Mitosis + Meiosis Flashcards
What are the four stages of the cell cycle?
Summary of what happens in each
Growth 1 - cell grows
S phase - chromosomes replicate
Growth 2 - cell prepares for cell divison
Cell division - mitosis or meiosis
What does diploid mean?
Where are they from?
Two copies of each chromosome
One maternal and one paternal
What are the two arms of a chromosome?
P - short
Q - long
What is at the end of each chromosome?
What are they?
Telomere
Repeat sequences
Name the four types of centromere from the central to close to the top
Metacentric
Submetacentric
Acrocentric
Telocentric
What is the appearance of chromosomes during metaphase?
Condensed
Different shapes and sizes
How are chromosomes grouped? (3)
How many groups are there?
Size, position of centromere, local differences
7
What groups are X and Y in?
C
G
What type of banding is used to stain chromosomes?
G staining (giema staining)
What occurs before a G stain is added?
Enzymatic digestion
What is G banding used to identify? (3)
Translocations
Duplications
Loss of Y chromosomes
What is turners syndrome?
One X chromosome missing
How are chromosomes occupied in the nucleus?
Occupy distinct territories
What do homologous chromosomes have the same of?
Same genes
What are alleles?
Variants of the same gene
How do sister chromatids and non sister chromatids compare?
Sister chomatids - same alleles
Non sister chromatids - different alleles
What are somatic cells?
Cells of the body
What happens in G1 phase?
Metabolic changes in preparation for cell division
What happens in S phase?
DNA synthesis replicates the genetic material
What happens in G2 phase?
Metabolic changes - assemble cytoplasmic materials for mitosis
What happens in G0 phase?
Cell is not growing or dividing
What happens in prophase?
Nuclear envelope dissolves
Nucleolus goes
Chromosomes condense
Spindle fibres form
What happens in metaphase?
Spindle fibres attach to chromosomes
Chromosomes align
What happens in anaphase?
Centromeres divide
Sister chromatids move to opposite sides
What happens in telophase?
Nuclear envelope forms
Chromosomes decondense
Spindle fibres disappear
What type of cells undergo meiosis?
Germline
What type of cells are the start and end of meiosis?
Diploid
Haploid
What happens in prophase 1?
Nuclear membrane dissolves
Chromosomes condense
Homologous chromosomes pair up
Crossing over occurs
What type of chromosomes are formed after crossing over occurs?
Recombinant chromosomes
What happens in metaphase 1?
Spindle fibres form
Chromosomes line up in the centre
What happens in anaphase 1?
Chromosomes migrate to opposite poles
What happens in telophase 1?
Nuclear membrane reforms
Chromosomes decondense
Cytokinesis occurs
What is the difference between meiosis 1 and 2?
No DNA replication in meiosis 2
What happens before meiosis 1?
DNA replication
What are the products of meiosis?
Four haploid daughter cells
What does meiosis ensure/why is it important?
How does this happen? (2)
Genetic diversity
Random assortment of chromosome
Crossing over
What is meiosis in sperm cells called?
Spermatogenesis
What are the four stages sperm cell in spermatogenesis?
Spermatogonium
Primary spermatocyte
Spermatids
Mature sperm
What is the process of meiosis in oocytes?
Oogonium
Primary oocyte
Polar bodies
Mature ovum
What is the condition in which a haploid organism has an abnormal number of chromosomes?
Aneuploidy
What causes aneuploidy?
Non-disjunction - failure to separate pairs of chromosomes lined up at the metaphase
What causes Down syndrome?
Non-disjunction
Trisomy of chromosome 21 (3)
