MCAT Biology - Reproduction

MCAT Biology - Reproduction

Diploid

contains two copies of each chromosome

Haploid

Contain only one copy of each chromosome

Cell Cycle

Series of phases cell grows, synthesizes DNA and divides

Interphase

Longest phase, the first three stages

G₀ Stage

Cell is simply living adn caring out its functions without preparation for division

Features of G₁ Stage

Cells create organelle for energy and protein production while increasing size

Features of S Stage

Cells replicate genetic material so each daughter will have identical copies

Features of G₂ Stage

Cell checks to ensure that there are enough organelles and cytoplasms for two daugther cells, check DNA replication proceeded correctly

G₁ / S Checkpoint

Cell determines if the condition of DNAS is good enough for synthesis

P 53

Main protein in control of G1/S checkpoint

G2/M Checkpoint

The cell is mainly concerned with ensuring that it is has achieved adequate size adn teh organelles ahve been properly replicated to support two daughter cells

Molecules responsible for cell cycle

Cyclin and Cyclin Dependant Kinases

Transcription Factors

Promote transcription of genes required for next stage of cell cycle

Metastasis

damage cells reaching other tissues, including local invasion as well as distant spread of cancerous cells through blood stream or lymphatic systems

Mitosis

Process by which two identical daughter cells are created from a single cell

Somatic Cells

Cells not involved in sexual reproduction

Cytokinesis

Splitting of cytoplasm and organelles between two daughter cells

Prophase

Condensation of chromatin into chromosomes, centriole pairs separate and move toward opposite poles of cells

Metaphase

Centriole pairs at opposite ends of the cell, chromosome line across the metaphase plate

Anaphase

Centromeres split so each chromatid has its own distinct centromere allowing sister chromatid to separate. Sister chromatid pulled toward opposite poles of cell by the shortening of the kinetochore fibers

Telophase

Spindle apparatus disappears. Nuclear membrane reforms around each set of chromosomes and the nucleoli reappear, the chromosome uncoil resuming their interphase form

Centrosome

Paired cylindrical organelles located outside nucleus and responsible for correct divison of DNA

Kinetochores

Protein structures located on the centromeres that serve as attachment points for specific spindle fibers of the spindle apparatus

Reductional Division

Generating of haploid daughter cells from homologous chromosomes being separated in Meiosis I

Equational Division

Separation of sister chromatids without a change in ploidy.

Synapsis

Process of homologous chomosomes coming together and intertwining

Mendel Second Law (of Independent Assortment)

Inheritance of one allele has no effect of the likelihood of inheriting certain allele for other genes

Prophase I

Chromatin condenses into chromosomes, the spindle apparatus forms, and the nucleoli and nuclear membrane disappears

Difference in Prophase between Meiosis and Meitosis

In Meiosis homologous chromosomes come together and intertwine (crossing over)

Metaphase I

homologous pairs align at the metaphase plate, each pair attaches to a separate spindle fibe by its kinetochore

Difference in Metaphase in Meiosis and Mitosis

In Mitosis, each chromosome is lined up on metaphase plate by two spindle fiber, in meiosis homolgous chromosome are lined up across from eachother at the metaphase plate and are had by one spindle fiber

Anaphase I

Homologous pairs separate and are pulled to opposite poles of the cell. This is Disjunction

Segregation

Separation of two homologous chromosome

Telophase I

Nuclear membrane forms arounds each nucleus, cells now haploid

Interkinesis

Short rest period between cell divisons during which chromosome partially uncoil

Prophase II

Nuclear envelope dissolves, nucleoli disappear, centrioles migrate to opposite poles, spindle apartus begin to form

Metaphase II

Chromosomes line up on the metaphase plate

Anaphase II

Centromeres divide, separating chromosome into sister chromatin. These chromatin pulled to opposite pole by spindle fiber

Telophase II

Nuclear membrane forms around each nucleus

Sex Linked Disorders

Mutations in the X Chromosome

SRY

Sex determining region Y, gene on Y chromosome codes for a transcription factor that initiates testis differentiation and, thus, the formation of male gonads

Carriers

Females carrying a diseased allele of X chromosome but not exhibiting the disease

Ejaculation

Sperm travel through the vas deferens and enter the ejaculatory duct at the posterior edge of the prostate gland

Semen

Combination of sperm and seminal fluid

Seminiferous tubule

Where sperm is produced

Interstital caps of Leydig

Secrete testosterone and other male sex hormones

Scrotum

An external pouch that hangs below the penis where testes are located

Epididymis

Where sperm flagella gain motility and stored until ejaculation

Vas Deferens

Tube carrying sperm from testis to the urethra

Urethra

carrier sperm through the penis as they exist the body

Seminal Vesicles

Contribute fructose to nourish sperm, give the fluid midly alkaline properties so the sperm can survive in acidity of female reproductive tract

Prostate Gland

Give the fluid mildly alkaline properties so the sperm can survive in the relative acidity of the female reproductive tract

Bulbourethral (Cowpers) Glands

Produce clear viscous fluid that cleans out any reminants of urine and lubricates the urethra during sexual arousal

Spermatogenesis

Formation of haploid sperm through meoisis

Where spermatogensis occurs

Seminiferous tubules

Spermatogonia

Diploid stem cells found adjacent to basement membrane within the seminiferous tubules

Primary Spermatocytes

After spermatogonia replace their genetic material, found between basement mebrane adn lumen of seminferous tubule

Secondary Spermatocytles

1st meiotic division of primary spermatocytes

Spermatids

Secondary spermatocytes undergoing meiosis II

Spermatozoa

After spermatid undergo maturation, found in lumen of seminiferous tubule

Head of Sperm

Contains genetic material

Midpiece of Sperm

Filled with mitochondria which generate energy for swimming through female tract

Acrosome

Necessary penetrate ovum, cap of head

Follicles

Multilayered sacs that contain, nourish and protect immature ova

Uterus

Site of fetal development

Vulva

External parts of female genital organs

Oogenesis

Production female gametes

Menarche

First menstrual cycle

Secondary Oocyte

Polar body

Zona Pellucida

Surrounds the oocyte itself adn is an acellular mixture of glyco proteins that protect the oocyte and contains compounds necessary for sperm cell binding

Corona Radiata

Outside the zora pellucida and layer of cells adhere to oocyte during ovulation

FSH role in male sexual development

Stimulates sertoli cells and triggers sperm maturation

LH role in male sexual development

Causes interstial cells to produce testosterone

Secondary Male Sexual Characteristics

Facial, axillary hair, deepening voice, increased muscle and bone mass

Estrogen role in embryo

Stimulate development of reproductive tract

Estrogen role in adults

Lead to thickening of the uterus

Corpus Luteum

remains of ovarian follicle following ovulation

Progesterone role

Involved in development and maintence of endomeitrum, just not inital thickening

Follicular Phase of Menstrual Cycle

Begins with menstrual flow, sheds uterine lining of previous cycle, GnRH seceretion increases in response to decreased concentration of esterogen and progesterone. Higher concentration GnRH cause increased secretions of both FSH and LH. Estrogen stimulates regrowth of endometrial lining, stimulating vascularization and glanduarization of the decidua

Ovulation

Surge in LH induces ovulation, ovulation releases the ovum from the ovary into the abdominal cavity

Luteal Phase in Development

LH causes ruptured follicle to form corpus luteum, which secretes progesterone, high progesterone levels cause negative feedback on GnRH FSH and LH, preventing ovulation of multiple eggs

Menstruation

Corpus luteum loses its stimulation from LH, turning into corpus albicans. Progesterone levels decline, uterine lining sloughed off. Loss of high levels of estrogen and progesterone, removes the block on GnRH so next cycle can begin.

hCG levels 2nd Trimester

Decline because placenta has grown to sufficient size to secrete enough progesterone and estrogen by itself.

Menopause

Estrogen and progesterone levels drop, the endometrium also atrophies, and menstraution stops, hot flases bloating and headaches accompany and commonly occurs between the age of 45-55