EXAM 1: Ch1-5 Flashcards
- Some people believe that SARS CoV-2 originated in a lab. What are three compelling genetic reasons why this is very unlikely to be the case?
- Closely related to a bat
- wild virus 96% match)
- If it was created, it would reveal a genetic backbone.
What does it mean to say that viruses undergo recombination?
Usually we think of recombination as something that occurs in meiosis (Chapter 2). But it can also occur in haploid cells like bacteria as well as viruses. In this case, it occurs when viruses that are distinct somehow come into close proximity (probably by coinfecting the same cell) and each ends up contributing part of their genome to new virus—a virus with a genome that is a new combination of genomic regions from the parental strains.
Using the concept of a molecular clock, how long ago did Boni et al. estimate that SARS 1 and SARS CoV-2 diverge?
The point estimate is around 1200 (800 years ago, but the confidence interval is wide and extends to 1600, or 400 years ago).
In biology, what do we call one of these branching figures with species or samples at the tips?
A phylogeny or a phylogenetic tree.
Are species (or samples) that are separated by short branches closely related or distantly related?
Extant species are at the tips of such a tree. You trace branches back to find forks, or nodes. These represent the common ancestor between the descendent species. How long the branches are you must trace back to find this common ancestor tells you how much genetic evolution separates the extant species. The answer to the question should be clear from what I’ve written.
What is molecular epidemiology? What is a superspreader event?
A superspreasder event is where many people become infected at the same time and place—either because someone is transmitting a lot of virus (highly infectious), because the conditions are perfect (e.g. indoors for a prolonged period of time without mask wearing), or, most often, both.
example, did scientists use air traffic data and contact tracing to know how the virus spread? Or is there something in the virus itself that records the pattern of how it spreads and, if so, what?
Mutations accumulate as viruses are transmitted from one host to the next. Because new mutations hardly ever overwrite (or reverse) previous mutations (at least on the short time scales we are talking about here), it means that the mutations contain a record of transmission patterns across time and space.
- Vaccines: What protein are the leading vaccines using as their target for eliciting an immune response? Why this protein and not others from SARS CoV-2?
Because this protein is the major target of our adaptive immune system when the virus infects our body.
Molecular Epidemiology
Using geniomic sequencing and modeling to infer the spread, dynamics of infectious diseases
Pseudotype
Unrelated virus with SARS protein Switching D (aspertate) for G (glycine) ever so slightly tweaks the spike protein
How would covid vaccine work @ a genetic level
focuss on th spike protein because we build antibodies on spike proteins (inject genetic info of spike protein into cells)
How can we make a tree describing the relationship of all living things when living things are some mind-blowingly different from each other? In other words, what feature do all living things share that we can use to build a tree?
all living things on Earth can trace their descent back to a common ancestor. … Then, we can use the shared derived traits to organize the species into
What are the major phylogenetic domains of all cellular organisms?
The three domains are the Archaea, the Bacteria, and the Eukarya
What domain of the biological world is not cellular and not readily comparable to cellular organisms?
Viruses
Which of the phylogenetic domains are the prokaryotes?
eubacteria and archaebacteria
What is the major differences between prokaryotes and eukaryotes?
eukaryotic cells have a distinct nucleus containing the cell’s genetic material, while prokaryotic cells don’t have a nucleus and have free-floating genetic material instead
T or F: all prokaryotes are more closely related to each other than they are to eukaryotes.
F
What are the three major divisions of genetics?
transmission genetics, molecular genetics, and population genetics
Why, in genetics, are we so obsessed with tracking chromosomes in mitosis and meiosis?
Although mitosis and meiosis both involve cell division, they transmit genetic material
What’s it mean to say that a cell is diploid? What does it mean to say it’s haploid?
Haploid” refers to any cell that has 23 chromosomes (half of the total 46). “Gametes” are specifically sex cells that have 23 chromosomes. “Diploid” refers to any cell that has all 46 chromosomes
Sars COV 2 orgin in bats is what division of genetics
Population
Bedfords discovery of transmission is what division of genetics
Transmission and population
D614G affects hydrogen bond is what division of genetics
Molecular
Karyotype
complete set of the chromosomes
T/F Archea is closer related to Eukaryotes than to bacteria
True
In mitosis, what are lined up alont the center and then pulled apart?
Sister Chromatids
What happens during meisosi 1 +2?
1: homologues are lined up and then pulled apart
2: sister chromatids are lined up then pulled apart
Crossing over, when does it occur?
prophase of meiosis 1
when does assortment occur?
Metaphase 1 and anaphase 1
If a species has n chromosomes how many ways can it be shuffled?
2^n, alot of genetic variation without crososing over
How are bacteria different from both archea and eukaryotes?
bacteria have no histones associated with their chromosomes and the other two groups do
In which stage of the cell cycle does the cell duplicate its DNA?
S phase
Eukaryotic cells that contain more than two sets of genetic information are referred to as…
polyploid
Function of the telomere?
to protect the end of the DNA molecule
What is the constricted region of the chromosome where the kinetochore forms
centromere
The products of mitosis normally are
genetically identical to the parent cell
What stage of mitosis involves sister chromatids separating and moving toward opposite poles?
anaphase
In order to pass the G2/ M checkpoint the cell must have
DNA replicated and undamaged
A cell has 6 chromosomes while in G1 stage. How many chromosomes and how many DNA molecules will it have in G2?
6 chromosomes and 12 DNA molecules
In which stage of meiosis does the separation of homologous chromosomes occur?
Anaphase 1
One source of genetic variation is the random distribution materna and paternal chromosomes, the other is ….
crossing over at prophase 1
Which statement is not a difference between meiosis and mitosis
sister chromatids seperate during mitosis but not meiosis
- separate in mitosis and 2nd division of meiosis
How many ova, plural ovum, can be produced from two primary oocytes through meiosis?
two
the two proceeses that can create genetic differences
independent assortment and crossing over
What is n in 2^n?
n represents the number of homologous chromosome paris per cell entering meiosis
crossing over shuffles alleles on
non sister chromatids of homologous chromosomes
Transmission genetics
how genes are passed from parents to offspring
Population genetics
how organisms that share genes (populations) change over time
Molecular genetics
molecular details of how genetic information is stored, replicated and processed
alleles
different versions of a gene
S phase
DNA duplicates
M phase
nuclear and cell division
Where do microtubules attatch?
kinetochore
Mitosis
sister chromatids seperate and move toward opposite poles
chromosomes line up on the metaphase plate
Meiosis
gametes are produced that carry half the normal # of chromosomes
Fertilization
two haploid gametes fuse and restore to diploid
Heterozygote
2 different alleles
Homozygote
2 copies of same alele
The principle of segregation
each individual diploid organism posseses two alleles for any particular characteristic. These two alleles segregate when gametes are formed and one allele goes into each game. the alleles segregate in equal proportions during meiosis.
Independent vs mutually exclusive
Independent= x ME= +
heterogametic
males XY
homogametic
females XX
Do all chromosomes benefit from recombination?
Not the Y chromosomes
SRY
a trasncription factor. Expressed or not expressed
protein that binds DNA near specific genes to turn then on.
Nondisjunction
when chromosomes dont segregate properly in meiosis. Various possibilities exhist
Which karotype is lethal?
YO- can live without a Y but cannot live without an X
Chromosomal mosacisim
Cell missing chromosome
Phenotypes
- Femalese are diploid (XX) recessive alleles are masked in heterozygotes. Males are haploid (X) recessive are unmasked
Autosomal phenotypes
everyone is diploid= recessive are masked in the heterozygotes, unmasked in homozygotes
Heredity
daughters always get their fathers X and a random one of their mothers two X’s/
sons get no X from their fathers (they get a Y) and they get a random one of mothers two Xs
Disappearing
affected fathers pass it to 100% of their daughters since usually the mother is a non-carrier, the daughters will be carriers
Reappearing
When the daughters grow up and have children, 1/2 of their sons will be affected
Dosage Compensation
Mechanisms to deal with unequal # of chromosomes
- doubled expression of genes on X in XY/XX
- inactive all but 1 X chromosomes
Incomplete Dominance
when the heterozygote has a phenotype intermediate between the two homozygotes
1:2:1
Complete Dominance
when the heterozygote phenotype matches the homozygote dominant
3:1
Codominace
both traits are shown
patchy color
blood types
AB can get any blood
O is universal donor
Epistasis
when the gynotype at one gene masks the genotype another
- antigen cannot be added
Epistatic
gene that does the masking
hypostatic
gene that gets masked
example of recessive epistasis
Labrador retriever color
anything with ee is yellow
Dominant epistasis
a dominant allele at one locus masks the effect of another locus
9:3:3:1 ?
dihybrid cross, two independent loci
With genetic sex-determination mechanism, what is true?
Sex is determined by genes on undifferentiated chromosomes
What did Mary Lyon propose about sex chromosomes in mammals?
One X chromosome in each female cell becomes inactivated, and the process of selection is random
A human male has XXXXXY would contain how many barr bodies?
2
In the evolution of a Y chromosome in mammalia, what can be assumed?
it evolved from an autosome
A mutant human gene will be inherited by
all of the sons but none of the daughters
model genetic organisms
organisms that are widely used in genetic research and can serve as models for genetic systems
Barr Bodies
dark staining bodies in the nuclei of cells from female cats discovered by Murray Barr
an inactive X chromosome
Lethal Alleles
2:1 ratio
F2 phenotypic ratio duplicate recessive
9:7
F2 dominant epistasis
12:3:1
F2 recessive epistasis
9:3:4
A _____ allele causes death at an early stage, often before birth and, therefore, some genotypes do not appear in the progeny.
lethal
Why does gene interaction often arise when different loci influence different steps in a common biochemical pathway?
the product of one enzyme affects the substrate of another
Anticipation is the
stronger or earlier expression of a trait as it is passed from generation to generation.
In the human ABO blood type system, which of the following outcomes is NOT expected to occur?
an AB child from a mating of an A individual and an O individual
True or False? It is possible to see gene interaction at multiple loci.
True
True or False? A father that is heterozygous for precocious puberty, a sex-limited characteristic, has a 50% chance of passing on the allele to his child, regardless of the child’s sex.
True
Characteristics that have a few easily distinguished phenotypes are called _____ characteristics.
discontinuous
A phenotype produced by an environmental effect that mimics a phenotype produced by a genotype is called a
phenocopy
A 13:3 ratio is produced by
gene interaction
