Why do cells need to divide As cells grow larger they start to face several difficulties in functioning Growth amp Repair In order for multicellular organisms to grow cells must divide If cells are lost due to injury or damage to DNA ID: 915327
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Slide1
Introduction to the Cell Cycle
Slide2Why do cells need to divide?
As
cells grow larger, they start to face several
difficulties
in functioning:
Growth & Repair
In order for multi-cellular organisms to grow, cells must divide. If cells are lost due to injury or damage to DNA,
new cells must replace old cells
.
Information
Overload
The larger a cell becomes, the
more demands
the cell places on its
DNA
.
There
needs to be enough DNA to support the
protein needs
of the
cell.
Exchanging Materials
The
rate of diffusion
is slower in larger cells and faster in smaller cells/
A
larger cell is
less efficient in moving nutrients
and waste materials across the cell membrane.
Slide3Surface Area to Volume Ratio
The
volume of the cell increases
faster than the surface area of the cell membrane!!
Volume = content inside the cell
Surface Area = Amount of Cell Membrane
Small cells have a LARGER surface area : volume ratio!
More cell membrane = faster exchanging of materials
Slide4Cell Division
The process by which a cell divides into two new “daughter” cells.
DNA replication
takes place
before the cell dividesCreates two identical copies of DNA (genetic information
)
Each daughter cell gets one complete copy of genetic information
Results in the an increase in the surface
area:volume
ratio for each daughter cell
Slide5Asexual Reproduction
The production of genetically identical offspring from a single parent.
Primary form of reproduction in single-celled organisms such as
Bacteria &
Protists
.
Unicellular Organisms
Bacteria
using cell division to reproduce is called
Binary Fission
.
Multicellular Organisms
Budding
- a new organism develops from an outgrowth or bud on another one due to cell division at one particular site. The new organism remains attached as it grows, separating from the parent organism only when it is
mature.
Slide6Asexual Reproduction
Advantages Do not need a partner to reproduce
Can reproduce quickly and easily
Disadvantages
Produce genetically identical offspring
Could result in death of a population if there is a change in the environment that is not favorable to the characteristics of that organism.
Slide7Sexual Reproduction
Offspring produced by sexual reproduction inherit some of their genetic information from each parent.
Offspring are produced by the fusion of reproductive cells form by each of the two parents.
Most animals and plants produce sexually, as well as some single-celled organisms.
Slide8Sexual Reproduction
Advantages Creates genetic diversity in a population
If the environment changes, some offspring may have the right combination of characteristics to survive
Disadvantages
Invest more time, energy, and resources
Need to find a mate
Growth, development, and caring for offspring
Slide9Slide10What is a chromosome?
DNA is packaged into chromosomes
.
Chromosomes
are threadlike structures of DNA wrapped around proteins.
CHROMATIN
– DNA tightly coiled around histone proteins
CHROMOSOME
Slide11Eukaryotic Chromosome Structure
C
hromosomes
are only visible when a cell is dividing so we usually see them in their double-stranded
form.
Slide12Eukaryotic Chromosome Structure
The halves of a double-stranded chromosome ( sister chromatids
) are identical to each other because the DNA (original chromosome) replicated
before
cell division.
(part of chromosome where the two chromatids attach)
Slide13Why are chromosomes important in cell division?
Chromosomes make it possible to separate DNA precisely
.
Each new cell will get the exact same DNA as the cell it came from.
DNA Replication takes place before cell division!
Slide14Prokaryotic Chromosome Structure
Where is the nucleus?THERE IS NO NUCLEUS! IT’S A PROKARYOTIC CELL! ONLY EUKARYOTIC CELLS HAVE A NUCLEUS!
Slide15Types of Cells
There are two types of human cells: somatic cells and gametes.
Somatic Cells
= body cells (brain, muscle, heart, liver, skin,
etc
)
Contain
46 chromosomes
in humans
Diploid
(2n)= cell that contains two sets of homologous chromosomes
Gametes
= sex cells (sperm or egg)
Contain
23 chromosomes in humansHaploid (n)= cell that contains one set of chromosomes
Slide16Fertilization
When sperm meets egg a zygote is formed. A zygote is the first cell of the embryo.
Which of the cells above are haploid (n)?
Diploid (2n)?
Slide17Homologous Chromosomes
Chromosomes containing the same type of genetic information one comes from male parent, one comes from female parent
DAD
MOM
Slide18Homologous Chromosomes
Slide19What is the diploid number of chromosomes in humans?
46
How many pairs of
homologous chromosomes
do humans have?
23
Slide20The chromosomes diagrammed below are arranged in a
karyotype
, the 46 chromosomes have been arranged in homologous pairs.
Slide21The first 22 pairs of homologous chromosomes are called
autosomes
or autosomal chromosomes.
The 23rd pair of chromosomes determines the sex of the individual and are called
sex
chromosomes.
The sex chromosomes of a female are
XX
.
The sex chromosomes of a male are
XY
.
Slide22What’s the difference?
Slide23Which of the following is an example of a haploid cell?
Stomach cell
Brain cell
Sperm Cell
Skin cell
1
0 of 28
Slide24How many chromosomes are in your body cells?
23
32
64
46
1
0 of 29
Slide25Your body cells have how many pairs of homologous chromosomes?
46 pairs
23 pairs
32 pairs
2 pairs
2
0 of 29
Slide26This is a picture of a
Single chromosome
Chromatin
Duplicated chromosome
Cell
1
0 of 29
Slide27_________ are located on chromosomes.
Cells
Karyotypes
Genes
Eggs
1
0 of 29
Slide28Human somatic cells contain _____ pair(s) of
autosomes.
22
1
23
46
19
Slide29Somatic cells contain _____ pair(s) of
autosomes.
22
1
23
46
Countdown
10
Slide30Gametes are _________, meaning they contain one set of chromosomes.
Diploid
Haploid
Triploid
Monoploid
14
Slide31If an organism contains 14 chromosomes in each somatic cell, then its gametes each contain ____ chromosomes.
7
14
21
28
28