4.3 Meiosis: Sexual Reproduction Flashcards
(14 cards)
Processes in Sexual Reproduction
- Formation of gametes, which are haploid sex cells
- Fertilization, when gametes meet and form a zygote.
Gene
Your gene codes for a trait: hair colour
Organisms possess two copies of each gene: one from each of their parents.
Allele
Your allele is the variation that you possess: brown, black, red, blond
Capital letters:
- indicate a dominant allele
This means it will show up
Lowercase letters:
- indicate a recessive allele
This means it only shows up if the dominant is not present
phenotype
represents the outward appearance of the individual according to their genotype
genotype
is the genetic makeup of the individual: which genes they possess
Meiosis
The process by which these alleles are separated into the gametes
Sexual reproduction depends on meiosis
It is a process involving two stages in which the resulting daughter cells have half the number of chromosomes (haploid) as the parent cell
Results in the formation of haploid sex cells (eggs & sperm)
Law of Segregation
Each parent passes one, and only one, allele to their offspring
Since a pair of chromosomes carries two alleles, only one chromosome can be passed along
Hence why there is a need for diploid cells to become haploid
Random Assortment
The number of possible combinations of chromosomes depends on the chromosome pairs, for diploid (2n) organisms the number of possible combinations is 2n
Law of Independent Assortment
The inheritance of one particular pair of genes (or one chromosome) does not affect the inheritance of any other pair of genes (or chromosomes).
Spermatogenesis
produces sperm
oogenesis
produces eggs
- In oogenesis, cytoplasm does not split evenly between eggs
- Cells that do not receive enough cytoplasm are called polar bodies, and die off.
- One oocyte (egg cell) is produced
Sex chromosomes
chromosomes that determine the individual’s sex
