Variation and inheritance Flashcards
What is variation
differences between animals interspecies and intraspecies - arise as a result of mutation, changes to the genetic code which are random and constantly taking place
What is chlorosis
leaves on plants look pale or yellow as their cells are not producing a normal amount of chlorophyll pigment
Causes of chlorosis: lack of light
plants turn of their chlorophyll production in absence of light in order to conserve resources
Causes of chlorosis: mineral deficiencies
lack of iron (cofactor on some enzymes that make chlorophyll) and magnesium (found at the heart of the chlorophyll molecule)
Viral infections
viruses interfere with metabolism of cells affecting chlorophyll production
Body mass as a result of genetic makeup
mutation on chromosome 7 - causes the pattern of fat deposition in the body to be altered. This gene acts in conjunction to other genes that regulate the energy balance of the body
How do we inherit combinations of alleles from our parents
determined by sexual reproduction involving meiosis (formation of genes) and random fusion of gametes at fertilisation - causes variation within species
What is genotype
alleles we possess as individuals/ genetic constitution of an organism
What is phenotype
the physical characteristics of an individual often affected by the environment
What is an allele
a version of a gene
Homozygous
two of the same allele
Heterozygous
two different alleles
Monohybrid
one gene being determined
Dihybrid
two genes are combined (e.g hair colour and hair length)
Dominant allele
version of the gene that will always be expressed if present in an organism (TT: blue eyes, Tt: Blue eyes tt: green eyes)
Recessive allele
will only be expressed if there are two copies of the same allele (homozygous recessive)
what is continuous variation
there are two extremes, with every degree of variation possible in between (e.g height or weight)
what is discontinuous variation
individuals fall into distinct groups and normally only one gene is involved, the environment as very little affect on this (e.g eye colour, hair colour, blood group)
Homozygous genetic cross
Mendel carried out crosses between homozygous yellow pea pot plants and homozygous green pea pot plants - all of the offspring are heterozygous which means all F1 will be green but have the genotype Gg
Heterozygous genetic cross
taking heterozygous offspring from the F1 and crossing them - F2 generation are produced and have a 3:1 ratio of green to yellow pea pod plants (GG, Gg, Gg, gg)
what is codominance
when two different alleles occur for a gene - both of which are equally dominant and so both are expressed in the phenotype of the organism (e.g if there is an allele that codes for red flowers/pigment and one that codes for white/no pigment they will be pink and so heterozygous
