Chapter 4 Flashcards
Extension of Mendelian Genetics (36 cards)
What is the central dogma?
DNA is used as instructions to make RNA (transcription) -> RNA is then used as instructions to make a protein (translation)
How do genes influence our phenotype?
Genes produce proteins, proteins are machines that carry out biological functions. These biological functions are our phenotype.
Define mutations
Change in nucleotide sequences of a gene.
What do mutated genes produce?
Produce defective proteins, altering an organism’s phenotype.
Why do we have the 3:1 phenotype ratio in mendelian genetics?
Due to mutated alleles. Since we have 2 copies of each gene, one good copy is enough to have a normal phenotype.
How is seed shape of peas influenced?
Protein normally produces rigid polysaccharides.
Mutated gene = defective protein = no rigid polysaccharides = wrinkly seed shape
Define WT allele
Wild type allele. Natural, normal, unmutated allele. Usually whichever is most common in a population.
Can be denoted as + in genotypes
Define LOF mutation
Loss of function mutation. Reduces function of the protein.
Typically recessive.
Define GOF mutation
Gain of function mutation. Increases function of protein.
Typically dominant due to gaining something extra from mutation which drowns out/masks the WT allele.
Define neutral mutation
Nucleotide change occurs, but doesn’t damage protein / protein structure.
Define incomplete dominance
When the phenotype is a cross between parent phenotypes. This is caused by an intermediate level of protein function
White + Red = Pink !!
Define codominance
2 phenotypes appear simultaneously in distinct areas of the same organism. When one allele is active in one area, and the other is active in another.
What is an example of a gene with more than 2 alleles?
ABO gene - blood type gene. (A, B, or O)
What is an example of a lethal mutation?
Agouti and yellow mice.
Mice that are homozygous dominant for yellow do not survive. This is due to the mutation affecting the MERC gene, which is essential for embryonic development.
Define recessive lethal allele
When you need BOTH alleles to die
Define dominant lethal allele
When you only need ONE copy of an allele to die.
What type of lethal allele is the agouti mutation?
Recessive lethal allele
Define polygenic traits
Traits controlled by more than one gene
Define gene interaction
When products of different genes influence the same trait
Define epistasis
When one gene influences the effect of another gene
What is an example of epistasis?
Bombay blood phenotype
How does the bombay blood phenotype function?
The FUT1 gene influences the activity of the ABO gene. When FUT1 is homozygous recessive, the ABO gene does NOT produce antigens.
FUT1 produces the chemical precursor for the antigen, so without this precursor the ABO gene can’t build antigens.
Define epistatic
Overrides the other gene
Define hypostatic
Overriden by the other gene.
