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Genetics > Exam 2 > Flashcards

Exam 2 Flashcards

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Biology 101 flashcards
1
Q

How is the influenza virus genome organized?

A

8 ssRNA negative strands (each in nucleoprotein complex) –> has multiple pieces of genome, as opposed to just one genome
enveloped virus –> easily transmitted
each segment encodes a protein

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2
Q

Which genes are important for infecting a cell?

A

immediate early genes
early genes
late genes

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3
Q

How can new strains of influenza arise?

A

proteins can change, new strand = one of the proteins has changed
coinfection with different influenza viruses = new combinations

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4
Q

What two types of infection do herpesviruses have? What regulates these?

A

latent (silent) and lytic
depends on how tightly DNA is wrapped with histones
condensed = latent
loose = lytic

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5
Q

What is unusual about the location of herpesviruses in the cell?

A

replicates in the nucleus of the cell (others usually replicate in cytoplasm)

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6
Q

Describe the process of infection by retroviruses and gene expression.

A

cell converts RNA from retrovirus into DNA –> inserted into DNA of host cell –> cell produces more retroviruses

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7
Q

What is a provirus?

A

virus genome that is integrated into DNA of host cell

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8
Q

What kind of mutation can be caused by retrovirus infection?

A

if it inserts in the middle of the gene, it’ll screw it up
if it’s next to another gene that has a strong promoter, it’ll make the gene really strong (?)

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9
Q

How are the immediate early and early proteins produced in a coronavirus infection?

A

ORF1b responsible for making proteins

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10
Q

What is unusual about the translation of ORF1b?

A

encodes 2 proteins
pseudoknot in mRNA stalls ribosome –> induces slippage
frameshift to new reading frame = new protein

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11
Q

How are the late coronavirus proteins produced?

A

encoded by sgRNAs after frameshift

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12
Q

How does coronavirus escape the RNAi machinery of the cell?

A
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13
Q

What are the different forms in which viral genomes are found? What are they in the viruses in this section?

A

enveloped (has a membrane) v.s. nonenveloped (no membrane)

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14
Q

How would the presence of a membrane on a virus affect its stability in the environment and its mode of exit from the cell?

A

enveloped = more sensitive to environment (like STDs and flu)
non enveloped = more stable

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15
Q

What are the three classes of genes that are generally found in viruses (depending on their genome size) and what are their functions?

A

immediate early genes - hijack cell, takes over host metabolism
early - replicate virus
late - make virus structural proteins

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16
Q

How does a virus enter a cell?

A

needs to be a receptor (protein on cell that virus recognizes)

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17
Q

What does host range mean?

A

types of organisms/cell that a virus can infect
these need to have the right receptor

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18
Q

What are the early genes in adenovirus and what is their function?

A

E1A, E1B - activates cell metabolism

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19
Q

How does late gene expression produce the variety of viral proteins?

A

mRNAs from major late promoter differentially spliced to produce viral proteins

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20
Q

How is the adenovirus genome used to generate vaccines? Why are E1 and E3 deleted in these vaccines?

A

you take some of the virus genes out and insert the gene for what you want
E3 supresses host immune response, makes virus into better vaccine
E1 - extra space to insert genes, also don’t want disease to be infectious

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21
Q

Which proteins of adenovirus and papillomavirus bind Rb and p53, and for what purpose?

A

E6, E7 - basically do the same thing as E1 in adenovirus

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22
Q

What is the relationship between the structure of a wart and papillomavirus gene expression?

A

gene expression/ which ones are turned on depends on where in the skin they are
cells at base are alive, don’t do much –> start dividing/differentiate = other proteins get made inside virus

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23
Q

How do the genomes of prokaryotes and eukaryotes differ?

A

prokaryotes - smaller, simpler, one chromosome
eukaryotes - bigger, more complex, multiple chromosomes

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24
Q

interphase

A

cell growth
divided into 3: G1, S, G2

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25
Q

interphase

A

nuclear envelope present, chromosomes relaxed

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26
Q

Describe the mechanisms of chromosome separation in mitosis

A

spindle microtubule anchors to kinetochore
chromosomes are pulled apart

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27
Q

how does meiosis differ from mitosis?

A

mitosis creates two identical daughter cells from one parent
meiosis creates cells that are unique from parent
1st division - homologous chromosomes separate
2nd division - sister chromatids separate

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28
Q

what happens in each step of prophase I in meiosis?

A

leptotene - chromosomes condense
zygotene - synaptonemal complex (protein that connects homologous chromosomes - looks like railroad tracks) forms
pachytene - crossing over; DNA exchanged btwn non-sister chromatids
diplotene - chiasma (point where chromosomes are crossed) visible in bivalent
diakinesis - nuclear membrane disintegrates

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29
Q

Distinguish the functions of mitosis vs. meiosis

A

mitosis - cell regeneration, growth, asexual reproduction (only in autosomes)
meiosis - production of gametes for sexual reproduction

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30
Q

in what ways is diversity in offspring generated through each meiotic division?

A

homologous chromosomes segregate to different cells; which goes where can vary
recombination - pieces get swapped, location can vary

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31
Q

contrast gametogenesis in male vs. female mammals

A

spermatogonium produces 4 sperm (basically sperm divides into 2 equal and then 4 equal sperm)
oogonium produces 1 ovum + 1 polar body (only has half DNA; unequal)

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32
Q

M phase

A

nuclear and cell division
mitosis and cytokinesis take place

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33
Q

G1

A

cell grows

34
Q

G0

A

non dividing phase (not every cell goes through)

35
Q

S

A

DNA replicates

36
Q

G2

A

cell prepares for mitosis

37
Q

prophase

A

chromosomes condense
chromosome has 2 chromatids
mitotic spindle forms

38
Q

prometaphase

A

nuclear membrane disintegrates
spindle microtubules (attached to centrosomes on one side) attach to chromatids

39
Q

metaphase

A

chromosomes line up on metaphase plate (middle)

40
Q

anaphase

A

sister chromatids separate and move towards opposite poles

41
Q

telophase

A

chromosomes arrive at spindle poles
nuclear membrane reforms

42
Q

what are 2 errors that can occur in cell division?

A

microtubule fails to attach to chromosome, chromosome is loose and is lost when nuclear envelope reforms = missing chromosome
sister chromatids don’t separate = extra chromosome in one cell

43
Q

State Mendel’s first law in your own words

A

each trait has 2 alleles
separate in gamete formation
separate in equal proportions

44
Q

monohybrid cross

A

2 parents, 1 trait

45
Q

dihybrid cross

A

2 parents, 2 traits
(RrYy)

46
Q

monohybrid and dihybrid testcrosses

A

cross with homozygous recessive (tt) to decide if individual is homozygous or heterozygous

47
Q

State Mendel’s second law in your own words. How do you explain these laws, given our knowledge of alleles and chromosomes (remember, Mendel had no knowledge of chromosomes)?

A

two traits don’t affect each other (not always true)
i.e. seed color (Y or y) doesn’t really affect seed shape (R or r)

48
Q

Describe the role of probability in analyzing genetic data

A

because we can only have a certain amount of options in what phenotypes are passed down/expressed, we can predict the probability

49
Q

What is the null hypothesis?

A

no relationship exists btwn the two sets of data (observed v.s. expected data)

50
Q

Of the different modes of sex determination, describe that in:
birds

A

ZZ- ZW system - present in birds, butterflies, some reptiles, amphibians, fish (sex can be determined based off temperature)
W is sex-determining
females ZW
males ZZ (so basically opposite of humans)

51
Q

Of the different modes of sex determination, describe that in:
Drosophila, role of doublesex gene

A

depends on X (number of sex chromosomes) : A (number of all other chromosomes) ratio
basically if it has XX (could be XX or XXY or XXXY) = female
XO is male (bcus no XX), but sterile (bcus no Y)

52
Q

Of the different modes of sex determination, describe that in:
mammals, including humans

A

Y chromosome determines gender
X chromosome is “normal” chromosome (has uses outside of sex)
XX = female
XY = male

53
Q

How can the Amami spiny rat have two sexes without a Y chromosome?

A

most mammals have Sry gene –> sox9 –> y chromosome
y chromosome not produced if sox9 inhibited (i.e. females)
amami don’t have Sry but do have 2 enhancers that work together to turn on sox9

54
Q

What causes Turner’s and Klinefelter’s syndromes?

A

Turner - XO (not male, but still lacking female hormones, can be treated with estrogen), infertile
Klinefelter’s - XXY (male, but with female traits, like smaller testes, breasts, lack of facial hair), infertile

55
Q

How do Turner’s and Klinefelter’s syndromes develop in meiosis?

A

nondisjunction - chromosomes/chromatids are supposed to separate in meiosis 1 or 2, but don’t
BE ABLE TO DRAW

56
Q

sex-linked traits

A

traits that only appear in one sex (usually male)

57
Q

Analyze crosses that involve sex chromosomes: contrast the results when the male vs. the female carries the trait

A

if trait is on X chromosome, females have another that make up for it, males don’t

58
Q

Contrast the structure of the X and Y chromosomes

A
59
Q

What is the pseudoautosomal region?

A

homologous gene sequences
parts of Y chromosome that have same sequences as X chromosome (and line up with during meiosis)

60
Q

dosage compensation –> why is it important?

A

this is what regulates how genes are expressed evenly despite different chromosomes (i.e. men are missing an X so how do all those genes get expressed?)

61
Q

how does dosage compensation happen in mammals?

A

one X chromosome usually shut down
Xist gene makes RNA, doesn’t encode protein, coats chromosome, facilitates methylation –> shuts down chromosome

62
Q

How does dosage compensation happen in Drosophila?

A

X linked genes expressed twice as much

63
Q

why do we even have sex differentiation?

A

meiosis - alleles get mixed up and things get switched around
sex depends on which genes are switched on and off

64
Q

incomplete dominance

A

heterozygous phenotype falls between two homozygous phenotypes
phenotype red + phenotype white = phenotype pink

65
Q

codominance

A

heterozygous phenotype expresses phenotype of both homozygous phenotypes

66
Q

penetrance

A

percentage of individual organisms having a particular genotype that express the expected phenotype
(i.e. 42 people have allele for trait, only 38 express, penetrance = 38/42)

67
Q

expressivity

A

degree to which trait is expressed (how much gene is expressed)

68
Q

lethal alleles

A

causes death at early stage of development

69
Q

multiple alleles

A

more than 2 alleles on same locus

70
Q

gene interaction

A

activity at one locus affects activity at another

71
Q

epistasis

A

gene interaction where different genes are dependent on one another
E –> F –> G
A B
if enzyme A is needed to turn E to F, but A is defective, then F won’t get made, B has nothing to work with, etc. –> i.e. B is dependent on A

72
Q

what does a skip in generation tell you about trait?

A

probably recessive since it needs 2 carriers

73
Q

How can a pedigree tell you if a trait is autosomal dominant?

A

doesn’t skip generations
only needs one parent to express trait
shows up equally in males and females

74
Q

How can a pedigree tell you if a trait is X-linked dominant?

A

doesn’t skip generations
females (if hetero) will pass it to 1/2 sons and 1/2 daughters
males will pass it to ALL daughters but NO sons

75
Q

How can a pedigree tell you if a trait is Y-linked?

A

only appears in males
all male offspring will be affected

76
Q

How can a pedigree tell you if a trait is X-linked recessive?

A

more frequent in males
males won’t pass it to sons
but can pass to daughters –> carriers
daughters with allele pass to sons who express the trait

77
Q

How can a pedigree tell you if a trait is autosomal recessive?

A

equally appears in both sexes
skips generations (needs 2 parents to be carriers)
likely in offspring from parents that are related

78
Q

dizygotic twins

A

nonidentical
2 separate eggs fertilized by 2 separate sperm –> genetically distinct zygotes
(basically no different from normal siblings except they were born at the same time)

79
Q

monozygotic twins

A

same egg, same sperm –> splits into separate embryos early on
share 100% same genes

80
Q

what is the general course of infection?

A

entry into cell (by binding to receptor)
unpacks nucleic acid
gene expression

Genetics (5 decks)

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