Gene expression Flashcards
What is a gene?
A length of DNA on a chromosome that codes for production of one or more polypeptide chains and functional RNA
What is meant by genotype?
The genetic makeup of an organism which includes the different alleles which the organism possesses
What is the phenotype
An organism’s observable characteristics.
What are alleles?
Different versions of the same gene
What is a dominant allele?
A version of a gene where only one copy is needed for it to be expressed
What is a recessive allele?
A version of a gene where two copies are needed for it to be expressed
What is meant when an organism is homozygous?
It has two copies of the same allele (2 dominant or 2 recessive)
What is meant when an organism is heterozygous?
When it has two different versions of the same gene, one dominant and one recessive
What is codominance?
Two dominant alleles that both contribute to the phenotype. The characteristics either blend together or show up both
What is an autosome?
A chromosome that is not an X or Y chromosome
What is a sex chromosome?
A chromosome that determines the sex of an organism. X and Y
Define monohybrid inheritance
Where one phenotypic characteristic is controlled by a single gene
What do family pedigrees show?
The inheritance of an allele over multiple generations
What is a sex-linked characteristic?
A characteristic where the gene responsible is located on a sex chromosome. This makes it more common in one sex than in the other
Give one example of a sex-linked trait
Red/green colorblindness is inherited on the X chromosome and is much more common in males
What is red/green colorblindness?
An X-linked condition which makes the individual unable to distinguish between red and green due to a lack of red or green photoreceptors
Why is red/green colorblindness significantly more common in males?
The faulty gene which causes it is located on the X chromosome. Men only inherit one copy of the X chromosome so they cannot inherit another non-faulty copy.
What is cystic fibrosis?
An inherited autosomal recessive genetic condition. It impairs the functioning of the gaseous exchange, digestive and reproductive systems. It produces a faulty copy of a protein involved in producing mucus
What is the genotype of individuals with cystic fibrosis?
Homozygous recessive
Why is the genotype of carriers of cystic fibrosis?
Heterozygous
What is meant by genetic screening?
Determining if an individual’s DNA contains a certain allele. This can allow prenatal diagnosis and earlier start of treatment
What is pre-implantation genetic diagnosis? (PGD)
The determination of genetic diseases during IVF before implantation of the embryo into the uterus
Describe the process of chorionic villus sampling
A sample of embryonic tissue is taken from the placenta at 8-12 weeks. It is screened for various disorders.
Describe the process of amniocentesis
A sample of amniotic fluid is taken at 14-16 weeks. The results are slower than CVS because the fetal cells have to be grown for 2-3 weeks before screening
Give some social and ethic issues surrounding prenatal genetic screening
-procedures carry risk of harming fetus
-may result in spontaneous miscarriage
-high cost of bringing up a baby with a genetic disorder
-emotional and mental stress on parents
Outline how genetic screening can be used to improve healthcare (3)
Refers to adults, not prenatal screening
-enables awareness of potential risks and introduction of lifestyle changes to reduce these risks
-enables treatment to begin early
-prediction of a patient’s reaction to certain drugs
Outline the drawbacks of genetic testing in healthcare (2)
Discrimination by employers if a person is likely to develop a disease. Person may develop anxiety, depression, etc.
