Chromosomes And Meiosis
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When is DNA replicated?
Interface
When does crossing over occur?
Prophase one
Instead of the centromeres splitting during anaphase one, what splits?
Bivalent chromosomes
Define chromosomes
Long thread life structures that form part of the chromatin network in the nuclei of cell
Define meiosis
Cell division that takes place in the reproductive organs of plants and animals to produce gametes and spores
Define crossing over
Mutual exchange of pieces of chromosome so that the whole group of genes are swapped between maternal and paternal chromosomes
What is the importance of crossing over?
• exchange of genetic material – increases variation • mutations – influence evolution
What is the importance of meiosis?
• Gametes are formed • Chromosome number is kept constant • Genetic variation
Similarities between mitosis and meiosis
• type of cell division • DNA is replicated during interface • during prophase chromosomes are short and fat
Define chromosome non-disjunction
Chromosomes failed to say parade correctly during meiosis
Aneuploidy
A zygote with an extra or missing chromosome
Syndrome
Physical or mental characteristics affect an individual
Diagnosis
Identify the nature of an event
Prognosis
Predicting how the event will develop
How does down syndrome occur?
During Genesis the number 21 chromosomes do not separate properly during phase one. Both go into one instead of in each of the two cells
Define a karyotype
Ace of chromosomes in a cell
What does a karyotype show?
Number, shape and size of chromosomes during meta phase of mitosis
Where is DNA found?
The nucleus of the cell
Define chromatin network
Chromosomal material made up of DNA, RNA and his stone proteins as found in non-dividing cells
Why is DNA an important part of chromosomes?
It makes up the chromatin network
What is DNA?
A double stranded molecule that produces exact copies of itself and encourage genetic information
What is extra nuclear DNA?
Occurs in the mitochondria and chloroplast
What is DNA made up of?
• Sugar - deoxyribose • phosphate molecule • nitrogenous basis
Define the nitrogenous bases
• Adenine • Thymine • Cytosine • Guanine