mitosis and meiosis- lecture 7 Flashcards
each cell nucleus contains about how many feet of dna
6 feet
dna is wrapped around special proteins called
histones
nucleosome
combined loop of dna and histone potein
chromatin
nucleosomes packed into a thread
chromosome
a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
short arm of chromosome
p arm
long arm of chromosome
q arm
middle of chromosome
centromere
tip of chromosome
telomere
heterochromatin vs euchromatin
gene poor repeat rich vs gene rich
sister chromatid
A sister chromatid refers to the identical copies (chromatids) formed by the DNA replication of a chromosome, with both copies joined together by a common centromere. In other words, a sister chromatid may also be said to be ‘one-half’ of the duplicated chromosome
centromere function and is home to
constricted region of the chromosome where the kinetochores form
home to kinetochore, where the spindle microtubules attach in mitosis and meiosis
dna replication
why do dna molecules (chromosomes) get shorter over time
unidirectional feature of dna polymerase
how do cells stop chromosomes from getting shorter
telomeres (like tips of shoelace) use enzyme telomerase to prevent division by division erosion of tips of chromosome
how to create karyotype
ease of viewing chromosomes facilitated by colchine, which disrupts spindle formation in mitosis and creates freeze frame mitotic moment that we can stain
how are chromosomes stained for a karyotype
stained using glemsa which stains preferentially a-t regions of the genome
chromosomes get categorized in what ways
where they keep their centromeres and size
n number
haploid chromosome complement (number of chromosomes)
diploid
two copies of each chromosome, one from each parent
homologous chromosomes vs non homologous chromosomes
Homologous chromosomes consist of alleles of the same gene type found in the same loci unlike non-homologous chromosomes, which constitute alleles of varying gene types
different ways of visualizing human chromosomes
you can id different chromosomes based on banding pattern and size
how do we lay out karyotypes
by size; chromosome 1 is the largest and 22 is the smallest
how many chromosomes do we have
Normally, each cell in the human body has 23 pairs of chromosomes (46 total chromosomes). Half come from the mother; the other half come from the father. Two of the chromosomes (the X and the Y chromosome) determine your sex as male or female when you are born.
trisomy 21
down syndrome- extra chromosome 21
aneuploidy
having extra or missing chromosomes
dosage imbalance
Genetic imbalance is to describe situation when the genome of a cell or organism has more copies of some genes than other genes due to chromosomal rearrangements or aneuploidy. Changes in gene dosage, the number of times a given gene is present in the cell nucleus, can create a genetic imbalance because youre pumping out too much of a protein when the amount of each protein in a cell is crucial
why is down syndrome more common than autosomal trisomies
chromosome 21 is a small chromosome so its impact on dosage imbalance is minor
chromosomal rearrangements
deletion
duplication
inversion
translocation
cell cycle
A cell cycle is a series of events that takes place in a cell as it grows and divides. A cell spends most of its time in what is called interphase, and during this time it grows, replicates its chromosomes, and prepares for cell division. The cell then leaves interphase, undergoes mitosis, and completes its division
stages of cell cycle
The cell cycle is a four-stage process in which the cell:
1) increases in size (gap 1, or G1, stage)
2) copies its DNA (synthesis, or S, stage)
3) prepares to divide (gap 2, or G2, stage)
4) divides (mitosis, or M, stage)
checkpoints of cell cycle
There are many checkpoints in the cell cycle, but the three major ones are:
the G1/S checkpoint, also known as the Start or restriction checkpoint or Major Checkpoint
the G2/M checkpoint
and the metaphase-to-anaphase transition, also known as the spindle checkpoint.