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TULANE / Cell and Molecular Biology / CELL 1030 / What are the meaning of cells and cell theory?

What are the meaning of cells and cell theory?

What are the meaning of cells and cell theory?


School: Tulane University
Department: Cell and Molecular Biology
Course: Heredity and Society
Professor: Ian townley
Term: Spring 2018
Tags: heredityandsociety, cases, Studyguide, tulane, Chromosomes, sex, and selection
Cost: 50
Name: Midterm 1 Study Guide
Description: Covering all 4 lectures as well as cases discussed.
Uploaded: 02/05/2018
14 Pages 135 Views 3 Unlocks

Heredity and Society

What are the meaning of cells and cell theory?

Midterm 1 Study Guide


Cells and Cell Theory 

• They compose all living things and are the most basic unit of structure, function  and organization.

• All cells arise from pre-existing, living cells 

Why is this important?

• Dysfunction in individual cells is the underlying reason of all human diseases. • A zygote (fertilized egg) creates all somatic cells in your body through the  controlled cell-division process of mitosis If you want to learn more check out Why france matters?

Organization of the cell If you want to learn more check out What is the definition of a genetic draft?

• Cells are made of macromolecules

o Carbs

Cells are made of what?

o Lipids

o Proteins

o Nucleic Acids

• Cells are surrounded by plasma membrane (PM)

o Space inside PM is the cytoplasm

▪ This consists of cytosol (a water solution w/ organic molecules  

necessary for chemistry of life)

• Cells contain organelles (little organs)

o Cells have DNA-containing control area

• Nucleus 

o Function: The nucleus protects DNA

▪ Genes (a heritable trait, and a protein) are made up of sequences of  DNA

What is the function of the nucleus?

▪ DNA is held on 46 chromosomes (23 from mom and dad)

▪ DNA is mutated by reactive molecules and some proteins found in  cytoplasm If you want to learn more check out What are the main market segments?

o A chromosome is one complete DNA molecule 

▪ Chromatin is ALL the DNA and proteins (primarily histones)

▪ Chromatin surrounds the nucleolus (center of the nucleus)

▪ Chromatin is formed by "beads on a string" coil in a coil in a coil • Plasma Membrane 

o PM is made of a phospholipid bilayer, hydrophobic in the center,  hydrophilic on the outside

o Phospholipid bilayer is SEMIPERMEABLE 

▪ CO2, H2O, and O2 can get through

▪ It controls what can and can't get through in order to maintain  


▪ DNA may not pass through

• Endoplasmic Reticulum (ER)

o Rough ER

▪ Where ribosomes make proteins that are targeted to other  

organelles, the PM or extracellular We also discuss several other topics like What are the 5 parts of the atmosphere?

o Smooth ER

▪ The site of lipid synthesis, lipids for PM If you want to learn more check out What happens to energy during endergonic and exergonic reactions?

▪ Metabolizes things like alcohol in your liver We also discuss several other topics like How does equality affect efficiency?

• Ribosome 

o Site of protein synthesis 

o NOT Membrane bound

o Single, free-floating

o Attach to ER if they need to drop off

• Golgi Apparatus 

o The UPS of the cell

o Processing and packaging of proteins from the RER (producing secretory  vesicles e.g. mucus)

• Lysosome 

o Garbage and recycling of cell

o Breaks down non-working organelles 

• Mitochondria 

o It is the powerhouse of the cell BECAUSE it transforms broken down  

nutrients (SUGAR+O2) into energy (ATP) 

o Each cell has 10-100s

o Muscle cells (especially legs) have a lot



Chromosomal Basis Of Inheritance 

• Main idea: Genes are located on specific positions on chromosomes • Inheritance patterns determined by:

o Molecular behavior of chromosomes during meiosis, the process of producing  sperm and eggs

o The random act of fertilization, when sperm and egg join

• The human Genome (N=23) 22 pairs of autosomes, 1 pair of sex chromosomes • We have ~30,000 genes and we know where each gene is located on our 23  chromosomes

• A GENE IS: a sequence of DNA, a variable trait

• The Human Genome, we are diploid organisms with a copy from each parent • How do chromosomes determine sex?

o Sex chromosomes have genes that determine with genitalia form and thus  which hormones are produced and at which levels (estrogen and testosterone) o The hormones influence development and secondary sex characteristics which  occur during puberty.

Sex Ratio 

• It SHOULD be 50/50 chromosomally because half of males sperm have an X  chromosome and half have a Y

• A person is considered chromosomally female due to a LACK OF THE Y  CHROMOSOME

Current Sex Selection Procedures 

o Sperm Sorting

• Cost between 4-6k

• Accuracy in 90% for female and 73% for male

• Developed in 1980s


▪ Relies on the fact that the X chromosome is larger

▪ When they are dyed (the membrane, cytoplasm and nucleus pick up  color), the X chromosomes glow brighter when exposed to a laser beam  and can be sorted into a different tube as X and Y

▪ Done with cell suspension, laser beams and flow cytometers

o Pre-implantation Genetic Diagnosis

• Cost between 12-15k

• Accuracy is almost 100%

• Developed in 1990s


▪ Ovarian stimulation (female takes drugs to create multiple viable eggs) ▪ Then the eggs are fertilized in a dish and once they've grown to 8 cell  embryos which are technically stem cells (meaning unspecialized cells,  they are all identical cells)

▪ They take one of those 8 cells and determine whether it is male or  female by testing the chromosomes using genetic sequencing technology  where they can see sex, genetic diseases etc.

▪ When they do this, they are fertilizing some eggs and only taking one, to  some this may be an ethical dilemma

▪ They then take 2-3 embryo of the chosen sex and plant it within the  woman's uterus

• IVF technology has resulted in more twins in our society due to  this factor of the process (having to implant multiple embryos to  

ensure a pregnancy)

o Although the procedure is regulated in all countries, some ban it for non-medical  purposes (Australia, Canada, China, India and UK)

• This leads to reproductive tourism in US, Mexico, Russia, Spain, Thailand etc.

Male Sex-Linked Genetic Disorders 

• Why do men get more sex-linked diseases

• Without two of the same X chromosomes, if one chromosome has an abnormality,  the other (X or Y) cannot fix or cover for the abnormality

Case Study A 

• Knowing how sex selection is accomplished, what do you think the Carters  should do and why (the Carters have had 3 sons and the wife has always wanted a  daughter)

• Should ability to pay limit access to sex selection? Should government programs  like Medicaid pay for this?

• Should Insurance cover it?

DEVELOPMENT FROM FERTILIZATION TO BIRTH - (Some Of These Milestones  Are Necessary Knowledge For Success In This Course) 

• Sperm can live in the fallopian tube for 6 days

• It take 30 minutes for sperm to reach egg in fallopian tube

o Once they mix (46 chromosomes total), a zygote has formed

o It takes 36 hours for the first cell division to occur

o This hollow ball of cells, a blastocyst forms by day 5 

• The inner cell mass contains the human embryonic stem cells  

which will ultimately divide into the 50 TRILLION cells which  

make up our bodies

o Implantation to the uterine wall occurs by day 6 or 7 

• Ovulation occurs around day 14 of the menstrual cycle and only has 12-24 hours  for fertilization

• By 12 days the embryo is embedded in the placenta and formed a protective  membrane called the CHORION 

• Chorion produces the human chorionic gonadotropin (hCG), which  prevents the uterine lining from breaking down as would normally  happen at the end of a cycle.

• Development does not really start until the placenta is formed about 2 weeks after  fertilization

o Weeks 5-6:

• Embryo grows to 11 inches

• Most organ system are formed including heart

• The head is large, but the rest of the body is not

o Week 7:

• Internal sex organs begin to develop

o Week 8:

• Embryo becomes a fetus meaning all organs are formed and  

functional enough to live within the uterus

o Week 12-15

• Sex organs visible by ultrasound

o Week 16  

• Skeleton starts to form

• Fetal movement begins, but it may be another month before  

mother feels it due to fetus' size

• BY the 4th month, the fetus has a well formed face, can open its  eyes and has fingers, toes, and nails

• Sex is one of thousands of traits determined in human gestation

• Sex Determination 

o Primarily dictated by XX or XY which determined how  

nonspecific sex organs called gonads develop

o SRY gene on Y chromosomes cause gonads to become  

testes and secrete testosterone and androgen (masculine  


• If this gene is not present the fetus will be female  

and produce estrogen

• Determined in 7th or 8th week of gestation 

o Testosterone and Androgen

• Causes male genitalia to develop

• Sperm production is caused

• Causes secondary sex characteristics in puberty

▪ Body and facial hair

▪ More muscle mass

▪ Depending of voice

o Estrogen and progesterone

• Cause female genitalia

• Causes female secondary sex characteristics

• More thigh muscle

• Enlargement of breasts

• Elbows hyperextend 5-8 degrees more than men

o Sex Determination Is Multifactorial

• Timing and level of expression of genes

▪ Chromosomal (XXY, X, XYY)

▪ Gene mutations (CIA)

• Hormones present in the uterine environment

▪ Expression of hormones from fetus OR mother

• Maternal uterine environment

▪ Exposure to endocrine disrupting chemicals

▪ Anti-androgens

▪ Estrogenic compounds


What are gametes? Reproductive haploid cells that are mainly responsible for  reproduction. There are two types of gametes: sperm (male gamete) and egg/ova/oocyte  (a female gamete). During sexual reproduction these gametes fuse or unite together and  form a zygote.

Female Reproductive System Components 

• Ovaries: produce eggs and female hormones

• Fallopian Tubes/oviducts: transport sperm and egg

• Uterus: holds embryo and fetus

• Myometrium: muscles of uterus

• Endometrium: lining of uterus

• Cervix: opening from uterus to vagina

• Vagina: connects uterus to outside the body

???? Oogenesis 

• Female’s ovaries produce eggs

o The oocytes are already formed at the woman’s birth

o Contain hundreds of follicles (structures that surround the developing  egg) 

▪ They protect and nourish the egg 

▪ They produce estrogen 

• The process of meiosis creates the egg (gamete or ovum) with ½ of the DNA  in a regular cell

o Also produces 3 polar bodies (discussed in lecture 4 notes under  “CHROMOSOMES”

• Process is promoted by the female hormone progesterone (produced by  corpus luteum) and estrogen

• What structure in the ovary produces progesterone?

o The follicles are one of the few

Male Reproductive System Components 

• Testes: produces sperm and male hormone

• Scrotum: holds testes away from the body to keep the temperature lower than  body temperature

• Epididymis: stores sperm

• Vas deferens: conducts sperm to the urethra (THIS IS WHAT IS CUT FOR A  VASECTOMY)

• Prostate gland: produces seminal fluid that nourishes sperm, which is primarily  fructose

• Bulbourethral or Cowper’s gland: creates a fluid that lubricates

• Track from body to sperm leaving body: Epididymis ???? Vas Deferens ???? Prostate  Gland ???? Penis


• Male’s testes produce sperm

o Seminiferous tubules: the region of the testes where sperm is produced  • Produces 4 sperm (gamete) through meiosis

o Spermatocytes (46 chromosomes) become spermatids (23 chromosomes) ▪ Spermatids transform into fully developed sperm with tails

o This is a continuous process 

• Androgens promote this process, including testosterone


- Infertility is the inability to conceive after 1 year of trying. 

• Successful conception requires:

o Healthy sperm

o Healthy egg

o Sperm and egg interaction

o The zygote needs a place to grow/develop

• 16% of couples have fertility trouble

o 40% due to women

o 40% due to men

o 20% unknown

Causes Of Infertility 


o Abnormal hormone levels 

o Responsible for 50% of ovulation troubles and 33% of other infertility  problems

o Overall, is responsible for almost ½ of female infertility


▪ Genetics

▪ Stress (a factor for up to 30% of infertile couples)

▪ Low body weight (primary cause in 6% of infertility

▪ Obesity (not overweight, primary cause in 6% of infertility)

▪ Poor nutrition

▪ Excessive physical conditioning (too little body fat)

▪ Endocrine disrupting chemicals

o Endometriosis 

o Tissue that normally lines the uterus grows outside of the uterus

▪ Endometrium tissue found on outside of ovaries, fallopian tubes of  intestines

▪ Affects the ability of egg to implant

▪ Main symptoms are pain and menstrual irregularities

o Accounts for 25% of infertility

o Blocked Fallopian Tubes 

o 15% of infertility in women


▪ STDs: Bacterial OR viral that cause inflammation, scarring and  closing of fallopian tubes

▪ Appendicitis or bowel problems: Cause inflammation in abdomen  causing pinching of the tubes

o Age and Infertility 

o All risk factors and complications increase  

after 35

▪ Doctors refer to these later pregnancies as  

“geriatric pregnancies”

▪ Single largest cause of increase in  

reproductive problems seen over the last  

40 years

▪ This is natural

o The largest cause of hormone imbalances in  

women is menopause


o Problems with sperm 

o Low sperm/no sperm/poor mobility

o 90% of male infertility cause

▪ Too few (or none) are being made in the testes

▪ And/or being formed improperly

• Two tails, two heads, no ability to sense surrounding,  

misshapen, too large or small

▪ Recent research has concluded that sperm counts in men have dropped  50% in the last 40 years, but it is unknown as to why


▪ Endocrine disrupting chemicals: pesticides, ibuprofen, lead, radiation ▪ Obesity of low weight (hormone imbalance)

▪ Tight underwear and biking due to poor temperature control of testes ▪ Drugs (marijuana and alcohol): Leads to low counts and  


▪ Genetics

o Impotence: Erectile Dysfunction  

o 8% of the male cause


▪ Hormone imbalance (age)

▪ Neurological and nerve disorder

▪ Legal and illegal drugs: Flomax, Lopressor, Xanax, Prozac, alcohol ▪ Diseases and Cardiac-related conditions

• Atherosclerosis

• Diabetes

• Obesity

Is Overall Infertility On The Rise? 

▪ No, or maybe slightly…

▪ Rates of infertility has increased from 17% to 46% since the 60s, but most of  this is attributed to people having children later in life 

▪ Infertility in married women has dropped for the last 3 decades o 8.5% to 6% (1980 to 2010)

o Reproductive technology most likely plays a part in the decrease in  these numbers

▪ Infertility in men has NOT increased since 2002

o But sperm counts are decreasing, which could pose a problem in the  future

o BUT, sperm counts ARE decreasing, which could pose future  


▪ Fertility rates are decreasing WORLDWIDE

What Technologies Are Available To Infertile Couples? 

▪ If a couple is infertile and hormone treatments do not help then there are three  main options

▪ Assisted reproductive technologies (ART)

o Donation of gametes (sperm and egg banks)

o In vitro fertilization

o Surrogacy

Donation Of Gametes 

▪ If a couple does not produce sperm or egg they can use a donor ▪ Sperm donation has been used for over 50 years

o Earn $1500

▪ Egg donation has been used since the 1980s

o Earn $10,000 because the process is time sensitive and requires surgery  (laparoscopy)

Money Aside, Are There Reasons To Donate Gametes? 

???? Donation of Gametes

• Donated sperm can be used to inseminate the mother

• Donated egg can be implanted in the mother

• If the mother is unable to carry the child, a surrogacy can be arranged o Woman who allows her own eggs to be inseminated by the father’s sperm o Woman who has the zygote from the couple transferred to her uterus to  carry the child for them

o This is helpful for same-sex couples as well as infertile heterosexual  couples

???? In Vitro Fertilization 

• Developed to help w/ blocked fallopian tubes

• Now used to help with  

o “Weak” sperm

o Old eggs (cytoplasm is replaced from a young egg that had been frozen o Intra-cytoplasmic sperm injection (ICSI)

o Screen for genetic diseases

• Complications of ART

o Hormones used to stimulate egg release causes too many eggs to be  released 

▪ Twinning rate is up 76% from the 1980s as of 2009

▪ Multiple births art at higher risk for premature delivery and low  birth weight

▪ Miscarriage is increased if using frozen embryos 

▪ Ectopic pregnancy rate is increased (implanted egg outside of  


▪ Stress (emotional and financial)

o IVF makes more fertilized eggs, embryos, than are implanted into a  mother. Options are:

▪ Destroy them

▪ Freeze and save them for later

▪ Donate them to other couples

o Should ART be regulated or restricted

▪ Who benefits from the procedure given its high costs?

• Doctors, hospitals

▪ Is it “right” to have a genetically related child?

o Most ART clinics are located on the East or West coasts

o What age groups are using ART?

• As you age, the likelihood of miscarriage will increase due to loss of feminine  hormones


• Each chromosome contains up to a few thousand genes

o Human somatic cells have 46… one from mom one  

from dad

▪ These are called homologous pairs

• One half of the chromosomes “X” shape is a chromatid 

What Can Cause Changes In The Number Of Chromosomes 

• Meiosis is cell division similar to mitosis  

• CROSSING OVER: How a mother and father’s genes conjoin to differentiate  your DNA 

• Why does Oogenesis only create one egg and 3 polar bodies? 

o It makes 3 little cells and one really big cell that holds all the energy and  proteins in order to maximize the difficult beginning of life 

Genetic Variation 

• Independent assortment during meiosis I in humans with 23 chromosomes leads  to 2^23 different combinations (8.3 million)

• Fusion of the male gamete with the female gamete to produce a zygote introduces  more variation (2^23*2^23) giving -70,000,000,000,000 different combinations • This calculation does not factor in homologous recombination!

• No one has EVER existed that is exactly like you 

• What happens when this process goes WRONG?

o Disjunction: the normal separation of chromosomes and chromatids  during meiosis I and meiosis II

o Non-Disjunction: when chromosome does not separate during meiosis I  

or II, this ends like: 

o What does non-disjunction cause?

▪ Missing chromosomes: Monomy 

• Embryo/Fetus will not survive

• Means 45 chromosomes

• Exception is this occurs on the 23rd chromosomes pair

▪ Extra chromosomes: Trisomy 

• Means 47 chromosomes:

• Down syndrome, Patau syndrome, Turner’s Syndrome,  

XYY Syndrome, and more

▪ If you are missing chromosomes, you don’t have enough protein  

for life to be viable

▪ If you have too many, there are other problems, but you will still  


Can We Identify Chromosomal Abnormalities In A Fetus? 

▪ Chorionic villus sapling (NEWER) 

o Removes cells from chorion that surrounds the embryo

o Performed at 10-12 weeks

o Risks miscarriage

o More popular as its earlier in pregnancy and so if abortion is an option it can  be decided more easily earlier

▪ Amniocentesis (OLDER) 

o Sampling cells in amniotic fluid

o Risks miscarriage equally as CVS

o Usually only done: if mother is over 45, has a child with aneuploidy, one  

parent has an abnormal chromosome, unexplained infertility

Next Generation Tests 

o From Fetal cells in mother’s blood

o Fetal cells cross placenta and enter mother blood

o Present in small numbers in blood

o Amniotic fluid contains free DNA from fetus

▪ DNA in the amniotic fluid broken down in fetal cells

▪ Obtaining a Karyotype is the best way to test for aneuploidy

o If patterns are off it may indicate a genetic disease

What Are The Effects Of Monosomy And Trisomy 

o Usually result in fatality and a miscarriage 

o 44% of miscarriages are due to aneuploidy or polyploidy

Down Syndrome 

o 47 chromosomes

o #21 Trisomy Nondisjunction

o 1 in 800 births

Patau’s Syndrome 

o 1 in 15,000 births

o 47 chromosomes

o #13 Trisomy nondisjunction

Other Genetic Abnormalities 

o Robertsonian Translocation: chromosome 14 swaps the short arm with the long  arm of chromosome 21 causing down syndrome 

o Does not immediately show as a phenotype, but can show up in the next  generation

o Uniparental Disomy (UPD)

o Zygote receives two copies of the same  

chromosome from one parent and none from the  


• Age Increases Risk Of Non-Disjunction Events

Is There A Way To Evaluate Genetic Risk? 

o Genetic counselors

o A health profession who explains genetic testing and the results o This profession is in higher demand now and is expected to grow 29%  annually  

o Who Needs A Genetic Counselor? 

▪ Family history of genetic disease

▪ Mexican citizenship and Native American tribe entry

▪ Children diagnosed with genetic abnormalities

Case A 

o Martha’s son has Jacob’s syndrome (XYY)

o Above average height and thin

o Personality issues are possible

o Normal lifespan

o 1 in 1000 male births

o Most live normal lives

o Some have learning disabilities

o Severe acne during adolescence  

o What can she do?

o Keep the child

o Get educated on Jacob’s syndrome

o Abortion

o Adoption

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