ANATOMICAL DEVELOPMENT: development of body parts (ANATOMY) also called MORPHOGENESIS
HOMEOBOX GENES: sequence of 180 bases coding for 60 AA forming a protein called HOMEODOMAIN
HOMEODOMAIN: protein that binds to DNA switching it on or off - GENE REGULATION
PAX 6 GENE: gene that controls eye development in all species as a mutation causes blindness in all species
HOX GENES: animal specific genes responsible for correct body part placement - animals have 4 clusters.
BODY PLAN: structural and developmental characteristsics used to identify an organism
DIPLO/TRIPLOBLASTIC: organisms with two/three layers of primary tissue
SOMITES: parts of the embryo directed by Hox genes to form certain body parts
APOPTOSIS: programmed cell death
Factors affecting regulatory genes can be external: light, temp, drugs or internal: hormones, physcological stress
1 of 4
Hox Genes
HOX GENES: genes which cotrol correct body part placement
Are themselves controlled by GAP GENES and PAIR RULE GENES which in turn are regulated by mature RNA
Hox genes in the head control limb placement and Hox genes in the thorax control wing or ribcage development
4 limbed animals have 4 clusters of Hox genes
Comparing Hox genes allows you to compare phyla, similarities and differences between phyla
Hox genes control boht mitosis and apoptosis
Process of APOPTOSIS: enzymes breakdown cytoskeleton > cytoplasm becomes densely packed with oorganisms > small dents in the cell appear called BLEBS > CHROMATIN condenses, DNA fragments and nuclear envelope breaks down > cell breaks into vesicles and in engulfed
webbed fingers and toes occur when apoptosis fails
2 of 4
Causes of Variation
PHENOTYPIC VARIATION is caused by a change in the GENOTYPE
A change in the genotype is caused by a MUTATION caused by MUTAGENS: PHYSICAL; X-rays, gamma rays, UV light. CHEMICAL; carcenogenics, acids, aromatic amines, free radicals. BIOLOGICAL; fungus, alcohol, chemicals in charred meat, some viruses
Mutations can be PERSISTENT; passed down through genetics or RANDOM; not directed by an organism
Sexual reproduction is GENTIC VARIATION: meiosis produces different gametes by: ALLELE SHUFFLING (swapping alleles on sister chromatids) in PROHPASE 1, INDEPENT ASSORTMENT of CHROMOSOMES in ANAPHASE 1/2 and the RANDOM FUSION of GAMETES
ENVIRONMENTAL VARIATION can be accents or loss of limb.
3 of 4
Inheritance
MONOHYBRID: one characteristic with one pair of contrasting traits e.g. plant height, hair/eye colour - F1 generation produces 3:1
HOMOZYGOUS: both alleles are the same e.g. BB for brown eyes
HETEROZYGOUS: alleles are different
Alleles can be DOMINANT; Bb for brown eyes or RECESSIVE; bb for blue eyes.
DIHYBRID: when there are 2 characteristics - F1 generation produces 9:3:3:1 PHENOTYPIC ratio
CODOMINANCE: where both alleles in a HETEROZYGOUS contribute to the PHENOTYPE
All chromosomes (apart from gametes) are AUTOSOMAL and therefore HOMOLOGOUS - they are the same length and contain the same genes at the same loci.
Because of this, if a female has a faulty gene on one X, she'll likely have a functioning gene on the other X. If a male inherits a faulty allele on his X, it will show in his PHENOTYPE. Males CANNOT be HOMO or HETEROZYGOUS for any X linked genes
Proves why TORTIES are always FEMALE - they have a black allele on one X and an orange allele on the other X
For males most genetic disorders are RECCESIVE SEX LINKED DISODERS
In all FEMALE nucleuses one X chromosome is INACTIVATED
Comments
No comments have yet been made