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  • Created by: Aniqa
  • Created on: 07-01-13 17:24

GENE EXPRESSION

Characteristics depends on information carried on a single gene that have two alternative alleles. Many depend on a single that has multiple alleles or POLYGENIC TRAITS: Phenotypic features result from interaction of number of different genes.

VARIATION

DISCONTINUOUS: Whether features present or not

- Blood group or sex

CONTINUOUS: Polygenic inheritance gives rise.

- Height or weight

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KEYWORDS

GENOTYPE: Alleles expressed in forms of letters

HOMOLOGOUS PAIRS: Half the chromosomes from male and from the female

ALLELES: Different versions of the same gene

- HOMOZYGOUS: Both alleles coding for particular characteristics are identical

- HETEROZYGOUS: Two alleles coding for characteristic are different

- GENES: Sequence of bases

- DOMINANT: Effects expressed (upper case letters)

- RECESSIVE: Only expressed in phenotype (lower case letters)

- EPISTASIS: Polygenic traits, one gene effects/alters another

- POLYGENIC: Different alleles interact which affect expression of particular characteristics. More than one gene is involved in influencing phenotype. Gene loci. 

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PHENOTYPE

Outward expression of a cell or organism.

SIAMESE CAT HAIR

  • Genotype: Gene codes for enzyme which makes dark fur
  • Environment: Enzymes at optimum temperature
  • Phenotype: Distinctive colouration of body extremeties 

LUNG CANCER AND SMOKING:

  • Genotype: Presence of enzymes regulating cell cycle
  • Environment: Chemical component alters genes
  • Phenotype: Cell cycle isn't regulated, the living cells keep dividing which makes a tumour grow. 
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NERVES

MONOAMINE OXIDASE A: Enzyme found in the nervous system

MONOAMINE: Transmits nerve impulses across synapse

  • High levels of enzymes formed:

Breaks down too many neurotransmitter molecules and functioning of brain affected.

  • Low levels of enzymes formed:

Linked to depression and addictive behaviour. 

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E.COLI: Gut bacteria

Lactose induces E. Coli to produce gut bacteria.

When lactose becomes available, the bacterial cell contains enzymes and molecules.

Lactose binds to repressor which makes it change shape.

BARR BODY

X chromosome is inactivated by supercoiling.

Random X chromosomes inactivated by embryonic cells

Cells which descend from that cell have the same inactivated chromosomes. 

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