Zusammenfassung der Ressource
GCSE AQA Biology 1 Variation, Genetics & Reproduction
- Variation
- Genetic
- Characteristics similar to parents'
- Genes inherited from parents
- Some genes
from mother,
some from father
- No 2 members of
species identical (apart
from identical twins)
- Environmental
- Differences that have been caused
by conditions organism lives in
- Characteristics affected by genetic
& environmental factors...
- Genes, chromosomes and DNA
- Cells have nucleus - contains genetic info in form of chromosomes
- Human cell nucleus contains 23 pairs of chromosomes
- Chromosomes carry genes - genes control development of different characteristics
- Gene is short length of chromosome, which is long length
of DNA - can be diffferent versions of same gene (alleles)
- DNA coiled up to form arms of chromosome
- Sexual reproduction
- Fusion of male & female gametes - 2 parents
so offspring contain mixture of parents' genes
- Each gamete contains 23 chromosomes
- When fertilised, form cell with full number of chromosomes
- Offspring inherits features from
both parents - produces variation
- Asexual reproduction
- Only 1 parent
- No fusion of gametes
- No mixing of chromosomes/no genetic variation
- Offspring are genetically identical (clones)
- How plant & animals grow/produce replacement cells
- Some organisms produce offspring using
asexual reproduction (bacteria & certain plants)