genetics exam 2

What was griffith’s experiment on S. pneumoniae and why was it beneficial?

he found that strains of bacterium that grow in mice have a smooth appearance or a rough appearance and the rough appearance does not cause the disease. when heat killed SIII and live RIII were injected, he found that the bacterial cells transformed through DNA showing that it is a hereditary molecule

What was avery, mcleod’s, mccarty experiment on S. pneumoniae and why was it beneficial?

they identified the role of DNA in transformation by eliminating lipids, polysaccharides, protein, RNA and DNA

what is a hershey-chase’s work on bacteriophages?

hershey-chase studied a T2 bacteriophage that had a protein coat with DNA that infects bacteria and produces new viral particles where phage DNA is transferred to host bacterial cells and directs synthesis sulfur represented proteins while phosphate represented DNA . essentially proved that DNA is a heritable material

what is meselson-stahl’s replication experiment?

used heavy and light N growth medium. they found there to be identification of semiconservative replication in bacteria and that all life shares the same general process of DNA replication

what is the building block of DNA, its components, and how are they structured?

nucleotides, consist of a phosphate, deoxyribose, and nitrogenous bases

what is the difference for the bases?

adenine and guanine (double-bonded O) are purines (double trouble) while cytosine and thymine (CH3) are pyrimidines

what are chargaff’s rules of base composition and how does it relate to the rules of base pairing?

A+G = T+C or A+C = G + T

%purine = pyrimidines

A + T does not necessarily equal G+C

what are the features of watson and crick’s DNA model?

they used Rosalind Franklin’s X-ray crystallography images to create a DNA model that showed phosphate + sugar backbone, anti-parallel double helix, base pairs inside, major (shallow) and minor (deep) grooves

what is the function of the 3’ site?

it is where new nucleotides are added

what is meant by conservative replication and how does it differ from semi-conservative and dispersive replication?

conservative: original molecule intact, new molecule made from two strands made from scratch

semi-conservative?

each resulting molecule has one original strand, another made from “scratch”

dispersive?

original broken and reassembled mixing new and original strands

what is DNA replication?

a biological process of producing two identical replicas of DNA from one original DNA molecule

how does DNA replication occur in prokaryotes?

they have a singular circle chromosome and may have small circular plasmids

what are origin sites for DNA replication and why are they AT rich?

a specific nucleotide sequence on a chromosome or plasmid (DnaA boxes). they are AT rich because the pairing only had two hydrogen bonds, making it easier to separate during replication

what are the roles of helicases?

it opens the helix by disrupting H-bonds to separate DNA into single strands

SSB?

they are single-stranded DNA-binding proteins to help stabilize unwound DNA

gyrase/topoisomerases?

helps to remove supercoils from DNA by breaking the DNA strands to rotate them to a relaxed states and ligates strands

what is supercoiling in DNA replication?

the tightening of DNA away from replication fork

what is a replication bubble in DNA replication?

what is a replication fork in DNA replication?

what direction does DNA replicate via how it is read and the direction is it built?

what is the name of the cofactors for DNA replication?

replisome

what is the role of primase?

adds an RNA primer

what are the roles of DNA polymerase III?

will add nucleotides on a 3’ C to grow new DNA strand in 5’ to 3’ with exonuclease activity from 3’ to 5’

what is sliding clamp in DNA replication?

keeps DNA polymerase on-site

what is DNA polymerase I?

how does replication proceed in the leading strand and lagging strand?

what direction does DNA replication proceed in?

5’ to 3’

what are Okazaki fragments?

replaces RNA primers with DNA nucleotides (DNA polymerase I) and joins the fragment and the replaced primer nucleotides with ligase

how is replication proof-read?

through DNA pol. I and III

how does DNA replication occur in eukaryotes?

through linear chromosomes of eukaryotes, which has multiple origins of replication

what is the role of telomerase?

to help replenish telomeres, which is shortening at 3’ end of chromosomes that causes DNA replication to be lost, helps to serve as template to rebuild other DNA strand

how does RNA differ from DNA?

what is mRNA and their purpose?

what is tRNA and their purpose?

what is rRNA and their purpose?

what are the features of a gene?

What are untranslated regions?

What are exon/introns?

What is the open reading frame (ORF) of a gene?

What is the difference between of upstream and downstream?

how does a Christmas tree diagram show us gene and transcription?

what is a promoter site in RNA transcription?

how does transcription initiate in prokaryotes?

how does transcription initiate in eukaryotes?

How does transcription terminate in Prokaryotes?

How does RNA decay in prokaryotes?

What is the role of RNA decay?

what is the type of RNA polymerase that transcribes each type of genes and how each initiates and terminates in eukaryotes?

how is RNA processed during and after translation in eukaryotes?

what is splicing in eukaryotes?

what is an exon in eukaryotes?

what is an intron in eukaryotes?

what are the benefits of splicing?

what is alternative splicing>

what are the different types of alternative splicing?

how does RNA decay take place in eukaryotes?

What cellular process leads to the recombination of linked genes?

crossing over in prophase I of meiosis

How can we estimate linkage and distances between genes?

by comparing the observed frequencies of gamete phenotypes, or the corresponding progeny phenotypes using a test-cross such as a heterozygous parent x recessive parent

what does it mean for a trait to be independent?

where it produces a 1 Dom Dom / 1 Dom Rec / 1 Rec Dom / 1 Rec Rec, with a 1:1:1:1 ratio

What are test-crosses? What are the phenotypic and genotypic ratios expected under a test-cross if genes are unlinked? For two-point crosses? For three-point crosses?

what type of frequencies should crossing over produce?

high frequency, intermediate, different medium, very rare, all at two phenotypes each

What is a three-point testcross?

triple heterozygote crossed with triple recessive: A/a B/b C/c x a/a b/b c/c where is produces 8 phenotype in 1:1 ratio such as 1/8 Dom Dom Dom. 1/8 Dom Rec Rec, 1/8 Re Dom Dom etc aka 1:1:1:1:1:1:1:1

what number of recombinant frequency determines if genes are linked?

if it is less than 0.50, the closer two genes are on the same chromosome the less they will assort independently

why are genetic maps beneficial?

they build complex genotypes for science/industry, they understand gene function at molecular level, helps with evolutionary mechanisms and processes, they identify genes linked to diseases

How do we use Chi-squared tests to determine whether 2+ genes are linked?

by comparing with null hypothesis if no linkage, expectation is 1:1:1:1 → ¼ of each type

what does it mean if alleles are on the same homolog?

there is no punctuation between them

what does a slash mean?

it separates two homologs

How are genes on different chromosomes separated by?

;

what to use for unknown linkage?

a dot (.)

what does it mean for a linkage to be cis?

adjacent conformation where the heterozygote has both dominants on same chromosome/homolog (AB/ab or ++/ab)

what does it mean for a linkage to be trans?

oporite where dominant alleles are on different chromosome/ homolog (Ab/aB or +b/a+)

What is a mapping unit?

it is the distance expressed in map units

What is the relationship between m.u. and recombination frequency?

recombinant freq. correlates to physical distance between two genes/loci on chromosome but the actual distance is expressed in mapping units 1 m.u. = 1cm = distance between genes for which 1 in 100 offspring is recombinant

How are recombination frequencies and physical distances related?

more distance, more recombination

How can recombination be used to determine ancestral events between two species?

helped determine interbreeding occurred between early humans and Neanderthaals

what is the coefficient of coincidence?

measures the percent of observed double recs to expected double recs based on distance between genes (observed(observed in test cross)/expected (multply dist. of genes and number of inds. counted)

What is interference?

measures % of expected double recs. that were not observed (I = 1 - C)

what is the purpose of a genetic map?

includes identity of genes as well as order, distances between each pair of gene

what does a double recombinant do?

tell us order of the genes, rarest typr

what does high freq. phenos mean in mapping?

parental

what does rarest freq. phenos mean?

double cross-over

what is the middle gene typically?

the one that “flipped” position in the double-recomb classes

what is the intermediate recomb?

distance between genes inends and middle