GN 301 Exam 1 Study Guide

Define Genetics

the study of heredity, or the transmission of traits/genes from generation to generation

What is the goal of Public Health programs?

The goal of public health programs is protecting and improving the health of people and their communities. This work is achieved by promoting healthy lifestyles, researching disease and injury prevention, and detecting, preventing and responding to infectious diseases.

List the 10 essential aspects of public health services

1. Monitor and evaluate health status to identify community health problems.
2. Diagnose and investigate health problems and health hazards in the community.
3. Inform, educate, and empower people about health issues.
4. Mobilize community partnerships to identify and solve health problems.
5. Develop policies and plans that support individual and community health efforts.
6. Enforce laws and regulations that protect health and ensure safety.
7. Link people to needed personal health services and assure the provision of health care when otherwise unavailable.
8. Assure a competent public and personal health care workforce.
9. Evaluate the effectiveness, accessibility, and quality of personal and population-based health services.
10. Research for new insights and innovative solutions to health problems

Describe several areas in which the fields of Genetics and Public Health intersect

The role of genetics in public health could be by the presence of a genetic susceptibility for the development of this disease or for response to treatment, or by the presence of protective genetic factors. You can also use technology to prevent genetic diseases and improve public health. You can also protect genetic information and DNA databases from being exploited by the public, enforcing privacy laws and benefiting the public.

Allele

one or more forms of a gene

Phenotype

the physical manifestation of genes

Genotype

the genetic makeup of an individual, could be physically seen or unseen

Homozygous

when an individual has two alleles for the same gene

Heterozygous

when an individual has two different alleles for the same gene

Dominant

The allele that is seen in the individual’s phenotype even if an individual has two different alleles for that gene

Recessive

The allele that is not seen in the individual’s phenotype unless an individual has two of the same alleles for that gene

Carrier

a heterozygous individual who carriers a recessive allele for a specific trait that is not expressed in them, but is still a part of their genetic makeup

What are the genetic basis and medical symptoms of the following: Osteogenesis imperfecta, Marfan Syndrome, Sickle Cell Anemia, Cystic Fibrosis, Xeroderma Pigmentosum

**Osteogenesis:** A dominant mutation with variable effects that may include multiple bone fractures and decreased mobility.

**Marfan Syndrome:** A dominant mutation that only requires one allele of the mutation to have it. People affected have long limbs. The disease weakens your aorta, which makes you bleed easily in the chest area.

**Sickle Cell Anemia:** A recessive mutation where an individual’s blood cells are sickled instead of smooth and round. The blood cells get stuck in the capillaries. 2 mutated alleles are required for this genetic disorder, which is most common in people of African descent.

**Cystic Fibrosis:** A recessive mutation that causes thick mucus to accumulate in the lungs, leading to respiratory infections and breathing difficulties. It occurs in a gene on Chromosome #7 and is common in those of European descent.

**Xeroderma Pigmentosum (XP):** A recessive mutation that causes excessive sensitivity to UV light. Persons affected must have two alleles of the gene to have the disease. They can get many small tumors on their body that look like freckles but is actually skin cancer.

Define Karyotype and describe the type of information that can be gained by looking at a karyotype

an organized array of a cell’s chromosomes. By looking at a karyotype, you can see which chromosomes are homozygous, if there are too many or too little chromosomes for a certain cell, or if the individual is male or female based on their X/Y chromosomes

Define autosomes

a chromosome that is not a sex chromosome (chromosomes 1-22)

Know that DNA is the genetic material. What does DNA stand for?

deoxyribonucleic acid

Where is DNA found in a human cell? How does this differ in plants?

In the nucleus and mitochondria. The DNA in plant cells is found in the nucleus, the mitochondria and the chloroplasts.

Define “Somatic Cell”

all cells that are not gamete/reproductive cells

How many chromosomes are found in a normal human cell? A human gamete?

In a normal human cell, 46 chromosomes are found. In a gamete, only 23 are found

Distinguish between monozygotic and dizygotic twins. Which are identical?

Monozygotic twins are **identical**. 1 sperm and 1 egg join together, and the embryo **divides into 2 fetuses.**

Meanwhile, dizygotic twins are **fraternal**. 2 eggs are fertilized at the same time (each with a different sperm) and **make one fetus each**. Unlike monozygotic twins, dizygotic twins **run in families**.

What proportion of their genes do dizygotic twins share?

50%

Define Mutation

An incorrect copy of DNA, or a change in the DNA sequence.

Define Evolution

The process by which organisms are assumed to have developed and diversified over time from their earlier, more simple forms.

Describe the symptoms and genetic basis of Huntington’s Disease.

Huntington’s Disease Symptoms: difficulting concentrating, memory lapses, irrational or irritable behavior, depression, mood swings, problems with coordination, weight loss

Inheritance: Huntington’s Disease is an autosomal dominant disorder, where you only need one copy of the gene to have the disorder. If your parent had the disorder, you have a 50% chance of getting it. You can also pass the gene down to your own children.

Two carriers of the sickle cell allele are expecting a child. What is the probability that this child will have sickle cell anemia?

If two carriers of the sickle cell allele (recessive) expect a child, their child has a 25% chance of getting sickle cell anemia.

A carrier of xeroderma pigmentosum marries an individual who has xeroderma pigmentosum. What is the probability that their first child will have this disorder?

Since xeroderma is a recessive mutation, a person affected must have two alleles for the same xeroderma gene. So their genotypes are Xx and xx. So there would be a 50% chance that their first child would have this disorder (Xx, Xx, xx, xx)

List several areas where Genetics is important in society

* The news
* Medicine
* Epigenetics
* Agriculture
* Pest management
* DNA sequence analysis bioinformatics
* Gene editing and gene therapy

Which gamete, the mother’s egg or the father’s sperm, determines the sex of the baby?

The **father’s sperm** determines the sex of the baby because only sperm can carry a Y chromosome. The egg always carries an X chromosome, but the **sperm can either carry an X or Y chromosome.** An XY combination creates a male and an XX combination creates a female.

Describe the role of mutation in evolution.

Mutation serves as a form of adaptation in evolution. When a species would benefit from a mutation, organisms with that mutation are favored in the reproduction cycle so that the mutation gets copied to other members of the species. Therefore, mutations are essential for helping a species grow and adapt to new environments over time.

Genetic Counseling

Genetic counseling is made for families who have the genes for genetic disorders and need help deciding a course of action. Genetic counselors **understand the medical facts and diagnosis** and are therefore equipped to **suggest the best course of action**. They understand how heredity contributes to the disorder and know alternatives for dealing with the risk of recurrence. Along with being knowledgeable about the disorder, genetic counselors also provide **support for families with the disorder** and connect them to support groups in the community. Genetic counseling aims to have a **nondirective** approach in providing patients with information so that the **patients themselves can make the final decision on what to do.**

In which stage of the cell cycle does DNA replicate? Pick the best answer.

S phase

The joining of the sperm and the egg is called

Fertilization

The two ways that meiosis generates variation from generation to generation are

Crossing Over and Shuffling Maternally and Paternally Derived Chromosomes

How many gametes are eventually produced from one secondary oocyte?

1

Identify the function of each of the following cell parts: plasma membrane, mitochondria, lysosome, Golgi body, endoplasmic reticulum, ribosome, nucleus, cytoplasm

**Plasma membrane:** provides protection for a cell and also transports toxic substances out of the cell.

**Mitochondria:** generates ATP for the cell to use as power

**Lysosome:** rid cells of waste products and uses its digestive enzymes to break down macromolecules

**Golgi body:** a factory in which proteins received from the ER are further sorted for transport to their eventual destinations

**Endoplasmic Reticulum:** Smooth and Rough ER. Smooth synthesizes and concentrates substances needed by the cell, while the rough has ribosomes that are involved with production, folding, and dispatch of proteins

**Nucleus:** house’s cell’s genome and acts as the cell’s control center

**Cytoplasm:** gel-like fluid in the cell where growth and replication are carried out

Relate the following disorders to alterations in function of specific cell components: Tay Sach’s Disease, Leber’s Disease, Long Q-T Syndrome, Cystic Fibrosis

Tay-Sach’s Disease results from misfunctioning lysosomes. An individual is missing a lysosomal enzyme, which leads to the build-up of a gritty substance that destroys nerve tissue.

Leber’s Disease results from genetic mutations in mitochondrial DNA, primarily in a mental aspect.

Long Q-T Syndrome results from a faulty gene inherited from a parent, caused by mutations of ion channel genes.

Cystic Fibrosis results from comes from malfunctioning chloride channels. The disorder is caused by a mutation on Chromosome #7.

What does the phrase “He is a carrier” of a genetic disorder imply about the individual’s genotype and phenotype and the inheritance pattern of the disorder?

He does not have the disorder, but he has a recessive allele for the gene that could possibly be inherited by his children if he marries someone with a recessive allele for that disorder as well. The disorder is present in his genotype, but not his phenotype. It will only be expressed if two recessive alleles for the trait join.

Identify and distinguish between: centromere, chromosome, chromatid, metacentric, acrocentric, sub- metacentric, telocentric

**Centromere** is the center part of a chromosome where microtubles of the spindle attach.

**Chromosome:** a threadlike structure of nucleic acids and protein found in the nucleus, carrying genetic information in the form of genes.

**Chromatid:** each of the two threadlike strands into which a chromosome divides during cell division.

**Metacentric:** the centromere is located in the middle of the chromosome

**Acrocentric:** The centromere is very off-centered

**Sub-Meta centric:** the centromere is slightly off-centered

**Telocentric:** the centromere is at the top of the chromosome

Note that a chromosome is composed of

approximately 15% DNA, 10% RNA and 75% protein

List the stages in the cell cycle and give a brief description of what occurs in each

G1, S phase, G2, and M phase.

* G1: Gap 1. Cells accomplish much of their growth, growing larger and making proteins and organelles needed for DNA synthesis.


* S: S-phase. The cell synthesizes a copy of the DNA in its nucleus.


* G2: Gap 2. The cell grows more as it makes more proteins and organelles, reorganizing its contents in  preparation for mitosis.


* M: M-phase. Nuclear division (mitosis) followed by cytoplasmic division (cytokinesis) 

Who determined that the correct number of chromosomes was 46?

J-H Tjio and A Levan

What do homologous chromosomes have in common?

The chromosomes in a homologous pair each have the same genes in the same order, but there may be variation between them, resulting in different alleles

What are the “rules” for constructing a karyotype (How are chromosomes arranged?)

22 pairs homologous autosomes are matched together and 2 sex chromosomes are also matched together

What does FISH stand for and what does this technique allow us to do?

Fluorescent in situ Hybridization. It’s purpose is to use fluorescent DNA probes to target specific chromosomal locations within the nucleus, resulting in colored signals that can be detected using a fluorescent microscope

What is the purpose of mitosis?

to replicate identical cells for different functions in the body

What is the purpose of meiosis?

to produce gametes, the sperm and eggs, with half of the genetic complement of the parent cells.

What stages of the cell cycle are considered to be interphase?

Interphase is composed of G1 phase, followed by S phase, followed by G2 phase

List the stages of mitosis in order and give a short description about what happens to the chromosomes in each stage.

Prophase: The chromosomes shorten and thicken.

Metaphase: Chromosomes line up in the middle of the cell.

Anaphase:  Chromatids break apart at the centromere and move to opposite poles.

Telophase: Chromosomes arrive at the cell poles and the mitotic spindle disassembles.

Know the stages of meiosis and a brief statement about what occurs in each stage.

When does crossing over occur? When do the centromeres divide? When does independent assortment occur? What is synapsis and when does it occur?

**Prophase:** The chromosomes begin to condense and pair up, aligning with their partner to match up at corresponding positions along the entire length. (Synapsis, the pairing of two chromosomes, occurs here)

**Crossing over:** chromosomes shuffle their alleles between each other

**Metaphase:** homolog pairs line up at the metaphase plate for separation (Independent assortment happens here)

**Anaphase:** Homologues break apart and move to opposite ends of the cell, while the sister chromatids remain attached (the centromeres divide here)

**Telophase:** The chromosomes end up on opposite poles of the cell, starting cytokinesis and producing 2 haploid daughter cells

\
Then Meiosis II occurs, where the 2 haploid daughter cells divide again to create 4 daughter cells.

Meiosis causes an increase in variability from generation to generation in two ways. Describe these 2 ways.

1\. crossing over: shuffling chromosomes between parents

2\.  independent assortment: genes independently separate themselves from one another when reproductive cells develop

Compare mitosis and meiosis.

* Meiosis is vital for fertilization. Mitosis is vital for cell replication for different tasks in the body.
* Meiosis maintains a constant number of chromosomes. Mitosis does not pair chromosomes and so it ends up producing twice the original amount of cells.
* Meiosis provides variation from generation to generation. Mitosis replicates the exact same cell without any variation.
* Meiosis shuffles chromosomes between parents (there are 2^23 possible combinations of chromosomes). Mitosis creates the same mitotic problems each time.

What is nondisjunction? When can it occur? How can it affect the gamete and individual that gets the gamete?

Nondisjunction is errors in the separation of chromosomes in meiosis. It occurs in Anaphase I or II when chromosomes move to opposite poles. Gametes are produced with abnormal chromosome numbers. If these gametes are fertilized, individuals can be born with an abnormal number of chromosomes which leads to genetic disorders.

Be familiar with the terminology used in gametogenesis: oogonium, primary oocyte, secondary oocyte, ootid, ovum and spermatogonium, primary spermatocyte, secondary secondary spermatocyte, spermatid, and sperm

\-- Be able to relate these terms to meiosis and know the number of chromosomes each is expected to have and whether each is considered to have a haploid or diploid number of chromosomes

\-- Other than the terminology and the fact that one occurs in males and the other in females, describe several differences between oogenesis and spermatogenesis.

oogonium: an immature female reproductive cell that gives rise to primary oocytes (diploid)

primary oocyte: The oocyte that arises from the oogonium via the process of oocytogenesis, and gives rise to secondary oocyte and polar body (diploid)

secondary oocyte: an oocyte that is produced by division of a primary oocyte in the first meiotic division (haploid)

ootid: a haploid cell formed by the meiotic division of a secondary oocyte (haploid)

ovum: a mature female reproductive cell which can divide to give rise to an embryo after fertilization (haploid)

spermatogonium: a cell produced at an early stage in the formation of spermatozoa, formed in the wall of a seminiferous tubule (diploid)

primary spermatocyte: a diploid cell that has been derived from a spermatogonium and can divide into two haploid secondary spermatocytes. (diploid)

secondary secondary spermatocyte: haploid cells, smaller than primary spermatocytes (haploid)

spermatid: an immature male sex cell formed from a spermatocyte that can develop into a spermatozoon without further division (haploid)

sperm: The male reproductive cell, formed in the testicle (haploid)

DIFFERENCES BETWEEN OOGENESIS AND SPERMATOGENSIS

**Spermatogenesis occurs in males and in the** seminiferous tubes. It takes 9-11 weeks to produce mature sperm. 1 billion sperm are produced a week.

In oogenesis, females are born with about 1 million egg cells that are in the prophase I stage of meiosis. Only one mature ovum is produced in oogenesis, and four mature sperm are produced in spermatogenesis.

Spermatogenesis leads to the formation of sperms, whereas oogenesis helps in the formation of ova. The fertilization of sperm and ova leads to the formation of a zygote which further develops into an embryo.

Approximately how may sperm can a healthy college-aged male make perweek?

1 billion

How long does the process of spermatogenesis take?

9-11 weeks

True or False: Oogenesis is a noncontinuous process.

true

What is a polar body?

the small cell that is a byproduct of an oocyte meiotic division, which usually just disappears

Oogenesis stalls prior to birth in females. At which stage of meiosis does oogenesis stall?

Prophase I

About how many primary oocytes does a female have at birth? About how many will she ovulate during her life?

1-2 million. Only around 400 eggs are ovulated in her lifetime.

Where does meiosis occur in each sex (what tissues)?

Meiosis takes place in the testes for males and ovaries for females

Which sex is more likely to produce gametes with the incorrect chromosome number?

Female

Which sex is more likely to produce gametes with a new mutation?

Male

Describe the relative sizes of the egg and sperm.

An egg is the largest cell in the human body at 100 microns. A sperm is about 60 microns long.

Which (egg or sperm) contains more genetic information? Why?

They are the same. An egg contains 23 chromosomes, and a sperm also contains 23 chromosomes.

Where are sperm made? Where are eggs made?

Sperm cells are produced in men's testicles and egg cells are produced in women's ovaries

About how many sperm are typically deposited into the vagina during sexual intercourse?

2-5 million

Approximately how many sperm reach the egg?

50

What are some of the barriers that a sperm faces when it tries to reach the egg?

The acidic pH of the vagina, cervical mucus, the fallopian tube, and protective layers of the egg.

Where does fertilization occur? Distinguish between fertilization and syngamy.

Fertilization is when male sperm penetrates a female egg, which join together. It occurs in the Fallopian tubes.

Syngamy is where the nuclei of the egg and the sperm fuse to form a zygote (4-5 hr after fertilization). It also occurs in the Fallopian tubes.

Relate the timing of ovulation, the second meiotic division, fertilization and syngamy: What is the correct order?

After ovulation, the oocyte is arrested in metaphase of meiosis II until fertilization. At fertilization, the secondary oocyte completes meiosis II to form a mature oocyte and a second polar body. Syngamy occurs next, where a zygote is formed.

About how long after fertilization does implantation occur? Where does implantation occur?

Once the embryo reaches the blastocyst stage, approximately five to six days after fertilization, it hatches out of its zona pellucida and begins the process of implantation in the uterus.

About how long after fertilization does the placenta start to develop?

The placenta begins to form after a fertilized egg implants in the uterus around seven to 10 days after conception

Whose cells (mother’s or baby’s) are use to make the following structures: placenta, umbilical cord, chorion, amnion?

Placenta is created by both the mother and the baby. The umbilical cord is created by both the mother and the baby. The chorion is created by the baby, and the amnion is created by the baby.

Whose gamete determines the sex of the baby - Mom’s or Dad’s?

the Dad because only he can provide a Y chromosome

The developing child is called an embryo up to 8 weeks after fertilization. From8 weeks to birth, the developing child is called

a fetus.

What can an ultrasound show about a developing fetus?

In ultrasounds, sound waves are used to form pictures inside the body. You can observe the development of a fetus, check for spine defects, head size, and confirm due dates. You can find out when your baby is due or if they have any spinal deformities. There are no known risks to this procedure.

What does CVS stand for?

Chorionic Villus Sampling

Describe the process of CVS.

In CVS (Chorionic Villus Sampling), chorion is taken from a fetus’s genotype by inserting a needle into the womb. Cells are checked from the placenta to detect chromosomal abnormalities.

Describe the process of amniocentesis.

In amniocentesis, a needle is put through the stomach which sucks amniotic fluid from the fetus. The amniotic fluid extracted can tell if the fetus has any chromosome abnormalities or genetic disorders.

Compare the pros and cons of CVS and amniocentesis. What factors would you need to consider if you had to choose one of these procedures over another? (Think about when each is done during the pregnancy and the amount of risk to the fetus)

In amniocentesis, a needle is put through the stomach which can lead to a risk of miscarriage, bleeding and infection because of the needle insertion.

In CVS, chorion is taken from a fetus’s genotype by inserting a needle into the womb, which could lead to a risk of miscarriage, bleeding, and infection.

Both of these procedures can offer insight into your baby’s genotype, but have a lot of risks attached. Amniocentesis seems to have a greater risk because you could accidently puncture the baby’s womb and lead to a miscarriage.

What is Cell Free DNA Testing? What can it show?

In cell-free DNA testing, blood is taken from the mother’s arm. You are able to see microdeletion or microduplication in bin count. You can find out whether your baby will have genetic disorders like Down Syndrome or trisomy 18. There are no known risks to this procedure.

What are some genetic disorders that are tested for in newborns?

* Sickle cell disease
* Phenylketonuria (PKU)
* Hypothyroidism
* Galactosemia

What is the role of public health officials when a newborn is shown to have a genetic disorder?

Public health officials notify the infant’s parent(s) and the newborn’s physician about abnormal findings and assist in securing appropriate follow-up testing and treatment when indicated. They refer critical infants to specialists that offer evaluation, treatment, and counseling services.

What does IVF stand for?

in vitro fertilization

Why might someone choose to use IVF?

If someone was having trouble getting pregnant, she might want to try in vitro fertilization, where an embryo is directly implanted in the womb.

What are some ethical concerns regarding in vitro fertilization and preimplantation genetic diagnosis?

Some people have objections to the use of these procedures, for a variety of reasons. Some have concerns that the procedure will eventually be used for eugenics, or the selection of certain characteristics over others. Others do not approve of the use of PGD to select embryos of a certain sex as a form of family balancing.

What guidelines are used regarding in vitro fertilization?

* Previous success with IVF
* Morphologically good quality eggs
* Excess embryos preserved
* First cycle embryos

What is a “favorable” situation regarding IVF?

You are potentially a good candidate for IVF if you have: Experienced difficulty becoming pregnant through sexual intercourse, especially combined with fertility medications, or blocked or missing fallopian tubes or other tubal problems.

Vocabulary: Define and significance in early development

* **Fallopian Tube (oviduct)**

The tubes provide a passageway for a fertilized egg to make its way to the uterus.

* **Uterus**

The uterus is where a fertilized egg is implanted during pregnancy, where a baby will develop until birth.

* **Cilia**

The cilia help push the immobile fertilized egg into the Fallopian tubes after fertilization.

Stages of a baby

1st: zygote--when a cell is fertilized by 2 gametes

2nd: embryo--an unborn offspring developing up to 8 weeks

3rd: fetus--a developing offspring after 8 weeks

Be able to identify the contribution of each of the following to the field of Genetics: Gregor Mendel, Friedrich Miescher, Boveri and Sutton, Avery, McCarty and MacLeod, Watson and Crick, Franklin and Wilkins, Chargaff

**Gregor Mendel:** Experimented with pea plant breeding which allowed him to develop three principles of inheritance that described the transmission of genetic traits

**Friedrich Miescher:** Identified DNA from white blood cells and called it nuclein, noting it was slightly acidic

**Boveri and Sutton:** Found chromosomes and proposed the chromosome theory of inheritance

**Avery, McCarty and MacLeod:** Showed that DNA can transform the properties of cells by studying how DNA transformed bacteria

**Watson and Crick:** Put together the first DNA replica structure from Wilkins and Franklin’s research

**Franklin and Wilkins:** Came up with x-ray experiment to take pictures of DNA structures, discovering that it was helical 

**Chargaff:** Researched the percentages of bases present in different animals and compared the ratios

What was thought to be the genetic material prior to the determination that DNA is the genetic material? Why?

Protein was thought to make up the genetic material because it makes up about 50% of the cell. People thought that because proteins have a lot of variability and are used for many functions.

Terminology including: protein, amino acid, codon, anticodon, peptide bond, hydrogen bond, phosphodiester bond, central dogma, purine, pyrimidine, transcription, translation, antiparallel

**protein:** large molecules with chains of amino acids

**amino acid:** a simple organic compound containing both a carboxyl and an amino group

**codon:** a sequence of three nucleotides

**anticodon:** a sequence of three nucleotides forming a unit of genetic code in a tRNA molecule

**peptide bond:** a bond between amino acids

**hydrogen bond:** a weak bond between two hydrogen atoms

**phosphodiester bond:** the bonds that join nucleotides

**central dogma:** a theory stating that genetic information flows only in one direction, from DNA, to RNA, to protein, or RNA directly to protein.

**purine:** Adenine and guanine. They have a two-ringed structure consisting of a 9-membered molecule with 4 nitrogen atoms.

**pyrimidine:** Cytosine, thymine, uracil. They have a single-ringed structure with 5-members and 2 nitrogen atoms.

**transcription:** The process of making RNA from DNA

**translation:** The process of making protein from mRNA

**antiparallel:** parallel but going opposite directions

Describe the components of DNA.

adenine, guanine, thymine, cytosine, phosphate, deoxyribose

Describe the components of RNA

adenine, guanine, uracil, cytosine, phosphate, ribose

What are the differences between the structure and components of DNA and RNA?

* RNA contains the sugar ribose, while DNA has deoxyribose. 
* DNA is double-stranded, RNA is single-stranded
* Thymine in DNA, uracil in RNA

There are 5 carbons in deoxyribose. Which connects to the phosphate? To the base? To the next amino acid in the nucleotide chain?

The 5’ carbon attaches to the phosphate. The 3’ carbon attaches to the base. The 3’ carbon attaches to the next amino acid in the nucleotide chain

What are the 4 bases in DNA?

adenine, cytosine, guanine, and thymine

What are the 4 bases in RNA?

adenine, cytosine, guanine, and uracil