Bio Heredity Flashcards
Monohybrid inheritance
1 characteristic, 2 contrasting forms
Controlled by a single gene -> one pair of alleles, dominant or recessive
Gene
Unit of inheritance on particular locus on a chromosome
Small segment of DNA, controls prod of a single polypeptide
Alleles
Diff forms of same gene, occupying same relative positions on a pair of HCs
Homologous chromosomes
Pairs, identical shapes sizes lengths, one from f one m parent
Same sequence of gene loci
Phenotype
Observable traits
Influenced by genotype and environment
Genotype
Genetic make-up
Homozygous: TT, tt
Heterozygous: Tt
Genetic diagram
Parents phenotypes
Parents genotypes
Gametes
F1 generation genotypes
F1 generation phenotypes
Ratio of F1 generation phenotypes
Codominance
Both alleles equally expressed in the heterozygous condition
Eg C^R C^R (red), C^RC^W (brown)
Eg blood groups in humans
Sex determination alleles
Eggs X
Sperm X or Y
Multiple alleles
Gene for trait exists in more than 2 alleles
Eg ABO human blood type
I^A(d), I^B (d), I^O (r)
Discontinuous variation
- a few phenotypes
- controlled by one or a few genes
- genes do not show additive effect
- not affected by enviro
Eg, either double or single eyelids
Continuous variation
- a range of phenotypes
- controlled by many genes
- genes show additive effect
- effected by enviro
eg skin colour range betw dark and fair
Mutations
- errors during replication of gene/ chromosome
Chromosome mutation
- change in structure / number
- eg Down syndrome
Gene mutation
- change in DNA structure
- prod variation due to new alleles
- eg albinism and sickle cell anaemia
Down syndrome
47 chromosomes instead of 46
Extra of C21
Albinism
Gene mutation of recessive allele
Absence of pigment melanin
Sickle cell anaemia
- Gene mutation in haemoglobin prod gene (recessive)
- sickle shaped -> lower O2 carrying capacity, clump tgt // v SA:V ratio, v rate of O2 diffing, v aerobic resp, v energy
- more resistant to malaria
Mutagenic agents
Radiation:
- UV light, X-ray
- alpha and beta rad
- gamma rays
Chemicals
- mustard gas
- formaldehyde
- LSD
Variation
- crossing over P1
- independent assortment M1
- mutation : new alleles for natural selection to act on
Impt to help orgs survive in changing enviro
Natural selection
- best adapted (favourable characteristics) orgs in pop survive and repro, pass genes to next gen
- selects: more disease resistant, better adapted
Natural selection vs artificial 4
Result of gene mutations / from human manipulation
Brought abt by enviro conditions change / humans select orgs w desired traits to repro
Very slow process / relatively faster
May be pos or neg/ always advantageous to man
