Molecular Genetics (Unit 3) - chapter 7 Flashcards
Archibald Garrod, in 1896, began studying ________ which is a condition where a person’s urine turns black on contact with air.
alkaptonuria
He found that people with alkaptonuria excrete a particular chemical in their _____.
urine
He hypothesized that people with this disorder were not ________
able to break down this chemical
Later research proved that people with
alkaptonuria have a_______ that codes for a defective enzyme that can no longer break down the ____________
mutated gene
amino acid tyrosine
Continual research into _____ and _____ prompted scientists to come up with a hypothesis that could explain the link between the two.
genes and proteins
One Gene-One Polypeptide Hypothesis
-Each gene codes for the synthesis of one ______
polypeptide
-Different polypeptides can be combined to form more _________
complex proteins
-Can form (3)
hormones, enzymes, antibodies etc.
the fundamental principle of molecular genetics, which states that genetic information flows from DNA to RNA to Proteins
Central Dogma
The Central Dogma Includes (3)
Transcription, Translation,
and Folding
information in DNA is copied into RNA
Transcription
RNA can exit the nucleus and enter the _____
cytosol
RNA acts as a copy of the instructions
contained in DNA that can be transported outside of the ______
nucleus
RNA can then be used to build ______
proteins
_______ information contained within RNA
is used to build proteins
Translation
___ contains instructions coding for a specific amino acid sequence
Involves the use of ______
RNA
Ribosomes
changing shape of an amino acid chain
into a functioning protein
Folding
_______ chains must fold properly in order
to become functioning proteins
Amino acid
RNA:
______ Stranded
single
RNA:
Adenine pairs with _______
Uracil (A-U not A-T)
RNA:
Contains _______ instead of deoxyribose sugar in DNA
Ribose sugar
Three major types of RNA include
-Messenger RNA (mRNA),
-Transfer RNA
(tRNA)
-Ribosomal RNA (rRNA)
translated by
ribosomes into a protein
Messenger RNA (mRNA)
Used to move the information from DNA to the ribosome where it can be translated
Messenger RNA (mRNA)
Varies in length depending on the length of the gene being copied
Messenger RNA (mRNA)
a carrier molecule that
binds to a specific
amino acid and adds
the amino acid to the
growing polypeptide
chain
Transfer RNA (tRNA)
tRNA Transfers amino
acids to ______ to
help build proteins
ribosomes
RNA molecules used
with proteins to make up ribosomes
Ribosomal RNA (rRNA)
DNA strand is called the
Template Strand
enzyme that reads DNA and
creates a complimentary strand of RNA
RNA Polymerase
Major component of ribosomes
Ribosomal RNA (rRNA)
Allow mRNA and tRNA to bind to ribosome
Ribosomal RNA (rRNA)
RNA is created _’ to _’
5’ to 3’
Initial RNA strand has to be _____ before it
can become ____ and is called pre-mRNA or
Precursor mRNA
modified
mRNA
The RNA alphabet consists of:
A U C G
specific coding relationship
between bases and the amino acids they code
for
Genetic Code
The DNA alphabet consists of:
A T C G
three base pairs that code for an individual amino acid
Codon
used to initiate translation
(methionine)
Start Codon (AUG)
used stop translation (UAA,UAG or UGA)
Stop Codon
The same ______ specify the same ______ in all living things (there are a few exceptions)
codons
amino acids
This demonstrates the fact that DNA evolved ____ in our evolution and remained relatively ____
throughout our history
early
unchanged
Transcription involves three main steps:
Initiation
Elongation
Termination
promoter sequence of DNA initiates RNA replication
Initiation
RNA molecule is made by
adding nucleotides
Elongation
RNA molecule is released once
it reaches a termination sequence
Termination
Enzyme_______ binds to DNA
at a _______ (a DNA sequence that lies just before a gene)
RNA Polymerase
Promoter
A key part of the Promoter is the _____ which is a sequence of DNA that contains _____ and _____ (These nucleotides make the DNA easier to unwind since they contain less hydrogen bonds)
TATA box
Thymine and Adenine
RNA is made in the __🡪 __ Direction (follows DNA from 3’🡪 5’) using _______
5’🡪 3’
template strand
Strand not used = _________
coding strand
Newly synthesised mRNA is the _____ as the coding strand (with exception of T/U)
same
_______ unwinds DNA and adds nucleotides to build an RNA strand
RNA Polymerase
This allows _______ of a gene to be _______
multiple copies
made simultaneously
RNA transcription
____ when _______ reaches a
termination sequence
stops
RNA polymerase
Once one RNA polymerase molecule has ________________ another can ________________
passed the beginning of a gene
attach and make another copy of the same gene
a section of bases at the
end of a gene that stops
RNA transcription
Termination Sequence
The recently made RNA needs to be modified before it can be used to help make _____
proteins
a chain of adenine added to the 3’ end of the RNA
Poly A Tail
seven guanine bases attached to the beginning of the RNA strand
5’ Cap
protects from _____ digestion during translation
enzyme
Acts as an attachment site for ____ to initiate translation
ribosomes
If transcribed, protein
would ________
fold improperly
Parts of mRNA in
Eukaryotes (_____) are
not transcribed—do not
code for proteins
introns
a non-coding sequence of DNA or RNA
Intron
Prokaryotes have no
introns (T/F)
TRUE
Introns need to be removed from RNA–_______
Introns stay in the _____
spliceosomes
nucleus
a sequence of DNA/RNA that has coding regions of a gene
Exon
Exons exit the _____
nucleus
_____ in RNA need to be connected by removing
introns
Exons
Spliceosomes cut off _____ and attaches the ___ together
intron loop
RNA
proteins that bind to introns and signals them for removal
Small Ribonucloproteins (snRNP’s)
snRNP’s bind to introns and form an ______
intron loop
enzyme that removes introns
from RNA
Spliceosome
a process that produces different mRNA’s from pre mRNA
Alternative Splicing
Allows for more than one ________ to be made from a single gene
polypeptide
Ex. Humans have _____ genes but can make ______ different proteins!
20,000
100,000
central dogma DNA to RNA is:
Transcription
central dogma RNA to protien is:
Translation
RNA molecules used with proteins to make up ribosomes is:
Ribosomal RNA (rRNA)
rRNA Allow mRNA and tRNA to bind for _______
translation
Recap Codons
Every __ nucleotides
on mRNA
3
The way the codons are
arranged in groups of
three is called the
________
reading frame
Three Steps of Translation
Initiation
Elongation
Termination
Initiation:
Ribosomal subunits
bind to mRNA at ___
cap
5`
Goal of translation:
to turn post-transcriptional
mRNA code into an
amino acid sequence
Initiation:
Binds to start codon:
_____
AUG
in Initiation: AUG
This always codes for
the amino acid
_______
methionine
Elongation:
Ribosomes move along the
mRNA in __🡪___ direction
5`🡪3
Elongation:
Reads _____ nucleotides at a
time—reads codons
three
Elongation:
Each ____ carries one specific
______ and delivers the
appropriate, corresponding
amino acid to the ribosomes to
build polypeptides
tRNA
anticodon
Elongation:
Ribosomes have three spots for tRNA to bind:
A Site: _______ site for aminoacyl tRNA to bind
P site: ______ site for peptide bonds to form
E site: _____ site, for tRNA to prepare to leave the complex
Aminoacyl
Peptidyl
Exit
_______ brings methionine to P-site
First tRNA
________ brings next amino acid to A-site
Second tRNA
________ formed between amino acids
Peptide bond
tRNA with met. now in in ____
E-site
Ribosome shifts over one codon; moving _______
first tRNA
Next tRNA will always enter _____
A-site
Process _____ until stop _____
repeats
codon
Termination:
_______ causes translation to terminate
Stop codon
Release factors cause the complex to dissassociate
releasing the _____ and ______
mRNA and ribosomes
______ folding then occurs and the cell further modifies it
for use
Protein
Controlling Gene Expression:
Not all _______ are required by all cells at all times
proteins
Cells regulate _______ in response to their own life cycles and environmental
conditions
gene expression
Ex – insulin only required when:
blood glucose levels are high
Gene expression in prokaryotes is regulated in response to the concentration of two
molecules:
lactose and tryptophan
Some genes are always required – called
____________ ex hemoglobin
housekeeping genes
Both of these responses are examples of:
negative feedback control
The Lac Operon:
To regulate the expression of genes required for _______ metabolism, prokaryotes use what is known as the _________
lactose
operon model
The lac operon consists of:
Promoter
Operator
Coding regions for the enzymes thatmetabolize lactose
The ___ operon is a cluster of three genes that
code for the proteins involved in the metabolism of lactose
lac
Upstream from the operon is a gene that codes
for a ______ protein
repressor
This allows ________ to bind to
the promoter and
transcribe the genes
RNA polymerase
In the presence of
______ the lactose
molecule itself binds
to the _______
protein.
lactose
repressor
When lactose is
_____ from the cells
environment, the
___________
binds to the operator
of the lac operon,
blocking transcription
absent
active lac repressor
The trp Operon:
_______ is an amino acid which is an important
component to many proteins.
Tryptophan
Prokaryotes can synthesis tryptophan directly or
_____________
through their environment
The trp operon has the same components as the
lac operon, but ________ acts in a different
manner to regulate gene expression
repressor protein
There is a ________ is a signal molecule
that binds to a repressor protein to control gene
expression
corepressor protein
When tryptophan is
absent, the trp
repressor is _____
inactive
When tryptophan is
______ in the cell’s
environment, the
amino acid binds to
and activates the trp
repressor.
present
changes in DNA sequence
Genetic Mutation
Genetic mutation May be caused by:
Radiation
Chemicals
Replication Errors
Genetic mutation Can change the _____ and _____ of a genome
structure and function
Keep in mind that mutations are _____ all bad
not
There are three basic categories of mutations:
Mutations with POSITIVE effects
Mutations with NEGATIVE effects
Mutations that do not cause any discernible changes
_______ have driven our evolution
Mutations
Do not affect large portions of DNA
Small-Scale Mutations
Small-Scale Mutations Involve the following types of mutations:
Substitution
Insertion
Deletion
Inversion
replacement of one base pair by another
Substitution
addition of a base pair or larger coding region
Insertion
removal of a base pair or larger
coding region
Deletion
bases switch positions
Inversion
Substitution Mutations:
________ - a mutation that changes a single amino acid in the coding sequence
Missense Mutation
Substitution Mutations:
________ – a mutation that results in a premature stop codon
Nonsense Mutation
Substitution Mutations:
________ – a mutation that does not alter the resulting amino acid sequence
Silent Mutation
a shift in the reading frame
resulting in multiple missense/nonsense effects
Frameshift Mutation
frame shift mutation May occur from an ______ or ______ of a base pair
insertion or deletion
Large-Scale Mutations
_______ - the movement of entire genes/sequences of DNA from one chromosome
to another
Translocation
__________ Can remove entire coding regions
Large Scale Deletions
Ex of ______: Deletion of Dystrophin gene causes muscular dystrophy
Large Scale Deletions
Large Scale _______:
The addition/duplication of large regions of DNA
Insertions
Large Scale Insertions:
Leads to a large number of the ______
Provides opportunities for new genes to _____
same gene
evolve
________ – caused by
environmental effects
Induced Mutations
Causes of Genetic Mutations:
_______ - caused by errors in DNA replication
Spontaneous Mutations
______ – an environmental agent
that directly alters the DNA within a cell
Mutagen
_______ – bonds to
nucleotides and negatively
affects replication
Benzene
Chemical Mutagens:
_________ – linked
to various forms of cancer
______ – inserts
itself between strands of
DNA and causes errors in
replication
Ethidium Bromide
Ultraviolet radiation may cause damage to DNA
and cause ________
skin cancer
_______ radiation may cause mutations
Electromagnetic
________/_______ can break bonds within DNA
molecules and cause cancer/super powers
X-Rays/Gamma Rays
________ are
passed on while negative
mutations are generally
lost quickly (species can’t
breed if they are dead)
Beneficial mutations
______ are responsible
for the variety of life we
see today
Mutations
The majority of mutations
are _____ (in non-coding
regions of DNA)
neutral
