Study questions 4.1
Lecture 20: Patterns of Inheritance and Lecture 21: Chromosomal inheritance
What is genetics?
Genetics: inheritance & how traits are passed from generation to generation
Who was Gregor Mendel?
Came up with the initial idea of genetics 1860's - the Principle of Segregation which described basic patterns of inheritance.
What did Mendel discover?
He studied genes for different types of trait (color) Genes have different forms, each person has two alleles for each trait, sex cells only have one gene/allele for traits so the alleles separate,
What were the strategies/approaches/ background he used that helped him to make his discoveries?
For a given single trait or gene, how many alleles does each cell of one individual usually have?
2
How many alleles for this trait would one gamete (a sperm cell or an egg cell) have?
1
Be able to state Mendel’s principle of segregation in simple terms.
According to the principle of segregation, for any particular trait, the pair of alleles of each parent separate and only one allele passes from each parent on to an offspring. Which allele in a parent's pair of alleles is inherited is a matter of chance. We now know that this segregation of alleles occurs during the process of sex cell formation
What does homozygous mean?
Same alleles for a gene - either both dominant or both recessive.
Heterozygous?
Different alleles for a trait - one dominant, one recessive
Dominant?
A type of phenotype
Recessive?
How do we represent alleles in writing? How are dominant alleles represented & how are recessive alleles represented?
BB, Bb, bb
What do homozygous dominant & homozygous recessive mean?
Homozygous dominant means that two dominant alleles were inherited for a trait (BB)
Homozygous recessive means that two recessive alleles were inherited for a trait. (bb)
What does genotype mean?
The exact genetic make up of an individual organism. Refers to the full hereditary information of an organism
What about phenotype?
The phenotype of an organism represents its actual physical properties, such as height, weight, hair color, and so on. It is the organism's physical properties that directly determine its chances of survival and reproductive output, while the inheritance of physical properties occurs only as a secondary consequence of the inheritance of genes. Therefore, to properly understand the theory of evolution via natural selection, one must understand the genotype-phenotype distinction.
What is the relationship between genotype and phenotype?
An organism's genotype is a major (the largest by far for morphology) influencing factor in the development of its phenotype, but it is not the only one. Even two organisms with identical genotypes normally differ in their phenotypes. One experiences this in everyday life with monozygous (i.e. identical) twins. Identical twins share the same genotype, since their genomes are identical; but they never have the same phenotype, although their phenotypes may be very similar. This is apparent in the fact that their mothers and close friends can always tell them apart, even though others might not be able to see the subtle differences. Further, identical twins can be distinguished by their fingerprints, which are never completely identical.
What is a Punnett square? What is it used for?
The Punnett square is a diagram designed by Reginald Punnett and used by biologists to determine the probability of an offspring having a particular genotype. It is made by comparing all the possible combinations of alleles from the mother with those from the father.
What do the letters along the top and side of the square represent?
The allele comginations of a trait of both the mother and the father. Father on top, mother on the side.
What do the paired letters within the squares represent?
The possible combinations of the parents alleles
For a simple F1 heterozygote vs. heterozygote cross (for example, Aa X Aa), what are the genotypic ratios and phenotypic ratios you expect to see in the offspring? (For example: How many AA vs how many Aa vs how many aa? Is this a genotypic or a phenotypic ratio?)
3 to 1 dominance - 1 homo dom, 2 hetero dom, 1 recess homo - This is genotypical
Be able to use the Punnett square to do any kind of simple cross and interpret the results.
What is a testcross and what is it used for? (If I gave you the results of a testcross, could you interpret these results?)
a procedure used especially in plant breeding whereby a plant's genetic constitution is inferred by examining the progeny resulting from crossing it with another individual of known genetic makeup
How do we represent a partially unknown genotype in writing?
A
What is the most common lethal genetic disease in the U.S.? Is this a recessive or a dominant genetic disorder? What are the symptoms of this disease?
Cystic Fibrosis - recessive
affects mainly the lungs and digestive system, causing progressive disability, and, for some, early death. Formerly known as cystic fibrosis of the pancreas, this entity has increasingly been labeled simply cystic fibrosis.[1] Average life expectancy is around 36.8 years, although improvements in treatments mean a baby born today could expect to live longer.[2]
Difficulty breathing and insufficient enzyme production in the pancreas are the most common symptoms. Thick mucus production, as well as a less competent immune system, results in frequent lung infections, which are treated, though not always cured, by oral and intravenous antibiotics and other medications. A multitude of other symptoms, including sinus infections, poor growth, diarrhea, and potential infertility (mostly in males, due to the condition Congenital bilateral absence of the vas deferens) result from the effects of CF on other parts of the body. Often, symptoms of CF appear in infancy and childhood; these include meconium ileus, failure to thrive, and recurrent lung infections.
What does it mean to say that someone is a carrier of a genetic disease?
It means that they carry a recessive allele for the disease and the potential to pass it on but do not have the disease itself.
What is sickle cell anemia? Is this a recessive or a dominant genetic disorder? What specific kind of change in a body/ a cell/ a molecule causes sickle cell anemia? What is the advantage of being a carrier of one sickle cell allele?
A genetically inherited disease that affects the protein polymers of the hemoglobin in red blood cell's cuasing them to take on elongated or jaggedly shaped cells rather than smoothly rounded cells. This results in abnormal clotting, vaso-occlusion (circulatory blockage) causing lack of oxygen, ischemia, and early mortality rates. It is a recessive disease but a heterozygous combination of the sickle cell alleles results in no manifestation of the disease but the potential to pass it on. As an advantage, heterozygous and homozygous alike are both immune to malaria.
Why are single-gene lethal disorders usually caused by recessive alleles rather than by dominant alleles?
Because of evolution/natural selection. Most species with this disease would die before they could reproduce so it is less common and have evolved into a recessive trait
What would be an example of an exception, and why is it possible for this lethal dominant allele to be passed from one generation to the next?
Huntington's disease - because they usually are in their mid - 3os before they get sick and have had children by that point.
As far as recessive disorders are concerned why are inbreeding or matings by close relatives generally not a good idea?
Because variation in traits would be limited and the likelihood of recessive combinations greater.
What is incomplete dominance?
Relationships described as incomplete or partial dominance are usually more accurately described as giving an intermediate or blended phenotype.
What genotype (homozygous dominant, heterozygous, homozygous recessive) would show the evidence of incomplete dominance?
heterozygous
What is an example in humans (from lecture or from lab) of incomplete dominance?
What are the four common blood types (= blood phenotypes) in humans?
AO
BO
ABO
O
How many different alleles are there for the blood type gene?
3 - ABO
How many alleles can one person have?
2
What are the possible genotype combinations (how many, what are they)?
AA, Ao, AB, BB, Bo, oo
What are the possible phenotype combinations (how many, what are they)?
A, B, AB, O
Which blood type is an example of co-dominance? (Note that co-dominance is a kind of incomplete dominance.)
AB
What is the cellular cause of the differences in blood types? (What occurs in/on cells that creates blood types? What makes A, B, AB and O blood types in/on cells?)
A chemical marker on the surface of the red blood cells called an antigen. They are different for A and B and absent in O. An AB type can receive either A, B or O type blood without ill effects, making them a universal recipient.
What happens if you give A type blood to a B type person? Why?
Antibodies reject the blood cells and cause abnormal clotting and death.
Which blood type is called the universal donor? Why?
O - because it has no antigens on its surface and can be accepted by any blood type.
Which blood type is called the universal recipient? Why?
AB - because it can take either A, B or O because it contains both A and B blood cells due to co-dominance, and O is a universal donor.
How can blood type information be useful in paternity testing?
It can only rule out the father in certain instances. For example - if a child is AB and the father a type O, it is impossible for him to have fathered the child. DNA testing is the only truly reliable source of paternity.
Be able to do a blood type Punnett square!
What is independent assortment?
Mendel's Second Law - the law of independent assortment; during gamete formation the segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair
How do chromosomes determine sex?
The chromosome X is carried only by females - XX. Men carry both XY. Therefore, whichever sperm inseminates the egg will determine the sex of the child.
What is a sex-linked trait or gene? (What chromosome are these genes usually found on?)
Traits (alleles) carried on the X or Y sex chromosome. They are usually found on the X but in rare instances, the Y
Can you give an example of a sex-linked trait?
Color blindness, hemophelia
What is the SRY gene, where is it found, and what does it determine?
It is a sex determining gene found on the Y chromosome
What is the pattern of inheritance seen for sex-linked genes? Why does it differ for males and females?
It is more common for males to inherit sex linked traits since they only need one x-linked trait to manifest the disease and women need 2 and sex linked genes are rare.
Be able to do a sex-linkage Punnett square.
How do we write the alleles for sex-linked traits? Can females have sex-linked traits? Why or why not?
BBx, AAy...rarely see above.
What is gene linkage? What is crossing over?
Genetic linkage occurs when particular genetic loci or alleles for genes are inherited jointly. Genetic loci on the same chromosome are physically connected and tend to segregate together during meiosis, and are thus genetically linked.
Chromosomal crossover (or crossing over) is the process by which two chromosomes, paired up during prophase 1 of meiosis, exchange some portion of their DNA. Crossing over is specifically initiated in pachytene, before the synaptonemal complex develops, and is not completed until near the end of prophase 1. Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome. The result of this process is an exchange of genes, called genetic recombination.
What is nondisjunction? What type of birth defects can this lead to?
failure of chromosomal separation: a failure of paired chromosomes or sister chromatids to separate during cell division
Nondisjunction is the failure of homologous chromosome pairs to separate properly during meiosis or mitosis. The result of this error is a cell with an imbalance of chromosomes. When a chromosome is lost, it is called a monosomy, in which the daughter cell with the defect will have one or more chromosomes missing from one of its pairs. When a chromosome is gained, it is called a trisomy, in the case of a human gamete after nondisjunction in Meiosis II, it will have a set of 24 chromosomes instead of the usual 23.
Edward's Syndrome (trisomy 18),Down's Syndrome(trisomy 21), Turner's Syndrome(x), Klinefelter's syndrome (xxy),
What makes accidents during meiosis more likely?
The age of the mother.
How, in a general way, do changes in sex chromosome number affect humans, in comparison to changes in the number of other types of chromosomes?
Sex chromosome numbers do not result in retardation. Some physical symptoms are noted with Turner's syndrome but in most cases the difference is not notable.
Lecture 22: biotechnology (Chapter 16)
Why is it critical for biotechnology that DNA from all organisms is essentially the same kind of molecule?
Because it creates the possibility of creating recombinant DNA
What are some of the uses of biotechnology?
You can make virus or insect resistant organisms, delay ripening, BGH for milk production, transplant possibilities (pigs organs in humans), genetically leaner meats...(enzymes - detergents, foods, textiles...
What kinds of organisms do many of the enzymes used in biotech come from
From viruses
What is a virus? Are they alive? What are they made of?
submicroscopic parasitic particle of a nucleic acid surrounded by protein that can only replicate within a host cell. Viruses are not considered to be independent living organisms but some arguments exist that they are on the "edge of life".
How does a virus get itself replicated?
They use the machinery of the host cell to reproduce copies of themselves. They cannot replicate on their own because they are acellular.
What are some of the ways that virus DNA or RNA can get into a host cell?
Endocytosis (absorbed by mucous membranes or blood) from the external enviroment.
What happens to the host cell after many copies of the virus have been made?
How are simple RNA viruses like influenza different from complex RNA viruses (retroviruses)? What does a retrovirus do that is unusual?
What are restriction enzymes? What do they do & where do they come from? (Review: what kind of biological molecule are enzymes? What does the root –ase mean?)
In the separation of the two sides of a DNA double helix for the purpose of trying to find certain DNA, why are the molecules heated?
What happens as a result of this heating? (Review: What would happen to enzymes if you heated them?)
They would denature
What is gel electrophoresis and what does it do? Why do the small molecules move further in the gel than the large molecule?
What is a DNA fingerprint?
What is the purpose of PCR? What is the original source of the DNA polymerase that is used in PCR?
Lecture 23: Immune system
What is phagocytosis? What do cells do with bacteria that they take in?
Phagocytosis is cell eating
What is a pathogen?
An infectious or biological agent that causes disease or illness to its host.
What parts of the human body function as the first level of non-specific defenses against disease-causing agents, and how do these different defenses work? (What does each type do?)
Skin (barrier), mucous (capture, expel), cilia, (capture, expel), tears, saliva (flushing), urine, diarrhea (expel, flushing)
What is the general role of white blood cells in the body?
To protect the body from disease and infection
What does the word macrophages mean? What do natural killer cells do?
It means "big eaters"...they eat the damaged cells.
Natural killer cells detect irregular cells and puncture them and cause them to lyse.
Where are complement proteins found, and what do they do? Where do interferons come from, and what do they do?
Complement proteins are found in plasma and they enhance the immune system's response. When they encounter and antibody/antigen combination they change in form and signal other proteins to do the same - the enter the cell and kill it.
Interferons are complement proteins that inhibit the replications of affected cells.
What are some of the symptoms of the inflammatory response?
Redness, swelling, heat
Which symptoms are results of white blood cell activity?
What does histamine do?
Which symptom is a result of prostaglandin activity?
Why is fever a useful response?
Because heat can kill a virus or bacteria.
What are the advantages of having an immune system?
What does it mean to say that immunity is adaptive?
What type of molecules/ structures on B and T cells are used in the process of learning to recognize pathogens?
Where in or on the cell are these receptors found?
What is an antigen?
What is an antibody? (What is the type of antibody that is not called an antibody?)
What do antibodies do?
How many different antibody sequences can one person have? Why is it valuable to have many different types?
What happens after a B cell receptor binds to an antigen? What are clones? What actually kills the invading cells?
What is a memory cell? Are memory cells long-lived or short-lived?
What happens after a T cell receptor binds to an antigen? What do cytotoxic T cells do?
What types of cells do T cells attack? What do helper T cells do?
How do vaccinations (active immunization type) create resistance / immunity to disease?
What is the role of self-proteins on human cells?
Why is understanding self-proteins (such as MHC proteins) important for understanding some of the potential problems with organ donation?
What are some of the dysfunctions of the immune system?
Biology 10 Fall 2007
Study questions 4.2
Lecture 24: Human past and human future
What is gestation? How do gestation times in humans compare to those of other animals of similar size?
Why can the relative immaturity of humans at birth be seen as a compromise between the selection for increasing intelligence & the limitations on birth canal size? What is the relationship between human pairbonding & the relative immaturity of humans at birth?
What mammalian order do humans belong to? What event probably led to the adaptive radiation of the mammals?
How similar are we, genetically, to our closest non-human relatives, the chimpanzees?
What is a hominid? (You won’t need to know the term for the test, but you need to know that this group exists.)
What are some of the characteristics that separate hominids from the groups that are closely related to them?
Which apparently evolved first, upright posture or brain enlargement, in hominids?
What kind of evidence do we base this conclusion on?
Where does the fossil evidence suggested that Homo sapiens mostly evolved?
What kind of evidence has been used in establishing a common ancestry, from about 100,000 years ago, for all humans in our biosphere today?
What factors do scientists think have interacted to select for darkly pigmented skin in tropical regions? What factors have selected for lighter skin in northern/ less tropical parts of the world?
What is cultural evolution? How is it different from biological evolution?
What are some of the biological and ecological issues facing us in this new millenium?
What is biodiversity? How do human activities influence biodiversity and habitat availability?
How do introduced / non-native species affect the species normally found in a region?
Why (what are some of the reasons) does biodiversity matter?
Why is increasing human population potentially a concern, in terms of our effects on the planet and the other species on the planet?
What are biodiversity hot spots? Why are they so important?
