MCBG - Mitosis And Meiosis Flashcards
True or false - one chromosome can be either one OR two DNA molecules?
True - a replicated chromosome is two DNA molecules rather than the usual one.
What are the names given to the arms of chromosomes?
P (short) and Q (long) arms
What are telomeres?
Repeated sequences at each end of a chromosome/chromatid.
Where is a metacentric centromere placed on the chromosome?
In the middle.
True or false - all of a human’s chromosomes have telocentric centromeres.
False - humans have none.
Where is an acrocentric centromere placed?
Very close to the top of the centromere.
What happens in prophase?
Spindle fibres appear and chromosomes condense
Describe prometaphase.
Spindle fibres attach to chromosomes, chromosomes condense further.
What happens in metaphase?
Chromosomes align down the equator.
What happens in anaphase?
Centromeres divide and sister chromatids move to opposite poles.
Describe telophase.
Nuclear membrane reforms, chromosomes decondense, spindle fibres disappear.
What occurs in cytokinesis?
Cytoplasm divides
True or false - sister chromatids have identical DNA and the same alleles?
True
Can homologous chromosomes have different alleles?
Yes, they often do.
What does meiosis produce?
Four non-identical cells with half of the chromosome content of the parental cell.
By which process are eggs and sperm produced?
Meiosis
What makes meiosis I different from meiosis II?
In meiosis I, homologous pairs of chromosomes line up and separate. In meiosis II, chromosomes line up and chromatids separate.
What are the consequences of meiosis?
Maintains constant chromosome number from generation to generation, and generates genetic diversity (random assortment of chromosomes and crossing over of genetic material).
How long does spermatogenesis take?
Around 60 days.
How many spermatids are produced from one spermatocyte?
4
How long does oogenesis take?
12-50 years
How many mature ova are produced from one primary oocyte?
One, and three polar bodies.
What is nondisjunction?
When both copies of the chromosome are pulled to one pole instead of splitting.
In what stage of the cell cycle does nondisjunction occur?
Anaphase
What is a “metaphase spread”?
A technique where stained metaphase chromosomes are spread over a glass slide for analysis.
What does this karyotype show? 46,XX
Female with no genetic conditions
What does this karyotype show? 47,XY,+21
Male with trisomy 21 (Downs syndrome)
What is aneuploidy?
Having the wrong number of chromosomes
What is mosaicism?
Presence of two or more cell lines in an individual, can be throughout the body or tissue limited.
