http://www.archive.org/details/GENETICS_27
- Review of cell structure
- • Plasma membrane → two layered structure surrounds the outside of the cell
- • Plant cell → cell wall – exterior to the plasma membrane and rigid structure supports the plant cell
- • Nucleus → membrane bound structure which contains the cells DNA
- • Nucleolus → site of ribosome production. rRNA synthesis and ribosome assembly
- • Prokaryote → the DNA is not surrounded by a membrane. DNA does congregate into a nucleoid region.
- • Cytoplasm → everything in the cell except the nucleus. Includes other organelles and an aquous solution
- • Cytosol → cytoplasm (minus) the organelles. It is primarily water but also other chemicals.
- • Cytoskeleton → a series of interconnected tubules which make up the cells skeletal system and muscular system.
- • Endomplasmic reticulum
- o Rough ER → covered in ribosomes and functions in protein synthesis
- o Smooth ER → functions in lipid and fatty acid synthesis
- • Mitochondria: functions to produce ATP for the cell. Primarily in animal cells but can function in plant cells as well.
- • Chloroplast: found in plant cells and used to accomplish photosynthesis . capturing energy from the sun and using that energy to make sugar.
- • How DNA is organized in the cell.
- o DNA exists in two forms
- • Interphase
- Chromatin: loose thread like structure
- • mitosis
- DNA in the chromotin condenses and forms distinct .
- o Two copies of each chromosome. Homologous chromosome
- o During mitosis and meiosis homologous chromosomes pair with each other.
- o centromere – place where homologous chromosomes are physically paired together.
- • 4 types of chromosome arrangements (slide 3, chap 2)
- o metacentric
- • centromere is directly in the middle
- • when you divide in anaphase you get an even distribution
- o submetacentric
- • between the middle and the end
- o acrocentric
- • very close to the end of the chromosome pair
- o telocentric
- • centrism is at the end of the chromosome pair
- • When you have an acrocentric and a submetacentric arrangement you get an uneven distribution and it leads to the formation of two distinct arms of the chromosome.
- o P arm (petite arm) – smaller of the two arms
- o Q arm – larger of the two arms
- • VOCAB –
- o Diploid # → refers to the total number of chromosomes in a cell
- o Haploid # → the total # of unique chromosomes in the cell
- o Genome : all of the DNA found in a human being
- o Loci : refers to a specific region of DNA
- o Alleles : alternative forms of the same gene
- o Sex chromosomes : pair of chromosomes that determines the sex of an organism
- • Males : XY and Females: XX
- • Mitosis and the cell cycle (slide 4 chap 2)
- o All diploid organisms (me) → an organims with two copies of each chromosome
- • Begin life when two haploid gametes fuse to form a zygote
- o Zygote proceeds to undergo mitosis many times. End result is a baby.
- o Human body loses 100 billion cells/day.
- o Mitosis is essential to replace those cells
- o Mitosis can be divided into two distinct portions.
- • Karyokinesis – dealing with the division of DNA
- • Cytokinesis – physical division of the cell in two
- o Cell cycle – series of orderly events. Duplicats its contents and divides them in half to create two new cells. Divided into:
- • Interphase
- Period of time between two cell divisions. Major event is the doubling of cell components.
- 3 Stages of interphase
- • G1 phase or gap 1 phase- starts immediately after mitosis completes. Period of growth, differentiation (doing the things that make you the type of cell that you are) and metabolic activity.
- • Cell than proceeds to S phase. Major event is DNA replication, copying your DNA
- • G2 or gap 2 phase – growth and metabolic activity. At the end of this phase the cell has doubled in volume and composition.
- • G0 phase – during G1 phase the cell makes a decision. It will either continue dividing and in turn proceed to S phase OR it can choose to stop dividing it then enters in the G0 phase in which it is no longer growing or dividing. Enter G0 phase until its triggered to exit G0 phase and continue dividing. Hallmarks of tumor cells is that they fail to enter G0 phase. IF they do enter they proceed through G0 rapidly
- • Mitosis slide 4, chap 2
- Division of those contents into two new cells.
- Prophase – condensation of DNA into chromosomes. Formation of centrioles and each cell will make two of these. Centrioles direct the formation of the mitotic spindle. These also serve as the poles for mitosis.
- PRometaphase – nuclear envolope breaks down. The mitotic spindle begins to form and attach to the chromosomes. Begin the migration of chromosomes to the center line of the cell. The site of attachment – kinetochore.
- Metaphase – chromosomes align along the midline of the cell.
- Anaphase – homologous chromosome pairs serperate and travel toward the centrioles
- Telophase – the nuclear envelope reforms around the DNA
- Cytokenisis - physically divide the cells
