Final - Exam 1+2+3 Flashcards
Eugenics laws passed by many states in the early 20th century were:
fundamentally unconstitutional and un-american in both premise and procedure AND based on untested scientific premises, which turned out to be scientifically wrong.
Which of the following significantly contributed to the difficulty of understanding whether a particular disease is genetic, and if so how is it inherited
small modern family size, long generation times combined with short memories, variable expressivity and incomplete penetrance, and failures of communication within families
Meiosis and mitosis are
both processes start with chromosomes that each consist of 2 chromatids
when discussing multiple alleles (2+) of a single gene, which of the following is true
A population may have more than 2 alleles
Cross occurs between AaBbCcddEe and aabbCCDdEe. What proportion of the offspring would be expected to be heterozygous at all 5 loci.
1/32
Mutations in DNA can alter phenotypes by changing the:
- amount of a particular protein produced2. sequence of amino acids in a protein
Which of the following are possible reasons why identical genotypes at a particular locus don’t always give identical phenotypes?
Could be because of epistatic interactions with other loci, sex-influenced or sex-limitation, or variations in the environment
Both parents are carries of cystic fibrosis allele. Assuming complete pentrance, if they have 3 children, what is the chance that at least one will eventually be affected with cystic fibrosis
37/64
PKU is caused by a recessive allele that produces an altered protein. Why is this allele recessive instead of dominant?
heterozygotes produce half the normal level of the functional enzyme, but that is enough for a normal metabolism
Gregor mendel utilize probability theory when analyzing his results
Because he recognized that a probabilistic process was at work
Human germ line cell immediately after meiosis contains
23 chromosomes, 46 chromatids
Cell cycle leading to mitosis is
continuously occurring in all of us
The profound retardation caused by PKU can be prevented by modifying the environment in what way?
limit the phenylaline in the diet
rare inheritance of 1/100,000 in a particular family, most probable mode of inheritance of this trait is? Pedigree B
mitochondrial
rare inheritance of 1/100,000 in a particular family, most likely explanation of the phenotype is? Pedigree B
Best explained as an example of incomplete penetrance
Many drugs that are safe for most of the population can cause lethal side effects in some individuals. Would we expect these side effects to show a familial pattern?
Yes, because families share genes
Hemochromatosis is an example of a very common, deleterious allele that demonstrates:
phenotypes depend on both genes and the environment
OMIM is part of the National Center for Biotechnology Information. What sort of information does OMIM contain
Information about individual genetic loci that have alleles that cause human disease
Pedigree C shows the inheritance of a common (1/400) trait in a particular family. What is the most probable mode of inheritance of this trait?
Too little info
Which of the following is true difference between DNA and RNA?
DNA used deoxyribose, RNA uses ribose
Mendel’s principle of Independent Assortment occurs because
chromosomes independently assort during meiosis and chromosomes routinely crossover during prophase 1.
Homologous chromsomes normally
have identical loci
The epidemiological evidence is that smoking starts 20 years or more before the age at which smokers start showing a significantly higher cancer rate. What is the most probable explanation?
- A normal cell requires multiple mutations in at least one daughter cell before that cell becomes fully malignant2. the first steps in the development of cancer are typically small and slow growing
Individuals with sickle-cell anemia, pain in many different parts of the body, strokes that cause cumulative brain damage, and sometimes, heart attacks. Thus the condition is an example of:
pleiotropy
Following can be directly explained by the biology of meiosis and fertilization
Mendel’s law of segregation and some alleles are dominant to others
The allele that is responsible for cystic fibrosis codes for an abnormal form of:
Protein that transports chloride ions across cell membranes
Which of the following is not directly involved in translation?
DNA
What where eugenics mistakes involving human genetics
Human phenotypes are almost totally genetically determined, bad genes that will be passed to children can readily by determined by looking at individuals, and some human races are obviously superior to others
the allele that is responsible for cystic fibrosis codes for an abnormal form of:
Protein that transports chloride ions across cell membranes
spermatogenesis and oogenesis both involve meiosis, but which of the following is a true difference between the 2 processes
oogenesis takes longer than spermatogenesis
Several human loci are known where normal alleles contain trinucleotide repeats. But some families transmit abnormal alleles that cause disease, and the disease often seems to get worse in succeeding generations. What do we believe is happening here?
Additional trinucleotides are added to the alle during gametogenesis, which worsens the phenotypic effect
The monohybrid crosses, Mendel deduced that one trait was recessive because that trait
Was not present in F1 by did reappear in F2
Phenotypically normal, 20 year old man learns that his paternal grandfather has been diagnosed as having Huntingdon disease. From this, what is the chance that his newborn son will eventually develop the disease?
1/8
Inheritance pattern of mitochondrial disorders is distinctive, and variable expressivity and incomplete penetrance commonly occur in these families. What biological facts cause this pattern
Mitochondria have their own chromosome which code for some mitochondrial functions, all (most) of our mitochondria come from our mothers, and there are multiple mitochondria in cells, and they are not uniformly divided during either mitosis or meiosis
Which of the following is true in eukaryotes like humans?
Much of the DNA sequence is not transcribed and even less is translate
Couple who have a child with cystic fibrosis ask a physician whether they will have another affected if they have a second baby. The doctor tells them that, since the chance of having an affected child is 1 in , and they’ve already had an affected child, the next 3 children will be normal. The advice is
Wrong, because each child is an independent event
Phenotypically normal couple have 2 normal sons, a normal daughter, and then a son with duchenne muscular dystrophy. What is the chance that the next child will also have muscular dystrophy?
Depends on child’s sex, 0 for a daughter, and 1/2 for a son
Pedigree d shows the inheritance of a rare 1/100,000 trait in a particular family. what is the most probable mode of inheritance of this trait?
X-linked dominant
What 3’ and 5’ important?
They refer to different directions along nucleic acid chains, and those differences are important for biological function
True-breeding line of black chickens is crossed with a true-breeding line of white chickens. The F1 are all gray. A gray hen is now crossed with a gray rooster. After 12 broods of chicks, their offspring include 27 white chickens, 48 gray chickens, 24 black chickens. This suggests that the inheritance of gray feather color in chickens is an example of:
incomplete dominance
Chin dimples are caused by an autosomal dominant allele. A couple has 20 children, 8 with dimples and 12 without. What are the probable phenotypes and genotypes of the parents
one has a dimple and is heterozygous, the other doesn’t and is homozygous
A female heterozygote for an X-linked mutant allele will pass it on to:
1/2 of her daughters and 1/2 of her sons
A proto-oncogene is a gene that:
- functions to promote cell division when the proper signals are received2. Can be mutated to form an oncogene
Each of a couple have a color-blind father, but both have normal color vision. What is the chance that they will have a color-blind daughter
0
Couple have achoo syndrome (sneezing in the bright light), which is caused by an autosomal dominant allele. each has one parent who does not have the syndrome. What is the chance that their first child will not have achoo syndrome
1/4
Ultraviolet light:
is a mutagen
What is the chance that if the above couple have 3 children, all of the 3 will have achoo syndrome both parents heterozygous
27/64
An individual is RrSsTt. What is the chance that he will produce a gamete that is rSs
0
A woman with blood type A and a man with blood type B have 8 children: 3 sons with Type AB and 5 daughters with Type A. Most probable geneotypes of the parents
IAIA x IBi
Females that are fully affected by Duchenne muscular dystrophy are only known in cases of rare chromosomal errors. Females that are fully affected by red-green colorblindness are uncommon compared to affected males, but not truly rare. Why are these two traits so different in their occurrence in females
Male reproduction is usually prevented by Duchenne muscular dystrophy, but not by color blindness
Cells in rapidly growing tissue are more susceptible to mutagens than cells that are slowly growing, whY?
There is insufficient time to repair DNA damage before replication in fast growing cells
Pedigree A shows the inheritance of a rare (1/100,000) trait in a particular family. What is the most probable mode of inheritance of this trait?
autosomal recessive
Which of the following situations is likely to result in a baby with hemolytic disease of the newborn? Assume that, unfortunately, RhoGam has never been appropriately administered?
Mother Rh negative, father Rh positive, 2nd or later pregnancy
Individuals with familial hypercholesterolemia have a dominant allele that causes severe atherosclerosis and leads to early (during middle age) heart attacks and strokes. About 1 per million births produce children who are affected with the condition, but so severely that the child starts having heart attacks and strokes by the age of 5. What does this tell us about the condition and these families?
The child is actually homozygous for the allele, both parents are heterozygotes
Whats true about human races
What race you consider a particular individual depends on your upbringing, more than their biology
Monozygotic twins (neither mosaic) are generally
genotypically identical
children that have been adopted are tested for trait T and compared to their biological mothers and their adoptive mothers. They turn out to be much more similar to their adoptive mothers. Their siblings (biological of the adoptive parents) in the adoptive families are almost always identical to their parents when tested for trait T. What should we conclude about trait T?
Trait probably has heritability near 0 or .1
Which of the following is true of a threshold trait that is known to be a complex trait?
Relatives of an affected individual will be more likely to be affected than nonrelated individuals, nephews of an affected aunt will be equally at risk as grandchildren of an affected grandmother, individuals who get the same alleles as the affected individuals will be affected in all cases, and all individuals who share the same family environment will be equally at risk
phenotypically normal individuals are sometimes found who have only 45 chromosomes, no normal #21 chromosomes, but have a robertsonian translocation chromosome that has two 21q arms joined at the centromere. If they marry a chromosomally normal individual, what is the chance that a child will down syndrome?
1/2 of all conceptions, but the other half will have 21 monosomy, so only Down syndrome babies will be born alive.
Which of the following is true about chromosome aberrations?
A large deletions is equivalent to a partial monosomy
A hormonal signal always need a receptor. Which of the following disorders demonstrates the consequences of a missing or non-functional receptor?
androgen insensitivity
An individual is found to have some tetraploid liver cells, but diploid kidney cells and white blood cells. Possible explanation?
A failure to complete mitosis in a liver cell in the embryo
Which of the following is true about height determination in humans and pea plants
eight is dependent on both genotype and environment in both peas and humans, mendel’s experimental conditions made height a discontinuous variable in peas, but it has always been a continuous variable in humans, and mendel picked peas that had only 2 alleles at a single locus that affected height, humans have multiple loci
Many more syndromes include mental retardation as one of their common aspects than include foot malformations. Why is this so?
The brain has a longer critical period than the feet
Which of the following is a demonstration of differing norms of reaction
Homozygotes for hemochromatosis often become ill from iron overload in our society, but were more likely to survive and reproduce than wild type homozygotes in some past societies
how common are babies born with ambiguous genitalia, and what should be done about deciding which sex the child should be raised
It’s a relatively common event (1/3000) and sex assignment can wait until parents and physicians have enough information to avoid mistakes
In cats, black or orange is determined by alleles at a locus on the X chromosome. Heterozygotes are described as “tortoise-shell” or “calico”. What kinds of kittens could be expected from the cross of an orange female with a black male?
tortoise-shell females, orange males
In the past, some cat fanciers thought they could breed a line of pure-breeding calicos if only they could find a calico male. After the large prices, some calico males were found, but almost all were infertile. We now can explain this infertility, because they male calicos were probably:
Klinefelter syndrome
An embryo with which of the following chromosomal abnormalities will NEVER survive
45, -x, y
What is the critical event in determining that the gonadal sex will be male
The SRY gene turns on and produces functional TDF
What determines the sexual identity of an individual?
Changes in the fetal brain resulting from the presence or absence of testosterone
How much alcohol is it safe for a pregnant women to drink?
None
Which of the following is true about Down Syndrome individuals?
Older fathers (>40) don’t raise the risk nearly as much as older mothers
Height has a heritability of at least .8. What conclusions can we draw from this fact?
Children will tend to be the same height relative to their generation as their parents were relative to their own generation
A body is normally found in the nucleus of which kind of cell
somatic cells of females
A continuously distributed trait is studied in a series of families. It is found that the children of parents with the same extreme phenotypes (whether high or low on the trait) shwow moderate regression to the mean. What conclusion can we draw from this?
The trait probably is complex, and the regression occurs because the children of extreme parental pairs are unlikely to have the same extreme environment as their parents
The food and drug administration requires that studies to determine whether new drugs work, must be done “double blind”. Similarly, research in human genetics that includes psychological evaluations is normally done “double blind” Why is a double blind procedure required for believable results
Humans ofter make results match expectations, even if they’re not consciously doing so
A baby is born with phenylketonuria, which is known as a recessive. His mother is a known carrier, but his father has no family history of phenylketonuria. But karotyping reveals that his father has a chromosome 12 with an inversion on the long arm, where the PKU locus is located, and the baby inherited this chromosome from his father. What explanation would be reasonable?
One of the break-points of the inversion is probably in the PKU locus
Karyotyping reveals that a down syndrome girl has a Robertsonian translocation between chromosomes 13 and 21, and her father is a translocation carrier. What is the chance that the phenotypically normal children are counted when figuring the odds.
about 1 in 2, or 50%
Sex chromosome trisomies are less damaging than autosomal trisomies. Why is this so?
Most genes on Y chromosome affect sperm production, only a small number are otherwise important and extra X chromosomes are mostly inactivated
what are the practical consequences of determining whether an abnormal condition is familial or heritable?
Whether it’s familial or heritable suggests what aspects we need to investigate futher to understand the condition
Geneticists used to assume that human sex determination was similar to Drosophila, where the ration of x chromosomes to autosomes determines the sex. Which conditions showed that this was wrong?
Klinefelters syndrome and Turner Syndrome
Which of the following can damage an embryo or fetus?
smoking, X-rays of the mother’s abdomen, some prescription drugs, vitamin deficiencies, vitamin supplement excesses
Karyotype for an embryo is 69, XYY. This individual is:
triploid
What is the most probable explanation for the above chromosomal constitution?
Dispermy
What is the most probable explanation for an embryo with 69, XYY
gonadally male, phenotypically ambiguous when the internal organs are examined
The pseudoautosomal regions of the X and Y are the explanation for:
How such different chromosomes manage to pair during meiosis and XXXXX having a very abnormal phenotype in spite of X inactivation
How many barr bodies would a XXXXY individual have?
4
Secondary sexual characteristics of females are due to:
estrogen and progesterone exposure during puberty and adulthood
Multiple books and articles have been written that explains that programs such as Head Start can never erase racial differences in school achievement because IQ has a high heritability. Does the scientific evidence suggest these authors are right or wrong?
Wrong, heritability measured in one environment don’t apply to other environments
What trait has the highest heritability? WhyMZ - A97, B77, C58, D46; DZ - A77, B75, C28, D31.
C, The difference between the MZ and Dz concordances,
Which trait has the lowest heritability? WhyMZ - A97, B77, C58, D46; DZ - A77, B75, C28, D31.
B, the lack of difference between the MZ and DZ concordances
The “triplet code” refers to the fact that:
3 nucleotides code for an amino acid
Base pairs of DNA are held together by hydrogen bonds, while the sugar phosphate backbone is covalently bonded. The consequences of this are:
- it requires specific enzymes to rejoin a broken sugar phosphate backbone2. random molecular motion at body temperature can separate portions of complementary DNA strands and they will spontaneously re-assemble
What is the difference between a human chromatid and a DNA molecule?
Chromatids contain multiple protein molecules along with DNA
A gene that had the 5’ promoter region deleted would:
not be transcribed
A man and a woman both have impaired metabolism of the amino acid alanine, and in both cases it is due to a genetic defect. They marry have a large family, all of whom have normal alanine metabolism. What is the most likely explanation?
The couple are each mutant heterozygotes, but a different loci
The tertiary or quaternary structure of a protein ultimately depends on:
the sequence of amino acids determined by the DNA sequence
How does the genotype at the beta-globin locus affect phenotypes?
- sickle-cell allele homozygotes have severe medical problems2. the norm of reaction for sickle-cell 3. heterozygotes is “wild type” population in the US
Mutation is a random process, and therefore we can never predict which nucleotide in the genome will be changed next. None the less, which of the following are true?
- Large genes have high mutations rates than small genes2. There are mutation hotspots in the genome
Which of the following is an explantation of how a mutation at a single locus can have pleiotropic effects?
- One enzyme can participate in multiple metabolic pathways2. Either a deficiency of a product produced by an enzyme or a buildup of a precursor can cause problems
The Watson-Crick model of DN was immediately recognized as important because the structure directly suggested how:
genetic information could be accurately copied repeatedly
A codon of the template DNA sequence is GCA. Which of the following would be the corresponding tRNA anticodon?
GCA
Cancers are typically a mixture of cells with different abnormal karyotypes. Why should a single cancer have multiple abnormal karyotypes?
These cells are typically mutated in both copies of a tumor suppressing gene, which allows more mutations, including chromosome mutations, to occur in daughter cells
Which of the following is true about hemoglobin?
Sickle-cell hemoglobin is only different from normal hemoglobin by the change of a single amino acid in beta globin
The following partial DNA sequence is a portion of the template strand of a gene. This portion includes the portion coding for N-terminal end of the protein. How many amino acids will be coded by the portion of the mRNA made from this sequence? CCC CAT TAC TTC GGG
3
Comparing Japan to the US, we find higher rates of colon cancer in Japan and lower rates of breast cancer. But when we look at cancer rates in 3rd or 4th generation Japanese-Americans, we find rates comparable to other Americans. Why are Americans of Japanese descent apparently different from their ancestors?
The American environment (probably diet) somehow varies from the Japanese
Metastasis refers to a process by which:
tumor cells spread from the initial site and start growing in other locations
After sequencing a gene, it is discovered an individual has a mutant DNA sequence, but produces a normal amount of a perfectly normal protein. Which of the following is the most likely site of the mutation?
middle of an intron
A mutation will always affect:
nucleotide sequence
A family with no history of the disease has a daughter, Helen, with retinoblastoma, an autosomal dominant condition with variable expression which produces eye tumors in children. Both of Helen’s eyes were affected, and 3 of her 5 children develop tumors in both eyes. Where did the original mutation probably occur?
in one of her parent’s gonads
A different family with no history of the disease also has a daughter, Diana, with retinoblastoma. One of Diana’s eyes were affected at age 2, but none of here 5 children develop eye tumors or any other early tumors. Where did the original mutation probably occur?
in Diana’s eye
Mutations that abolish function in tumor suppressor genes are commonly recessive alleles when considered at the cellular level. But the family inheritance pattern for susceptibility to particular cancers looks like dominant with incomplete penetrance. Why is this so?
Only having one functional allele of a gene in all cells makes each cell vulnerable to a somatic mutation in that allele
Achrondroplasia is an autosomal dominant form of dwarfism that seems to be completely penetrant. If we find 39 achondroplastic births to unaffected parents in a total of 499,000 births, what is the mutation rate per gene per generation?
4 x 10^-5
Which of the following mutations would be most likely to produce a significantly different phenotype?
adding two bases to the middle of an exon
Comparing the sickle-cell allele to wild-type, is it a good allele or a bad allele?
This is too simple of a classification, since heterozygotes are the best genotype in some environments
A portion of a DNA strand has the following sequence: ATT CCG AA. What is the complementary strand?
TAA GGC TT
In the above 8 base pairs, how many hydrogen bonds should we expect?
19
