the role of genes in the production of proteins, the way in which the activity of genes is controlled and regulated, and the way in which genes are passed from generation to generation.
How are they inherited?
In each cell in your body, your entire genome is contained in 23 pairs of chromosomes. You inherit, at random, half of those chromosomes from your mother and half from your father.
What is a mutation?
The changing of the structure of a section of DNA which may result in an altered gene which alters the protein it codes for to be different in some way. This could lead to a disease or illness because the protein is not acting in the way that it should.
What is a chromosome?
Our genes are packed together into 23 pairs of chromosomes. 22 of these pairs are the same for men and women but the last pair is different.
what is an autosome?
The 22 pairs of chromosomes that are the same for men and woman are referred to as ‘autosomes’.
What is the chromosomal difference between men and women?
Women have two X chromosomes but men have an X and a Y chromosome. Men inherit their Y chromosome from their father and X chromosome from their mother. Women inherit a X chromosome from both parents.
What are the four main forms of inheritance conditions?
Autosomal dominant, autosomal recessive, X-linked recessive, X-linked dominant, mitochondrial, chromosomal, epigenetic and polygenic.
What is Autosomal dominant inheritance?
A child will risk suffering from a condition when a gene inherited from either one of the parents (either from the egg or sperm) has a mutation. The other copy of the gene inherited from the unaffected parent cannot compensate. However in few circumstances, not every person with the gene change necessarily develops the condition (particularly men with BRCA1 and BRCA2 mutations as they have little breast and no ovarian tissue) and therefore the condition can appear to skip a generation.
What is Autosomal recessive inheritance?
This is where a gene inherited from both of the parents (in the egg and sperm) has a mutation. The parents are carriers of the disease. The affected child has two altered copies and therefore is at high risk of disease. This type of inheritance is more common when inter-marrying occurs as we share genes in common with our relatives.
What does it mean to be a carrier of a disease?
When an individual has one altered copy of a disease and another normal copy, but because it is a recessive condition they are able to compensate and do not show symptoms of the condition. You can not be a carrier for a dominant condition.
What is an X-linked condition?
If a condition is inherited in a X-linked dominant fashion it affects men and women and looks very similar to an autosomal dominant condition but there is no male-to-male transmission of disease, as men inherit their Y chromosome from their father. As women have two copies of their X chromosome and are therefore able to compensate, X-linked recessive conditions are more common in men and there is no male-to-male transmission as men inherit their Y chromosome from their father.
What Mitochondrial inheritance?
Mitochondria are the energy centres within our cells and have their own DNA which is inherited through our mother. Alterations in these genes can cause metabolic and neurological problems.
What is chromosomal inheritance?
Our genes are packaged into chromosomes. Gain or loss of large sections of the genome can be inherited from either parent or occur for the first time when the egg or sperm is made. About one person in 150 has inherited a rearrangement of the chromosomes whereby parts of two chromosomes (at least) have swapped places. This usually causes few problems but can cause multiple miscarriages or learning and physical problems in subsequent generations.
What is Epigenetic inheritance?
This involves conditions that are caused by alterations that occur in the genome that are not due to spelling mistakes in the DNA code itself. Some of these changes can occur under stressful conditions when the eggs are first developing in an embryo. The grandmother’s health while pregnant with the mother may affect the genetics of the child.
What are the three main categories for Epigenetic Inheritance?
- Chemical changes to the DNA molecule at the on and off switches of genes called promoters.
- Changes to the folding of the genes around proteins when forming chromosomes which can affect how the gene produces proteins.
- Inheriting both copies of the genes on a chromosome from one parent rather than one copy from each. This can be a problem even if the genetic code is normal as some genes are switched on and off depending on whether they have been inherited from the mother or father. As a result it is possible that certain genes will be either completely switched off or even become over active causing disease.
What is polygenic inheritance?
This is the most common inheritance pattern, which encompasses the combination effect of environmental forces and the effect of multiple different genetic factors which are inherited by both parents. For example: asthma, psoriasis, exzema, diabetes and congenital dislocation of the hip.
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