D3.2 Inheritance

phenotypic plasticity

The ability of an organism to exhibit variations in its physical characteristics or traits in response to environmental influences. changes can be reversed, important as a means of survival or changing climate

sexual reproduction plants

pollen moves to stigma, when it arrives pollen tube grows and carries pollen to ovary

self pollination

pollen from ne plant lands on the stigma of the same plant

cross pollination

pollen from one plant lads on another plant of same specie

breeding and genetics

genetic crosses are widely used to breed new varieties of crop or prnamntl plant, specific individuals can be selected to ensure that the offspring have desired characteristics such as breeding climate smart crops

allele

different from of a gene

genotype

allele combination inherited by an organism

phenotype

outward expression of the combination of alleles, along with the influence of environmental factors

PHENOTYPE EXAMPLES

genotype: have two ears, phenotype: tattoo phenotype&genotype: skin colour

recessive genetic condition

individual needs to be recessive homozygous to have the trait, example: phenylketonuria (PKU)

phenylketonuria (PKU)

caused by mutation in gene on chromosome 12, codes for an enzyme used in metabolism that converts amino acid phenylalanine (Phe) into tyrosine (Tyr) in most countries babies are tested for it at 1-2 days, can be managed for a diet plan , if left untreated brain damage can occur

SNP’s

patterns of SNP’s can be examined and patterns have been found among different human populations, pooling data meant that a data base of SNP associated traits can be built up to examine health disease and drug response, the more SNP’s in a gene the more different the alleles will be

Multiple alleles

eg blood type

ABP blood groups

each make their own enzyme which catalyses production of specific carbohydrate chains on the outside of the red blood cells, capable of producing an immune response (antigens), in blood transfusions antibodies in the plasma can cause clotting

universal donor

type O, no antigens

universal recipient

AB both surface antigens but no antibodies in their plasma and so can receive all blood

codominant

neither is dominant over the other both expressed AB blood

incomplete dominance

offspring phenotype intermediate between two parent types

incomplete dominance example

Marvel of Peru, allele for red flower not completely dominant over white, in heterozygous they are pink (three possible phenotypes)

Female and Male chromosomes

Female: XX and Male: XY, sperm ultimately defines sex, particular gene on Y chromosome (SRY gene) important in allowing zygote to develop into male embryo

sex linked genetic disorder

X chromosome 3 times larger than Y greater possibility of mutations and disorders, if present on X chromosome any individual would then be positive

sex linked genetic disorder example

certain inherited conditions are found on the long arm of X chromosome, including colour blindness and haemophilia (blood fails to clot properly)

importance of genetic variation

important as it results in a specie being able to adapt to environmental changes, breeding within a spec pop reduces variation, any disease within a smaller gen pool will be more likely observed , consanguineous arrange can lead to increased presence of autosomal recessive disorders and congenital abnormalities

polygenetic inheritance and example

when more than one gene controls a characteristic eg skin colour, environmental factors can also contribute, skin: some genes code for melanin and some don’t even sibs can have Dif skin colour due to combination of alleles they inherited is unique to them. the more genes expressing melanin the darker the skin

linked genes

when genes are found on the same chromosome and are close together

unliked genes

when genes are found on different chromosomes, linked and unliked effects how genes end up in gametes in meiosis.

law of independent assortment

separation of homologous chromosomes and sister chromatids being independent of their pair during meiosis due to random orientation

9:3:3:1

two heterozygous parents

1:1:1:1

heterozygous for both traits and homozygous for both traits

gene loci

position of a gene on a chromosome, genes are located at same position called loci, there are codes to identify them

linked genes

genes on the same chromosome, can fail to assort independaltyy and so do not follow menders second law, they cab close and travel s a unit or if they are further part there may be exchange of material between maternal and paternal unit, the further apart the genes the more likely crossing ver happens at least once