genetics Flashcards
what are human genetics?
a term referring to heredditary features and tries to predict characteristics of children from production.
what is a dominant allele?
it is always expressed, even if one copy is present. Dominant alleles are represented by a capital letter
what is a recessive allele?
it is only expressed if the individual has two copies and does not have the dominant allele of that gene. Recessive alleles are represented by a lower case letter
what does homozygous mean?
means that the genotype could be the same. e.g the mum and dad likely have the same genotypes.
what does heterozygous mean?
means that the genotype could be different. e.g. the mum and dad have different genotypes.
what is a genotype?
is the inherited genetic information responsible for a particular trait
what is a phenotype?
is the resulting physical characteristic / appearance, depending on what genes were inherited
what happens when there’s a new mutation in a body cell
the effect will be minimal and only cause harmful effects in the new cells that divide from that cell
what happens if there’s a new mutation in the sperm/ ovum
If it becomes a zygote- it will divide multiple times to form a human. every cell with therefore carry the mutation.
what causes Down syndrome?
those who inherit an unbalanced translocation involving chromosome 21 may have extra genetic material from chromosome 21, this causes down syndrome.
what causes mosaic down syndrome?
it is not inherited. it occurs as a random event during call division early in foetal development.
how many chromosomes does someone with Down syndrome have?
a total of 47. usually an extra chromosome 21
what is Huntington’s disease
an inherited disease that results in the death of brain cells. medication cannot cure it, however it can help to slow down the symptoms.
what is cystic fibrosis causes by?
it’s caused by a recessive allele, so both parents must posses this faulty allele. the individual will have needed to inherit two copies of the faulty allele to be born with CF.
what is sickle cell caused by?
it is caused by a defective allele that interfere with the normal production of red blood cells, which carry oxygen in the blood.
what is PKU
it is where the body cannot break down the amino acid- phenylalanine, which then builds up in the blood and brain. this can lead to brain damage. it is caused by a recessive allele
how is cystic fibrosis diagnosed?
by a sweat test, looking at if the persons sweat is abnormally salty
how is PKU diagnosed?
can be diagnosed shortly after birth using a heel prick test to look for high levels of phenylalanine.
how is Down syndrome diagnosed?
can be aided by the persons external features
how is sickle cell diagnosed?
by a blood test that identifies red blood cells that show sickling
how is Huntington’s diagnosed?
can be confirmed through chorionic villus sampling
chorionic villus sampling: where is the sample taken from and at what week of pregnancy?
taken from the placenta after the 10th week of pregnancy
what is found in the membranes surrounding the foetus?
the chorion and amnion
how is the sample of the chorion found before being taken?
the placenta is located by ultrasound or endoscopy and a small sample of the villi is removed
