Sister chromatids are separated although the resulting cells are haploid rather than diploid
What happens in Meiosis II?
Homologous chromosomes, each composed of two sister chromatids are separated from one another
What happens in Meiosis I?
Meiosis begins after the chromosomes have been duplicated during interphase
When does Meiosis begin?
Sister Chromatids: identical, carry the same versions of all their genes because one was produced as an exact copy of the other
Homologous Chromosomes: the 2 chromosomes of a homologous pair are ind chromosomes that were inherited from dif parents; may contain different versions of some gene
Homologous Chromosomes: the 2 chromosomes of a homologous pair are ind chromosomes that were inherited from dif parents; may contain different versions of some gene
What is the difference between homologous chromosomes and sister chromatids
(ex. 1 chromosome may contain a form of the gene for freckles while the homologous chromosome at the same location ctains a form of the gene for the absense of freckles
How can homologous chromosomes contain different versions of some gene?
1. Meiosis produces 4 new offspring cells, each w/ 1 set of chromosomes-thus 1/2 the # of chromosomes as the parent cell. Mitosis produces 2 offspring cells, each w/ the same # of chromosomes as the parents cells
2. Meiosis involves the exchange of genetic material b/w homologous chromosomes (crossing over)
2. Meiosis involves the exchange of genetic material b/w homologous chromosomes (crossing over)
How is Meiosis different from Mitosis?
Meiosis produces haploid daughter cell from specialized cells in diploid organisms
What types of cells does Meiosis produce?
It restores the diploid chromosome number, & the zygote’s 46 chromosomes are passed on to all the other diploid body cells
What does fertilization do?
cells involved in fertilization would produce new organisms w/ twice the # of chromosomes as those in the previous generation; alternation of meiosis & fertilization keeps the # of chromosomes in a species the same from generation to generation
What would happen if Meiosis did not occur?
Producing haploid gametes by meiosis keeps the chromosome number from doubling in every generation
Why is it essential to produce haploid gametes?
Having two sets of chromosomes, one inherited from each parent is key to the life cycles of all sexually reproducing organisms
Why is it essential to have two sets of chromosomes ?
The fertilized egg is known as the zygote (diploid) as it has 2 homologous sets of chromosomes w/ 1 set from each parent
What is the fertilized egg known as? What is is composed of?
Yes, and they control the same inherited characteristics
·-Gene influencing eye color located at a particular place on 1 chromosome, then the homologous chromosome also has a gene for eye color in the same place although the 2 genes may be slightly different versions (blue/brown/green eye color)
·-Gene influencing eye color located at a particular place on 1 chromosome, then the homologous chromosome also has a gene for eye color in the same place although the 2 genes may be slightly different versions (blue/brown/green eye color)
Does each chromosome in a pair carry the same sequence of genes?
Sister chromatids are duplicated copies of a single chromosome that are attached to each other and are identical
What are sister chromatids?
type of cell division that produces 4 cells, each w/ half the # of chromosomes as the parent cell; occurs in sex organs
Meiosis
46
A typical human has how many chromosomes?
You inherit one chromosome of each pair from your mother and the other from your father
How are chromosomes passed to offspring?
Most of the genes carried on the X chromosome do not have counterparts on the tiny Y, and the Y has genes that are lacking on the X
What is the relationships between the X and Y chromosome?
contain 2 homologous sets of chromosomes (the total # of chromosomes, 46, in humans is referred to as the diploid #)
Diploid
a cell w/ a single set of chromosomes (23 chromosomes for humans)
Haploid
Gametes- eggs & sperm cells (sex cells): each gamete has a single set of chromosomes (haploid)
Gametes
the fusion of the nuclei along w/ the cytoplasm from the gametes
Fertilization
chromatids do not seperate
Metaphase I
pulling apart chromatids
Metaphase II
Prophase II
What does Meiosis II start with?
No offspring would be produced
What would happen if the DNA did not replicate in Interphase I of Meiosis I?
They can’t cross over
If the chromosome are not homologous, what can they NOT do?
cell duplicates its DNA; each chromosome consists of two identical sister chromatids
What happens in Interphase before Meiosis?
Diploid cell; Haploid cell
Meiosis I starts with a? Meiosis II starts with a?
the exchange of genetic material between homologous chromosomes; occurs during Prophase I of Meiosis
Crossing Over
Makes it possible for cells to inherit genetic information in the form of chromosome copies
Meiosis makes it possible for what?
parents pass on to their offspring separate and distinct factors (today called genes) that are responsible for inherited traits; these heritable factors retain their identity generation after generation
Particulate Hypothesis of Inheritance
2 alleles for a character separate during the formation of gametes so each gamete carriers only one allele for each character
Principle of Segregation
during gamete formation in a F2 cross, a particular allele for one character can be paired with either allele of another character. (ex. R can end up with either Y or y and r can end up with either Y or y)
Principle of Independent Assortment
genes are located on chromosomes and the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns
Chromosome theory of inheritance
