Chapter 9 Flashcards
what is the outmermost layer of your skin composed of
dead epithelial cells
what is the outer layer of skin
epidermis
what is the inner layer of skim
dermis
what does the dermis do
the cells present in the dermis are responsible for reproducing in order to replace any lost or dead skin cells.
4 differences between sexual and asexual reproduction
- a: 1 parent involved s: 2 parents involved
-a: results in offspring that are genetically identical to both the parent and other offspring s: results in offspring that are genetically different to both their parents and other offspring
-a: involved mitosis s: involves meiosis
-a: happens most frequently in unicellular organisms s: happens most frequently in multicellular organisms
how and why are sexually and asexually offspring different
asexual reproduction results in offspring that are genetically identical to the parent and other offspring, as all genetic material is received from. a single parent that duplicates its own DNA. sexual reproduction however, results in offspring that are genetically different to the parents as well as otehr offspring, this is because genetic material is received from both parents.
relate cell reproduction to replacing skin cells
underneath the layer of dead skin is a layer of epithelial cells called the epidermis- the outer layer of the skin, and underneath the epidermis lies a layer of cells responsible for the constant reproduction of new skin cells via mitosis. these new cells will travel through the dermis and replace lost/damaged/deas cells
how is cell division involved in growth
cell division produces new cells, enabling an organism to increase in size
chromatin
-genetic material in the form of very long fibres that cannot be observed under a light microscope
-observed in non-dividing cells
-consists of DNA and proteins
chromosomes
-formed in preparation for cell division as chromatin fibres condense and form compact structures-chromosomes
-are visible under a light microscope
-number of chromosomes vary from species to species
centromere
region in which two sister chromatids are joined tightly together
sister chromatids
two identical joined copies of the same chromosome
prokaryote
type of cell that does not have a nucleus or any membrane-bound organelles
Eukaryote
type of cell that has a nucleus and membrane-bound organelles
cell cycle
the sequence of events eukaryotic cells that divide go through from birth as a result of cell reproduction to the time the cell itself reproduces
interphase
stage of the cell cycle in which a cell synthesizes its DNA, synthesizes proteins, grows in size, and increases its number of organelles. 90% of the cell cycle is spent during interphase
how does the structure of DNA vary during the cell cycle?
genetic material is found in the form of chromatin fibers everwhere during the cell cycle except for at the beginning of the mitotic phase, when they start to condense into chromomomes.
mitotic phase
the stage of the cell cycle in which the cell is actually dividing. includes 2 processes: mitosis and cytokinesis
stages of the cell cycle
birth of 2 identical daughter cells by cell reproduction -> G1 cell grows -> S duplication of genetic material -> G2 cell prepares to divide -> mitotic phase cell actually divides
mitosis(miotic phase)
process of the mitotic phase in which the nucleus and duplicated chromosomes divide and are evenly distributed forming 2 daughter nuclei
cytokinesis
process of the mitotic phase in which the cytoplasm divides in two. usually occurs before mitosis is completed
stages of mitosis
4 stages of mitosis :i) prophase
ii) metaphase
iii) anaphase
iv) telophase
mitotic spindle
an apparatus of microtubules that controls chromosome movement during mitosis
centrosome
microtubule organizing centers in which the assembly of spindle microtubules begins/region in which spindle microtubules are produced
centriole
two cylindrical structures located perpendicularly to one another within the centrosomes of animal cells (most plant cells do not have them and their role is not yet clear)
occurrences in G2
-organelles already duplicated as well as DNA in chromatin fiber form
-nuclear envelope is still present
occurrences in prophase
-centrosomes start moving to opposite poles of the cell, forming the spindle
-DNA in the form of chromosomes, each consisting of a pair of sister chromatids, joined at the centromere
-nuclear envelope breaks down
-chromatids attach to the microtubules of the spindle, and the microtubules tug the chromosomes to the center of the cell
zygote
fertilized egg cell
resulting cells of fertilization
fertilization
the union of 2 sex cells (EGG AND SPERM CELL)
metaphase
-“meta” as in middle
-chromosomes gather on a plane in the middle of the cell
-the mitotic spindle is fully formed
-all chromosomes are attached to the spindle microtubules with their centromeres lined up halfway between the 2 poles of the spindle
anaphase
-sister chromatids separate into 2 daughter chromosomes
-daughter chromosomes move along the spindle microtubules to opposite poles thanks to the proteins found in the centromere
-spindle microtubules already attached to daughter chromosomes shorten in order to bring them closer to the poles
-microtubules not yet attached to daughter chromosomes grow longer, pushing the poles further apart
telophase
-occurs when chromosomes reach the poles of the spindle
-processes of prophase are reversed
-spindle disintegrates
-two nuclear envelopes form, one for each set of daughter chromosomes
-chromosomes uncoil and lengthen
cytokinesis in animal cells
involves a ring of microfilaments creating an indentation down the middle of the parent cell, this ring of microfilaments will contract like a drawstring, deepening the indentation until eventually, the parent cell splits in two resulting in two new daughter cells
cytokinesis in plants
involved a a disk of cell wall material called the cell plate forming inside the cell and growing outwards until it reachest the edges of the parent cell wall, dividing the cell in two as it itself becomes part of the cell wall, resulting in 2 daughter cells bound by their own continuous membranes and walls.
Meiosis
type of cell division involved in the production of 4 haploid gametes/sex cells
karyotype
a display of the 46 chromosmes of an individual
homologous chromosomes
two individual chromosomes that have the same genes in the same order, shape, and size but are inherited from different parents and may code for different variations of the same gene
are X and Y hiomologous chromosomes?
no, only small parts of the x and y chhromosmes are homologous, making them parttly homolgous. The X chromsome is much larger than the Y chromsomes which leads to most of the genes present in the X chromsomes not having counterparts on the tiny Y, and Y having genes that X lacks.
differences between meiosis and mitosis
1) results in 2 daughter cells // results in 4 daughter cells
2) results in diploid cells // results in haploid cells
3) produces genetically identical daughter cells // produces daughter cells with genetic variation due to genetic recombination
4) number of chromsomes stays constants i.e number of chromsomes in parent cell and daughetr cells is the same// number of chromsomes halves
5) no crossing over: crossing over
6) 1 cell division// 2 cell divisions
differences between sister chromatids and homologous chromosomes
homologous chromosomes are 2 individual chromosomes, each derived from a different parent. they have the same shape and size and contain the same genes in the same order however may contain different versions of the same genes. Sister chromatids, on the other hand, when formed, are genetically identical because of the nature of how they are formed, carrying the same version of all their genes.
results of meiosis 2
4 haploid daughter cells, each with 23 full-fledged chromosomes
results of meiosis 1
2 haploid daughter cells, each with 23 duplicated chromosomes,. i.e sister chromatids still attached
prophase 1
-centrosomes start moving to opposite poles of the cell, forming the spindle
-DNA in the form of chromosomes, each consisting of a pair of sister chromatids, joined at the centromere
-nuclear envelope breaks down
-tetrads attach to the microtubules of the spindle, and the microtubules tug the tetrads to the center of the cell
- proteins cause homologous pairs of duplicated chromosomes to stick together along their lengths, forming tetrads that attach to the spindle
- tetrads exchange some genetic material during the process of crossing over
metaphase 1
-the tetrads move to the middle of the cell and line up across the spindle
-the meiotic spindle is fully formed
anaphase 1
-homologous chromosomes separate as they migrate to opposite poles of the spindle
-sister chromatids stay attached and migrate together
telophase 1
-chromosomes arrive at the poles on either side of the dividing parent cell
- each pole has a haploid daughter nucleus, each consisting of 23 duplicated chromosomes
-cytokinesis usually occurs alongside telophase 1, splitting the cytoplasm to produce 2 haploid daughter cells
metaphase 2
-chromosomes gather on a plane in the middle of the cell
-the mitotic spindle is fully formed
-all chromosomes are attached to the spindle microtubules with their centromeres lined up halfway between the 2 poles of the spindle
prophase 2
-centrosomes start moving to opposite poles of the cell, forming the spindle
-DNA in the form of chromosomes, each consisting of a pair of sister chromatids, joined at the centromere
-nuclear envelope breaks down
-chromatids attach to the microtubules of the spindle, and the microtubules tug the chromosomes to the center of the cell
anaphase 2
-sister chromatids separate into 2 daughter chromosomes
-daughter chromosomes move along the spindle microtubules to opposite poles thanks to the proteins found in the centromere
-spindle microtubules already attached to daughter chromosomes shorten in order to bring them closer to the poles
-microtubules not yet attached to daughter chromosomes grow longer, pushing the poles further apart
telophase 2
-occurs when chromosomes reach the poles of the spindle
-processes of prophase are reversed
-spindle disintegrates
-two nuclear envelopes form, one for each set of daughter chromosomes
-chromosomes uncoil and lengthen
how does meiosis 1 reduce the number of chromosomes in the daughter cells?
homologous chromosomes separate from one another into 2 daughter cells. since each cell only received 1 of each pair, the number of sets of chromosomes is reduced from 2 in the parent cell to 1 in each daughter cell
diploid
a cell that contaisn 2 sets of homologous chromosomes. in humans, a diploid cell would have 46 chromosomes, or 2n, 2 sets of 23 chromosmes
haploid
a cell that contains only 1 set of chromosomes. in humans, a haploid cell would have 23 chromosmes, or just n, 1 set of 23 chromsomes.
3 events that happen during meiosis 1 but not mitosis
1) unlike in mitosis, in prophase 1 of meiosis 1, duplicated homologous chromosomes attach to form tetrads along their lengths with help of proteis and non-sister chromatids cross over their genetic material
2) during metaphse 1, the tetrads are aligned in the centre of the cells, wheread in metapahse of mitosis, idnidviausl duplicated chromsomes line up in a single-file formation along the metaphase plate
3) in anapahse 1, the isster chromatids fo not seperate from their partners like in anaphse of mitosis, rather, it is the pairs of homologous duoliacted chromsomes that are sperated from one another
name & explain the 2 events that contribute ti genetic variation in sexually reproducing organisms
1)how the chromosomes in each hoomologous pair line up and separate in meisosi 1 is all a matter of chance and so the assortment of chromosomes that en up in the resulting ecl occurs randomly which increases the chance of offspring having diffrent assortments of genes
2) teh exhange of genetic materials between homolous chromosomes by crossing over adds more genetic variation. this is because crossing over can produce a single chromsomes that contains a new combination of genetic infomration from different parents, a result called geentic recombination and because chromosomes may contain hudnreds of genes a single corssover event can affect many genes, and the fact that multiple crossovers can occur in each tetrad, the possibility for genetic variation grows even more
crossing over
the process in which the non-sister chromatids of a pair of duplicated homologous chromosomes involved in a tetrad exchange egentic information
occurs after tetrads are formed, during prophase 1
the exchange of genetic material between homologous chromosomes
when crossing over begins, homologous chromosomes are closely paired all along their length. There is a precise gene-by-gene alignment between adjacent chromatids of the two chromosomes and segments of the two chromatids can be exchanged at one or more sites
tumour
an abnormal mass of cells created by out-of-control cell reproduction
benign tumour
-an abnormal mass of essentially normal cells.
-they may cause health problems depending on where they are located but can usually be removed surgically.
-the cells of benign tumours stay at their original site in the body
malignant tumour
-masses of cells that result from the reproduction of cancer cells
-the most dangerous characteristic of cancer cells is their ability to spread, a malignant tumour displaces normal tissue as it grows and if it is not removed or killed it may spread into surrounding tissues. additionally, cancerous cells may split off from the tumour and travel to other parts of the body where they can form new tumours, in other words, they can metastasise
cancer
A disease caused by the severe disruption of the mechanisms that control the cell cycle. this disruption leads to uncontrolled cell division, which if unchecked can lead to death
types of cancer treatments
sometimes malignant tumours can be removed by surgery, however it I sdifficut to successfully remove all traces of cancer cells with surgery. to treat cancer at a cellular level, physicians ometiems use radiation therapy or chemotherapy, both of which attempt to stop the spread of cancer by stopping the cancer cells from diving
radiation therapy
involves exposing parts of the body with cancerous tumours to high energy radiation, which disrupts cels diivion. because cancer cells divide more often than most regular cells, they are more likely to be dividing at any given time, an dos , radiation therapy can kill cancer cells with minimal damage to regular cells
chemotherapy
involves treating the patient with drugs that disrupt cell division. these drugs work in a variety of ways some called antimitotic drugs prevent cell diciion by interfering with the mitotic spindle. one antimitotic drugs prevents the spindle from forming in the first place and another freezes the spindle after its formation so it cannot function.
radiation and chemo side effects
both radiation and chemo can acsue undesried side effects in normal body cel;ls that divide fairly often.
radiation: can damage the cells of the ovaries or testes , causing sterility
chemo: affects intestinal cells or hair follicle cells can be affected causing nausea or hair loss
metastasis
the spread of cancer cells beyond their original site
genetic recombination
Genetic recombination is the result of the exchange of genetic material during meissis between non sister chronatids of a pair of duplicated hmologous chromosomes of a tetrad that leads to a single chromsome having a new conbibation of genetic material from different patterns
recombinant chromosome
an altered chromsome resulting from th exchange of segments between chromosomes
