b6 Flashcards
what is inheritance?
to derive a quality or characteristics genetically from one’s parents or ancestors
what are alleles?
different versions of the same gene. you have two alleles for each feature one from each parent
why was the importance of mendel’s work only later recognised?
- people had not discovered dna and didn’t know chromosomes occurred in pairs
- people had alternative theories of blending of inherited characteristics
- his mathematical approach was a new concept
- he was not part of an academic establishment (he was a monk)
- work was published in an obscure journal
- peas have unusual results compared to other species. mendels work was not corroborated until later
what is polydactyly caused by?
dominant allele
what is cystic fibrosis caused by?
a recessive allele
what does cystic fibrosis result in?
disorder of cell membranes
results in production of thick sticky mucus which affects many vital organs like reproductive digestive and respiratory systems
what is a carrier?
people that are heterozygous and have one allele for a recessive genetic disease
what two ways can an embryo be screened?
- amniocentesis
- chorionic villus sampling
how does amniocentesis occur?
carried out around 15–16 weeks of pregnancy
involves taking amniotic fluid from around the developing foetus
how does chorionic villus sampling occur?
carried out around 10-12 weeks of pregnancy
involves taking a small sample of embryonic cells from developing placenta
in embryonic screening, what do we do with embryonic cells?
1 dna isolated from embryo
2 fluorescent probe mixed with embryo dna
3 probe then bins with embryo dna
4 uv light to show alleles for disorder
what is genetic testing?
genetic testing involves analysis of a persons dna to see if they carry alleles that cause a genetic disorder
what is a gene probe?
a section of dna that is complementary to a particular disease allele and carries a tracer to identify the gene
what is variation?
variation is the difference in characteristics of individuals in a population
what is variation caused by?
- the genes they have inherited
- environmental conditions
- combination of both
what is evolution?
the gradual change in inherited characteristics over time
what is natural selection?
a theory that explains how evolution occurs based on reproductive success
who creates theory of natural selection?
darwin and wallace
what is the theory of evolution by natural selection
all species of living things have evolved from simple life forms that first developed more than three billion years ago
explain the sequence of natural selection
1 individuals in a species show genetic variation due to mutations
2 organisms with beneficial traits are better adapted and more likely to survive
3 these organisms reproduce and pass on the gene for the beneficial trait
4 over many generations the beneficial trait increases in the popultion
what is a species?
organisms that can breed together to produce fertile offspring
what is speciation?
the formation of new and distinct species that are reproductively isolation from another.
describe the structure of a nucleotide
phosphate is attached to a sugar which has 1 of 4 bases, A C G and T
