Intro to Cell Life Exam 3

What did Griffith study?

bacterial transformation

What were the 2 kinds of strains of bacteria that Griffith experimented with?

R strain and S strain

What’s the difference the r strain and the s strain?

r strain= can’t infect humans (nonpathogenic strain)

s strain= can infect humans (pathogenic strain)

What did Griffith experiment show?

dead S bacteria when paired up with live R strain can be transformed into R strain

What did Avery, MacLeod, and McCarty study?

what the transforming material was

What did Avery, MacLeod, and McCarty discover?

DNA is the transforming material

What did Hershey and Chase study?

what part of the virus carried instructions

What is the virus structure?

proteins holds DNA and nucleic acid is in protein

What did Hershey and Chase discover?

DNA carries the genetic info

What did Chargaff discover?

nitrogenous base composition of DNA

What are the nitrogenous base pairs in DNA?

Adenine=Thymine

Guanine=Cytosine

What did Franklin, Wilkins, Watson, and Crick discover?

structure of DNA

What are the characteristics of the structure of DNA?

double helix

antiparallel(3’-5’ then 5’-3’)

complementary base pairing

DNA replication steps:

Parental strands are melted apart which then become templates for new strands. Then, new strands are synthesized using complementary base pairing.

What are the three types of replication they thought DNA went through?

conservative, semi-conservative, and dispersive

What did Meselson and Stahl study?

mechanism of DNA replication

What did Meselson and Stahl discover?

DNA shows semi-conservatism replication mechanism

What is DNA and RNA?

nucleic acids (nucleotides)

What makes up proteins?

amino acids

What does DNA contain?

genes

What is RNA?

copy of a gene

What’s the difference between a gene and a genome?

gene= 1 product

genome= all DNA

What do proteins do?

gives organism specific traits

What is a nucleotide made up of?

1 phosphate group, 1 sugar (deoxyribose), and 1 base (A,G,C, or T)

What kind of bonds do nucleotides use?

covalent bonds

Where is the covalent bond at in nucleotides and what is the chain called?

between sugars and phosphates

sugar-phosphate backbone

What does a strand of DNA look like?

5’→ phosphate group & 3’→ OH group

What are characteristics of the structure of DNA?

Nucleic acid, double helix, antiparallel, and complementary base pairing

What is nucleic acid made up of?

nucleotides

What does double helix mean when it comes to DNA?

2 strands of nucleotides twisted into spiral where sugar phosphate backbone is on outside and bases use hydrogen bonds on inside

What does anti-parallel mean for DNA?

5’→ 3’ (Ps→ Ps) to 3’→5’ (Sp→ Sp)

What is complementary base pairing during DNA?

A (double H bond) T & C (triple H bond) G

What is the origin of replication?

Where DNA replication starts (DNA strands separate)

What is the replication fork?

where DNA has not separated yet

What are the enzymes involved in DNA replication?

Helicase, Single-Strand Binding Protein (SSBP), Topoisomerase, Primase, DNA polymerase

What does Helicase do?

separates DNA strands at replication fork

What does SSBP do?

binds single stranded DNA

What does topoisomerase do?

relieves tension (breaks DNA)

What does primase do?

starts adding nucleotides to RNA primer

What does DNA polymerase do?

adds DNA nucleotides

What direction is DNA made?

from 5’→ 3’ direction (grows from 3’ end)

What happens when nucleotide bonds to OH?

phosphodiester bond is formed and 2 phosphate groups are released (energy)

Characteristics of leading strand

replication is continuous and moves same direction as replication fork

Characteristics of lagging strand

replication is discontinuous and moves opposite direction of replication fork

What happens as DNA separates?

replication is continuous and replication fork moves

What happens when RNA is synthesized?

new DNA is added to 3’ end of primer and moves opposite direction of fork

What are the small fragments in the lagging strand called?

Okazaki fragments

What happens when RNA primers are removed?

empty space is filled with DNA nucleotides and ligase enzyme comes in and makes covalent bond between them

What do prokaryotes go through?

binary fission (circular chromosomes and 1 origin of replication)

What do eukaryotes go through?

cell cycle (linear chromosome and multiple origin of replications on each chromosome)

How many chromosomes do humans have?

23 chromosomes

What is telomerase used for?

replicate ends of chromosomes in eukaryotic sex cells

What are the 3 parts of transcription?

initiation, elongation, and termination

What do transcription factors do?

brings RNA polymerase to promoter sequence

What does RNA polymerase do?

binds to promoter and does transcription ( DNA is used as template to make RNA polymer)

What is elongation in transcription?

RNA polymerase temporarily separates DNA strands to use as template

What is termination in transcription?

RNA polymer “falls” off DNA template

What happens during RNA processing?

5 prime cap is added to protect mRNA and poly A tail is added which helps transport

What’s an intron and exon?

intron- unwanted sequence (spliced)

exon- kept/wanted sequence (pasted together)

What happens to introns and exons during RNA processing?

introns are cut out and exons spliced together

What are codons?

3 RNA bases

What makes up translation?

mRNA + Ribosome + tRNA + Amino Acids

What do ribosomes do?

make peptide bonds

What is tRNA?

has anticodon that matches up with codon on mRNA

What does tRNA do?

brings amino acid to RNA codon

Ribosome characteristics

made up of large subunit, small subunit, and mRNA binding site

What are the 3 ribosomes?

E (exit), P (middle), and A (arrival) (all in large subunit)

What is initiation in translation?

small subunit binds mRNA, initiator tRNA binds start codon, and large subunit attaches (tRNA in P site)

What is the energy for translation?

GTP

What is elongation in translation?

new tRNA goes to A site (complimentary to codon), peptide bonds are formed, polypeptide associated with tRNA in A site, and translocation

What is translocation?

tRNA moves P→ E and falls out

What is termination in translation?

stop codon (release factor bind) and polypeptide released (components separate)

Where do bacteria live?

in unstable environments

When are transcription and translation regulated?

when absolutely necessary

How do bacteria organize their genetic info?

operons

What are operons?

cluster of related genes controlled by a single promoter

What is needed by all cells?

tryptophan

Characteristics of tryptophan

can be in an environment or made by a cell

What is a repressor?

control if transcription occurs or not

What contributes to making tryptophan?

trp genes

What is a trp repressor default mode?

inactive- cannot bind to operator so will not prevent transcription

What happens when tryptophan is present in environment?

tryptophan will bond to repressor, which will then change shape, then it can bind to operator and block transcription

What is trp operon default mode?

on but can be switched off by presence of tryptophan (repressible operon)

What is a lac operon?

regulates making proteins that break down lactose

What is an inducible operon?

transcription off (repressed) by default but can be turned on by a signal from presence of lactose

What happens when lactose is present?

binds to repressor which then charges it and no longer binds to operator and falls off no longer repressing the operon