B 2 - Reproduction Flashcards
Define DIPLOID cells
Diploid (2n) cells have TWO copies of each chromosome
Define HAPLOID cells
Haploid (n) cells have ONE copy of each chromosome
What are the 5 stages of the CELL CYCLE
G1 - presynthetic gap S - synthesis G2 - postsynthetic gap M - mitosis G0 - everyday function
Define CHROMATIN
DNA in an uncoiled form
What stages of the CELL CYCLE are termed INTERPHASE
G1, S & G2
Describe G1 stage
In G1 stage, cells create organelles for energy and protein production and increase their size
The RESTRICTION POINT, during which DNA is checked for quality, must be passed for the cell to move into the S stage
Describe S stage
In S stage, DNA is replicated. The strands of DNA, called CHROMATIDS, are held together at the centromere
Describe G2 stage
In G2 stage, there is further cell growth and replication of organelles in preparation for mitosis.
Another quality checkpoint must be passed for the cell to enter into mitosis
Describe M stage
Mitosis and cytokinesis occur
Describe G0 stage
In G0 stage, cell performs its functions without preparing for division
What is the role of the p53 protein in the CELL CYCLE
p53 plays a role in the two major checkpoints of the cell cycle (G1-to-S & G2-to-M)
Describe CYCLINS and CDKs
Cyclins and cyclin-dependent kinases (CDKs) rise and fall during the cell cycle.
Cyclins bind to CDKs, phosphorylating and activating TRANSCRIPTION FACTORS for next stage of the cell cycle
How does CANCER usually occur?
Cancer occurs when cell cycle control becomes deranged, allowing damaged cells ot undergo mitosis without regard to quality or quantity of hte new cells produced.
Cancerous cells may begin to produce factors that allow them to delocalize and invade adjacent tissues or metastasize elsewhere
What does mitosis produce?
Mitosis produces 2 genetically identical DIPLOID daughter cells from a single cell
occurs in SOMATIC CELLS
What are the 4 phases of MITOSIS?
Prophase
Metaphase
Anaphase
Telophase
Describe PROPHASE
In prophase, the chromosomes condense, the nuclear membrane dissolves, nucleoli disappear, centrioles migrate to opposite sides of the cell, and the spindle apparatus begins to form
The kinetochore of each chromosome is contacted by a spindle fiber
Describe METAPHASE
Chromosomes line up along the metaphase plate (equatorial plate)
Describe ANAPHASE
Sister chromatids are separated and pulled to opposite poles
Describe TELOPHASE
Nuclear membrane reforms, spindle apparatus disappears, and cytosol and organelles are split between the two daughter cells thru cytokinesis
What type of cells can undergo MEIOSIS
Gametocytes (germ cells) only – reproductive cells
What does MEIOSIS produce?
meiosis produces UP TO four nonidentical haploid sex cells (gametes)
How many rounds of replication and division does MEIOSIS have?
1 round of replication
2 rounds of division (reductional and equational)
Describe what occurs in MEIOSIS 1?
In meiosis 1, homologous pairs of chromosomes (homologues) are separated from each other
Define HOMOLOGUES
Homologues are chromosomes that are given the same number, but are of opposite parental origin
Describe PROPHASE 1
In prophase 1, the same events occur as in prophase of MITOSIS, except that homologues come together and intertwine in a process called SYNAPSIS
The four chromatids are referred to as a TETRAD, and CROSSING OVER exchanges genetic material between one chromatid and material from a chromatid in the homologous chromosome. – this accounts for MENDEL’s SECOND LAW (OF INDEPENDENT ASSORTMENT)
Describe METAPHASE 1
Homologous chromosomes line up on opposite sides of the metaphase plate
Describe ANAPHASE 1
Homologous chromosomes are pulled to opposite poles of the cell. – this accounts for MENDEL’s FIRST LAW (OF SEGREGATION)
Describe TELOPHASE 1
The chromosomes may or may not fully decondense, and the cell may enter INTERKINESIS after CYTOKINESIS
Describe MEIOSIS 2
Sister chromatids are separated from each other in a process that is functionally identical to MITOSIS.
Define SISTER CHROMATIDS
Sister chromatids are copies of the same DNA held together at a centromere
Which chromosome is responsible for biological sex determination?
Biological sex is determined by the 23rd pair of chromosomes in humans, with XX being female and XY being male
Describe the X chromosome
X chromosome carries a sizeable amount of genetic information
Mutations of X-linked genes can cause sex-linked disorders
Define HEMIZYGOUS
Males are defined as hemizygous with respect to unpaired genes on the X chromosome, so they will express sex-linked disorders, even if they only have one recessive disease-carrying allele
Define CARRIER
Women with one copy of a sex-linked recessive allele are called CARRIERS because they will not express the allele, but will carry it
Describe the Y chromosome
The Y chromosome carries little genetic information, but does contain the SRY (sex-determining region Y) gene, which causes the gonads to differentiate from the testes
How are male and female reproductive systems different?
Male contains both internal and external structures
Female contains only internal structures
Describe the SCROTUM / TESTES
The testes are located in the scrotum, which hands outside of the abdominal cavity and has a temperature 2-4 degC lower than the rest of the body
Describe the EPIDIDYMIS
Once formed, sperm gain motility in the epididymis and are stored there until ejaculation
Describe EJACULATION
During ejaculation, sperm travel through the VAS DEFERENS to the ejaculatory duct, and then to the urethra and out through the penis
Describe SEMINAL VESICLES
The seminal vesicles contribute fructose to nourish sperm and produce alkaline fluid
Describe PROSTATE GLANDS
The prostate gland also produces alkaline fluid
Describe BULBOURETHRAL GLANDS
The bulbourethral glands produce a clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal
Describe SEMEN
Semen is composed of sperm and seminal fluid from the prostate/bulbourethral glands
Describe SPERMATOGENESIS
Four haploid sperm are produced from a SPERMATOGONIUM
Describe the different nomenclatures of germ cells in spermatogenesis
Primary spermatocyte - After S stage
Secondary spermatocyte - After meiosis 1
Spermatids - after meiosis 2
Spermatozoa - after maturation
What 3 elements make up a sperm structure?
Head, midpiece and flagellum
Describe the HEAD of sperm
The head contains the genetic material and is covered with an acrosome – a modified Golgi appartus that contains enzymes that help the sperm fuse iwth and penetrate the ovum
Describe the MIDPIECE of sperm
The midpiece generates ATP from fructose and contains many mitochondria
Describe the FLAGELLUM of sperm
The flagellum promotes motility
Describe the OVA
Ova are eggs that are produced in FOLLICLES in the OVARIES
What occurs each month to an OVA/egg?
Once each month, an egg is OVULATED into the PERITONEAL SAC and is drawn into the FALLOPIAN TUBE (OVIDUCT)
