genetic inheritance

Genetics

• heredity

• Genotype

• Phenotype

Mendel

• documented the mechanism of inheritance genetic in sexually reproducing organisms

True breeding

• when the plants self pollinate, all their offspring are the same variety

Hybridisation

• mating, or crossing of 2 variants

Monohybrid cross

• a cross between 2 parents that breed true for different versions of a single trait

P generation

• true breeding parents

F1 generation

• hybrid offspring of the p generation

F2 generation

• offspring from the self fertilisation of the F1 hybrid

Mendel experiment

• cross pollinated 2 true breeding varieties (p generation, p gen) studying each trait one at a time, yellow and green pea colour

• he recorded the inheritance of the chosen trait in the next gen

• all the F1 hybrids resembled only one of their 2 parents

• Mendel allowed the F1 plants to self fertilise and observed the F2

• trait that disappeared in F1 returned

• 75% of the offspring had yellow peas, 25% had green peas

Mender's first postulate

• Mendel proposed that the inheritance of traits is governed by hereditary factors

• factors come in alternative versions and organisms have pairs of factor version

Homozygous

• an organism prossessing 2 identical alleles for that trait (gene)

• the F1 hybrid plants, on the other hand, had recieved 2 dissimilar alleles

Heterozygous

• an organism possessing 2 different alleles for that trait

Independent segregation

• during the formation of gametes, 2 copies of each gene present in the parent separate so that each gamete receives only one allele for each trait

• during fertilisation, a sperm cell carrying one or other allele fuses with an egg cell carrying one of the alleles to produce a zygote with 2 alleles

Albinism

• disorder that results in little or no production of the pigment melanin

• the dominant allele of the gene encodes an enzyme involved in making melanin, the recessive one is non/ low active

Alleles for different traits segregate independently

• during gamete formation, different pairs of alleles segregate independently of one another

• alleles that secreate independently are packaged into gametes

• gamete are allowed to combine at random to produce the F2 gen

Single gene disorders

• caused by changes or mutation that occur in the DNA sequence of single gene

• mutation can lead to gain or loss of functions

• resulting protein alteration is responsible for the disease symptoms

• condition that is present form birth

Autosomal dominant

• if a single mutated allele is sufficient to cause the disease

Autosomal recessive

• if both mutated allel must be inherited to be affected

X linked recessive or dominant

• mutated gene is present on the X chromosome

Missense mutation

• these are base changes that alter the codon for an amino acid resulting in its replacement with a different amino acid

Nonsense mutation

• base changes that convert an amino acid codon to stop codon, resulting in premature termination of translation and the production of a shortened protein

Frameshift mutation

• these mutation result from the insertion or deletion of one or more bases causing the alteration of reading frame

Promoter mutations on other regulatory sequence

• affect the way gene transcription is regulated, often abnormally reducing or enhancing the expression of certain gene

Sickle red blood cell

• red blood cells form an abnormal crescent shape

• haemoglobin is abnormally shaped

• don't make easily through your blood vessels

• form clumps and get stuck in the blood vessels

Cystic fibrosis

• for a point missense mutation in the CFTR gene within the chromosome 7

• mucus secretion accumulate in the lung which block the airways, cause persistent infection and permanent lung damage

Huntington disease

• Huntingtin gene located on chromosome 4

Numerical abnormalities

• when an individual is missing either a chromosome from a pair or has more than 2 chronometer of a pair

Structural abnormalities

• when the chromosomes structure is altered

Multi factor disorders

• disease that show familial clustering but do not conform to any recognised pattern of single gene inheritance are termed multi factorial disorder

Activating the expression of oncogenes

• proto- oncogenes in normal cells stimulate cell growth and division, in response to specific signals

• in cancer they become permanently switched on

Inactivating tumor suppressor gene

• in normal cells, they block cell division at the checkpoint, if cells are not ready to go on

• in normal cells they also imitate the process of apoptosis

• in cancer they are permanently switched off

G0

• tumor cells are unable to stop the cell cycle and enter G0

Genetic instability of cancer cell

• single transformed cell grows to become a primary tumour, accumulates more mutation and become more aggressive

Genetic polymorphisms

• 2 or more existing different forms of DNA sequence in certain locus within a population, present in at least 1% of the population. Mutation are usually present in lower than 1%

• determine the diversity of individuals and sometime have a role in drug response, forensic purposes or could respresent risk factors for multi factor disease