University:
High School
Course:
High School Genetics
Academic year:

2023
Views:

358

Pages:

7
Author:

InterstellarInnovator

Genetic Diversity and Differentiation Genetic Diversity • The amount of genetic variation in a species or population – The more different gene combinations, the greater the genetic diversity • Increased in Meiosis by: – Crossing over – Independent Assortment Crossing Over • Parts of homologous chromatids cross over in Prophase I – Pieces (genes) break off & switch places • **IMPORTANT - Crossing over = genes switching Independent Assortment of Chromosomes • Anaphase I - homologous chromosome separate randomly • **IMPORTANT – Independent Assortment = Chromosomes mix • Increases the possible combinations of genes in each gamete, which increases genetic variation Meiosis Errors • Nondisjunction – Chromosomes do not always separate correctly – Results in an abnormal number of chromosomes in the gametes & ultimately the zygote Formation of Gametes • Spermatogenesis = formation of sperm cells – Each of the four haploid cells created by meiosis develops into a mature sperm cell • Oogenesis = formation of egg cells (ova) – Only one of the four haploid cells created by meiosis develops into a mature egg cell (ovum) • Remaining 3 cells are called polar bodies Asexual & Sexual Reproduction • Asexual Reproduction – No meiosis or union of gametes – Offspring are genetically identical to parents; no variation. – Examples: binary fission (done by bacteria), budding (living sponges, anemones, flatworms) • Sexual Reproduction – Has meiosis and gamete union – Offspring are genetically different from parents – Increases genetic variation among individuals - they are NOT genetically identical – ***Advantage: enables species to adapt rapidly to changing environmental conditions Differentiation • You started from one cell • Mitosis divides that cell into ~ 2 trillion – Each with the same copies of the DNA in that first • Cells become specialized for specific functions – Not all of the DNA makes all of the proteins possible – Cells will make specific proteins based upon where they are located in the organism