2.15-2.18 : gene expression unit 1

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 e.g. X and Y chromosomes in humans and other mammals

define monohybrid inheritance

where one phenotypic characteristic is controlled by a single gene

what do family pedigrees show

the inheritance of an allele over mulitple generations

what is a sex linked characteristic

• a characteristic where the gene responsible for its located on a sex chromosome

• this makes it more common in one sex than another

give one example of a sex linked trait

red/green colour blindness is a sex linked trait as it is inherited on the X chromosome and so much more common in males

what is red/green colour blindness

an x-linked genetic condition which results in a inability to distinguish between red and green due to a lack of red or green photoreceptors

why is red/green colour blindness significantly more common in males

• the faulty gene which causes red/green colour blindness is located on the x chromosome

• males only inherit one copy of the X chromosome and so they cannot inherit another non-faulty copy of the gene

what is cystic fibrosis

an inherited autosomal recessive genetic condition which impairs the functioning of the gaseous exchange, digestive and reproductive systems by producing a faulty copy of the protein involved in the production of mucous, digestive juices and other fluids

what is the genotype of individuals with cystic fibrosis

homozygous recessive (ff)

what is the genotype of carries of cystic fibrosis

heterozygous (Ff)

what is meant by genetic screening

determining if an individual’s DNA contains a certain allele, usually one that may result in a genetic disorder, this can allow prenatal diagnosis, and for treatment to be started earlier

what is pre implantation genetic diagnosis (PGD)

the determination of genetic diseases during in vitro fertilisation (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 around 8 to 12 weeks of pregnancy , it is screened for various disorders and results are available quickly

describe the process of amniocentesis

a sample of amniotic fluid is taken at around 14 go 16 weeks of pregnancy, the foetal cells have to be grown for 2-3 weeks before screening can take place, meaning results are slower than CVS

give some social and ethical issues surrounding prenatal genetic screening

• procedures carry risk of harming foetus

• may result in abortion, which many people object to

• high cost of bringing up a baby with a genetic disorder

• emotional and mental stress on parents

what is genetic screening

a method of testing an individual’s genome for faulty alleles that may make them more susceptible to certain diseases and disorders

outline how genetic testing can be used to improve healthcare (3)

• enables awareness of potential risks and the introduction of lifestyle changes to reduce these associated risks

• enables early treatment plans to begin

• prediction of a patient’s reaction to certain drugs - ‘personalised medicine’

outline the drawbacks of using genetic testing in healthcare (2)

• discrimination by employers, insurance firms etc. if a person is likely to develop a disease

• person may develop anxiety, depression, etc