Chapter 23 - Characteristics Of Offspring Flashcards
What is consanguineous Union?
Marriage between cousins (double horizontal lines)
Melanin vs melanocytes.
Melanin is a yellow- balky pigment produced by special skin cells called melanocytes creating one of the human traits - skin colour.
Who are albinos?
The production of melanin by the melanocytes is dependent on on particular enzymes.
Some Individuals fail to have synthesised one of the enzymes and pigmentation does not occur.
When 2 recessive genes for skin colour pigmentation occurs.
These individuals are called albinos and they white hair, skin, pink eyes (due to reflection of blood vessels)
What is Probability?
Probability is the chance that something will happen (expressed as fraction, decimal or percentage).
What are the patterns of inheritance in pedigrees?
- Every person who shows a dominant Characteristic needs only have one allele for that characteristic, and every person possessing such an allele must show the characteristic.
- A person with a dominant characteristic must have at least one parent with the characteristic. It cannot skip a generation
- Two people with a dominant characteristic can have a child without that characteristic
- Two people who do not posses a dominant characteristic cannot have a child with such a characteristic
- Every person who shows a recessive characteristic must have two alleles for that characteristic
- A person with a recessive characteristic does not have to have parent with the characteristic. It can skip a generation.
- Two people without a recessive characteristic have a child with the characteristic
- Two people without a receive characteristic can have a child without the characteristic
- A characteristic linked to the X-chromosome cannot be passed from a father to a son. Fathers can only pass such characteristics to their daughters
- 2 people without an X-linked characteristic can have a son with the characteristic but not a daughter.
What are single gene disorders?
Disorders caused by the inheritance of a single defective gene or disorders that refits from the mutation of the structure of a single gene.
What are some autosomal Dominant inheritance?
- Huntington’s disease
- Achondroplasia
- Facioscapulohumeral muscular dystrophy
- Neurofimbrosis
What is achondroplasia?
A form of dwarfism characterised by short limbs, prominent head, normal intelligence and waddling gait
What it’s facioscapulohumeral muscular dystrophy
A rare form of muscular dystrophy affecting the facial muscles.
Other muscles are gradually affected, making it difficult to raise the arms above the shoulders, to lift objects or to walk normally.
What is neurofibromatosis
Inherited as a dominant characteristic; affected individuals exhibit numerous tumours along the peripheral nerves.
The tumours are composed of a dense proliferation of nervous and fibrous tissue, and cause abnormalities of the skin and flesh as well as distortions of bone structure.
What are some recessive inheritance disorders?
- Thalassaemia
- PKU
- Cystic Fibrosis
Explain what cystic fibrosis
Disorder controlled by a recessive allele.
Children with the condition suffer from chest infections, lack of digestive enzymes and increased salt loss.
It is the most common lethal genetic disease in people of European origin, in whom up to 3% of the population are thought to be carriers.
Blood sample is usually taken from the baby’s heel within 2-3 days after birth.
When child is identified as having the disease, it is given special diet low in fat and high in carbohydrates and protein.
The diet is supplemented with pancreatic extract and large dose of vitamin A,D and K.
This does not cure the disease but it does enable the child to function. As normally as possible.
Couples concern that they may be carriers of cystic fibrosis can be tested via a laboratory test done on a sample of blood saliva.
If Results show prospective parents are carriers genetic counselling should be considered before starting a family.
What is Dominant inheritance
Dominant inheritance means an abnormal gene from one parent can cause disease.
The abnormal gene dominates.
This disease can also occur as a new condition in a child when neither parent has the abnormal gene.
What is recessive inheritance?
Recessive inheritance means both genes in a pair must be abnormal to cause disease.
People with only one defective gene in the pair are called carriers. These people are most often not affected with the condition.
However, they can pass the abnormal gene to their children. CHANCES OF INHERITING A TRAIT
What is Co-dominance inheritance
In codominant inheritance , two different versions (alleles) of a gene are expressed, and each version makes a slightly different protein.
Both alleles influence the genetic trait or determine the characteristics of the genetic condition
