long biology Flashcards
what is mitosis?
cell division that produces 2 daughter cells that have the same number of chromosomes so are genetically identical.
what is the role of mitosis?
growth and repair, plus replacement.
what is meiosis?
cell division that produces 4 daughter cells, known as gametes, which have a single set of chromosomes (are haploid), each with different combinations of parent cells’ dna.
what is the role of meiosis?
reducing the chromosome number so that the full chromosome complement is restored at fertilisation.
what does asexual reproduction produce?
clones
how many parents does asexual reproduction involve?
1
are offspring of asexual reproduction genetically identical?
yes
in most mammals, what are the female sex chromosomes?
XX
in most mammals, what are the male sex chromosomes?
XY
what is a gene?
a section of dna that codes for a specific protein.
what is an allele?
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
what is a dominant trait?
a trait that is phenotypically expressed in heterozygotes.
what is a recessive trait?
the variant of a gene for a particular characteristic that is masked or suppressed in the presence of a dominant variant.
what is homozygous?
If the two alleles at a locus (fixed position on a chromosome) are identical to each other, they are homozygous eg bb
what is heterozygous?
If the two alleles at a locus (fixed position on a chromosome) are different to each other, they are heterozygous eg Bb
what is a phenotype?
the set of observable characteristics of an individual.
what is a genotype?
the genetic constitution of an individual organism.
how is cystic fibrosis screened in the UK?
all newborn babies are screened for cystic fibrosis as part of the newborn blood spot test (heel prick test) carried out shortly after they’re born.
if the cystic fibrosis test is positive, what additional tests confirm the baby has it?
1) a sweat test – to measure the amount of salt in sweat, which will be abnormally high in someone with cystic fibrosis.
2) a genetic test – where a sample of blood or saliva is checked for the faulty gene that causes cystic fibrosis.
what is cystic fibrosis?
an inherited condition that causes sticky mucus to build up in the lungs and digestive system. This causes lung infections and problems with digesting food.
is cystic fibrosis dominant or recessive?
recessive
what is polydactyly?
an inherited condition in which a person has extra fingers or toes.
is polydactyly dominant or recessive?
dominant
how and when is huntington’s screened?
PGD, only available at certain clinics licensed by the Human Fertilisation and Embryology Authority. or PND, prenatal diagnosis, only used if the couple intend to terminate if the test is positive (testing once the embryo is implanted)
what does pgd involve?
removing a cell from an IVF embryo to test it for a specific genetic condition before transferring the embryo to the uterus.
what are chromosomes made of?
dna lol
what is the bond between the sugar residue and the phosphate group in dna?
covalent bond formed by condensation reaction- phosphodiester bond.