Meiosis Flashcards
What is Genetics?
Scientific study of heredity and Variation
What is heredity?
transition of traits from one generation to the next
What is variation
Differences in appearance that offspring show from thier parents and siblings
what are gametes?
reproductive cells (sperm and eggs)
What are genes?
Units of heredity and are made up of segments of DNA- have a specific locus on a certain chromosome
What are Asexual reproduction and sexual reproduction
Asexual- one parent produces genetically identical offspring by mitosis
sexual- two parents give rise to offspring that have a combination of genes inherited from both
What is a life cycle?
Generation-to-generation sequence of stages in the reproductive history of an organism
what is fertilization?
The union of gametes (sperm and egg)
What is a zygote?
A fertilized eg- has one set of chromosomes from each parent
What is a haploid cell?
Gametes that contain one set of chromosomes (23)
Gametes are only types of human cells produced by meiosis rather than mitosis
What is a diploid zygote
Result of fertilization between sperm and ovum
what are homologous chromosomes?
the two chromosomes in each par of chromosomes
they have the same size, same centromere position and same number of genes in the same order
What is a karyotype
ordered display of the pairs of chromosomes from a cell
What are sex chromosomes?
X and Y chromosomes. they determine sex of the human (Female =XX, Male =XY)
what are some examples of Chromosomal disorders?
Down syndrome (3 copies of chromosome 21) Klinefelter syndrome (XXY Male) Turner syndrome ( an XO female)
How many cell divisions are in meiosis
2, Meiosis I and Meiosis II
What does meiosis result in?
four daughter cells (rather than 2 in mitosis)
-each daughter cell has only half the parents chromosomes
What happens in Meiosis I
Homologous chromosomes seperate. Starts with one diploid parent and results in 2 haploid daughter cells REDUCTIONAL DIVISION
What is the result of Meiosis II
Sister chromatids separate- results in four haploid daughter cells EQUATIONAL DIVISION
What is unique about prophase I?
SYNAPSIS- homologous chromosomes loosely pair up, aligned gene by gene. they exchange DNA segments CROSSING OVER at the chiasmata
What are the main differences between Mitosis and Meiosis
Mitosis conserves the number of chromosome sets (cells genetically identical to parent cell)
Meiosis reduces the number of chromosome sets from diploid to haploid. (resulting cells are genetically different from parent)
What are the 3 events unique to meiosis?
Synapsis and crossing over: exchange of genetic information segments
At metaphase plate there are paired homologous chromosomes (tetrads) instead of individual replicated chromosomes
Homologous chromosomes separate instead of sister chromatids
What are Mutations?
Changes in organisms DNA- source of genetic diversity.create different versions of genes
What 3 mechanisms contribute to genetic variation?
Independant assortment of chromosomes
Crossing Over
Random Fertilization
