B13 (Reproduction and Genetics) Flashcards
Gametes
Sex cells and contain 23 chromosomes, one of each from the mother and father
Chromosomes
Very long molecules of DNA, found in the nucleus
Alleles
different versions of the same gene, that codes for a different version of a characteristic
Dominant
When an alleles coded by a phenotype is only in one of the chromosomes
Recessive
When an Alleles coded by a phenotype is in both chromosomes
Homozygote
Pair of alleles that produces the same characteristics
Heterozygote
Pairs of alleles that produce different characteristic
Genotype
Description of the pair of alleles present for characteristics
Phenotype
Physical expression of the alleles
Sexual reproduction
- genetic info transferred 2 different organisms
- eg. Egg and sperm fertilise
Asexual reproduction
- only one parent
- this means offspring is a clone of parent
- occurs through mitosis
4 Advantages of Sexual (over Asexual)
- variation of offspring
- increased chance of surviving if change environment
- speed up natural selection and pass desirable genes
- increases food production as could destroy genetic diseases
3 advantages of Asexual (over sexual)
- only need one parent
- uses less energy as don’t need to find mate
- faster than sexual
5 stages of Meiosis (Sexual)
1) Cells divides and duplicates forming 2 chromosomes with genetic info
2) Chromosomes line up in centre
3) Paris pulled apart with parts from each parent
4) 2nd division as chromosomes line up again and pul apart
5) four gametes (daughter cells) each with single set of chromosomes and genetically different
3 examples of reproduction both ways
- malaria as reproduce sexually, but asexually in human host
- fungus has asexual spores to produce and asexual spores for variation
- Strawberry produces seeds sexually, then asexually for clones