REPRODUCTION AND CONTINUITY OF LIFE

early embryonic development

- may occur externally or internally -when differentiation happens and cells divide by mitosis to form different specialized cells (different genes activated in different cells)

internal fertilization

- occurs in both aquatic and (mostly) terrestrial organisms -sperm and egg unite inside of the body of the female -greater success rate than external fertilization

internal development

-fertilized egg (zygots) develop inside of the body of the female -most often occurs with terrestrial organisms -developing offspring are provided with nutrition and protection by the mother -greater success rate of offspring than with external development

external fertilization

-occurs ONLY in aquatic organisms -both sperm and egg are released directly into the water -water provides an adequate environment for the survival of the sex cells -sperm joins with egg outside of the organism's body

external development

-zygotes develop outside of the body -most often occurs in water but may occur on land -amniotic egg-prevents drying out of developing embryo -developing offspring are vulnerable to predators and changing environmental conditions

result of meiosis I

2 HAPLOID daughter cells are created, either being paternal or maternal with chromosomes in the replicated form

identical chromosomes

2 copies make up a pair, one egg, one sperm,

result of meiosis II

4 HAPLOID daughter cells/gametes that are all GENETICALLY DIFFERENT

Tetrad

4 sister chromatids

prophase

Chromatin in the nucleus starts condensing and chromosomes become visible all chromosomes now have two chromatids that are joined together at the centromere the nuclear membrane dissolves

events of Interphase I

DNA replication forms replicated chromosomes

Diploid number and abbreviation

Diploid number= 46 abbreviation= 2N

telophase

End of nuclear division new nuclear membranes form around two daughter nuclei while chromosomes start dispersing cytokinesis begins

interphase

G1: growth and normal metabolic activities S: synthesis, when DNA is replicated G2: growth and preparation for mitosis majority of cell cycle is spent in interphase, happens before mitosis and meiosis

events of Metaphase I

Spindle fibers attach to the chromosomes as they line up in the middle of the cell and *Independent assortment occurs*

events of Anaphase I

Tetrads separate and move toward opposite ends of the cells

cytokinesis

The cytoplasm of the daughter cells is divided by a cell membrane and implant a cell wall in animal cells the daughter cells separate as the new cell membrane pinches in towards the middle of the cell in plant cells a new cell wall begins to form in the center of a cell between the two new daughter nuclei This is called the cell plate at the end of cytokinesis the daughter cells are separate and independent

anaphase

The sister chromatids separate and move to opposite ends of the cell

metaphase

The spindle fibers line the chromosomes up in the middle of the nucleus the organization that helps make sure that when chromosomes separate in anaphase the new nuclus will receive one copy of each chromosome

haploid

a cell with only one copy of each chromosome (have one copy of either the maternal or paternal chromosome, but not both)

diploid

a cell with two copies of each chromosome (one copy from mom and one copy from dad)

meiosis

a special type of cell division in which the number of chromosomes is reduced by half. produces gametes for sexual reproduction. there are two cell divisions that go from haploid to diploid. 4 cells are produced in total, and all are genetically unique and have variation. this variation is due to independent assortment and crossing over

4 bases in DNA

adenine, guanine, thymine, cytosine (a+t, c+g)

semi-conservative

after the DNA is replicated, the replicated chromosome has 2 strands of original DNA, and two of new DNA. a semi conservative model is a chromosome that has an original and new strand in one sister chromatid, and a new and original in the other. this is the structure of replicated chromosomes.

somatic cell

any body cell BESIDES a sex cell

forms of asexual reproduction

binary fission, budding, regeneration, vegetative propagation, sporulation

helicase

breaks the hydrogen bonds in DNA and separates the double helix

coiling and condensing of chromosomes

chromosomes condense before mitosis to allow them the ability to move smoothly, without becoming entangled and breaking

paternal chromosomes

comes from the father and makes up one of the pair in homologous chromosomes

maternal chromosomes

comes from the mother and makes up one of the pair in homologous chromosomes

placenta

connection between embryo and mother. delivers nutrients and oxygen and removes metabolic wastes. the blood from the mother and baby never mix, they are separated by the chorion, but drugs, alcohol, viruses and bacteria can cross the membrane. the placenta is the embryos organ of respiration, nutrition, and excretion

penis

connects the urethra to the outside of the body

set

copy of chromosomes 1-23. it is half of the chromosomes in the cell

replication in eukaryotes vs prokaryotes

euk- nucleus prok- cytoplasm

egg/ovum

female sex cell/gamete that consists of 23 chromosomes

Gametogenesis

formation of the gametes/egg and sperm

different words for the products of meiosis

gametes sex cells egg/ovum sperm

haploid number and abbreviation

haploid number= 23 abbreviation= N

crossing over

happens during prophase I when homologous chromosomes exchanges portions of their chromatids. AN IMPORTANT SOURCE OF GENETIC VARIATION

moms blood

has oxygen, vitamins, glucose, amino acids

stem cells

have the potential to grow into any type of cell. this is what the planaria have, thats why they can regrow

risks to an embryo

inadequate diet, substance use, toxins, infections, inherited disease

sperm

male sex cell/gamete that consists of 23 chromosomes

events of Prophase I

maternal and paternal homologous chromosomes find each other and form a tetrad. *Crossing over occurs*

ovulation

mature ovum is released from the ovary. follicle ruptures and releases its ovum. ovum is swept in the fallopian tube and pushed along by cilia lining the fallopian tubes. when ovum in in the tubes, it can be fertilized

rule of complementary bases

means that adenine always bonds with thymine and cytosine always bonds with guanine. when the two strands are compared side by side, the pairings will always be there, a across from t and c across from g

genetic recombination

new combinations of existing genes on each chromosome as a result of crossing over

events of Telophase I

nucleus divides and cytokinesis separates the two daughter cells

events of Telophase II

nucleus separates and cytokinesis splits the cytoplasm and distributes organelles

sexual reproduction

offspring receives half of its information from mom and half from dad. offspring will not be identical to parents.

gametogenesis of the egg

results in the formation of 1 large haploid egg cell and three smaller cells called polar bodies that are not involved in reproduction... only ONE egg develops per month

gametogenesis of the sperm

results in the formation of 4 equal-sized haploid sperm cells

cell cycle

sequence of events from the point when a new cell is created until it divides into 2 daughter cells interphase and the mitotic phase (division of the nucleus) and mitosis is followed cytokinesis

sister chromatids and centromere

sister chromatids are two strands of DNA. the centromere is the part of the chromosome where the sister chromatids are held together.

sporulation

spore formation, reproduction involving specialized single cells coming from one parent

structures of the male reproductive system

testes epididymis vas deferens urethra penis

implantation of blastocyst

the blastocyst attaches to the uterine lining, and the blastocyst has undifferentiated cells (stem cells)

homologous chromosomes

the cell has two sets of each chromosome. one of the pairs is derived from the mother and the other from the father. the maternal and paternal chromosomes in a homologous pair have the same genes at the same loci, but possibly different alleles. the chromosomes correspond maternal to paternal

independent assortment

the different ways in which a tetrad RANDOMLY lines up along the metaphase plate in relation to other tetrads which leads to many possible combinations of genes in the gametes

mitosis

the division of the nucleus of eukaryotic cells leading to the formation of two daughter nuclei each with identical chromosomes to that of the original nucleus. it is one cell division that goes from haploid to diploid. mitosis is making identical body cells. two cells are produced and there is no variation. the two daughter cells are identical to each other and the original cell. the cells divide for growth, development, repairing, restoring.

binary fission

the division of unicellular organisms into two equally sized daughter cells. the parent cell doesn't exist after the division. parent=daughter cell=daughter cell

DNA polymerase

the enzyme that builds DNA

events of Prophase II

the homologous chromosomes are no longer in the same cell and begin to move toward the middle of the cell

regeneration

the regrowth of an entire organism from a small part of the organism. the organisms grow back a missing part. this is what we did with the planaria

events of Metaphase II

the replicated chromosomes line up and attach to the spindle fiber

events of Anaphase II

the sister chromatids separate and move toward opposite ends of the cell

chromosome

tightly coiled condensed DNA wrapped around histones

vas deferens

tube from the scrotum to the body merges with the urethra

replicated/double stranded chromosome

two sister chromatids(two strands of DNA) attached at the centromere, each chromatid will go into one daughter cell. chromosomes are tightly coiled, there is 6 feet of DNA in 1 nucleus.

cleavage

type of mitotic rapid cell division that change a zygote into a morula, which is the solid ball that turns into a blastula

mitosis and meiosis similarities

types of cell division, S phase replication before division, cells need own genetic material

single stranded chromosome

unreplicated, only existent when in G1 of interphase. this is when the chromosome is not visible

replication: what, where, when and why

what: DNA being copied accurately where: in nucleus or cytoplasm depending on if it is eukaryotic or prokaryotic when: S phase of interphase why: so that each daughter cell following cell division will have their own copy of DNA

budding

when a complete new organism grows from the body of the parent organism and detaches from it. one is much larger than the other

vegetative propagation

when an entire new plant grows from the roots, stems, or leaves of the parent plant.

mutation

when an error happens in a cell destined to become an egg or sperm cell. mutations occur when DNA is copied incorrectly. as a result of a mutation, the sequence of bases is different, the genetic code is different and the gene cannot direct the cell to produce correctly.

nondisjunction

when chromosomes fail to separate, resulting in chromosomal disorders like down syndrome

fertilization

when the gametes unite to form a zygote which contains the complete genetic information for the offspring

DNA replication

when the original DNA molecule is copied, first the DNA must be separated. the double helix is unwinded by the enzyme helicase. the DNA molecule is now in two strands or unzipped. once unzipped, all of the bases are accessible and the information is exposed. the second step is the rebuilding of new strands by the enzyme DNA polymerase. new bases come in along with new sugar and phosphate subunits. the result is two identical DNA molecules. this all happens during interphase, more specifically in S phase (synthesis phase) in the nucleus

testes

where sperm are produced

epididymis

where sperm finish maturing and are stored

advantages and disadvantages of asexual reproduction

you don't need to find a mate, and it is a very fast process, but the parent is identical to the offspring, so there is no variation, which makes the species more prone to extinction