Biology Molecular Genetics

DAT Biology section

central dogma

the _____ is a theory that states that in cells, information only flows from DNA to RNA to proteins

nucleotide

a ____ is the basic unit of DNA

sugar, phosphate group, and nitrogenous base

a nucleotide is composed of a ______ bonded to both a ______ and a _______

Purines & pyrimindines

what are the two classes of nitrogen bases found in nucleic acids

Adenine & Guanine

the purines include _____ & _____

Cytosine, thymine, uracil (replaces thymine in RNA)

the pyrimidines include ______ and ______

antiparallel DNA strands are held together by _____ ______ between the bases oriented towards the center

hydrogen bonds

Adenine

In DNA, thymine forms 2 hydrogen bonds with

Uracil

In RNA, _____ forms 2 hydrogen bons with adeinine

Cytosine

In DNA & RNA, guanine forms 3 hydrogen bonds with ____

1 side of the DNA helixx runs in the opposite direction to the toerh (5’ to 3’ and 3’ to 5’) - this is known as the _____ of DNA

antiparallel arrangement

Watson ; Crick

the DNA structure was dicovered by _____ and _____

DNA helicase

What is the enymze that breaks the hydrogen bonds between nitrogenous bases during DNA replication?

Replication fork

the _____ is the Y-shaped region where the parentl strands of DNA are being unwound

Semiconservative

DNA replication is _____, meaning that each daughter strand will have 1 new and 1 old strand

DNA polymerrase

_____ is the enzyme that reads the parent DNA strand and creates a complementary, antiparallel daughter strand

3’ —→ 5’

DNA polymerase always reads the template strand in the _______ direction

5’ —→ 3’

DNA polymerase creates the complimentary strand in the ____ direction

leading strand

the ____ is the DNA strand that is continually synthesizes by DNA polymerase

lagging strand

the _____ is the DNA strand that is synthesized discontinously, due to a limited reading direction of DNA polymerase

Okazike Fragments

____ are short fragments that result from the discontinous synthesis of the lagging strand

uracil (both are pyrimidines)

In RNA thymine is replaced with

DNA is transcribed into mRNA and arranged into triplets known as ____

codons

Codons are translated from mRNA into ____

amino acids

most amino acids have more than one codon coding for them - this is known as ____ or ____

degeneracy; redundancy

_____ carries the complement of a DNA sequence from the nucleus to the ribosomes for protein synthesis

messenger RNA (mRNA)

_____ assists in translation by bringing amino acids to teh ribosomes during protein synthesis

transfer RNA (tRNA)

anticodons

in tRNA, triplet sequences of nucleotides that are completary to mRNA codons are called ______

Ribosomal RNA (rRNA)

the nucleotide structural component of ribosomes is ____

2

mRNA sequences pass through ____ ribosomal subunits during translation

transcription

what is the process where DNA gene sequences are copied into mRNA?

RNA plolymerase

the promoter region is where ____ binds to DNA during transcription

promoter region

the ____ is a short DNA sequence found upstream from the site where transcription of a specific RNA is going to take place

TATA box

what is the typical human promoter region?

transcription bubble

RNA polymerase is the enzyme that binds to DNA and creates a _____

RNA nucleotides

RNA polymerase recruits and adds complementary _____ based on the DNA sequence during transcription

RNA nucleotides

RNA polymerase recruits and adds complementary ___ based on the DNA sequence during transcription

5’ —→ 3’

RNA polymerase synthesizes a daughter strand of RNA in the ___ direction

introns

_____ are exta sequences

exons

____ are the nucleotides necessary to make the protein

spliced, spliceosome

the introns are ____ out by the ____ leaving only the exons behind

Eukaryotes

the spliceosomes is only found in ____

guanine cap, poly-A tail

a 5' _____ _____ and a 3' _____ _____ are post-transcriptional modifications to mRNA, which provide protection against enzyme degradation after the mRNA leaves the nucleus

cytoplasm; polypeptide

translation occurs in the _____, and it is the process through which mRNA codons produce a _____

what are the three distinct stages of translation?

initiation, elongation, termination

5’ end

initiation is the stage of translation in which the ribosome binds to the mRNA near its ____

Start codon (AUG)

in translation initiation, the ribosome scans the mRNA until it binds to the ___

AUG = methionine

The start codon is the codon that signals the start of translation - what is it and what amino acids does it code for?

methionine - tRNA

the initiator aminoacyl-tRNA complex, _____, base pairs with the start codon during translation initiation

elongation

_____ is the stage of translation in which hydrogen bonds form between the mRNA codon in the A site of the ribosome and its complementary anticodon on the incoming aminoacyl-tRNA complex

peptide bond; ribosome

a _____ is formed between the amino acid attached to the tRNA in the A site and the amino acid attached the tRNA in the P site of the _____ during elongation

P site; A site

after the peptide bond formation of elongation, a ribosome caries unbound tRNA in the _____ and peptidyl-tRNA in the _____

translocation

_____ is the stage of translation in which the ribosome advances three nucleotides along the mRNA in the 5' --> 3' direction

E site; P site

the unbound tRNA from the P site is expelled at the _____ and the peptidyl-tRNA from the A site moves into the _____ during translocation

polyribosome

a _____ is a group of several ribosomes attached to, and translating, the same messenger RNA molecule

termination

_____ is the stage of translation in which 1 of 3 special mRNA codons, or stop codons, arrives in the A site

stop codons

_____ do not code for amino acids; rather, they signal the ribosome to stop translation (termination)

UAG, UAA, UGA

what are the 3 stop codons

Ribosome

what is the machine that carries out translation?

A Site

the ribosomal ____ bind to the next incoming aminoacyl-tRNA complex

P Site

the ____ is the ribosomal binding site for peptidyl-tRNA

E Site

the releases empty tRNAs from the ribosome

Nucleosome

a _____ is a unit of chromatin consisting of a DNA strand wrapped around histone proteins

Bacterial

Histone proteins are not found in ___ DNA

nine

each nucleosome contains ____ histone proteins

H1

which histone protein keeps the DNA wrapped around the histone core in a nucleosome?

Euchromatin

____ represents parts of DNA that consist of "loosely-packed" nucleosomes

Easy

euchromatin is _____ for RNA polymerases to access and transcribe

heterochromatin

_____ represents parts of DNA that consist of "tightly-packed" nucleosomes

inactive

heterochromatin tends to be ____ in transcription

Positively

Histones are ____ charged

Negatively

DNA is _____ charged

Euchromatin; transcription

acetylation of histones increases _____ levels and therefore increases _____

heterochromatin; transcription

deacetylation of histones increases _____ levels and therefore decreases _____

Both increases and decreases

histone methylation ____ DNA transcription levels

Decreases

DNA methylation typically ____ transcription levels

Particular sequence of DNA where replication begins

What is the origin of replication?

bactera only have one origin, while eukaryotes have multiple

how does the origin of replication differ between eukaryotic and bacterial DNA?

Phosphodiester

Each single strand of DNA is made of a chain of nucleotides, which are linked together by _____ bonds

5’

the ____ end of DNA has the terminal phosphate group

3’

the ___ end of DNA has the terminal hydroxyl group

A=T

origins of replication tend to occur at ____ rich segments

single strand binding proteins

after helicase unzips DNA duirng replication, _____ attach to each strand of uncoiled DNA to keep them separated

Topoisomerase

____ creates small nicks within the DNA double helix ahead of the replication fork, to relieve tension created by DNA helicase.

DNA gyrase

____ is a subtype of DNA topoisomerase gound in bacteria and plants

telomeres

____ are sequences of repeated nucleotides at the end of a chromosome that don’t code anything

Eukaryotic

Telomeres are only necessary in ____ organisms

they have circular chromosomes

Why are telomeres not necessary in prokaryotes?

telomerase

____ is an enzyme that catalyzes the lengthening of telomers in eukaryotic cells

3’ hydroxyl group

DNA polymerase can only add DNA nucleotides off an existing ____

primase

____ provide a 3’ hydroxyl group for DNA polymerase to attach new nucleotides to

DNA sliding clamp

a ____ is a protein that helps to hold DNA polymerase to the template strand

DNA ligase

_____ is an enzyme that covalently links DNA ends together, which is important for connecting Okazaki fragments

Cytosol

In prokaryotes, transcription occurs in the ____ (location)

-10 and -35 elements

Which two elements are present in bacterial promoters that help initiate transcription?

sigma factor; RNA polymerase holoenzyme

prokaryotic core RNA polymerase combines with _____ to form _____, which has the ability to target the promoter region of bacterial DNA

rho dependent, rhododendron independent

what are the two types of transcriptional termination in bacteria?

operon

an _____ is when a group of related genes are under the control of 1 promoter site, and they function to make sure the cell conserves its resources

lac operon

the _____ is an inducible operon that aids in control of transcription of lactose metabolizing genes in E. coli

inducible

an _____ operon is one that is usually inactive, unless it is made to become active