Chapter 8 Flashcards
Cell Division & Reproduction
cell division
cell reproduction;
- genome duplication / cytoplasm division
- makes 2 genetically identical daughter cells
chromosomes
gene structure in nucleus
- long DNA molecule and proteins
asexual reproduction
genetically identical offspring w/ only 1 parent
- no gametes
clone
group of genetically identical individuals
sexual reproduction
genetically unique offspring w/ 2 parents
- fusion of two gametes (fertilization)
- forms diploid zygote
cell division in protists are used for what ?
reproduction only
cell division in the human body is used for what ?
- development
- growth
- repair
binary fission
parent organism duplicates itself into two genetically identical individuals
- asexual reproduction
do eukaryotes or prokaryotes hold more genes ?
eukaryotes; 7x more than prokaryotes
- 21000 vs 3000
how many chromosomes are in a cell of an organism ?
depends on organism
how many chromosomes are in humans, dogs, hedgehogs ?
46; 78; 90
chromatin
DNA / protein that make up chromosomes
- long form of chromosomes
- coils up / distinct chromosomes when dividing
sister chromatids
two identical chromatids on a duplicated chromosome
centromere
spot where two sister chromatids of duplicated chromosome attach to each other
when does chromosome consist of two identical sister chromatids ?
when cell is prepping to divide / before dividing
cell cycle
ordered sequence of events from cell formation to duplication
- interphase
- mitotic phase
interphase
growing stage of cell’ 90% of total cell cycle
- G1
- S phase
- G2
G1
first gap; prep for duplication (cell growth)
- synthesize mRNA / proteins in prep for mitosis
S phase
chromosome duplication (sister chromatids are formed)
- 50% of interphase
G2
second gap; finish prep for cell division
- ensure all parts of cell are ready to divide
mitotic (M) phase
cell division; 10% of total cell cycle
- mitosis
- cytokinesis
mitosis
nucleus, contents, duplicated chromosomes divide
- form 2 identical daughter nuclei
cytokinesis ?
begins at end of mitosis, cytoplasm splits into two separate daughter cells
how often does an error occur in mitosis ?
~ 1/100,000; extremely accurate
1) prophase
- nuclear envelope disappears
- chromatin condenses
- mitotic spindles begin to form
2) metaphase
duplicated chromosomes line up in middle
3) anaphase
sister chromatids separate
- mitotic spindles pull sis. chromatids to opposite ends of cell
4) telophase / cytokinesis
daughter nuclei form and cell divides into two daughter cells
mitotic spindles
spindle microtubules for chromosome movement
- found in centrosomes
centrosomes
structure in animal cells where microtubules form / organize
- contain 2 centrioles
cytokinesis in animal cells vs plant cells
animal cells = cleavage furrow
plant cell = cell plate
how does cleavage furrow work ?
actin microfilaments contract toward each other, cleaving cell in two
how does cell plate work ?
vesicles collect along middle of cell and form new cell wall
what type of environment would constitute more cell division ?
a more abrasive environment
anchorage dependence
cell division requires cells to be attached to a surface
density dependent inhibition
cell division stops when cell is in-contact w/ another cell
what happens to density dependent inhibition when the cell is cancerous ?
cancer cells ignore this inhibition, they keep dividing forming clumps if overlapping cells
growth factors
protein secreted by body cells
- stimulates cells to divide
- different cells respond to different / combinations of growth factors
what is the biggest thing growth factors do ?
signals cell cycle to continue / stop
cell cycle control system
set of proteins tat trigger / coordinate events in cell cycle
- triggers mitosis
- checks if key components of cell are completed
- checkpoints
G1 checkpoint
signal allowing start of S phase
- checks cell size, nutrients, growth factors, DNA damage
what happens if G1 checkpoint never gets signaled ?
cell goes into G0 phase
- permanent non-dividing state
G0 cell examples
mature nerve / muscle cells
G2 checkpoint
after G2 is done, before mitotic (M) phase
- checks for DNA damage after chromosome replication
M checkpoint
(spindle checkpoint) after cell replication, before cytokinesis
-checks if all sister chromatids are correctly attached to microtubules
at which checkpoints are chromosomes duplicated ?
G2 / M
what is cancer
a disease of the cell cycle
- cells divide uncontrollably
what do cancer cells have altered that allow them to divide uncontrollably ?
cells w/ altered proteins that fail to be killed by immune system
tumor
abnormal mass of rapid growing tissue within normal tissue
- ignores cell cycle control system
- proceed past checkpoints w/o growth factors / can make own growth factors
benign tumor
abnormal mass of cells that remains in its original site
- removal by surgery
- no immediate threat unless left alone
malignant tumor
abnormal mass that can spread to neighboring tissue / other body parts
- cancerous
- spread via blood / lymph system and start forming new sites
cancer
disease due to malignant tumors within the bodt
metastasis
process of spreading cancer within the body beyond its original site
somatic cells
body cells
- have 46 chromosomes
- in mitosis; 23 sets of duplicated chromosomes
homologous chromsomes
homologs; two chromosomes that make a matched pair within diploid cell
- same centromere position, length, gene loci, staining, etc
- one from mom, one from dad
locus (loci)
site where specific gene is found on chromosome
- same gene is found in same loci on different chromosomes
sex chromosomes
X/Y chromsome; determines sex
- XX = female
- XY = male
autosomes
any chromosome other than X/Y
- doesnt affect sex
are all chromosomes for male and female homologous ?
no
- female = 23 homologs (22 autosomes + XX)
- male = 22 homologs (22 autosomes + XY)
life cycle
sequence of stages in life
- one adult to next generation adult
diploid (2n)
somatic cells
- set of homologous chromosomes (46)
- in organisms that reproduce sexually (one set from each parent)
human 2n = ?
46 (23 sets)
haploid (n)
sex cell
- single set of chromosomes (23)
- in organisms that reproduce sexually
human n = ?
23
gametes
sex (reproductive) cells (egg/sperm) formed by meiosis
- single set of chromosomes (23)
- fusing of two gametes forms zygote
fertilization
nucleus of sperm / egg combine
zygote
diploid fertilized egg
- one set of chromosomes from each parent
- mitosis of zygote makes all somatic cells
how many autosomes and which sex cells are in human sperm ?
22 autosomes and XY
meiosis is also known as what ?
reduction division
meiosis
divide single diploid cell into 4 genetically unique haploid daughter cells
- only sexual reproduction
- fertilization restores diploid state
- duplication of chromosomes followed by two cell divisions
meiosis I
crossing over of chromosomes from parents occurs and homologs split
- homologs separate
prophase I
- chromosomes condense
- homologs pair
- non-sister chromatids of homologs cross over
metaphase I
- microtubules attach to individual chromosomes
- homologs line up in middle next to each other
anaphase I
homologs separate to opposite ends
meiosis II
sister chromatids separate
- like mitosis but x2 (2 cells into 4 haploid cells)
tetrad orientation equation
2^n
- n = haploid # of organism
total # of possible tetrad orientations in humans ?
human n = 23
2^23 ~ 8mil
organisms w/ a diploid # of 10 have how many possible tetrad orientations ?
32;
2n = 10 —> n = 5
2^5 = 32
crossing over
homolog non-sister chromatid synapsis during prophase I
- where loci swap genes
chiasma
site where crossing over between non-sister chromatids occur
recombinant chromosomes
chromosome name after crossing over
how many crossing overs occur in a human chromosome on average ?
1-3
are chromosomes in gametes going to look like chromosomes in skin cells ?
no; gametes have half the # of chromosomes compared to autosomes and more varied (cut/paste) segments from a homolog pair
nondisjunction
anaphase in mitosis / meiosis homologs / sister chromatids fail to separate
how does nondisjunction affect a fertilized zygote ?
that zygote will transmit abnormal # of chromosomes to all of its cells
- 10-30% of all human conceptions
- main reason for miscarriages
nondisjunction in meiosis I will affect the chromosomes of the 4 haploid daughter cells how ?
2 cells = n +1
2 cells = n - 1
nondisjunction in meiosis II will affect the chromosomes of the 4 haploid daughter cells how
2 cells = n
1 cell = n - 1
1 cell = n + 1
how could nondisjunction turn a gamete diploid ?
if in meiosis I and II all chromosomes are affected
- all chromosomes in meiosis I pulled into 1 daughter cell
- all chromosomes in meiosis II pulled into 1 daughter cell
karyotype
display of metaphase chromosomes by descending shape / size
- 46 chromosomes total (22 homologs / 1 pair sex chromosomes)
male sex chromosomes
XY
female sex chromosomes
XX
normal female karyotype will display how many homologs ?
23 homologs (22 homologs and XX)
normal male karyotype will display how many homologs ?
22 homologs (22 homologs and XY)
trisomy 21
disorder w/ extra chromosome 21 (3 total)
- heart / respiratory defects
- varying lvls of mental retardation
- majority cases of abnormal chromosomes
what can abnormal chromosome #s lead to ?
spontaneous embryo abortion (miscarriage)
down syndrome
condition of having trisomy 21
- 1/850 kids
- all / half of all affected sexually underdeveloped / sterile
- 50% all female eggs have extra chromosome
- risk of birthing child w/ disorder starts to increase at 40+
will abnormal amounts of X/Y sex chromosomes compared to abnormal amounts of autosome chromosomes have more of an affect on the child ?
no, abnormal autosome chromosome # affects child more
characteristic of the Y sex chromosome
small and few genes
can people afford to live with only one X sex chromosome ?
yes;
- males already only have 1 X chromosome - females can survive w/ only 1 because they have a set
klinefelter syndrome
extra X chromosome in men (XXY, XXXY, XXXXY)
- more X chromosomes = more likely for harmful disorders
extra X in females are shown in person how ?
- slightly taller
- higher risk of learning disabilities
- really cannot distinguish from normal XX
extra Y in males are shown in person how ?
normal male
- no symptoms
turner syndrome
Xo female
- lacks 1 X sex chromosome
- sterile / lesser development of secondary sex characteristics
- only case where 45 chromosomes in a human is NOT fatal
total # of autosomes in female w/ turner syndrome ?
44 + 1 X sex chromosome
how can new species arrive due to chromosomal errors ?
polyploidy; 2n = 4
meiosis fails —> gametes form by mitosis
2n gamete + 2n gamete = 4n zygote
new species (diff. chromosome #) w/ only ONE generation
polyploidy
more than 2 sets of homolog chromosomes
colchicine
disrupt microtubule formation —> no separation of chromosomes
- new species due to new chromosome #
chromosome breakage caused by ?
- errors in meiosis
- damaging agents (radiation); mutagens / mutagenesis
chromosome fragment
at least 1 nucleotide
deletion
fragment becomes detached from chromosome
duplication
repeated part of chromosome due to re-entry of a chromosome fragment from homolog
inversion
re-attaching fragment to same chromosome but in reverse orientation
which forms of chromosome breakages are more severe ?
deletion / duplication
- complete loss / double fragment in one chromosome
why are inversions and translocation not as severe as deletion / duplication ?
still have the gene, just not correct
“cry of the cat” syndrome
deletion in chromosome 5;
- developmental disabilities
- smaller head / unusual facial features
- shrill cat-like cry
myelogenous leukemia (CML)
translocation of chromosome 22 w/ tip of chromosome 9;
is cancer caused by chromosomal mutations heritable ?
no not usually;
- chromosomal mutations are usually in somatic cellsho
how is reciprocal translocation different than crossing over
reciprocal translocation is swapping of fragments between NON homologs
- crossing over is in a pair of homologs